NO170751B - APPLICATION OF A COMPOSITION OF Lactic Acid for Stimulating Plant Productivity - Google Patents

Description

The present invention relates to the use of a composition comprising lactic acid, its anhydride or the corresponding polylactides, for stimulating the productivity of plants. Such compositions are therefore useful for regulating plant growth.

Plant growth regulators can be defined as compounds and/or preparations which, in very small quantities, change the behavior of ornamental plants and/or useful plants and/or the products from such plants by physiological (hormonal) rather than physical action. They can either accelerate or retard growth, prolong or break a dormant state, promote root formation, fruiting, or increase fruit size or quantity, or affect the growth and/or productivity of the plants in other ways. Plant growth regulators are currently classified into one or more of six categories: auxins, gibberellins, cytokinins, ethylene generators, inhibitors, and retarders. Examples of known auxins are indole acetic acid, 2,4-D (2,4-dichlorophenoxyacetic acid), MSPA (4-chloro-2-methylphenoxy-acetic acid), MCPB (4-((4-chloro-0-tolyl)oxy )formic acid) which susceptible plants oxidize to MCPA, and BNOA (beta-naphthoxyacetic acid). Gibberellins include gibberellic acids and their derivatives, while cytokinins include preparations such as zeatin, kinentin, and benzyl anidene. Current known ethylene generators include ethylene and "Ethephon" ((2-chloroethyl) phosphoric acid). Current: known inhibitors include benzoic acids, gallic acids, cinnamic acids, while retardants, a later developed class of plant growth regulators, include preparations that are particularly useful in controlling plant height,

especially in commercial types of plant cultivation in greenhouses.

Lactic acid (alpha-hydroxypropionic acid) is well known and widely used in industry as a chemical intermediate. It is usually present in the form of the racemic mixture which is a mixture of equal molar parts of the two possible optical isomers of alpha-hydroxypropionic acid - the levorotatory and dextrorotatory isomers. Levorotation (1) the isomers are isomers of an optical

active compound that rotates a beam of polarized light to the left; dextrorotation (d) the isomers are isomers of the same compound that rotate a beam of polarized light to the right. Another convention used to define the configurational relationships between different functional groups bound to an asymmetric carbon atom, the Fischer method, is based on the geometric arrangement of functional groups relative to each other rather than the direction (left or right) in which a standard resolution of the compound rotates a ray of polarized light. According to the Fischer method, any compound containing an asymmetric carbon atom of the same configuration as the asymmetric carbon atom in the random standard dextrorotatory glyceraldehyde is classified in the D series, while compounds in which the asymmetric carbon atom has the opposite configuration are classified in the L series. Although the Fischer D and L classifications do not correlate with dextro- (d) and levorotation (1) optical activity for all compounds, these classifications can be used in combination with the d and 1 optical activity classifications to

define both the geometric arrangement and the specific optical activity of any optically active isomer. Accordingly, the L-isomer of lactic acid, which is dextrorotatory, is defined as L-(d)-lactic acid, and the D-isomer is defined as D-(1)-lactic acid. However, for relatively simple compounds such as lactic acid, both of these properties can be satisfactorily 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 Fischer. For this reason, the D and L isomers of lactic acid are usually identified only by the D and L designation without explicit reference to the optical

the activity. The procedure for Fischer's classification is known in the art and is discussed in detail in "Introduction to Organic Chemistry", Fieser and Fieser, D.C. Health and Co., Boston, Mass., (1957) pages 209-215.

Lactic acid is widespread in a number of synthetic and naturally occurring products such as dairy products and fermentation products in which it exists mainly as the racemic mixture. Specialized fermentation processes can be used to selectively produce either the levorotatory or dextrorotatory isomer. Although some commercially available agricultural products contain fermentation products and lactic acid, and are marketed for various applications within the agricultural industry, it has not been observed or suggested that L-(d)-lactic acid is an active plant growth regulator. Furthermore, the lactic acid-containing preparations that are marketed within the agricultural industry usually contain the racemic mixture of both optical isomers in addition to cations, such as sodium, potassium, ammonium, etc., and/or other compounds such as surfactants, pesticides, etc., which may react with L-lactic acid and destroy its growth-regulating activity.

