CA1276802C - Methods for regulating the growth of plants and growth regulant compositions - Google Patents

Abstract

ABSTRACT

L-(d)-lactic acid, the dextrorotatory isomer of lactic acid, is an effective plant growth regulant which exhibits classical growth regulant activity at very low concentrations and dosage rates. It can be employed to beneficially stimulate the growth of all plant varieties and is particularly useful for stimulating the growth of commercial crops. As is the case with other growth regulants, L-lactic acid can also be employed to inhibit the growth of plants when applied at sufficiently high concentrations. Thus, L-lactic acid can be employed to stimulate the growth of desired plants, to stimulate the fruit production of fruit-bearing plants, and to inhibit the growth of undesired vegetation. Novel compositions which comprise mixtures of L-(d)-lactic acid and one or more preservatives which are sufficient to prevent the hydrolytic and/or bacterial decomposition of the active isomer are also disclosed.

Description

~27~ 2 METHODS FOR REGULATING THE GROWTH OF PLANTS
AND GROWTH REGULANT COMPOSITIONS

This invention relates to methods of regulating the 5 growth of plants and, in particular, it relates to methods useful for stimulating the growth and/or fruit production of plants, to methods of inhibiting the growth of undesired vegetation, and to compositions useful for regulating plant growth.
Plant growth regulants can be defined as compounds and/or preparations which, in minute amounts, alter the behavior of ornamental and/or crop plants and/or the produce o~ such plants through physiological (hormonal) rather than physical action. They may elther accelerate 15 or retard growth, prolong or break a dormant condition, promote rooting, fruit-set, or increase ruit size or quantity, or affect the growth and/or productivit~ of ~- plantAs in other ways. Plant growth regulants are currently classified into one or more of six categories:
20 auxins, gibberellins, cytokinins, ethylene generators, inhibitors, and retardants. Illustrative of known auxins are indole acetic acid, 2,4-D (2,4-dichlorophenoxyacetic ~ acid), MCPA (4-chloro 2-methyl phenoxyacetic acid), MCPB
: (4-[(4-chloro-0-tolyl~oxy] butyric acid) which susceptible 25 plants oxidize to MCPA, and BNOA (beta-napthoxyacetic acid). Gibberellins include gibberellic acid and its derivatives, while cytokinins include compositlons sllch as zeatin, kinentin, and benzyl anidene. Presently known - ethylene generators include ethylene and Ethephon ~ 30 ~(2-chloroethyl) phosphoric acid]. Presently known - inhibitors include benezoic acid, gallic acid, and ~-~ cinnamic acid, while retardants, a recently developed class of plant growth regulants, include compositions which are especially useful in plant height control, ~-` 35 .

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particularly in commercial greenhouse-grown floricultural crops.
Lactic acid (alpha-hydroxypropion`ic acid) is well known and is widely employed in industry as a chemical 5 intermediate. It is usually present in the form of the racemic mixture which is an equal molar mixture of the two possible optical isomers of alpha-hydroxypropionic acid -the levorotatory and dextrorotatory isomers. I,evorotatory (l) isomers are isomers of an optically active compound ~o which rotate a beam of polarized light to the left; the dextrorotatory ~d) isomers are isomers of the same compound which rotate a beam of polarized light to the right. A second convention employed to define the configuratlonal relationships of dissimilar functional 15 groups bonded to an asymmetric carbon atom, the Fischer method, is based on the geometric arrangement of functional groups relative to each other rather than on the direction (left or right) in which a standard solution of the compound rotates a beam of polarized li~ht. In 20 accordance with the Fischer method, any compound which contains an asymmetric carbon atom of the same configuration as the asymmetric carbon in the arbitrary standard dextrorotatory glyceraldehyde is classified in - the D series while compounds in which the asymmetric 25 carbon atom has the opposite configuration are classified in the L series. Althouyh the Fischer D and L
classifications do not correlate with dextro- (d) and levorotatory (l) optical activity for all compounds, those classifications can be used in combination with the 30 optical activity classifications d and l to define both the geometric arrangement and specific optical activity of any optically active isomer. Thus, the L-isomer of lactic acid, which is dextrorotatory, is defined as L-(d)-lactic acid, and the D isomer is defined as D-(l)-lactic acid.
35 However, both of these characteristics of relatively .~

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~;276E3~;2 simple compounds such as lactic acid can be adequately defined by reference to only one classification system.
L-lactic acid is known to be dextrorotatory and l-lactic acid is known to have the D configuration according to 5 Fischer. For this reason, the D and L isomers of lactic acid are usually identified only by the D and L
designations and without explicit reference to their optical activity. The Fischer classification method is well know in the art and is discussed in more detail in 10 n Introduction to Organic Chemistry", Fieser and Fieser, D.
C. Health and Co., Boston~ Mass., (1957~ at pages 209-215.
~ actic acid is prevalent in a variety of synthetic and naturally occurring products such as dairy products and fermentation products in which it occurs primarily as 15 the racemic mixture. Specialiæed fermentation processes can be employed to selectively manufacture either the levorotatory or dextrorotatory isomers. Although some commercially available agricultural products contain fermentation products and lactic acid and are marketed for 20 various applications in the agricultural industry, it has not been observed or suggested that L-(d)-lactic acid is an active plant growth regulant. Furthermore, the lactic acid-containing compositions which are marketed in the agricultural industry usually contain the racemic mixture 25 Of both optical isomers in addition to cations such as ; sodium, potassium, ammonium, etc., and/or other compounds such as surfactants, pesticides, etc., which can react with L-lactic acid and destroy its growth regulant acti.vity O
It has been suggested that alpha-hydroxy carboxylic acids of higher molecular weight than lactic acid exhibit specific growth regulant activity regardless of the configuration or optical activity of the carboxylic acid employed. U.S. Patent 3,712,804, Mueller et al., 35 discloses that certain alpha-substituted carboxylic acids . . .
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increase the yield of eertain crops by improving the a~ility of the plant to assimilate water from its environment. The aeids have 7 to 10 carbon atoms per molecule, and the alpha carbon atom is substituted with 5 one or more functional groups ineluding oxy, hydroxy~
; amine, and carboxyl groups. The acids are applied to very young plants, and the salts and lower alkyl esters and amines have growth regulant activity similar to that of the free acid. The compositions ean also contain wetting 10 agents.
The plant growth regulants referred to above and otherwise known in the art, ineluding those discussed in U.S. 3,712,804, all suffer from certain disadvantages that make their use, at least in some applieations, less 15 desirable than would be the use of L-laetie acid. Many growth regulant eompositions, partieular:ly those whieh exhibit herbieidal aetivity at higher dosage rates, are ; toxie to plants, the environment, and/or animals, ineluding humans. Many are not readily available and are 20 relatively expensive to manufacture as compared to L-laetic aeid. Also, many of the known growth regulants sueh as the alpha-functional carboxylic acids, salts, esters and amines diseussed in U.S. 3,712,804, require plant treatment at a time that may not be opportune for 25 the grower in all instanees. Furthermore, many known regulants exhibit a limited speetrum of growth regulant aetivity, are not useful with many plant varieties, and/or do not adequately regulate erop produetivity.
Aecordingly, a need exists for improved methods for regulating the growth of plants and for improved compositions useful in sueh methods. In partieular, a need exists for improved methods and eompositions for stimulating the desired growth of plants, inhibiting the ~` growth of undesired vegetation, reducing the toxie effects 35 of sueh methods and eompositions on the environment and ~"
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animals, including human~, and reducing the expense of so regulating plant growth.
It is therefore a principal object of this invention to provide novel methods for regulating the growth of 5 plants.
Another object oP thi~ invention is t~e provision of novel plant growth regulant compositions.
Yet another object of this invention is the provision of methods and compositions for stimulating the growth and 10 productivity of agricultural and ornamental plants.
Yet another object i8 the provision of improved methods and compositions for inhibiting the growth of undeRired vegetation Another object of thls invention i9 the provision of lS plant grow~h regulant composi~ion~ which are non toxic to animals and to the environment.
Another object of this invention is the provision of : relatively inexpensive methods for regulating the growth of plan~s which do not require exposure of applicators, 20 other personnel, or the environment to either toxic or corrosive materials.
: Other objects, aspects and advantages of this ; invention will be apparent to one skilled in the art in view of the following disclosure, the drawings, and the 25 appended claims Brie~ly, the invention provides novel methods for regulating the growth of plants and compositions useful in such methods. The methods of this invention involve : regulating the growth of plants by contacting the plants 30 with a growth regulating amount of the dextrorotatory L-(d)-isomer of lactlc acid. The L-lactic acid should constitute at least a major portion of the lactic acid present when so applied. These methods can be employed ei*her to stimulate the growth and/or frui~ produc:tion : 35 of crop :

