WO1997023130A1

WO1997023130A1 - Plant growth regulator formulations and process of using the same

Info

Publication number: WO1997023130A1
Application number: PCT/EP1996/005669
Authority: WO
Inventors: Charles W. Finch; Wilhelm Rademacher; Charles W. Helpert; Mary Callan; Hans J. Von Amsberg
Original assignee: Basf Corporation
Priority date: 1995-12-21
Filing date: 1996-12-17
Publication date: 1997-07-03
Also published as: JP2000502112A; EP0874545A1; AU1373897A; BR9612240A; TR199801143T2; AR005254A1

Abstract

Provided herein is a plant growth regulator formulation comprising a plant growth regulator dispersed in polyvinyl alcohol ('PVA') particles having a mean diameter greater than 1 micron. The present invention also includes an emulsion containing an aqueous dispersion of PVA mean diameter greater than 1 micron. The above formulations are useful in methods of improving a plant growth factor in a plant.

Description

PLANT GROWTH REGULATOR FORMULATIONS AND PROCESS OF USING THE SAME

Description

The present invention is related generally to the field of agri¬ culture and specifically to compositions and use of plant growth regulators.

Agriculture workers actively seek ways to improve the economic output of commercial crops. For example, in cotton crops, workers seek to improve such growth factors as an increased in boll set, increased in floral initiation, decreased floral abscission, de- creased boll abscission, and enhanced root growth. Workers also seek to a increase plant in tolerance to environmental stress.

Formulations containing plant growth regulators (PGRs) have been developed to improve the economic yield of agricultural plants. Plant growth retardants and inhibitors of ethylene biosynthesis or action are two types of PGRs. Some plant growth retardants have been shown to inhibit gibberellin biosynthesis resulting in the reduction of shoot height in small grains and cotton. This reduction in shoot height has a strong economic benefit since it provides for less lodging in small grains and reduction of exces¬ sive vegetative growth. It also provides more uniform ripening in cotton.

Three groups of gilbberellin biosynthesis inhibitors are known. The first group encompasses compounds with quaternary ammonium, phosphonium or sulphonium moieties. One example of a compound from this group is mepiquat chloride, described in U.S. Patent No. 3,905,798 and incorporated herein by .reference. Mepiquat chloride increases cotton yields, boll load, lint yield and seed yield. Mepiquat chloride is also known to reduce vegetative growth, plant height and boll rot. Mepiquat chloride also induces uniform ripeness if the plants are treated early during their de¬ velopment. Chloromequat chloride is also a representative compound of this group.

The second group of plant growth retardants encompasses compounds with a nitrogen containing heterocycle such as flurprimidol, pa¬ clobutrazol, uniconazole and ancymidol.

The third group encompasses acylcylcohexanediones (such as tri- nexapac-ethyl and prohexadione-Ca) and daminozide. It is known that ethylene is involved in plant senescence and plant stress reactions. Ethylene is also involved in leaf, flower, and fruit abscission. Hence, agents that inhibit or regu¬ late the production of ethylene or control its action in plants have been developed in an effort to improve the yield of agri¬ cultural crops. Inhibitors of ethylene biosynthesis include sub¬ stituted oxime-ethers as described in U.S. Patent No. 4,744,811, incorporated herein by reference. These compounds are also de¬ scribed in PCT Application WO 95-02211, incorporated herein by reference, as being soil amendment compositions that increase the assimilation of nitrogen by higher plants.

Other inhibitors of ethylene biosynthesis or action include ami- noethoxyvinylglycine ("AVG"), aminooxyacetic acid ("AOA"), rhizo- bitoxine, and methoxyvinyl glycine ("MVG"). Silver ions ( e. g. silver thiosulfate) , and 2, 5-norbornadiene inhibit ethylene ac¬ tion.

Plant growth regulators have also been used to protect crops from the effects of environmental stress. Gianfagna, T.J. et al. "Mode of Action and Use of Growth Retardants in Reducing the Effects of Environmental Stress on Horticultural Crops: Karssen CN. et al . (eds.) Progress in Plant Growth Regulation, pp. 778-87 (1992). For example, researchers found that if ethephon was applied at a low rate (0.08 mM) it significantly delayed bloom in peach and reduced side effects. Researchers also found that ethephon in¬ creased the yields and hardiness of several horticultural plants.