It has been suggested that alpha-hydroxycarboxylic acid of higher molecular weight than acetic acid exhibits specific growth-regulating activity regardless of the configuration or optical activity of the carboxylic acid used. US Patent No. 3,712,804 describes that certain alpha-substituted carboxylic acids increase the yield of certain plants by improving the plant's ability to assimilate water from the environment. The acids contain 7 to 10 carbon atoms per molecule, and the alpha carbon atom is substituted with one or more functional groups including oxy, hydroxy, amine and carboxyl groups. These acids are used on very new plants,

and the salts and lower alkyl esters and amines have growth regu-

learning activity corresponding to that of the free acid. The preparations may also contain humectants.

The plant growth regulators discussed above and otherwise known in the art, including that discussed in US Patent No. 3,712,804, all have certain disadvantages that make their use, at least in certain applications, less desirable than would be the case for L-lactic acid . Many preparations for growth regulation, especially preparations which show herbicidal activity at larger doses, are toxic to plants, the environment and/or animals, including humans. Many are not readily available and are relatively expensive to produce compared to L-lactic acid. Furthermore, many of the known growth regulators, such as the alpha-functional carboxylic acids, salts, esters and amines, disclosed in US Patent No. 3,712,804, require plant treatment at a time that is not favorable for growth in all cases. Furthermore, many known regulators exhibit a limited spectrum of growth regulatory activity, are not useful with many plant types, and/or do not satisfactorily regulate crop productivity.

Accordingly, there is a need for improved regulation of the growth of the plants and more particularly there is a need for improved stimulation of the desired growth of plants, reduction of the toxic effects in this connection on the environment and animals, including humans, and reduction of the costs associated with such regulation of plant growth.

The purpose of the present invention is thus to use certain compositions or preparations for stimulating the growth and productivity of agricultural crops and ornamental plants, which preparations are non-toxic to animals and to the environment and do not require those who apply the agents or other personnel or the environment to be exposed to neither toxic nor corrosive materials.

According to the present invention, a composition comprising lactic acid, its anhydride or the corresponding polylactides, where the L-(d)-isomer of lactic acid constitutes 80-100% of the lactic acid, is thus used for stimulating the productivity of plants. The L-lactic acid preferably constitutes at least a major part of the lactic acid present in the preparation used, which can be used to stimulate growth and/or fruit production for useful crops and ornamental crops.

The composition used according to the present invention shows plant growth-regulating activity and contains lactic acid, of which at least a major part is the L-(d)-isomer of lactic acid. The composition or preparation may also contain a non-reactive preservative such as e.g. a sufficient amount of acid to keep the pH of the preparation within a range of approx. 5 or less and/or a sterilizing agent sufficient to inhibit the bacterial breakdown of the lactic acid.

The composition, which uses a relatively low concentration and dosage of the growth-active L-isomer of lactic acid, is useful for increasing growth and/or fruit production for essentially all types of plants. On fruit-bearing plants, the composition can be used to increase both the size and quantity of the fruit produced. This can also accelerate the ripening of the fruit, thereby shortening the crop cycle and it can increase the growth rate of agricultural grass or ornamental grass, such as alfalfa, protective ryegrass, etc. Furthermore, aging can be delayed and thereby extend the fruiting period for annual fruit plants, such as tomatoes and corn , the fruiting period for perennial plants, such as citrus, grapes, etc. The application has the further advantage that the compositions used are non-toxic to the environment and animals, and at the levels used for stimulating plant growth, they are non-toxic to the the treated plants or the harvested components of fruiting plants, such as food products. Furthermore, the preparations are non-corrosive during storage, transport and in connection with application equipment and for animal and vegetable tissues. Consequently, they can be easily and safely handled without damage to equipment, personnel, the crop or the environment. The active component of the preparations - L-lactic acid - is readily available commercially and is relatively inexpensive, especially compared to various other plant growth regulators which are expensive, sophisticated chemical compounds that require relatively complicated methods of manufacture.

The present invention will be better understood with reference to the drawings in which: Figure 1 is a graphic representation of the results from watercress experiments showing root growth stimulation and inhibition activity of L-lactic acid and of indole acetic acid;

and

Figure 2 is a corresponding graphical presentation of data showing the root growth-regulating activity of L-lactic acid and of D-(1)-lactic acid.