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: . ' ~Z~B~2 25053-362 plants and ornamental plants or ko inhibit the growth of undesired vege-tation.
The novel compositions of this in~ention exhibit plant growth regulant activity and contain a plant growth regulating effective amount of lactic acid of which at least a major portion is the L-(d)-isomer of lactic acid and a diluent acceptable for regulating growth of plants. These compositions preferably also contain a nonreactive preservative such as a sufficient amount of acid to maintain the pH of the composition within the range of about 5 or less and/or a sterilant which is sufficient to inhibit the bacterial decomposition of the lactic acid.
Compositions for regulating the growth oE plants, pre-ferably contain (1) lactic acid, of which at least a major portion is the dextrorotatory L (d)-isomer of lactic acid and (2) a preservative selected from the group consisting of (a) sufficient acid to maintain a pH in said composition of about 5 or less, (h) a sterilant, and (c) combinations of (a) and (b).
Compositions o~ matter characterized by plant growth stimulating activity are preferably aqueous solutions of lactic acid in which the L-(d)-isomer of lactic acid constitutes at least ~ about 60 percent of the total lactic acid and is present in the ; solutions at a concentration of about 10 10 to about 10 2 molar.
Compositions of matter characterized by plant growth stimulating activity more preferably contain lactic acid of which about 80 to 100 percent of the lactic acid is the ~-(d)-isomer of lactic acid and is present in the composition at a concentration :

'', ~ . '' ' '` ' ~ : . ' , , ~ 25053-362 of about 10 10 to about 10 2 molar.
Preferred compositions useful for regulating the growth of plants contain (1) a plant growth regulant consisting essentially of lactic acid of which at least a major portion is the L-(d~-isomer of lactic acid and (2) a preservative selec-ted from the group consisting of (a) sufficient acid to maintain a pH in said composition of - 6a -' .,.! .~;
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about 5 or less, (b) a sterilant, and (c) combinations of (a) and (b).
Methods for regulating the growth of plants include contacting plants with a growth regulating amount of 5 composition which contains the L-(d)-isomer of lactic acid.
Methods for regulating the growth of plants involve contacting plants with a plant-growth regulating amount of a composition which contains lactic acid, wherein the 10 dextrorotatory L-isomer of lactic acid constitutes about 80 to about 100 percent of the total lactic acid present.
Methods for stimulating the growth of plants involve contacting plants with a growth stimulating amount of a composition which contains lactic acid, wherein the 15 L-isomer of lactic acid constitutes about 80 to 100 percent of the tot~l lactic acid pres~nt.
Methods for stimulating the fruit production of fruit-bearing plants involve foliarily applying to fruit-bearing plants during the fruit bearing cycle a j 20 composition containing lactic acid in which the L-(d)-isomer of lactic acid constitutes about ~0 to 100 percent of the total lactic acid present, and in which the composition is applied to the fruit-bearing plants at a fruit production stimulatin~ dosage rate corresponding to 25 at least about 2 ounces per acre of the L-(d)-isomer of ;~ lactic acid.
Methods for stimulating the growth of vegetable, grain, tuber-crop, timber crop, grass, ornamental 10wering, and/or fruiting plants involve contacting the 30 plants with a growth-stimulating amount of lactic acid, wherein the L-isomer of lactic acid constitutes at least a major portion of the total lactic acid present.
Methods for stimulating the growth of plants involve ~ contacting plants with a growth-stimulating amount of ; 35 _7_ ' ':

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lactic acid, wherein the lactic acid consists essentially of L-lactic acid.
The methods of this invention which employ relatively low concentrations and dosage rates of the growth-active 5 L-isomer of lactic acid are useful for increasing the growth and/or fruit production of essentially all plant - varieties. On fruiting plants, the methods af this invention can be employed to increase both the size and quantity of the fruit produced. These methods also hasten 10 maturity of fruit thereby shortening the crop cycle, and they increase the growth rate of agricultural and ornamental grasses~ such as alfalfa, rye grass, etc. They - can be employed to delay the senescence, and thereby extend the fruiting period, of annual fruit plants such as 15 tomatoes and corn and to extend the fruiting period of perennials such as citrus, grapes, etc. These methods have the further advantage that they are non-toxic to environment and to animals, and, at levels employed for stimulating plant growth, the compositions useful in the 20 methods of this invention are non-toxic to the treated plants or the harvested component of fruiting plants such as food products. Furthermore, the compositions useful in the methods of this invention are noncorrosive to storage, transport and application equipment and to animal and 25 vegetable tissue. This, they can be easily and safely handled without damage to equipment, personnel, the crop~
or the environment. The active component of the compositions useful in the methods of this invention -L-lactic acid - is readily available commercially and is 30 relatively inexpensive, particularly in comparison to various other plant growth regulants which are expensive, sophisticated chemical compounds which require relatively sophisticated processes for their manu~acture.
By the use of higher dosage rates of the L-lactic 35 acid component, the methods of this invention can be .

-' ~L~2 employed to inhibit the growth of undesired vegetation without the disadvantages attendant to the use of various other herbicidal growth regulants such as toxicity to the environment and animals and corrosivity toward application, storage or shipping equipment and personnel.
~ 11 of the benefits associated with the use o~ the methods of this invention discussed above also result from the use of the novel compositions of this invention in such methods, whether those novel compositions are employed to sti~ulate or to inhibit vegetative growth.
The methods and compositions of this invention will be better understood by reference to the drawings of which:
Figure 1 is a graphic presentation o~ Cress Test results illustrating the root growth stimulating and inhibiting activity of L-lactic acid and of indoleacetic acid; and Figure 2 is a similar graphic presentation of data illustrating the root growth regulating activity of L-lactic acid and of D-(1)-lactic acid.
This invention provides novel methods for regulating the growth of plants and novel growth regulant compositions useful in such methods~ The methods of this invention involve either stimulation or retarding the gro~th of plants (depending upon the dosage rate of the growth regulating composition employed) by contacting the plants with the dextrorotatory isomer of lactic acid which is preferably in a composition form that additionally contains a suitable diluent. The novel compositions of this _ g _ . 1 .
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.. ,' ' ' invention comprise lactic aeid of which at least a major portion is the L-(d)-isomer of laetic aeid and a suitable diluent, and optionally and preferably a preservative whieh is nonreactive with the laetic acid and which is sufficient to reduee or prevent the hydrolytic and/or bacterial decomposition of the lactic acid.
The methods of this invention can be employed to increase vegetative growth and to inerease the fruit production of '.~' ~ - 9a -..
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fruit-producing plants. They can also be employed to hasten the maturity of plant fruit, delay the senescence (and thereby extend the fruiting period) of annual plants, and to e~tend the fruiting period of perennial plants.
The compositions useful in the methods of this invention are broad spectrum plant growth regulants thus they can be employed to stimulate the growth and/or fruit-producing capacity or to inhibit the growth of all plant varieties, including fruiting and principally 10 vegetative plants. Fruiting plants, for the purposes of this invention, include plants that bear any variety of ; produce other than vegetative growth such as annual and perennial vegetables, fruits, nuts, grains, fiber crops, and the flowering plants. Plants grown primarily for 15 their vegetative producti~ity (the principal illustration being the wide variety of grasses grown for animal feeds and decorative purposes) can also be treated in accordance with the methods of this invention. Thus, the methods of this invention can be employed to stimulate the growth and 20 fruit-bearing capacity (where relevant) of vegetables, fruits, nuts, grains, grasses, fiber crops, wood crops, ~` and flowering plants.
~` All varieties of vegetables can be treated in accordance with these methods including lettuce, broccoli, 25 asparagus, onions, tuberous crops such as potatoes, sugar beets and peanuts, tomatoes, beans, etc. Illustrative of fruits that can be treated in accordance with the methods - of this invention are peaches r apples, citrusl avocados, ~ cherries, grapes (varietal and table), bananas, etc.
- 30 Treatable nut crops include walnuts, pecans, almonds, ;~ cashews, etc. Essentially all grains can be treated including corn, wheat, sorgham, maize, rice, barley, oats, -` etc. Illustrative grasses include alfalfa, bermuda, rye, and bluegrass, while illustrative fiber crops include 35 cotton and flax. All wood crops can be stimulated by the .~ .