Although PGRs have been developed as a means to improve agri- cultural crop yields, certain obstacles make the actual use of the PGR prohibitive. For example, many of the compounds display phytotoxicity. Other compounds are difficult to synthesize.

Many compounds require high rate applications to be effective. For example, PCT Application WO 93/07747, incorporated herein by reference, describes an improvement in a plant growth factor by applying aminoethoxyvinylglycine CAVG"), an inhibitor of ethylene biosynthesis, to cotton plants. As the rate of AVG treatment increased, so did the improvement. (WO 93/07747, Exam- pies 2-4) . Assuming that a spray volume of 500 1/ha was used, the rates of application described in WO 93/07747 would be approxi¬ mately 62.5 to 500 g ai/ha. The maximum rate response occurs at the highest rates.

High rate applications may result in a significant waste of mate¬ rial and may result in the discharge of the PGRs into the sur¬ rounding environment. Also, although many of these compounds may induce a beneficial growth habit, they do not provide consistent improvement in plant growth factors. Other compounds may lose their effectiveness or cause a reduction in yield when applied to species which are under some form of environmental stress.

Encapsulated herbicides, pesticides and plant growth regulators have been described in the prior art. The use of interfacial polymerization to microencapsulate both water-soluble and water- insoluble materials using polymers is known. Others have de- scribed entrapped water-insoluble PGRs in starch. U.S. Pat. No. 4,382,813.

Polyvinyl alcohol (PVA) has been described as: a protective colloid in an emulsion formed by the dispersion of an organic solution containing a plant growth regulator, U.S. Pat.

No. 5,160,529; as a dispersant in an oil-in-water emulsion, U.S. Pat No. 4,871,766; as an ingredient in powders, granules or lat¬ tices, U.S. Pat. No. 4,486,128; and as an ingredient in oil-in- water emulsions having particles from 1 to 200 microns wherein the emulsion also contains a thickener., U.S. Pat. No. 4,283,415.

U.S. Pat No. 4,997,642 discloses stable oil-in-water emulsions containing a PVA, a surfactant, a salt, and a water-insoluble oily compound, such as a plant growth regulator, wherein the compound is dispersed as a particle having an average size of less than one micron.

Although these formulations provide unique benefits in the art, obstacles still are encountered by those of ordinary skill in the art in developing formulations containing encapsulated plant growth regulators having a particle size of greater than one mi¬ cron which are stable, provide for increased improvements in plant growth factors, and that do not need a thickener. Further, many of the prior art formulations do not provide for the slow release of the active ingredient. Obstacles still remain in pro¬ viding formulations that are not phytotoxic.

Hence, it is an object of this invention to not only provide a stable formulation, but one that also provides for a stable active compound in solution. It is also an object of the inven¬ tion to provide a slow release formulation that improves a plant growth factor. It is still yet further an object of the present invention to provide a PGR that has lower application rates, has limited environmental impact, and has reduced plant toxicity. According to a first embodiment of the invention, provided herein is a plant growth regulator formulation comprising a plant growth regulator dispersed in polycinyl alcohol ("PVA") particles having a mean diameter greater than 1 micron. The present invention also includes an emulsion containing an aqueous dispersion of PVA en¬ capsulated plant growth regulator particles wherein said par¬ ticles have a mean diameter greater than 1 micron. Thus, present invention is directed to a particle comprising a plant growth regulator contained in a polyvinyl alcohol matrix.

According to a further embodiment of the invention, a composition in provided comprising a plant growth regulator contained in a polyvinyl alcohol matrix as defined before and, as a second com¬ ponent, a plant growth retardant. Further preferred embodiments of the invention are set forth in the claims.

Finally, processes for improving plant growth factors using the inventive compositions are also a subject of the invention.

The above formulations are useful in methods of improving a plant growth factor in a plant comprising administering to said plant a plant growth regulator formulation comprising the formulations of the present invention, i.e., a plant growth regulator dispersed in polyvinyl alcohol ("PVS") particles having a mean diameter greater than 1 micron. The methods also include applying an emul¬ sion containing an aqueous dispersion of PVA encapsulated plant growth regulator particles wherein said particles have a mean di¬ ameter greater than 1 micron.