The preparations in question are broad-spectrum plant growth regulators; consequently, these can be used to stimulate the growth and/or the fruit-producing capacity of all plant types, including fruit-bearing and mainly vegetative plants. Fruiting plants, for the purposes of the present invention, include plants that bear a variety of products other than vegetative growth such as a

annual or perennial vegetables, fruits, nuts, grains, fiber crops, and flowering plants. Plants that grow mainly for their vegetative productivity (the main example being the large number of grasses that grow as animal feed and for decorative purposes) can also be treated. Accordingly, the compositions can be used to

stimulate the growth and the fruit-bearing capacity (where this is relevant) of vegetables, fruits, nuts, grains, grass, fiber crops, tree crops, and flowering plants.

All types of vegetables can be processed, including leaf lettuce, broccoli, asparagus, onions, tubers such as potatoes, sugar peas and peanuts, tomatoes, beans, etc. Examples of fruits that can be processed are peaches, apples, citrus fruits, avocados, cherries, grapes ( varietal and table grapes), bananas, etc. Nut crops that can be processed include walnuts, hickory nuts, almonds, acajou nuts, etc. Basically all grain types can be processed, including corn, wheat, durum wheat, cornmeal, rice, barley, oats, etc. Examples of grass types include alfalfa, bermuda, rye and rough grass species, while examples of fiber plants include cotton and flax. All three plants can be stimulated by the present application including both hardwoods and conifers, such as oak, elm, maple, walnut, spruce, hemlock, alder, loblolly pine, redwood, mahogany, cypress, cedar, Douglas fir and white fir. Flower plants that can be treated include all types of privately raised and commercially raised flowers, such as orchids, roses, chrysanthemums, azaleas, camellias, carnations, pansies, ornamental snapdragons, etc.

The preparations used according to the present invention include, as mentioned, a growth-regulating amount of L-(d)-lactic acid; i.e. the dextrorotatory isomer. The effectiveness that such preparations show in stimulating the growth and/or the fruit-bearing ability of plants can apparently be attributed to the plant growth-regulating activity of the non-complexed, monomolecular, L-(d)-isomer of lactic acid. The D-(1)-isomer of lactic acid not only promotes vegetation growth or fruit productivity, it appears to inhibit the activity of the L-isomer to the point that the racemic mixture, i.e., the 50-50 mixture of the left-handed and right-handed

the isomer, has only marginal growth-regulating activity,

if any at all.

It has also been found that L-lactic anhydride and the polylactides of the L-isomer (itself the esterification product of lactic acid) are

active plant growth regulators and are as active as monomolecular L-lactic acid. All these compounds show regulatory activity at very low concentrations, e.g. of approx. 10 ^ molar or less. Lactic anhydride and

higher polylatides are formed from monomolecular lactic acid at lactic acid concentrations of approx. 50% or higher in water. Both lactic anhydride and polylactides return to monomolecular lactic acid when diluted with water to concentrations below 50%. The active form of the growth regulator in the plant can be monomolecular L-lactic acid or polylactides of L-lactic acid of varying molecular weight. The polylactides can be formed on the leaves of treated vegetation (such as when monomolecular lactic acid is applied in relatively dilute solutions) by evaporation of water from the applied solution. The 2-olylakids probably hydrolyze, if they are applied as such or formed on the plant leaves, inside the plant (on exposure to water) so that monomolecular lactic acid is formed. Correspondingly, compounds which, in the plant environment, are converted to L-lactic acid or to the anhydride or polylactides of L-lactic acid, are also effective for introducing the active growth-regulating agent into the treated plants. Regardless of what the active species really is, monomolecular L-lactic acid and the anhydride and higher polylactides of L-lactic acid have been found to exhibit growth regulatory activity when contacted with plants. When, consequently, the term L-lactic acid is used to describe the different features

in the present invention, the term shall be understood as including the anhydride and higher polylactides of L-lactic acid and compounds which are converted to L-lactic acid

acid or its anhydride or polylactides, when supplied to the plant, as well as L-lactic acid itself.

One of the unexpected discoveries of the present invention is that the D-(1)-isomer shows little, if any, plant growth-regulating activity, this being at least 10 times, and probably at least 100 times less active than L-(d)- the isomer. Furthermore, the D-isomer appears to inhibit or suppress the activity of the L-isomer. Consequently, the preparations used according to the invention include those in which the L-isomer makes up 80 to 100%, and preferably 100%, of the lactic acid found in the preparation being applied. The L-isomer can be supplied pure, although this is usually undesirable for plant growth stimulation due to the highly specific activity of the L-isomer. The L-isomer stimulates plant growth at concentrations down to 10 molar. Supply of the pure material ella: concentrated solutions also complicates the distribution of the active component on the treated plant. Accordingly, the preparations usually constitute solutions of the L-isomer in a suitable solvent such as water, low molecular weight mono- and polyhydric alcohols, ethers, carbon disulphide,