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methods of this invention including both hardwoods and conifers, such as oak, elm, maple, walnut, spruce, hemlock, alder, loblolly pine~ redwood, mahogan~, cypress, cedar, Douglas fir, and white pine. Flowering plants 5 which can be treated in accordance witl~ the methods of this invention include all varieties o:E domestic and commercially grown flowers, such as orchids, roses, chrysanthemums/ azaleas, camellias, ca:rnations, pansies, snapdragons, etc.
All plant varieties, including all of the annual and perennial, fruiting and vegetative plants referred to above can be inhibited and eliminated by the methods of this invention. However, it is usually preferable to inhibit the growth only of undesired vegetation such as 15 weeds, brush and grasses that occupy vacant land ancl which can infiltrate commercial crops and domestic plantings.
Illustrative of vegetation which is usually desirable to inhibit or eliminate are black mustard (brassica nigra), ~ curly dock (rumex crispus), common groundsel (senecio - 20 vulgaris, pineapple weed (matricaria matricarioides), swamp smartweed (kelp, polygonum coccineum), prickly lettuce ~lactuca scariola), lance-leaved groundcherry (physalis lanceifolia)~ annual sowthistle (sonchus oleraceus), london rocket (sisymbrium irio), common 25 fiddleneck (amsinckia intermedia), hairy nightshade (solanum sarrachoides), shepherd's purse (capsella bursa-pastoris), sunflower (helianthus annuus), common knotweed (polygonum aviculare), green amaranth (amaranthus :hybridus), mare's tail (conyza canadensis), henbit (lamium ~:30 amplexicaule), cocklebur (xanthium strumarium), cheeseweed (malva parviflora), lambsquarters (chenopodium album), puncture vine ltribulus terrestris), common purslane ~:(portulaca oleracea), prostrate spurge (euphorbia supina), telegraph plant (heterotheca grandiflora), carpetweed (mollugo verticillate), yellow starthistle (centaurea ' , ,.

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-solstitialis), milk thistle (silybum marianum), mayweed ~anthemis cotula~, burning nettle ~urtica urens), fathen (atriplex patula), chickweed ~stellaria media), scarlet pimpernel (anagallis arvensis), redroot pigweed ~ 5 (amaranthus retroflexus), minnerslettuce (montia ::~ perfoliata), turkey mullein (eremocarpus setigerus), nettleleaf goosefoot (chenopodium murale), prostrate pigweed (amaranthus blitoides), silverleaf nightshade (solanum elaeagnifolium), hoary cress (cardaria draba), 10 largeseed dodder (cuscuta indecora), California burclover ~medicago polymorpha), horse purslane (trianthema portulacastrum), field bindweed (convolvulus arvensis), Russian knapweed (centaurea repens), flax-leaved fleabane (conyza bonariensis), wild radish (raphanus sativus), 15 tumble pigweed (amaranthus albus), stephanomeria (stephanomeria exigua), wild tu~nip (brassica campestris), buffalo goard (cucurbita foetidissima~, common rnullein (verbascum thapsus), dandelion (taraxacum officinale), spanish thistle (xanthium spinosum) r chicory (cichorium 20 intybus), sweet anise (foeniculum vulgare), annual yellow sweetclover (melilotus indical), poison hemlock (conium maculatum), broadleaf filaree (erodium botrys), whitestem ~: filaree (erodium moschatum), redstem filaree (erodium ~` cicutarium), ivyleaf morning-glory (ipomea hederacea) 25 shortpod mustard (brassica geniculata), buckhorn plantain (plantago lacenolata), sticky chickweed (cerastium viscosum), himalaya blackberry (rubus procerus), purslane speedwell (veronica peregrina), Mexican tea (chenopodium ambrosioides), Spanish clover (lotus purshianus), 30 Australian brassbuttons (cotula australia), goldenrod (solidago californica), citron (citrullus lanatus), hedge mustard (sisymbrium orientale), black nightshade ~solanum nodiflorum), Chinese thornapple (datura ferox)/ bristly ~: oxtongue (picris echioides), bull thistle (cirsium vulgare), spiny sowthistle (sonchus asper), tasmaian :, . . . : : .- ..
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gooseEoot (chenopodium pumilio), goosefoot ~chenopodium botrys), wright groundcherry (physalis acutifolia), tomatillo groundcherry (physalis philadelphica), pretty spurge (euphorbia peplus), bitter apple (cucumis 5 myriocarpus), indian to~acco ~nicotiana bigelovii), common morning-glory (ipomoea purpurea), waterplantain (alisma triviale), smartweed (polygonum lapathifolium), mature sowthistle (sonchus asper), yellow nutsedge (cyperus esculentus), purple nutsedge (cyperus rotundus), lupine (lupinus formosus), and grasses of the family Gramineae such as annual rye grass, blue grass, water grass, barnyard grass, bermuda grass, fescue, mat grass, Johnson grass, and the like.
The compositions useful in the methods of this 15 invention comprise a growth regulating amount of the L-(d)~lactic acid; i.e., the dextrorotatory isomer. The effectiveness o such compositions to stimulate the growth and/or fruit-bearing capability of vegetation and to inhibit the growth of or kill vegetation (depending on 20 dosage rate) is apparently attributable to the plant growth regulant activity of the uncomplexed, monomolecular, L-(d)-isomer of lactic acid. The D-(1)-isomer of lactic acid not only does not promote vegetative growth or fruit productivity, it appears to 25 inhibit the activity of the L-isomer to the point that the racemic mixture, i.e., the 50-50 blend of the levorotatory and dextrorotatory isomers, has only marginal growth regulant activity, if any. As in the case with all -compounds which are applied to plants as solutes, the 30 D-lactic acid does exhibit phytotoxicity if sufficient quantities of that material are applied to the plant.
Such activity is very similar to that observed with very simple compounds such as sodium chloride and other soluble salts, which exhibit phytotoxicity when foliarily applied 35 to essentially any crop. At sufficient dosage rates, such :
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compounds will inhibit the growth of plants and willultimately kill the treated plants.
I have also found that L-lactic anhydride and polylactides of the L-isomer (self esterification products 5 of lactic acid~ are active plant growth regulants and are as active as monomolecular L lactic acid. All of these compounds exhibit regulant activity at very low concentrations, e.g., of about lO lO molar and less.
Lactic anhydride and higher polylactides form from 10 monomolecular lactic acid at lactic acid concentrations of about 50 percent or greater in water. Both lactic anhydride and polylactides revert to monomolecular lactic acid upon dilution with water to concentrations below 50 percent. The active form of the growth regulant in the 15 plants may be monomolecular l.-lactic acid or polylactides of L-lactic acid of varying molecular weight. ~he polylactides could form on the foliage of treated vegetation (even when mono~olecular lactic acid is applied in relatively dilute solutions) upon evaporation of water 20 from the applied solution. The polylactides, if applied as such or formed on the plant foliage, probably hydrolyze within the plant (upon exposure to water) to form monomolecular lactic acid. Similarly, compounds which, in a plant environment, are converted to L-lactic acid or the 25 anhydride or polylactides of L-lactic acid, are also effective for introducing the active growth regulant into treated plants. Whatever the active species actually is, I have found that monomolecular L-lactic acid and the anhydride and higher polylactides of L-lactic acid exhibit ` 30 growth regulant activity when contacted with plants.
Accordingly, when employed to describe the various aspects of this invention, the term L-lactic acid is intended to incorporate the anhydride and higher polylactides of L-lactic acid and compounds which convert to L-lactic acid ~`