An improvement in a plant growth factor is defined as an agro¬ nomic improvement of plant growth such as increased floral βsquare) initation, increased flower retention, increased root growth, decreased internode length, darker green pigmentation, increased germination rate, increased tolerance to low and high temperatures, and increased crop yield. That is, a favorable al¬ ternation of the physiology or growth of plants or an increase or decrease in plant growth which leads to an economic or agronomic benefit. Improvement in growth factors that result from the in¬ hibition of ethylene production is preferred.

The emulsions of the present invention are particularly suitable for formulations containing pVA encapsulated inhibitors of ethylene biosynthesis or action, preferably substituted oxime- ethers having the formula:

or

where R¹ and R² independently of one another are Cχ-C₆-akyl, n is 2 or 3 and R³ is hydrogen or Ci-Cβ alkyl.

Examples of other compounds that may be used include [ (isopropy- lidene)-amino]oxy acetic acid represented by the structure:

Another example of a compound that may used in the present inven¬ tion is aminooxyacetic ("AOA") acid represented by the following structure:

O HO—^ _(IV)

H₂N-0 Preferred oxime-ethers for use in the method include the follow¬ ing compounds:

1) {[isopropylidene)-amino]oxy}-acetic acid-2-(methoxy) - 2-oxoethyl ester represented by the structure:

2) { [isopropylidene) -amino]oxy}-acetic acid-2-(hexyloxy)- 2-oxoethyl ester represented by the structure:

and 10 3) {{cyclohexylidene)-amino]oxy}-acetic acid-2- (isopropy- loxy)-2-oxyethyl ester (methoxy)-2-oxoethyl ester represented by the structure:

20 The most preferred compound for carrying out the present inven¬ tion comprises { [isopropylidene)-amino]oxy}-acetic acid- 2- (methoxy)-2-oxoethyl ester.

Other compounds that may be encapsulated according to the inven- 25 tion include aminoethoxyvinylglycine and methoxyvinyl glycine.

Although water-soluble and water-insoluble compounds may be en¬ capsulated according to the present invention, the preferred compounds for carrying-out the invention are substantially water-

30 insoluble, i.e. have a very low solubility in water. Compositions of the invention generally contain, by weight, about 0.1 % to about 90% plant growth regulator, about 0.1% to about 30% PVA, about 1% to about 10% buffer, and about 50% to about 99% water. Preferred formulations contain, by weight, about 1% to about 10%

35 plant growth regulator, about 2% to about 8% PVA, about 2% to about 6% buffer with the remaining weight of ingredients contain¬ ing water and optionally a biocide and a surfactant. The range, by weight, of biocide useful in carrying-out the invention is up to about 25%, preferably from about 0.1 to about 5%. The range of

40 the surfactant is preferably up to about 20%, most preferably from about 2 to about 6%.

The PVA for use in the invention preferably include those having a weightaverage molecular weight of 15-72K, 44-65K, 70-90K, 45 44-65K, 7K and 9-13K (K = 1,000 Dalton) . The PVA for use in the invention also includes those with partial hydrolysis of 87-89% and 78-82%; intermediate hydrolysis of 95.5-96.5%; full hydroly- sis of 98-98,8%; and super hydrolysis of greather than 99.3%. Preferred PVA include those with percent hydrolysis greater than 85%.

The most preferred formulation is a plant growth regulator formulation consisting essentially of about 5% of {[isopropyli¬ dene)amino]oxy} -acetic acid-2- (methoxy}2-oxoethyl ester, about 5% of polyvinyl alcohol, about 0.26 % sodium phosphate dibasic and about 90% water.

This embodiment of the invention may further include a biocide.

The particles dispersed in the formulation are greater than about one micron and typically have a mean volume diameter of about greater than 1 micron to about 80 microns. Further embodiments of the invention include particles having a size of about greater than one micron to about 50 microns. Another range of particle size useful in practicing the present invention is a particle that has a mean volume diameter greater than about five microns to about 15 microns. A preferred particle size (mean diameter) is about 6 microns to about 10 microns.