and similar solvents which do not react with the L-isomer (and thereby nullify its activity) under normal handling, storage and use conditions. Aqueous solutions of the L-isomer are highly active growth regulators and are preferred on

the current time. The L-isomer will usually be present in the supplied solution at a concentration of at least 10~<10> molar. Although L-lactic acid remains active in solution even at lower concentrations, it is difficult to supply sufficient amounts of this compound to the treated plants when lower concentration solutions are used because

the added solution runs off the plant leaves. Accordingly, solutions useful in the application of the present invention will typically have L-lactic acid concentrations in the range of 10 to

4 molar, normally from 10~<9> to 2 molar. Dilute solutions within these limits are usually preferred to stimulate growth and promote fruit production. Accordingly, when plant stimulation is desired, the L-isomer should be present in the supplied solution at a concentration in the range from 10 -10 to 10 2 molar, generally from 10"<9> to 10"<2> molar, preferably from

IO"20 to 10"<2> molar.

It has also been found that metal 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 regulators than L-lactic acid itself. The salts of lactic acid can be formed in solutions of the L-isomer containing significant amounts of metal cations such as calcium, nickel, cobalt, magnesium, manganese, zinc, sodium, potassium, etc. The concentration of such metal cations in many sources of irrigation water, such as water from the Colorado River, is sufficient to significantly reduce the activity of a solution of the L-isomer prepared from such water. It has also been found that compounds containing active acid and/or alcohol groups can react with lactic acid, so that inactive esters are formed at pH levels below approx. 3 or above 10, and that such esters can also be formed at pH levels in the range from 3 to 10, albeit at a lower rate. : Consequently, the activity of the L-isomer for regulating the growth of plants may be reduced or lost due to the formation of esters with other compounds containing active acid and/or alcohol groups. Compounds containing such functional groups are preferably excluded from the preparations used in the present invention.

Although the L-lactic acid-containing preparations described above are active plant growth regulators and can therefore be used according to the present invention, they are hydrolytically unstable under certain conditions and are susceptible to bacterial attack. Bacteria can convert the active L-isomer into inactive species within a relatively short time at temperatures as low as 27°C. Although the L-lactic acid solution can be sterilized during manufacture, there is consequently a significant risk of bacterial contamination during storage, transport, mixing and application.

Consequently, such preparations which are stabilized against hydrolytic decomposition and bacterial attack are preferred at the present time for use in regulating the growth of plants.

These preparations include lactic acid, a major part of which is the dextrorotatory L-(d)-isomer of lactic acid and a preservative sufficient to prevent a conversion of the L-isomer to an inactive form caused by bacterial attack. Suitable preservatives include sufficiently acidic concentrations to maintain a pH of about 5 or lower, and/or sterilizing agents that prevent bacterial growth.

The hydrolytic stability of the L-isomer can be maintained in aqueous solutions by keeping the solution's pH range from 3 to 10, most preferably within the range from 4 to 8, and most preferably within the range from 4 to 6. The lactic acid will react with water at relatively low temperatures down to approx. 27°C under either basic or acidic conditions outside the preferred ranges. The rate of hydrolytic conversion of the L-isomer is also relatively low at the pH level of 3 and 10, and increases dramatically when the pH falls below 3 or is increased to levels above 10. The rate of hydrolysis can also be reduced by reducing the water concentration in the preparation, i.e. .by increasing the lactic acid concentration. However, the hydrolytic conversion of L-lactic acid can increase dramatically by diluting the concentrated acid before application if the pH of the solution is not kept within the indicated ranges. Accordingly, the preferred aqueous solutions according to the present invention contain sufficient acid and/or base to keep the pH of the solution within the ranges indicated above. pH buffers are also particularly suitable for this purpose, and should have buffer points in the range from pH 3 to pH 10, preferably pH 4 to pH 6. The buffers should also be non-reactive with the L-lactic acid. Suitable pH buffers include H-jPO-xH2PO4, citric acid-x-citrate (wherein x denotes a monovalent cation such as sodium, potassium and ammonium), and other buffer pairs having buffer points within the indicated ranges. The salt cation present 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 currently preferred since this does not form insoluble lactates which cause precipitation of the active component from the aqueous solution.