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or its anhydride or polylactides when applied to plants~
as well as L-lactic acid itself.
One of the unexpected discoveries in the present invention is that the D-(l)-isomer exh:ibits little, if 5 any, plant growth regulant activity, being at least 10 times, and probably at least 100 times, less active than the L-(d)-isomer. Further the D-isomer appears to inhibit or suppress the activity of the L-isomer. Accordingly, the preferred compositions useful in the methods of this 10 invention comprise those in which the L-isomer constitutes at least a major portion of ~he lactic acid present.
Usually the L,-isomer will comprise at least about 60, preferably at least about 80, and most preferably at least about 90 percent of the lactic acid contained in the 15 composition Presently, the most preferred compositions are those in which the l,-isomer constitutes 80 to l00 percent, and preferabl~ 100 percent of the lactic acid contained in the composition as applied.
The L-isomer can be applied neat although this 20 procedure is usually undesirable for stimulating plant growth due to the high specific activity of the L-isomer.
The L-isomer stimulates plant growth at concentrations as low as 10 molar. Application of the neat material or -concentrated solutions also complicates the distribution 25 of the active component to the treated crop. Accordingly, the compositions useful in the methods of this invention usually constitute solutions of the L-isomer in a suitable solvent such as water, lower molecular weight mono- and polyhydric alcohols, ethers, carbon disulfide, and similar 30 solvents which do not react with the L-isomer (and thereby negate its activity) under normal handling, storage and application conditions Aqueous solutions of the L-isomer are very active growth regulants and are presently -~
preferred. The L-isomer will usually be prese~t in the 35 applied solution at a concentration of at least 10 10 . .
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molar. Although L-lactic acid remains active in solution at even lower concentrations, it is diEficult to apply sufficient amounts of that compound to the treated plants when using solutions of lower concentration due to run-off 5 of the applied solution from the plant foliage.
Accordingl~, solutions useful in the methods of this invention will usually have L-lactic acid concentrations within the range of lO lO to about 4 molar, normally about lO 9 to about 2 molar. Dilute solutions within these 10 ranges are usually preferred to simulate growth and promote fruit production. Thus, when plant stimulation is desired, the L-isomer should be present in the applied solution at a concentration within the range of about lO lO to about lO 2 molar, generally lO 9 to about lO 2 15 molar r and pref~rably, about lO 7 to about lO 2 molar.
Solutions containiny higher concentrations of the active L-isomer can be conveniently employed to inhibit the growth of undesired vegetation. Concentrated solutions facilitate the application of dosage rates sufficient to 20 inhibit plant growth as discussed hereinafter. Thus, the solutions employed to effect growth-inhibiting response will usually contain the L-isomer in concentrations of at least about lO 7 molar, generally at least about lO 5 to about 2 molar.
I have also found that metallic salts of L-lactic acid and esters of L-lactic acid with either alcohols or acids other than L-lactic acid are less active as growth regulants than L lactic acid itself. The salts of lactic acid can form in solutions of the L-isomer which contain 30 significant amounts of metal cations such as calcium, nickel, cobalt, magnesium, manganese, zinc, sodium, - potassium, etc. In fact, the concentration of such metal cations in many irrigation waters, such as Colorado River water, is sufficient to significantly reduce the activity 35 of a solution of the L-isomer prepared from such waters.

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i86)2 I have also found that compounds having active acid and/or alcohol groups can react with lactic acid to form inactive esters at pH levels below about 3 or above lO, and that such esters also can form at pH levels within th~range of . 5 about 3 to about lO, albeit at a slower rate. Thus, the activity of the L-isomer for regulating the growth of plants can be reduced or lost due to t:he formation of esters with other compounds containing active acid and/or alcohol groups. Compounds containing such functional 10 groups are preferably excluded from the compositions used in the methods of this invention.
While the L-lactlc acid-containing compositions described immediately above are active plant growth regulants and thus can be employed in the methods of this 15 invention, they are hydrolytically unstable under certain conditions and are subject to bacterial attack. Bacteria can convert the active L-isomer to inactive species within a relatively short period of time at temperatures as low as ~0F. Thus, while the L-lactic acid solution can be 20 sterilized during its manufacture, there remains a significant risk of bacterial contamination during storage, transportation, mixing, and application.
~ ccordingly, the novel compositions of this invention which are stabilized against hydrolytic decomposition and 25 bacterial attack are presently preferred for use to regulate the growth of plants in accordance with the methods of this invention. These novel compositions comprise lactic acid of which a major portion is the dextrorotatory L-~d)-isomer of lactic acid and a 30 preservative which is sufficient to prevent conversion of the L-isomer to an inactive form by bacterial attack.
Suitable preservatives include sufficient acid concentrations to maintain a pH of about 5 or less and/or sterilants which inhibit bacteria growth.

.

~' -The hydrolytic stabllity of the L-isomer can be maintained in aqueous solutions by maintaining solution pH
within the range of about 3 to about lO, preferably within the range of about 4 to about 8, and most preferably 5 within the range of about 4 to about ~. Lactic acid will react with water at relatively mild temperatures as low as ~0F. under either basic or acid conditions outside the preferred ranges. The rate of hydrolytic conversion of the L-isomer is also relatively low at pH levels of about 10 3 and about 10, and increases dramatically as pH drops `~ below 3 or is increased to levels above lO. The rate of hydrolysis can also be reduced by reducing the water concentration in the composition, i.e., increasing the lactic acid concentration. However, the hydrolytic 15 conversion of L-lactic acid can increase dramatically upon dilution of the concentrated acid prior to application if the solution pH is not maintained within the prescribed ranges. Accordingly, the preferred aqueous solutions of this invention contain sufficient acid and/or base to 20 maintain the pH of the solution within the ranges described above. pH buffers are also particularly convenient for this purpose and should have buffer points within the range of about pH 3 to about pH lO, preferably about pH 4 to about pH 6. The buffers also should be 25 nonreactive with the ~-lactic acid. Suitable pH buffers include H3PO4-xH2PO~, citric acid - x-citrate (wherein x connotes a monovalent cation such as sodium, potassium, and ammonium), and other buffer pairs which have buffer points within the prescribed ranges~ The salt cation 30 contained in the buffer pair should not be present in a concentration sufficient to deactivate a significant portion of the lactic acid. For the same reason, the ammonium form of the buffer salt is presently preferred since it does not produce insoluble lactates which cause -1~-.