The surfactants of this invention include salts of alkyl sul¬ fates, alkyl or aryl sulfonates, dialkylsulfosuccinates, salts of polyoxyethylene alkyl aryl ether, phosphoric acid, esters, naph- thalenesulfonic acid/formaldehyde condensates, polyoxyethylene alkyl ether, polyoxyethylenepolyoxypropylene block copolymers, sorbitan fatty acid esters, or polyoxyethylene sorbitan fatty acid, esters, monalkyl quaternary salts, dialkyl quaternary salts, di uaternary salts, ethoxylated monoquaternary salts, ethoxylated diquaternary salts, and lauryl betaine.

An additional release slowing component may be added or dissolved in the water-insoluble plant growth regulator. This component acts to slow the rate of release of the plant growth regulator from the PVA matrix. The preferred release slowing component is polyvinyl acetate having a molecular weight of from about 10K to about 200K.

The formulations are particularly useful as they provide signifi¬ cant improvements in a plant growth factor and are stable, not any against particle aggregation, but the PVA also acts to stabi¬ lize the plant growth regulator compound. These formulations pro¬ vides this benefit in the substantial absence of the following ingredients: 1) a thickener; 2) a surfactant (preferably less than 0.1 weight percent); 3) a salt (preferably less than 1%); 4) a xanthate; 5) a starch; and 6) a hydrocarbon (as described in U.S. Patent No. 4,871,766).

The formulations of the invention are particularly useful as sus- tained release formulations. Further benefits are that the for¬ mulations provide significant improvement in a plant growth fac¬ tor and also provide a formulation that has low phytotoxicity.

In the embodiment of the invention, according to which the inven- tive compositions contain, in addition to the component described hereinbefore, a plant growth retardant, said plant growth retar¬ dant is preferably selected from compounds comprising quaternary ammonium, phosphonium or sulphonium moieties.

Preferred examples of such plant growth retardants are mepiquat chloride and chloromequat chloride.

Further examples of suitable plant growth retardants include compounds containing a nitrogen containing heterocycle, e.g. flurprimidol, paclobutrazol, uniconazol and ancymidol.

Suitable are furthermore acyclcyclohexanediones (e.g. trinexapac- ethyl and prohexadione-Ca) and da inozide.

Mepiquat chloride is the most preferred plant growth retardant.

The weight ratio of the active ingredients in the inventive mix¬ tures is not particularly limited and usually in the range of from 1:50 to 50:1, preferably 1:10 to 10:1.

Preferred formulations of the invention also provide a signifi¬ cant benefit in that they produce a significant improvement in a plant growth factor when applied at low rate. Low rate application is defined as a single application rate lower than about 50 g ai/ha (grams of active ingredient per hectacre) . An effective number of low rate applications can be made throughout the growing season. Preferably, the low rate application is per¬ formed from one to about ten times during the growing season, most preferably from one to about ten times during the growing season. Preferred embodiments of the present invention comprise single application rates ranging from about 100 mg ai/ha to about 50 g ai/ha applied from one to four times during a growing season and ranging from about 500 mg ai/ha to about 10 g ai/ha applied from one to four times during a growing season. Other rates use- ful for carrying-out the invention include a rate of less than or equal to about 2 g ai/ha and down to about 100 mg ai/ha applied from one to four times during a growing seasons. The most pre- 9 ferred single application rate is about 500 mg ai/ha to about 1.5 g ai/ha applied from one to four times during a growing sea¬ son.

The present invention finds its best results in horticultural and agricultural plants and crops. The invention provides most con¬ sistent improvement of at least one plant growth factor in the following plants: cotton, soybean, peanut, pepper, tomato, wheat, barley, rice plant, apple, citrus, grape, corn and canola.

The formulations described in this invention are generally applied to the foliage prior to bud and flower development but they can also be applied to the foliage, buds, flowers, or fruits beginning at early bud development (e.g., matchhead square in cotton) in one to four sequential applications. If sequential, ap¬ plications are used, applications are preferably timed at approx¬ imately 10 to 14 days apart. When applied by spraying, the active ingredient is generally mixed with water as a carrier solution in a dilution sufficient to cover the area. Typically the spray volume of the aqueous treatment solution would be about 150 to 500 1/ha for arable crops and up to about 1,500 1/ha fruit trees. Soil drenching is another method of application that is useful when practicing the invention.