Essentially any acid, including lactic acid, can be used to maintain a pH

of approx. 5 or lower in the compositions or preparations used and thereby minimize the bacterial deactivation of the L-isomer. However, there are concentrations of lactic acid that are sufficient to maintain

pH levels of approx. 5 or lower often higher than the concentrations desired in the supplied solution. Consequently, the addition of other acids is preferred. Examples of suitable acids are phosphoric acid, sulfuric acid, nitric acid, hydrochloric acid and similar acids which do not form stable esters or salts with the L-isomer component.

Bacterial decomposition of the L-isomer can also

is inhibited, or excluded, by any of a number of known sterilizing agents, such as the bacteriolytic and bacteriostatic preparations.

As is the case with the other components in the preparations used according to the invention, the sterilizing agent should not react with the lactic acid so that stable salts or esters are formed under normal handling conditions. Example: on sterilizing agents that can be used in

the new preparations according to the present invention are ethanol, formaldehyde, terramiacane, xylene, toluene, phenyl mercuric nitrate, phenyl mercuric acetate, copper sulphate, sodium azide, hydrogen peroxide, chlorine, benzoisothiozolone, 2-((hydroxymethyl)amis)ethanol,

1-(3-Chloroalkyl)-3,5,7-triaza-1-azoneadomantane chloride, dibromocyanobutane, ose. Other stable sterilants, i.e., sterilants that do not react with lactic acid, can be identified by mixing the sterilant with the desired aqueous solution of L-lactic acid, and monitoring the stability of the lactic acid in the sterilant-containing solution by nuclear magnetic resonance (NMR). NMR can be used to monitor the frequency of the magnitude of spectral peaks characteristic of a selected nucleus, e.g. a hydrogen nucleus in the L-lactic acid molecule. Persistent size, of spectral peak and frequency above

a period of 5 or 6 hours indicates the stability. Decreasing size or a shift in peak frequency associated with the chosen hydrogen nucleus indicates instability, i.e. the arrangement of functional groups

in the lactic acid molecule is modified. Examples of

unstable sterilants are thiophosphate esters such as melathion, parathion, etc., which generally should not be used in the preparations according to the present invention as they react with the L-lactic acid and reduce or eliminate its activity as a growth regulator. Sterilizing agent concentrations in the range from 10 to 4,000 parts per parts per million (ppm) are usually effective for most applications.

In the application according to the present invention, the plants which can be regulated are brought into contact with a growth-regulating amount of the preparations - The L-(d)-lactic acid-containing preparation can be added to the leaves and/or to the roots of the treated plants. The timing of the application is relatively important when it is desired to increase fruit production for fruit-bearing plants. In general, the L-lactic acid component should be applied to the plants during the flowering stage or in the early stages of the fruiting cycle, or both. Ideally, the L-lactic acid component can be applied to the plants one or more times between the first bud stage and the fruit-setting stage, preferably between the first bud stage and the petal drop stage for both annual and perennial types. Significant increases, e.g. 10% and more, in fruit production, can be achieved by treatment at essentially any time within these stages of plant development. However, it is now preferred that at least one supply of the L-lactic acid component is carried out within several days after the first bud stage of development. However, it is preferred by at least one addition of L-lactic acid to be carried out during several days after the first bud stage of development.

Significant improvements in leaf development on non-fruiting plants, such as grasses and woodland plants, can be achieved at any time during the growth stage, usually between spring and autumn, when the plant is in its most active growth cycle.

Significant increases in the growth of non-fruit-bearing plants and in the growth of fruit production for fruit-bearing plants can be achieved by foliar application of the L-lactic acid component at doses ranging from 140 g to 7 kilos, usually

show 280 g to 3.5 kilos, and preferably

to 1,750 g L-lactic acid per hectare.. The lower dose range of 280 to 1,750 g per hectare is ideally suited for most row plants in agriculture and flower nurseries. Plants that have a large amount of foliage, such as woodland plants and some grain and fiber plants such as wheat, maize, and cotton, can benefit from contact with higher doses within the wide range from 140 g to 7 kg per hectares, of L-lactic acid. Significant growth regulation can also be achieved by applying the L-lactic acid to the soil near the plant roots.

Suitable dosages for this delivery method are usually in the range from "560 g to 28 kilos per

hectare, preferably 7 g to 14 kilos per hectares of lactic acid.

The increase in vegetation growth and the increase in fruit production is ddse-sensitive to a certain extent for any plant.