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precipitation of the active component from the aqueous solution.
Essentially any acid, including lactic acid, can be employed to maintain a pH of about 5 or less in the 5 compositions of this invention and thereby minimize the bacterial deactivation of the L-isomer. However, concentrations of lactic acid which are sufficient to maintain p~ levels of about 5 or less are often above the concentration desired in the applied solution.
10 Accordingly, the addition of other acids is presently preferred. Illustrative of suitable acids are phosphoric, sulfuric, nitric, hydrochloric, and slmilar acids which do not form stable esters or salts with the L-isomer component.
Bacterial decomposition of the L-isomer can also be inhibited, or negated altogether, by any one of various known sterilants, such as the bacteriol~tic and bacteriostatic compositions. As is the case with other components of the novel compositions of this invention, 20 the sterilant should not react with lactic acid to form stable salts or esters under normal handlin~ conditions.
Illustrative of sterilants that can be employed in the novel compositions o~ this invention are ethanol, formaldehyde, terramiacan, xylene, toluene, phenylmercuric 25 nitrate, phenylmercuric acetate, copper sulfate, sodium azide, hydrogen peroxide, chlorine, benzisothiozolone, 2[(hydroxymethyl)amis]ethanol, 1-(3-chloroalkyl)-3,517-triaza-l-azoneaodamantane chloride, dibromocyanobutane, etc. Other stable 30 sterilants, i.e., sterilants which do not react with lactic acid, can be identified by blending the sterilant with the desired a~ueous solution of L-lactic acid, and monitoring the stability of the lactic acid in the sterilant-containing solution hy nuclear magnetic 35 residence (NMR~. NMR can be employed to monitor the .. ,''',' ',' ' , : " .,' ' ' "-;'~ "' ' ' ' :' ''', : ~
- '~ .

'' frequency and magnitude of spectral peaks characteristic of a selected nucleus e.g., a hydrogen nucleus in the L-lactic acid molecule. Persistent spectral peak magnitude and frequency over a period of five ~r six hours 5 indicate stability. Diminished magnitude or a shift in peak requency associated with the selected hydrogen nucleus indicate stability, i.e., that the arrangement of functional groups in the lactic acid molecule has been modified. Illustrative unstable sterilants are 10 thiophosphate esters such as melathion, parathion, etc~, which should ordinarily not be employed in the compositions of this invention since they react with - L-lactic acid and reduce or eliminate its activity as growth regulant. Sterilant concentrations within the 15 range of about lO to about 4,000 parts per million (ppm) are usually effective for m~st applications.
In accordance with the methods of this invention, the plants to be regulated are contacted with a growth regulating amount of the compositions useful in this 20 invention. The L-(d)-lactic acid-containing composition can be applied to the foliage and/or to the roots of the treated plants. The timing of application is relatively important when it is desired to increase the fruit production of fruit-bearing plants. In general, the 25 L-lactic acid component should be applied to the plants during the flowering stage or in the early stages of the fruit-bearing cycle, or both. Ideally, the L-lactic acid component can be applied to the plants at one or more times between the first bud stage and the fruit-set stage, 30 preferably between the first-bud stage and the petal-drop stage for both annual and perennial varieties.
Significant increases, e.g., lO percent and more, in fruit production can be achieved by treatment at essentially any time within these stages of plant development. However, 35 it is presently preferred that at least one application of . ' ' ' ' the L-lactic acid component be made within several days of the first-bud stage of development.
Significant improvements in foliage development on non-fruit bearing plants, such as grasses and timber 5 crops, can be accomplished at any time during the growth stage, usually between the spring and fall when the crop is at its active growing cycle.
Application timing is not critical with resp~ct to the herbicidal activity of the L-lactic acid compositions 10 useful for the methods of this invention. Thus, such compositions can be employed to control the growth of vegetation at any time during the growth cycle. However, it is presently preferred that the undes~ired vegetation be treated during the early stages of its development.
Significant increases in the growth oE non-fruit bearing crops and in the growth of fruit production of fruit-bearing crops can be reali~ed by foliar application of the L-lactic acid cornponent at dosage rates within the range of about 2 to about 100, usually about 4 to about 20 50, and preferably about 4 to about 25 ounces of L-lactic acid per acre. The lower dosage rate range of 4 to about 25 ounces per acre is ideally suited to most agricultural row crops and flowering nursery crops. Crops which have a larger abundance of foliage, such as wood crops and some 25 grain and fiber crops such as wheat, corn, and cotton, benefit more by contact with higher dosages within the broader range of about 2 to about 100 ounces per acre of L-lactic acid. Significant growth stimulation can also be achieved by applying the L-lactic acid to the soil in the 30 vicinity of the plant roots. Suitable dosage rates for this mode of application are usually within the range of about 8 to about 400 ounces per acre, preferably about 10 to about 200 ounces per acre of L-lactic acid.
The enhancement in vegetative growth and the increase in fruit production is dose-sensitive to some extent for . ' ~ ' '' .

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-~27~

each crop. AS a rule, crops having a greater abundance of vegetative growth, such as cotton and wood crops, are treated wi~h higher dosage rates of L-lactic acid than are physically smaller plants such as vegetables and tuberous 5 crops which have lesser amounts of vegetative growth.
Undesired vegetation can be eliminated by treating the foliage or soil in the vicinity of the plant roots with the L-lactic acid component at herbicidically effective dosage rates. Herbicidally effective dosage 10 rates usually correspond to at least about 50, generally at least about 80, and preferably at least about lO0 ounces per acre of L-lactic acid. Adequate control of most plants can generally be achieved at dosage rates within the range of about 80 to about 2,000, preferably 15 about lO0 to about 2,000 ounces per acre when foliarily applied.
The concen~ration and dosage rate of the h-lact:ic acid component should be correlated to provide adequate spray volume to contact a significant portion of the 20 treated foliage and enable adequate distribution of the applied solutions as a spray with available equipment.
Spray volumes in the range of about 5 to about 200 gallons per acre are sufficient to afford adequate coverage and spray distributiun for essentially all plant types. Spray 25 volumes of about S to about lO0 gallons per acre are usually adequate for most agricultural crops, and spray volumes within the range of about lO to about 60 gallons per acre are presently preferred for the treatment of agricultural row crops and nursery plants. As in the case 30 of dosage rate, the optimum spray volume will vary depending upon crop type, and primarily as a function of the amount of vegetative growth presented by the treated plants. Thus, relatively higher spray volumes are better suited for the treatment of larger crops such as cotton, 35 corn and tree crops, while lower spray volumes are better ' , . .

z suited for the treatment of vegetables and ~uberous plants. When the L-lactic acid is injected into the plant root zone, the volume of L-lactic acid solution injected per acre should be sufficient to afford adequate distribution of the L-lactic acid throughout the root zone of the treated plants. Dosage rates suitable for this purpose will usually be within the range of about lO to about 400, generally about 20 to about 400, and preferably about 30 to about 300 gallons per acre.
The invention is further described by the following examples which are illustrative of specific modes of practicing the invention and are not intended as limiting the scope of the invention as defined by the appended claims.
EXAM~L~ l Separate portions of pure L-(d)-lactic acid are diluted with disti:Lled water to produce Pive different solutions having concentrations of 10 1, lO 3, lO 5, lO 7, 20 and lO 9 molar. Three separate 5 ml portions of the lO l ; molar solution are then placed in three separate petri dishes lined with filter paper and each containing approximately 15 garden cress seeds. Three separate 5 ml portions of the remaining four solutions are also placed 25 in filter paper-lined petri dishes containing approximately 15 garden cress seeds. A sixth series of three petri dishes containing approximately 15 garden cress seeds is treated only with distilled water. The garden cress seeds are germinated in the dark for three 30 days after which each seed root in each petri dish is measured, and all root lengths for each series of three ~ replicates are averaged to obtain an average root length ; for that treatment~ The average length of each replicate is then divided by the average length of the control ; 35 (water only) to yield a root length ratio LteSt/Lcontro . :
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.

-(Lt/LC). Values below l indlcate that the root length inthe test series is less than that of the control series and that root growth suppression has occurred. Values for the Lt/LC ratio greater than 1 indicate root ~rowth 5 enhancement.
These results are presented graph:ically in Figure l and indicate that the root growth suppression-stimulation promoted by a L-lactic acid solution is characteristic of classical auxin-like activity. Also illustrated 10 graphically in Figure l are data pu~lished in the literature for indole acetic acid (IAA), a widely studied plant growth regulant.
Significant root growth stimulation occurred with L-L,actic acid at concentrations approximately 2 orders of 15 magnitude below those at which similar responses were induced by indole acetic acid. Thus, L-lactic acid is a much more active plant growth regulant than is indole acetic acid, at least so far as that activity is evidenced by the cress seed root elongation test.