Accordingly, the present invention provides a method which im¬ proves the economic or agronomic output of agricultural crops and decreases the amount of material that needs to be used to obtain improvement in a plant growth factor.

Examples

1. Cotton trials. Field tests with Cotton plants were conducted as follows: Cotton plots were laid out about four rows wide and 30 to 40 feet long. The center two rows of each four row plot were treated sprayed over the foliage, buds, blooms, and fruits with the respective applications and the outer two rows were not treated in order to provide a buffer row between plots. In most experiments each treatment was repli¬ cated four times and organized in randomized complete block design.

The first treatments were applied when the plant squares [??] flower buds (i.e., "squares") reached the size of a "match¬ head", i.e. when the first square of a typical cotton plant was about the size of a matchhead, and when 50% of the plants had one or more matchhead squares. Generally, the formula¬ tions, except for the mepiquat chloride, were applied at 1, 20, 20, 50 and 100 g ai/ha. The amount of formulated material to be applied to each treatment was calculated on the basis of the amount of the area to be treated with each rate. For example, a treatment applied at a rate of 1 g of the active ingredient required four applications of 0.022 g ai/ha when four plots (2133 square feet) were treated. Thus, 0.022 g of active material was mixed with one liter of water or the amount of water necessary for the treated area for the spray volume to be equivalent to about 150 to 205 1/ha.

Subsequent to the second and/or final applications the num¬ bers and locations on the plant of the squares, flowers, and bolls were recorded, and when possible, either boll weights or seed cotton yields were obtained.

Greenhouse tests were conducted as follows: [BRIEFLY DESCRIBE AS COMPARED TO FIELD TEST]Cotton was sown in 2 to 5 liter pots in the greenhouse, approximately one plant per pot, ei¬ ther in field soil or soilless planting mix. Plants remained in the greenhouse, and at the matchhead square stage de¬ scribed in the field methods previously, treatments were applied to the foliage, squares, flowers, and/or bolls either by spraying in a laboratory chamber sprayer (Allen Machine Works, Midland, MI), or by placing the pots on the ground outside the greenhouse and spraying with a hand-held spray boom. Spray volumes were approximately equivalent to that de¬ scribed in the field methods. Plants were then returned to the greenhouse and boll counts, boll weights, or seed cotton yields were obtained from the plants.

2. Soybean trials. Soybean trials were conducted in a green¬ house. Soybean seeds were planted in 1000 ml pots in loamy sand soil, fertilized with a slow release fertilizer and al¬ lowed to germinate. Plants were thinned to tow two per pot. When the plants reached the third trifoliate stage, equivalent to 11 true leaves, the plants were treated with the appropriate spray solutions AND applied over the top of the plants to the foliage.

The plants were placed inside a laboratory spray chamber (Al¬ len Machine Works, Midland MI) . As noted above, the foliage was sprayed over the top in order to mimic a typical field application. The plants were returned to the greenhouse. Pe¬ riodic height measurements, pod numbers, and general plant vigor assessments were conducted. At maturity (approximately six to eight weeks after spraying) the pods were harvested, counted, and the dry-weights recorded.

Control plants were either those completely untreated or those 5 treated with mepiquat chloride (Pix® plant growth regulator ") alone. Mepiquat chloride was applied either alone or in combina¬ tion with the ethylene biosynthesis inhibitors was used as the control and was applie at a rate of 100 to 200 g ai/ha. When applied in combination, the two compounds were applied using the 10 same "tank-mix" spray solution. However, combinations of mepiquat chloride and ethylene biosynthesis inhibitors may also include separate applications made within 72 hours of each other on the same plants.

15 EXAMPLE 1

Formulations containing polyvinyl alcohol (PVA) encapsulated { [isopropylidene)-amino]oxy}-acetic acid-2-(methoxy) -2-oxoethyl ester (99% Technical Grade; BASF Corporation) were prepared by 20 first making a 10% solution of PVA in an aqueous solution of so¬ dium phosphate dibasic buffer. Various PVA (Air Products, Inc.) was used having different molecular weights and various degrees of hydrolysis. Table 1 lists the different PVA used.