As a rule, plants that have a more extensive growth, such as cotton and forest plants, are treated with higher

doses of L-lactic acid a physically smaller plant such as vegetables and tubers that show a smaller growth scale.

The concentration and dosage of the L-lactic acid component should be correlated to provide suitable spray volume to contact a significant portion of the treated foliage and enable suitable distribution of the applied solutions as a spray with available equipment. Spray volumes in the range from 4 7 to 1870 liters per hectare is sufficient to provide satisfactory coverage and spray distribution for essentially all plant types. Spray volumes of 47 to 935 liters per hectare, is usually satisfactory for most agricultural plants, and spray volumes in the range from 94 to 560 liters per hectare, is currently preferred for the treatment of row crops within agriculture and plants within nurseries. Like the dosage, the optimum spray volume will vary depending on the plant type, and mainly as a function of the extent of vegetation growth of the treated plants. Consequently, relatively high spray volumes are better suited for the treatment of large plants, such as cotton, maize and tree plants, while lower spray volumes are more suitable for the treatment of vegetables and tuber crops. When the L-lactic acid is injected into the zone at the plant root, the volume of the L-lactic acid solution injected per hectare, be sufficient to provide suitable distribution of the L-lactic acid through the root zone of the treated plants. Dosages which are suitable for this purpose will usually lie in the range from 94 to 3740, generally 187 to 3740-, and preferably 280 to 2800 liters per hectares. In what follows, the invention will be described using the following examples.

Example 1

Separate portions of pure L-(d)-lactic acid are diluted with distilled water to produce five different solutions having concentrations of 10-1, 10~<3>, 10~<5>, 10~<7>, and 10 ~<9> molars. Three separate. 5 ml portions of the 10 ^ molar solution are then placed in three separate Petri dishes lined with filter paper and each containing approx. 15 seeds of garden cress.

Three separate 5 ml portions of the remaining four solutions are also placed in Petri dishes lined with filter paper containing approx. 15 seeds of garden cress. A sixth series of three Petri dishes containing approx. 15 seeds of garden cress are treated only with distilled water. The seeds of garden cress are germinated in the soil for three days after which each seed root in each petri dish is measured, and the average of all the root lengths for each series of three samples is calculated so as to obtain an average root length for this treatment. The average length of each replicate is then divided by the average length of the control sample (water only) to obtain a root length ratio L-trial/L-control (Lt/Lc). Values undec 1 indicate that root length in the experimental series is less than the root length of the control series, and that a suppression of root growth has taken place.

Values of the Lt/L^ ratio greater than 1 indicate

an increase in root growth.

These results are reproduced graphically in figure 1,

and shows that root growth suppression/stimulation promoted by an L-lactic acid solution is characteristic of classical auxin-like activity. Figure 1 also shows graphical results published in the literature for indole acetic acid (IAA), a plant growth regulator that has been subjected to extensive studies.

Significant stimulation of root growth took place with L-lactic acid at concentrations approx. two orders of magnitude below those by which corresponding responses were induced by indole acetic acid. Consequently, L-lactic acid is a far more active plant growth regulator than indole acetic acid, at least as far as the activity is evident from the root elongation experiment on the watercress seeds.

Example 2

The experiment with root elongation-suppression on seeds of garden cress described in example 1 is repeated using three replicates of each of four different concentrations of L-lactic acid in distilled water, the concentrations corresponding to 10 , 10 . 10 , and 10 molar. Germinated root lengths for the seeds are measured, and the average is calculated as described in example 1. These results are reproduced graphically in Figure 2. The part of the curve in Figure 2 that represents

-7

the response to L-acetic acid concentrations below 10 molar for roots on seeds of cress is reproduced based on the results of Example 1.

Example 3

The root elongation suppression experiment on cress seeds described in Example 1 is repeated using four different concentrations of D-lactic acid (the levorotatory isomer) in distilled water. These concentrations correspond to IO"<1>, IO"<3>, IO"<5> and IO"<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 shown graphically in Figure 2.

Comparison of the results in Examples 2 and 3 illustrates that the levorotatory [D-(D-) isomer of lactic acid has little, if any, growth regulatory activity and is a far less active plant growth regulator than the levorotatory isomer. The results in Example 3 also show that D-lactic acid has little, if any, tendency to stimulate the growth of germinating seed roots even at relatively low concentrations.