The garden cress seed root elongation-suppression test described in Example l is repeated using three replicates each of four different concentrations of 25 L-lactic acid in distilled water, which concentrations corresponded to lO l, lO 3, lO , and lO molar.
Germinated seed root lengths are measured and averaged as described in Example l. These results are presented graphically in Figure 2. The portion of the curve in 30 Figure 2 which represents the response of the garden cress seed roots to L-lactic acid concentrations below lO 7 molar is reproduced based on the results of Example l.
~ ' .

~' ': ' , . ' ' ' :
-: , , , -~ 2 The garden cress seed root elongation--suppression test described in Example 1 is repeated employing four different concentrations of D-lactic acid (the 5 levorotatory isomer) in distilled water. These concentrations correspond to 10 1, 10 3, 10 5, and 10 7 molar. Three separate replicates are tested at each concentration and root lengths are measured and averaged as described in Example 1. The results are presented 10 graphically in Figure 2. Comparison of the results of Examples 2 and 3 illustrates that the levorotatory [D-(l)-~ isomer of lactic acid has little, if any, growth regulating activity and that it is a far less active plant growth regulant than is the levorotatory isomer. The 15 results of Example 3 also indicate that the D-lactic acid has little, iE any, tendency to stimulate the growth of germinating seed roots even at relatively low concentrations.

Yellow flowering variety alfalfa seeds are planted in a sandy loam soil after with 20 ml of a 10 5 molar solution of L-lactic acid are applied topically to the ; soil. Four replicates are treated and these are compared 25 to four replicates of the same seed population planted in the same soil but not treated with the L-lactic acid solution. More seeds germinate in the treated plots than in the untreated (control) plots. All plants are harvested after nine weeks of growth and weighed. The 30 alfalfa treated with L-lactic acid produces 25 weight percent more vegetative growth than does the untreated control.
~' ~ 35 ,.

.. .

, -The operation of Example 4 is repeated with the exception that 50 ml of the 10 5 molar L-lactic acid solution is applied to the soil surface after planting of 5 the yellow ~lowering variety alfalfa seeds. Again more plants survive in the treated plots, and the treated plants produce approximately 25 percent more vegetation growth than the control.

Approximately equal numbers of yellow flowering variety alfalfa seeds are planted in several pots containing a sandy loam soil. Four series of four pots each are treated with 20 ml of a 10 5 molar solution of lS L-lactic acid in distilled water. The solution is applied to the plants by Poliar spraying at emergence (S days after planting), and three weeks, six weeks, and nine weeks after emergence. The plants are harvested twelve weeks after emergence, weighed, and compared to an 20 untreated control. The test se~ies which are treated five days after planting and three weeks and six weeks after emergence all produce approximately 20 to 25 weight percent more vegetative growth than do the control series.
The plants treated nine weeks after emergence do not 25 produce an amount of vegetative growth above that produced by the untreated control plants, which could be defined as statistically significant.

The operation of Example 6 is repeated with the exception that 50 ml of the 10 5 molar L-lactic acid solution is applied to each test series. As in the case of the 20 ml treatments, the plants treated 5 days after planting, and two weeks and six weeks after emergence show 35 approximately 20 to 25 weight percent greater vegetative :.

' ' ' -.. ' ~ ,, . : ,: . : .. . . .

growth than the control, while the plants treated nlneweeks after emergence and harvested twelve weeks after emergence do not evidence a significant gain in vegetative growth over the control. The a~sence of a statistically 5 significant gain in vegetative yrowth Eor the nine week treatment may be due to the relatively short time between treatment and harvest.

EXAMPLE ~
Tiny Tim tomatoes which have already set fruit which is approximately 0.5 to 1.5 centimeters in diameter are treated with an aqueous solution of L-lactic acid in distilled water having a lactic acid concentration of lO 5 molar. The solution is applied to the plant foliage at a 15 rate oE approxim~tely 4 ml per plant. No significant increase in fruit size or quantity is obtained in comparison to untreated control plants.

The operation of Example 8 is repeated with the exception that the L-lactic acid solution foliarily applied to the Tiny Tim tomato plants has a lactic acid concentration of lO molar. Again no increase in fruit size or quantity is observed as compared to the untreated 25 controls.

; EXAMPLE lO
` The operation of Example 8 is repeated with the exception that the tomato plants are treated with two 30 separate foliar applications of approximately 4 ml each of the lO 3 molar L-lactic acid solution in distilled water.
The first application is made at the full-bloom stage (maximum flowering) and the second application is made two weeks later tafter fruit set). The tomatoes are harvested 35 after reaching maturity and the treated tomatoes are approximately 15 percent larger and mature approximately 50 percent faster than do tomatoes on the untreated control plants.

The operation of Example 10 is repeated with the exception that the L-lactic acid solution applied to the tomato plants has an L-lactic acid concentration of 10 molar. As in the case of the 10 3 molar solution, the 10 treated plants yield tomatoes which are approximately 15 percent larger by weight and which mature approximately 50 percent faster than the untreated controls.

, .
~avel orange trees are treated by foliar application at the fi.rst petal-drop stage of five ounce,s per acre o L-lactic acid in 30 gallons per acre aqueous spray volume.
The crop is allowed to set and mature and is harvested and weighed. The untreated control plot produces 820 boxes of 20 navel oranges per acre while the treated plo-t produces 1,218 boxes of the oranges per acre.
'~

Cabernet grapes are treated by foliar application of 25 L-lactic acid at a dosage rate corresponding to 8 ounces of L-lactic acid per acre dissolved in 30 gallons per acre spray volume. The foliar application is made at the first berry stage and the grapes are allowed to mature and are harvested. The yield from the treated grape plants is 15 30 to 20 percent greater than that of untreated control plants in the same population and the sugar content of the treated grapes is approximately 2 percentage points higher than is the sugar content of the untreated grapes.

; -28-.: ' ' ~,: ' ' ' ' I "' ~ '~

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EXAMPI,E 14 - Sylvaner Riesling grapes are treated by foliar application of L-lactic acid at a rate corresponding to 8 ounces per acre in 30 gallons per acre of spray volume at 5 the first berry stage. The grapes are allowed to mature and are harvested and compared to grapes produced by untreated control plants in the same population. The yield from the treated Riesling grape plants is 15 to 20 percent greater than that of the untreated controls.

Murietta tomatoes are treated by foliar application of a solution of L-lactic acid at a dosage rate corresponding to 8 ounces of L-lactic acid per acre 15 dissolved in 30 gallons per acre spray volurne. The application is made at peak flowering and the fruit is allowed to set and mature and is harvested and compared to fruit obtained ~rom untreated plants in the same population. The yield of the treated plants is 20 approximately 30 percent higher than that of the untreated plants.
':

~ Pima cotton is treated by foliar application of an - 25 aqueous L-lactic acid solution at a dosage rate corresponding to 16 ounces of L-lactic acid per acre dispersed in 30 gallons per acre of spray volume. The application is made at peak flowering and the cotton is allowed to mature and is harvested and compared to cotton 30 obtained from untreated, control plants in the same population. The treated plants yield approximately 20 percent more cotton than the untreated plants.

..
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EXAMPLE ~7 Valencia oranges are treated by foliar application o~
16 ounces per acre of L-lactic acid in 30 gallons per acre of aqueous solution spray. The spray is applie~ at the 5 first petal-fall stage ~peak flowering), and the fruit is allowed to mature and is harvested under normal horticultural conditions. The treated trees produce 1,400 boxes per acre of Valencia oranges as compared to 800 boxes per acre for untreated control trees in the same 10 population.