25 Table 1

Polyvinyl Alcohol

PVA Type Molecular weight (K) Degree of hydrolysis

AIRVOL"* 205 S 15-27 Partial (87-S9%)

30 AIRVOL^® 523 S 44-65 Partial (87-89%)

AIRVOL^® 540 S 70-90 Partial (87-*9%)

AIRVOL^® 125 44-65 Super (99.3% +)

AIRVOL* 325 44-65 Full (98-98.8%)

AIRVOL^® 523 S 44-65 Partial (87-89%)

Jb AIRVOL^®425 44-65 Intermediate (95.5-96.5%)

AIRVOL¹⁸ 603 7 Partial (78-«2%)

AIRVOL^® 203 9-13 Partial (87-89%)

The pH of the 10% PVA solutions was adjusted to about 4.1. The 40 oxime-ether was mixed into the PVA solution under A high shear until a finely dispersed emulsion was obtained. A biocide (Pro- xel^® GXI biocide) was added to the emulsion and mixed. The solu¬ tions were passed once through a high shear Eiger Mini 50 (e.g., a bead mill with an 85% chamber loading of 1 mm glass beads) at ^⁵ 3000 RMP. A milky solution was obtained and passed through a 0.45 micron screen. The formulations prepared contained about 5% sub- stituted oxi e-ether, about 5% PVA, about 0.12% biocide, about 0.26% sodium phosphate dibasic and about 89.62% water.

Particle size was measured using an Accusizer Optical Particle Sizer. The particle size measured (mean volume) for each formulation was about ten microns.

The formulations were tested in soybeans at rates of 1,10 and 20 g ai/ha (greenhouse) and compared to a control and unencapsu- lated { [isopropylidene)-amino]oxy}-acetic acid-2- (methoxy)-

2-oxoethyl ester (99% Technical Grade; BASF Corporation) . The re¬ sults are displayed in Table 2.

TABLE 2 Soybean

Number of Pods rate kg aiha 0.0010 0.010 0.020 control 18.2 18.2 18.2 tech. grade 23.2 (127%) 18.4 (101%) 21.6 (119%) encap. tech. grade 23.2 (127%) 21.8 (120%) 21.3 (118%) (205s) encap. tech. grade 20.4 (112%) 22.6 (124%) 23.0 (126%) (523s) encap. tech. grade 25.8 (142%) 191 (105%) 19.2 (105%) (540s)

The results establish that at low rates the encapsulated { [isoprnpylidene)-amino]oxy}-acetic acid-2-(methoxy)-2-oxoethyl ester significantly and consistently improves the number of pods in the soybean plant.

EXAMPLE 2

Encapsulated { [isoprnpylidene) -amino)oxy}-acetic acid-2- (methoxy)-2-oxoethyl ester formulations were prepared as in Example 1 and combined with mepiquat chloride and mixed in one liter of water. Two formulations were prepared. The first formulation contained PVA with a molecular weight of 44-66K and partial degree of hydrolysis (87-89%) (AIRVOL^® 523 S polyvinyl al- cohol) . The second formulation contained PVA with a molecular of 70-90k and was partially hydrolyzed (87-89%) . Cotton plants were treated as described above. The plants were treated and mepiquat chloride treated plants were used as a comparison (Application rate at about 0.012 kg ai/ha) . The number of squares and boils were measured sand the results are displayed in Tables 3-5 TABLE 3 Cotton

D Measured after two of four sequential applications (field test) mc = mepiquat chloride

TABLE 4 Cotton

^xFour applications (field data)

²Three applications (field data)

³Four applications (field data)

⁴Collected after the second of two sequential applications mc = mepiquat chloride TABLE 5 Cotton

iFour applications (field data) ²Three applications (field data) mc = mepiquat chloride

Examination of the data in Tables 3-5 confirms that the present invention provides consistent improvement in a plant growth fac- tor at low rates. At the low rate application of 1 g ai/ha, the formulation provides significant improvement (about 10% to about 60%) over the mepiquat chloride treated plants.

The formulations were also tested in soybeans at rates of 1, 10 and 20 g ai/ha (greenhouse) and compared to an untreated control. The formulations showed an improvement over the untreated control and were comparable to the plants treated with mepiquat chloride.