Example 4

Yellow flowering seeds of alfalfa varieties are planted in

a sandy clay soil after which 20 ml of a 10"<5> molar solution of L-lactic acid is topically applied to the soil.

Four replicates are treated and these are compared with four replicates of the same seed population planted in the same soil but not treated with the L-lactic acid solution. More seeds germinated in the treated plots than in the untreated (control) plots. All plants are harvested after nine weeks of growth and weighed. The alfalfa treated with L-lactic acid gives 25% by weight more vegetative growth than is the case for the untreated control sample.

Example 5

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 the yellow slow-growing seeds of the alfalfa variety. Here again several plants survive in the treated plots and the treated the plants give approximately 25% more vegetative growth than the control.

Example 6

Approximately equal numbers of yellow, flowering seeds of the alfalfa variety are planted on several plots containing a sandy loam. Four series of four plots of soil are each treated with 20 ml of a 10"<5> molar solution of L-lactic acid in distilled water.

The solution is applied to the plants by spraying leaves at emergence (5 days after planting), and three weeks, six weeks and nine weeks after emergence. The plants are harvested twelve weeks after emergence, weighed and compared with an untreated control. The test series that are processed five days after planting and three weeks and 6 weeks after emergence all give approx. 20 to 25% by weight more vegetative growth than is the case for the control series. The plants treated nine weeks after emergence do not produce an amount of vegetative growth above that obtained by the untreated control plants, which can be defined as statistically significant.

Example 7

The operation in example 6 is repeated with the exception that

50 ml of the 10"<5> molar L-lactic acid solution of-

is carried on each test series. As in the case of the 20 ml treatments, the plants treated five days after planting, and two weeks and 6 weeks after emergence, show

about. 20 to 25% by weight greater vegetative growth than the control,

while the plants treated nine weeks after emergence and harvested twelve weeks after emergence do not show a significant increase in vegetative growth compared to the control. The absence of a statistically significant increase in vegetative growth for the nine-week treatment may be due to the relatively short time between treatment and harvest.

Example 8

"Tiny Tim" tomatoes that have already set fruit that have

a diameter of approx. 0.5 to 1.5 cm, is treated with an aqueous solution of L-lactic acid in distilled water which has a lactic acid concentration of 10"<5> molar. The solution is applied to the leaves of the plant at a dose of about 4 ml per plant. No significant increase in fruit size or quantity is achieved compared to untreated control plants.

Example 9

The operation of Example 8 is repeated with the exception that the L-lactic acid solution applied to the leaves of the "Tiny Tim" tomato plants has a lactic acid concentration of 10 to <3> molar. Nor did the controls have an increase in fruit size or quantity compared to the untreated controls.

Example 10

The operation in example 8 is repeated with the exception that the tomato plants are treated with two separate foliar applications of approx. 4 ml each of the 10"<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 (after fruit set). The tomatoes are harvested after reaching maturity, and the treated tomatoes are about 15% larger and ripen about 50% faster than the tomatoes on the untreated control plants.

Example 11

The operation in 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"<5> molar. As in the case of the 10"<3> molar solution, the treated plants produce tomatoes that are approx. 15% larger calculated by weight and which matures approx. 50% faster than the untreated controls.

Example 12

"Naval" orange trees are treated by foliar application at the stage where the first petals fall, of 350 g per hectare of L-lactic acid in 280 liters per hectare of aqueous spray volume. The fruit is allowed to set and ripen and be harvested and weighed. The untreated control plot yields 202 6 boxes of "novel" oranges per hectare, while the treated piece of land yields 3,010 boxes of oranges per hectares.

Example 13

Cabernet grapes are treated by foliar application of L-lactic acid in a dose corresponding to 560 g per hectares of

The L-lactic acid dissolved in 280 liters of spray volume per hectares. Foliar application is carried out at the first berry stage, and

the grapes are allowed to ripen and be harvested - The yield from the treated grape plants is 15-20% greater than from the untreated control plants in the same population and the sugar content in the treated grape plants is approx. 2% points higher than the sugar content from the untreated grapes.

Example 14

Sylvaner Riesling grapes are treated by foliar application of L-lactic acid in a dose corresponding to 560 g per hectares

in a spray volume of 280 liters per hectares at the first berry stage. The grapes are allowed to ripen and be harvested and compared with grapes produced on untreated control plants within the same population. The yield from the treated Riesling grape plants is 15-20% higher than from the untreated control plants.