EXA~PLE 18 ~ infandel grapes are treated by foliar application of 4 ounces per acre o~ L-lactic acid in 30 gallons per acre 15 of aqueous solution spray volume. The spray is applied at the first berry stage, and the grapes are allowed to rnature and are harvested under normal horticultural conditions. The yield of the treated Zinfandel yrape plants is 12 percent higher than that of untreated plants 20 in the same population.

Barley plants, approximately 12 inches high, are treated with L-lactic acid by foliar application of 25 sufficient aqueous solution containing 25 weight percent L-lactic acid to cover the plant foliage. Control plants were foliarly contacted with an equal quantity of distilled water. Severe damage results to the L-lactic acid~treated plants within two hours of application. Some 30 minor revegetation occurs within two weeks. There is no damage to the control plants which are treated only with water.
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EX~MPLE 20 The operation of Example 19 is repeated with the exception that the applied solution contains 6 weight percent L-lactic acid. Some foliar damage is apparent 5 within 2 hours of application. All plants recover in approximately two weeks.

Mature, Tiny Tim tomato plants are treated by foliar 1~ application of sufficient aqueous solution containing 25 weight percent L-lactic acid to cover the plant foliage.
Control plants of the same population are foliarly treated with water only. Severe foliage damage is apparent withing 2 hours and all treated plants ultimately die.
15 There is no damage to the control plants.

EXAMPLE_22 The operation of Example 21 was repeated with the exception that the foliage of the tomato plants is 20 contacted with an aqueous solution containing 6 weight percent lactic acid. Again, severe damage is apparent within 2 hours and results in the complete mortality of the treated plants. There is no damage to control plants which are foliarly treated only with distilled water.
While particular embodiments of the invention have been described, it will be understood, of course, that the invention is not limited thereto since many obvious ~ modifications can be made, and it is intended to include `~ within this invention any such modifications as will fall 30 within the scope of the appended claims.
Having described my invention, I claim:

;

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Claims (63)

1. A composition for regulating the growth of plants which composition comprises (l) a plant growth regulating effective amount of lactic acid, of which at least a major portion is the dextrorotatory L-(d)-isomer of lactic acid and (2) a preservative which is nonreactive with lactic acid and is selected from the group consisting of (a) sufficient acid, other than lactic acid, to maintain a pH in said composition of about 5 or less, (b) a sterilant in an amount sufficient to inhibit bacterial decomposi-tion of lactic acid, and (c) combinations thereof.

2. The composition defined in claim 1 having a pH within the range of about 3 to about 10 sufficient to maintain the hydrolytic stability of said lactic acid.

3. The composition defined in claim 1 having a pH of about

4 to about 6 sufficient to maintain the hydrolytic stability of said lactic acid, which composition comprises a pH buffer having a buffering point between about pH 4 and about pH 6.

4. The composition defined in claim 2 further comprising a pH buffer having a buffer point within the range of about pH 3 to about 10.

5. The composition defined in claim 3 wherein said pH buffer is selected from the group consisting of H3PO4 - x-H2PO4, citric acid - x-citrate, and combinations thereof, wherein x is a mono-valent cation other than hydrogen.

6. The composition defined in claim 1 wherein said L-lactic acid constitutes at least about 60 percent of said lactic acid contained in said composition.

- 32a -

7. The composition defined in claim l wherein said lactic acid is present in a form selected from the group consisting of mono-molecular lactic acid , lactic anhydride, polylactides of lactic acid, and combination thereof.

8. The composition defined in claim l having a pH
within the range of about 3 to about 8 and which further comprises a pH buffer having a buffer point within the range of about pH 3 to about 8, and a sterilant sufficient to inhibit bacterial decomposition on said lactic acid.

9. The composition defined in claim l wherein said composition comprises an aqueous solution of said lactic acid, said L-lactic acid is present in said solution at a concentration of about 10-10 to about 10-2 molar, and said composition is characterized by plant growth stimulant activity.

10. The composition defined in claim 9 wherein said L-lactic acid is present in said solution at a concentration of about 10-10 to about 10-4 molar.

11. The composition defined in claim l which comprises an aqueous solution of said lactic acid, said L-lactic acid is present in said solution at a concentration greater than 10-2 molar, and said composition is characterized by plant growth inhibiting activity.

12. The composition defined in claim l wherein said L-lactic acid constitutes about 80 to about 100 percent of said lactic acid.

13. The composition defined in claim 1 wherein said lactic acid consists essentially of said dextrorotatory L-isomer of lactic acid.

14. The composition defined in claim 1 which composition is substantially free of metal cations and organic and inorganic compounds which react with said lactic acid in said composition to form salts or esters of said lactic acid.

15. A composition of matter characterized by plant growth stimulating activity which composition comprises an aqueous solution of lactic acid in which the L-(d)-isomer of lactic acid constitutes at least about 60 percent of said lactic acid and is present in said solution at a concentration of about 10-10 to about 10-2 molar.

16. A composition of matter characterized by plant growth stimulating activity which composition comprises a solution of a solvent suitable for stimulating plant growth activity and lactic acid dissolved therein in which the L-(d)-isomer of lactic acid constitutes about 80 to 100 percent of said lactic acid and is present in said solution at a concentration of about 10-10 to about 10-2 molar.

17. The composition defined in claim 16 which composition is substantially free of metal ions and organic and inorganic compounds which react with lactic acid in said composition to form salts or esters of said lactic acid.

18. The composition defined in claim 16 which composition further comprises a preservative which is nonreactive with lactic acid and which is selected from the group consisting of (a) sufficient acid, other than lactic acid, to obtain a pH in said composition of about 5 or less, (b) sterilant, and (c) combina-tions thereof, which preservative is sufficient to inhibit the bacterial degradation of said lactic acid.

19. A composition for regulating the growth of plants which composition comprises (1) a plant growth regulant consisting essentially of the L-(d)-isomer of lactic acid and (2) a preser-vative which is nonreactive with lactic acid and is selected from the group consisting of (a) sufficient acid, other than lactic acid, to maintain a pH in said composition of about 5 or less, (b) a sterilant in an amount sufficient to inhibit bacterial decomposition of lactic acid, and (c) combinations thereof.

20. A plant growth regulating composition which comprises a plant growth regulating amount of lactic acid, of which at least a major portion is the dextrorotatory L-(d)-isomer of lactic acid, and a diluent which does not react with the lactic acid under normal handling, storage and application conditions and is acceptable in regulating the growth of plants.

21. The composition defined in claim 20, which is an aqueous solution containing the lactic acid in an amount of 10-10 to about molar.

22. The composition defined in claim 21, wherein the lactic acid is present in a form selected from the group consisting of mono-molecular lactic acid, lactic acid anhydride, polylactides of the lactic acid and a combination thereof; and the L-(d)-isomer constitutes about 80 to about 100 percent of the lactic acid.

23. A method for regulating the growth of plants which com-prises contacting said plants with a growth regulating amount of lactic acid wherein the L-(d)-isomer of lactic acid constitutes at least a major portion of said lactic acid.

24. The method defined in claim 23 wherein said L-(d)-isomer of lactic acid is present in the form of a member selected from the group consisting of mono-molecular lactic acid, lactic anhydride, polylactides of lactic acid, and combinations thereof in a composition form which further comprises a diluent acceptable in regulating the growth of plants.

25. The method defined in claim 23 wherein said composition further comprises a nonreactive preservative selected from the group consisting of (a) sufficient acid to maintain a pH in said composition of about 5 or less, (b) a sterilant, and (c) combinations thereof.

26. The method defined in claim 23 wherein said.
composition has a pH within the range of about 3 to about 10 sufficient to maintain the hydrolytic stability of said L-(d)-isomer of lactic acid.