EXAMPLE 3

In the experiments 50 to 102 seeds were counted and used for each treatment, [isopropylidene) -amino} .acetic-2- (methoxy) -2-oxoethyl ester (99% Technical Grade ("tech."); BASF Corporation) was apl- lied either alone or as an encapsulated formulation as described in Example 1. A treatment solution volume of 10 to 50 ml/kg seed was prepared. The formulations were applied at rates of about 1 to 200 mg ai/kg seed. The seeds were mixed and wet with the treatment solutions in flasks and allowed to absorb the applied solutions.

After the seeds had absorbed most of the treatment solutions, they were placed in germination media. The germination media was placed in growth chambers. The growth media consisted of either a loamy sand or an absorbent foam cores (OASIS^® CELAN START^® grow- ing media) . The seeds were placed at uniform depth in the media. Growth chamber temperatures were held at approximately 70°F night/80°F day (12h/12h) for the warm treatments, and approxi- ately 55°F night/70°F day (12h/12h) for the cool treatments. Emerged seedlings were counted on a regular basis. Radiant energy was provided by fluorescent and incandescent light sources for the daytime period. The results for the cool treatments are listed Table 6.

TABLE 6

Seed Dressing (Cotton)

Table 6 shows an improvement in the rate of germination at cool 5 temperature. Signification improvement was seen with the 205S formulation at about five days (e.g., about a two-fold increase in germination rate up to a four-fold increase in germination rate) .

0 Seed dressing experiments were performed in a Greenhouse study in peanuts with the same treatments. However no cold treatments were performed. The data indicate an increase in shoot growth of most of the plants that were treated with PVA encapsulated formula¬ tions. 5 EXAMPLE 4

Soybean seeds were planted in loamy sand soil in 1 liter pots in the greenhouse and thinned to three plants per pot after emer- 5 gence. When the plants reached about the first trifoliate stage of the early bloom stage, 100 ml of a solution containing the equivalent of 0, 30, or 100 or 300 g ai/ha { [isopropyli- dene) -amino} -acetic acid-2- (methoxy) -2-oxoethyl ester (99% Tech¬ nical Grade ("tech."); BASF Corporation) (free and encapsulated) 10 was applied, directly to the soil around the base of the plants. Plant heights were measured at regular intervals and upon matu¬ rity, the plants were harvested for fresh and dry weights of the shoots and the bean pods. The results are displayed in Tabeles 8 & 9.

15

TABLE 7

Soil Drenches in Soybeans

Fresh Weight of Pods (g)

?n

Rate (kg ai/ha) 0.03 0.1 0.3

Untreated 7.6 7.6 7.6

AIRVOL^® 125

2-3 Trifoliate 10.9 (143%) 9.4 (124%) 9.0 (118%)

25 Early Bloom 11.7 (154%) 10.4 (137%) 10.8 (142%)

AIRVOL^® 54OS

2-3 Trifoliate 12.3 (163%) 10.9 (143%) 11.5 (151%)

Early Bloom 12.2 (161%) 12.4 (163%) 12.7 (167%)

AIRVOL^® 205S

30

2-3 Trifoliate 12.3 (162%) 9.6 (126%) 12.6 (166%)

Early Bloom 10.5 (138%) 11.9 (157%) 11.6 (153%)

AIRVOL^® 325S

2-3 Trifoliate 10.1 (133%) 12.4 (163%) 13.2 (174%) 5 Early Bloom 11.5 (153%) 11.8 (155%) 11.6 (153%)

AIRVOL^® 523 S

2-3 Trifoliate 12.2 (161%) 12.8 (168%) 12.8 /168%)

Early Bloom 12.0 (158%) 13.2 (174%) 11.6 (153%)

AIRVOL^® 425 0

2-3 Trifoliate 13.7 (180%) 11.6 (153%) 11.9 (157%)

Early Bloom 12.0 (158%) 12.4 (163%) 10.5 (138%)

5 TABLE 8

Soil Drenches in Soybeans

ς Dry Weight of Pods (g)

Rate (kg ai/ha) 0.03 0.1 0.3

Untreated 3.1 3.1 3.1

AIRVOL^® 125

2-3 Trifoliate 5.6 (187%) 5.0 (161%) 5.0 (161%) 0 Early Bloom 6.8 (219%) 6.5 (210%) 5.7 (184%)

AIRVOL^® 5 OS

2-3 Trifoliate 7.1 (229%) 6.3 (203%) 6.7 (216%)