Example 15

Murietta tomatoes are treated by foliar application of a solution of L-lactic acid at a dosage corresponding to 560 g per hectare of L-lactic acid dissolved in a spray volume of 280 liters per hectares. Application is made at peak flowering, and the fruit is allowed to set and ripen and is harvested and compared with fruit obtained from untreated plants in the same population. The yield from the treated plants is approx. 30% higher than from the untreated plants.

Example 16

Pima cotton is treated by foliar application of an aqueous L-lactic acid solution at a dose corresponding to 1120 g per hectare of L-lactic acid dispersed in a spray volume of 280 liters per hectares.

The application is made at maximum flowering and the cotton is allowed to mature and harvested and compared with cotton obtained from untreated control plants in the same population. The treated seedlings give approx. 20% more cotton than the untreated plants.

Example 17

Valencia oranges are treated with foliar application of

1120 g per hectare of L-lactic acid in 2 80 liters per

hectares of an aqueous spray solution. The spray is applied at the stage where the first petals fall, (maximum flowering), and the fruit is allowed to ripen and be harvested under normal agricultural conditions. The treated trees give 3460

boxes per hectares of Valencia oranges compared to 1,977 boxes per hectares for untreated control trees in the same population.

Example 18

Zihfandel grapes are treated by foliar application of 280 g

per hectare of L-lactic acid in 280 liters per hectare of a spray in the form of an aqueous solution. The spray is applied at the first berry stage, and the grapes are allowed to ripen and be harvested under normal horticultural conditions. The yield of the treated Zinfandel grape plants is 12% higher than from the untreated plants in the same population.

Example 19

The barley plants, approx. 30.5 cm high, are treated with L-lactic acid by foliar application of sufficient aqueous solution containing 25% by weight of L-lactic acid to cover the plant's foliage. Control plants were brought into contact with an equal amount of distilled water on the :hladverket. Severe damage occurred on the L-lactic acid-treated plants within 2 hours of application. Some minor revegetation took place within 2 weeks. No damage occurred to the control plants treated only with water.

Example 2 0

The procedure from example 19 is repeated, with that exception

that the applied solution contains 6% by weight of L-acetic acid. Some damage to the foliage is visible within 2 hours of application. All plants recover within approx. Two weeks.

Example 21

Mature "Tiny Tim" tomato plants, treated by foliar application

of sufficient aqueous solution containing 25% by weight of L-lactic acid to cover the foliage of the plant. Control plants of the same population are treated on the foliage with only water. Severe damage to the foliage is observed within 2 hours and all the treated plants eventually die.

No damage is observed on the control plants.

Example 22

The procedure from example 21 was repeated with

the exception that the leaves of the tomato plants are brought into contact with an aqueous solution containing 6% by weight of lactic acid. Igjéh severe damage occurs within 2 hours and results in the death of the treated plants.

No damage occurs to control plants treated on the foliage with only distilled water.

Claims (12)

1. Use of a composition comprising lactic acid, its anhydride, or the corresponding polylactides, where the L-(d)-isomer of lactic acid constitutes 80-100% of the lactic acid, for stimulating the productivity of plants. 2. Use according to claim 1 of lactic acid comprising polylactides of L-lactic acid. 3. Use according to claim 1 or 2 of the composition in a dosage quantity which is sufficient to stimulate the plants' growth. 4. Use according to any one of claims 1, 2 or 3 of the composition in a dosage amount corresponding to from 140 g to 7 kg of said L-isomer per hectares. 5. Use according to any one of claims 1-4 on the leaves of the plants. 6. Use according to claim 5 on fruit-bearing plants in that the composition is applied to the leaves during the plants' fruit-bearing cycle. 7. Use according to claim 5 in cereal, vegetable, tuberous or fruit-bearing crops, the composition being applied to the leaves of the plants at a time between the first bud stage and the fruit-setting stage in the plants' fruit-bearing cycle. 8. Use according to any one of claims 1-7 of lactic acid essentially consisting of L-lactic acid. 9. Use according to any one of claims 1-7 of lactic acid consisting of 100% of the L-isomer. 10. Application according to any one of claims 1-9 on the plant's leaves of lactic acid in the form of an aqueous solution. 11. Use according to claim 10 of lactic acid concentrations in said solution in the range 10"<10> to 10"<2> molar. 12. Use according to any one of claims 1-5 or 8-11 on citrus fruits, tomatoes, berries and cotton.