27. The method defined in claim 23 wherein said composition has a pH within the range of about 4 to about 6 sufficient to maintain the hydrolytic stability of said L-(d)-isomer of lactic acid.

28. The method defined in claim 26 wherein said composition further comprises a pH buffer having a buffering point within the range of about pH 3 to about pH
10.

29. The method defined in claim 27 wherein said composition further comprises a pH buffer selected from the group consisting of phosphoric acid x-dihydrogen phosphate, citric acid x-citrate, and combinations thereof, wherein x is a monovalent cation other than hydrogen.

30. The method defined in claim 23 wherein said L-(d)-isomer of lactic acid constitutes at least about 60 percent of the lactic acid contained in said composition.

31. The method defined in claim 23 wherein said L-(d)-isomer of lactic acid constitutes about 80 to about 100 percent of said lactic acid, and said composition has a pH within the range of about 3 to about 8 and further comprises a pH buffer having a buffer point within the range of about pH 3 to about pH 8, and a sterilant, which sterilant is sufficient to inhibit the bacterial decomposition of said L-(d)-isomer of lactic acid.

32. The method defined in claim 23 wherein said composition comprises an aqueous solution of said L-(d)-isomer of lactic acid in which the concentration of said L-(d)-isomer is within the range of about 10 10 to about 10-2 molar, and said composition is characterized by plant growth stimulating activity.

33. The method defined in claim 23 wherein said composition is applied to said plants at a dosage rate sufficient to stimulate the growth of said plants, and said L-(d)-isomer constitutes at least about 60 percent of said lactic acid.

34. The method defined in claim 33 wherein said composition is applied to the plants at a dosage rate corresponding to about 2 to about 100 ounces of said L-(d)-isomer of lactic acid per acre.

35. The method defined in claim 33 wherein said composition is applied to said plants at a dosage rate corresponding to about 4 to about 50 ounces of said L-(d)-isomer of lactic acid per acre.

36. The method defined in claim 33 wherein said composition is applied to said plants at a dosage rate corresponding to about 4 to about 25 ounces of said L-(d)-isomer of lactic acid per acre.

37. The method defined in claim 30 wherein said composition is applied to a member selected from the group consisting of the foliage of said plants, the ground in the vicinity of the roots of said plants, and combinations thereof, at a dosage rate corresponding to at least about 2 ounces of said L-lactic acid per acre, and said L-(d)-isomer constitutes about 80 to about 100 percent of said lactic acid.

38. The method defined in claim 37 wherein said composition is applied to the foliage of said plants.

39. The method defined in claim 37 wherein said composition is applied to the ground in the vicinity of the root zone of said plants, either before. or after the emergence of said plants, and said plants are selected from nonfruiting grasses.

- 38a -

40. The method defined in claim 38 wherein said plants are selected from the fruit-bearing plants, and said composition is foliarily applied to said fruit-bearing plants during the fruit-bearing cycle of said plants.

41. The method defined in claim 40 wherein said plants are selected from grains, vegetables, tubers, and fruiting plants, and said composition is foliarily applied to said plants at a time between about the first bud stage and the fruit-set stage of said fruit-bearing cycle of said plants.

42. The method defined in claim 40 wherein said composition is applied to said plants at a dosage rate corresponding to about 2 to about 100 ounces of said L-isomer of lactic acid per acre.

43. The method defined in claim 42 wherein said lactic acid consists essentially of said L-isomer.

44. The method defined in claim 43 wherein the concentration of said L-lactic acid in said composition corresponds to about 10-10 to about 10-2 molar.

45. The method defined in claim 23 wherein said plants are selected from the group consisting of vegetables, grains, fiber crops, tuberous crops, timber crops, grasses, ornamental flowering plants, and fruiting plants.

46. The method defined in claim 23 wherein said L-(d)-isomer constitutes about 80 to 100 percent of said lactic acid.

47. A method for regulating the growth of plants which comprises contacting said plants with a plant-growth regulating amount of a composition which comprises lactic acid, wherein the dextrorotatory L-isomer of lactic acid constitutes about 80 to about 100 percent of said lactic acid.

48. The method defined in claim 47 wherein said lactic acid consists essentially of said L-isomer of lactic acid.

49. The method defined in claim 47 wherein said lactic acid consists essentially of the L-isomer of lactic acid, and said composition further comprises a preservative selected from the group consisting of (a) sufficient acid, other than lactic acid, to maintain a pH
in said composition of about 5 or less, (b) a sterilant sufficient to inhibit bacterial decomposition of said lactic acid, and (c) combinations thereof.

50. A method for stimulating the growth of plants which method comprises contacting said plants with a growth stimulating amount of a composition which comprises lactic acid, wherein the L-isomer of lactic acid constitutes about 80 to 100 percent of said lactic acid.

51. A method for stimulating the productivity of plants selected from the group consisting of vegetables, fruits, nuts, grains, grasses, fiber crops, wood crops, flowering plants, and combinations thereof, which method comprises foliarly applying to said plants, during the bearing cycle of said plants, a composition comprising lactic acid in which composition the L-(d)-isomer of lactic acid constitutes about 80 to 100 percent of said lactic acid, and wherein said composition is applied to said plants at a productivity stimulating dosage rate corresponding to at least about 2 ounces per acre of said L-(d)-isomer of lactic acid.

52. The method defined in claim 51 wherein said plants are selected from the group consisting of grains, grasses, fiber crops, fruiting plants, and combinations thereof, said lactic acid consists essentially of said L-isomer of lactic acid, and said composition is applied to said plants at a period between the first-bud stage and the fruit-set stage of said plants.

53. The method defined in claim 52 wherein said plants are selected from citrus, tomatoes, berry crops and cotton.

54. The method defined in claim 51 wherein said lactic acid consists essentially of the L-isomer of lactic acid, and said composition further comprises a preservative sufficient to prevent the bacterial decomposition of said lactic acid.

55. The method defined in claim 51 wherein said L-(d)-isomer of lactic acid is present in said composition at a concentration within the range of about 10-10 to about 10-2 molar, and said composition is applied to the foliage of said plants at a dosage rate corresponding to about 2 to about 100 ounces of said L-(d)-isomer of lactic acid per acre.

56. A method for stimulating the growth of plants selected from the group consisting of vegetables, grains, tuberous crops, fiber crops, timber crops, grasses, ornamental flowering plants, and fruiting plants, which method comprises contacting said plants with a growth-stimulating amount of lactic acid, wherein the L-isomer of lactic acid constitutes at least a major portion of said lactic acid.

57. A method for stimulating the growth of plants, which method comprises contacting said plants with a growth-stimulating amount of lactic acid, wherein said lactic acid consists essentially of L-lactic acid.

58. A plant growth regulating composition which comprises an aqueous solution comprising lactic acid in a concentration of about 10-10 to about 10-2 molar, in which composition said lactic acid consists essentially of the L-(d)-isomer of lactic acid.

59. The composition defined in claim 58 which further comprises a member selected from the group consisting of (a) sufficient acid, other than lactic acid, to maintain a pH below about 5 in such composition, and (b) a sterilant, and combinations thereof.

60. A use of lactic acid, of which at least a major portion is the dextrorotatary L-(d)-isomer of lactic acid, for regulating the growth of plants.

61. The use defined in claim 60, wherein the lactic acid is present in a form selected from the group consisting of mono-molecular lactic acid, lactic acid anhydride, polylactides of the lactic acid and a combination thereof; and the L-(d)-isomer constitutes about 80 to about 100 percent of the lactic acid.

62. The composition defined in claim 15, 16, 17, 20, 21 or 22, which is contained in a commercial package bearing instructions that the composition be used for regulating the growth of plants.

63. A plant growth regulating composition which comprises a plant growth regulating amount of lactic acid, of which about 80 to about 100 percent of the lactic acid is the L-(d)-isomer of lactic acid, a diluent, and a member selected from the group consisting of acids other than lactic acid, sterilants, and combinations thereof.