Plant husbandry – Process
Utility Patent
1999-01-26
2001-01-02
Patterson, Jr., Charles L. (Department: 1652)
Plant husbandry
Process
C504S100000, C504S118000, C504S140000, C504S292000, C071S016000, C071S027000, C536S020000, C514S055000
Utility Patent
active
06167652
ABSTRACT:
FIELD OF INVENTION
The Invention is directed to a method for treating cotyledonous plants to improve the yield, health, and vigor of the plant by spraying an aqueous solution of a chitosan salt onto the leaves of the plant.
BACKGROUND OF THE INVENTION
Chitosan is a naturally occurring polymer found in many fungi. It may be broadly described as a copolymer of D-glucosamine and N-acetyl-D-glucosamine in which 65-100% of the monomer units are D-glucosamine. Since it is a member of the chemical class known as amines, which are weakly basic, it readily and reversibly forms salts with acids such as mineral acids and carboxylic acids. Many of these salts are water soluble at acid pH values. In a system in which chitosan and an acid are present, both electrically neutral glucosamine units and units in which the glucosamine unit is protonated and associated with the anion corresponding to the acid will be present in the polymer chain in proportions which are dependent on pH. Such a system is commonly referred to as a chitosan salt without regard to the extent to which the glucosamine units are protonated.
As used herein, the term “chitosan salt” includes not only the chitosan salt, but also any partially unprotonated chitosan which may be present in acidic media.
It has been demonstrated that application of chitosan salt to the seeds of cereal crops results in dramatic changes in the biochemistry of the emergent plant. Included among these changes are an increased production of a class of compounds known as the phytoalexins, which provide protection against localized microbial infection, and increased production of callose and lignin which provide structural strength and a barrier to the spread of infection. These changes occur as a result of activation of the gene encoding the enzyme phenylalanine ammonia lyase, which is involved in the rate determining step of the phenylpropanoid metabolism pathway. The chitosan salt has been shown to induce synthesis of the terpenoid phytoalexins, which are closely involved in the biosynthesis of growth hormones such as gibberelic acid and abscisic acid. Chitosan salt also induces activation of genes which produce chitinase and glucanase enzymes that are known to be both fungal inhibitors and to play a role in pollen development and seed germination. It also induces activation of genes which produce protease inhibitors that help protect the plant from insect attack. These changes result in enhanced root development, reduced lodging (plants falling over before harvest), enhanced yield, and resistance to certain plant diseases.
In U.S. Pat. No. 4,812,159, Freepons discloses, in detail, treatment of soil in the seed planting zone with an aqueous solution of chitosan salt, application of a chitosan salt solution to plant seeds, treatment of soil in the seed planting zone with a mixture of solid chitosan and a solid acid, and treatment of soil in the seed planting zone with a solid chitosan salt. The preferred chitosan salt solution is one that contains more than 1.5 equivalents of glutamic acid per mole of amino function in the chitosan. Application of chitosan salt to the foliage of an emerging plant is mentioned, but there is no disclosure of the methods required to accomplish such treatment, or of the results thereby achieved. For all of these treatments it is stipulated that when an acidic component is used in making the chitosan salt preparation, the acid must be selected from the group of non-phytotoxic acids, which are defined as those acids that will not cause a significant adverse effect on germination of seeds or on development of the seedling, i.e., seed phytotoxicity.
In U.S. Pat. No. 4,964,894, which is a continuation-in-part of U.S. Pat. No. 4,812,159, Freepons notes that glutamic acid, tartaric acid, citric acid, adipic acid, hydrochloric acid, formic acid, and nitric acid meet the criteria of non-phytotoxicity. Acetic acid and butyric acid were found to be phytotoxic and harmful to the development of the plant seedlings. This would make these acids unsuitable for use according to the teachings of Freepons.
According to U.S. Pat. No. 4,812,159, the treatment of seed is accomplished by applying a chitosan preparation to the seed or by immersing the seed in such a preparation, followed by drying. The drying step is necessary to prevent premature germination of the seed in the time interval between the treatment with chitosan and planting. In the absence of a drying step, the patent recommends that planting occur within 60 hours of seed treatment.
While seed treatment is easily accomplished on a small scale using the methods disclosed by Freepons, the treatment protocols are difficult to extend to commercial scale operations without devising specialized equipment or modifying specialized equipment commonly used in the seed coating industry such as grain angering devices like the Gustavson seed coater. This is a serious drawback in commercial operations where the same piece of equipment must also be used to carry out other treatments (e.g., application of fungicides) to seeds and cannot economically be dedicated for use only with chitosan-containing materials. Furthermore, such treatment is limited to a single application of chitosan salt at the very earliest stage of plant growth, which may not be repeated and reinforced at other key stages of plant growth such as seed formation, rapid growth phases, flowering and ripening.
Treatment of soil in the seed planting zone with a chitosan salt preparation requires that the preparation be distributed in a region in close proximity to where the seed will be or has been planted. Specialized equipment is therefore required to limit the treatment to the region where the seed will eventually germinate. While this may be readily accomplished in the case of mechanized seeding, this technique is not compatible with other methods such as aerial seeding or broadcast seeding. In addition, the two techniques utilizing chitosan salt in the form of a solid require that the solid be introduced in the form of very small particles of 0.5-100 micrometers. Therefore, elaborate pre-processing of the chitosan salt is required to put it in a form suitable for application. As with seed treatment, treatment of soil in the region of seed germination is limited to a single treatment at the very earliest stage of plant growth, lest the root system of the plant be disrupted.
While this patent superficially discloses the application of chitosan to the foliage of emerging plants, there are no data to show any beneficial effect. Furthermore, the teaching is limited by implication to the earlier stages of plant growth. Thus, the patent teaches nothing about the treatment of plants having leaves capable of photosynthesis.
In U.S. Pat. No. 4,964,894, Freepons again describes the techniques noted above and then describes an elaborate procedure involving seed germination studies for identifying non-phytotoxic acids. Glutamic acid, tartaric acid, citric acid, adipic acid, hydrochloric acid, formic acid and nitric acid met the criteria for non-phytotoxicity. Acetic acid and butyric acid were found to be phytotoxic and therefore detrimental to development of the seedling. The preferred chitosan salt solution is taught to be one that contains more than 1.5 equivalents of glutamic acid per mole of amino function in the chitosan.
Another seed treating technique is described in U.S. Pat. No. 5,554,445 (Kivekas, Struszczyk), which involves spraying seeds with a liquid dispersion of microcrystalline chitosan, followed by drying to form a film of the chitosan polymer around the seed. In order to form an appropriate film on the seed, the chitosan is specified to have a water retention value of 200-5,000%, hydrogen bonding potential of 10-25 kJ/mol, and particle size of 0.1-100 micrometers. As in the cases noted above, these procedures require specialized equipment, elaborate pre-processing of the chitosan, and are limited to a single treatment at the earliest stage of plant growth.
In U.S. Pat. No. 4,886,541, Hadwiger discloses the application
Bjornson August S.
Heinsohn George E.
DCV, Inc.
Patterson Jr. Charles L.
Saidha Tekchand
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