Early Bloom 6.7 (216%) 6.8 (219%) 7.0 (226%)

AIRVOL^® 205S 5

2-3 Trifoliate 6.7 (216%) 5.4 (174%) 6.9 (226%)

Early Bloom 5.6 (181%) 5.3 (171%) 5.8 (187%)

AIRVOL^® 325S

2-3 Trifoliate 5.2 (168%) 6.8 (219%) 7.1 (229%) 0 Early Bloom 5.5 (177%) 6.1 (197%) 6.5 (210%)

AIRVOL^® 523 S

2-3 Trifoliate 6.8 (219%) 6.8 (219%) 6.8 (219%)

Early Bloom 6.9 (223%) 7.2 (232%) 6.4 (206)

AIRVOL^® 425 ς

2-3 Trifoliate 7.3 (235%) 6.0 (194%) 6.8 (219%)

Early Bloom 6.7 (216%) 6.3 (203%) 5.5 (177%)

The data show that the plants treated with the encapsulated for¬ mulations display a significant increase in the weight of the 0 shoots.

EXAMPLE 5

Ethylene inhibition was determined in barley leaves treated with {[isopropylidene) -amino] oxy} -acetic acid-2- (methoxy) -2-oxoethyl ester (99% Technical Grade ("tech."); BASF Corporation) (both en¬ capsulated and free) using various formulations ad described in Example 1. The formulations were applied to seven-day-old green¬ house grown barley leaves at rates of 30 g ai/ha and 300 g ai/ha. The treatments were carried out in a spray chamber at 750 1/has in aqueous solutions made with 0.1 M potassium phosphate buffer. The leaves were wilted for one hour and incubated in a gas-tight 55 ml vial for 150 minutes. A one ml gas sample was taken through the septum and analyzed for ethylene content using a gas chroma- tograph on a Al₂θ₃ column. The results are shown in Table 9. TABLE 9 Barley Leaves

The data in Table 9 show significant inhibition of ethylene pro¬ duction at 30 and 300 g ai/ha. The data further demonstrate that a ten-fold decrease in application rate, the encapsulated formulation significantly inhibited the production of ethylene whereas the unencapsulated formulation showed no improvement.

The invention has been described with reference to various spe¬ cific embodiments. However, many variations and modifications may be made while remaining within the scope and spirit of the inven¬ tion.

Claims

CLAIMSI claim:

1. A particle comprising a plant growth regulator contained in a polyvinyl alcohol matrix wherein said particle has a mean volume diameter greater than about 1 micron.

2. The particle of claim 1 wherein the plant growth regulator comprises a substituted oxime-ether of the formula:

where R¹ and R² independently of one another are Ci-Cε-alkyl, n is 2 or 3 and R³ is hydrogen or Cι-C₆-alkyl.

3. The particle as recited in claim 2 wherein the oxime-ether is selected from the group consisting of { [isopropyli- dene) -amino] -oxy} -acetic acid-2- (methoxy) -2-oxoethyl ester, { [isopropylidene) -amino]oxy} -acetic acid-2-hexyloxy-2-oxoe¬ thyl ester, and { {cyclohexylidene) -amino] oxy} -acetic acid-2- (isopropyloxy) -2-oxyethyl ester- (methoxy) -2-oxoethyl ester.

4. The particle as recited in claim 2 wherein the substituted oxime-ether comprises { [isopropylidene) -amino]oxy} -acetic acid-2- (methoxy) -2-oxoethyl ester.

5. The particle as recited in claim 1 wherein the plant growth regulator is selected from the group consisting of {(isopro¬ pylidene)amino}oxy acetic acid and a inooxyacetic acid.

6. The particle as recited in claim 1 wherein the plant growth regulator is selected from the group consisting of aminethox- yvinylglycine, methoxyvinyl glycine and rhixobitoxine.

7. A composition comprising a plant growth regulator in accor¬ dance with any one of claims 1 to 6 and a plant growth retar¬ dant.

8. A composition as claimed in claim 7 wherein the plant growth retardant is mepiquat chloride.

9. A method of improving a plant growth factor in a plant com¬ prising administering to said plant a formulation comprising a plant growth regulator as claimed in any one of claims 1 to 6 or a composition as claimed in claims 7 and 8.