Compositions and methods for preventing leaf yellowing in...

Plant protecting and regulating compositions – Compositions for preservation or maintenance of cut flowers – Containing organic nitrogen compounds

Reexamination Certificate

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Details

C504S217000

Reexamination Certificate

active

06455466

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to compositions and methods for preserving plants and plant parts. In particular, it relates to compositions comprising substituted urea compounds (e.g., thidiazuron) to inhibit senescence in plants.
BACKGROUND OF THE INVENTION
Leaf yellowing is a common symptom of the onset of leaf senescence in plants, and is often a problem in horticulture or other agricultural production systems (Funnell, K. A., et al.,
Hortscience
, 33:1036-103 (1998); Tollenaar, M.,
Crop Science
, 31(1):119-124 (1991)). Yellow leaves are unsightly and reduce the quality, value and shelf life of ornamentals such as potted roses, potted and cut lilies, flowers of Alstroemeria, and leafy vegetables (Tjosvold, Steven A., et al.,
Hortscience
, 29:293-294 (1994); Staby, G. L., et al.,
Florists Rev
., 161:38 (1977); Hibma, J. T.,
Verslag Centrum voor Agrobiologisch Onderzoek
, 91:26 (1988)). Early onset of leaf senescence can affect agricultural productivity in diverse ways, for example yield in grain and legume crops and success of propagation of leafy cuttings (Martin del Molino, I. M., et al.,
Physiol. Plant
, 66(3):503-508 (1986); Caldiz, et al.,
Plant Growth Regulation
, 10(3):197-204 (1991); Finnan, J. M., et al.,
Agriculture Ecosystems & Environment
, 69:27-35 (1998)).
Application of the synthetic cytokinin, benzylaminopurine (BAP) to leaves is known to prevent leaf yellowing and senescence (Richmond, A. E., et al.,
Science
, 125:650-651 (1957); Dyer, T. A., et al.,
Journal of Experimental Botany
, 22:552-560 (1971); Gan, S., et al.,
Bio Essay
, 18:557-565 (1996)) This material along with Gibberellic acid (GA, another plant hormone with anti-senescence activity) are now in commercial use to prevent leaf yellowing in cut chrysanthemum flowers and potted roses, among others (van Doom and de Wit, 1992; Tjosvold, Steven A., et al.,
Hortscience
, 29:293-294 (1994); Han, S. S.,
Journal of the American Society for Horticultural Science
, 122::869-872 (1997); Funnell, K. A., et al.,
Hortscience
, 33:1036-103 (1998)).
The compound is registered for use as an herbicide and defoliant. It has high activity as a cytokinin, which probably is the basis of its herbicidal and defoliation properties. It is commonly used as substitute for BAP, zeatin, and other cytokinins that are used in plant tissue culture, because of its high activity (10 to 100 times that of BAP) and because plants do not metabolize it (Genkov, T.,
Bulgarian Journal of Plant Physiology
, 21:73-83 (1995) and Murthy
In vitro Cellular and Developmental Biology Plant
34::267-275 (1998)).
There is a real and continuing need for effective preservation formulations to inhibit senescence of leaves and other chlorophyll-containing plant organs. Such formulations can be used, for example, to preserve fresh cut flowers or potted plants. The present invention addresses these and other needs.
SUMMARY OF THE INVENTION
This invention provides compositions and methods for preserving plants, such as plant parts (e.g., cut flowers) and potted plants. The methods are based on the observation that compounds of Formula I are useful to prevent senescence in plants, particularly in chlorophyll-containing tissues. For example, the compounds maintain leaves in cut flowers or potted plants. In addition, in potted plants the compounds of the invention enhance growing buds and maintain flowers.
wherein:
R
1
, and R
4
are independently selected from the group consisting of hydrogen and lower alkyl,
R
2
and R
3
are independently selected from the group consisting of substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl; and X is an oxygen or sulfur atom.
If R
2
or R
3
is alkyl it can be substituted or interrupted at least once by oxygen or sulfur. If R
2
or R
3
is cycloalkyl its can be substituted at least once by alkyl. If R
2
or R
3
is aryl substituted at least once by a member of the group consisting of alkyl, halogen, alkyl mercapto, alkoxy, trifluoromethyl and NR
5
R
6
, wherein R
5
and R
6
are independently selected from the group consisting of H or lower alkyl. In some embodiments R
2
and R
1
or
3
and R
4
together with the N atom, form a heterocyclic or heteroaryl ring, such as a morpholino, a piperidino, or a pyrrolidino moiety.
A preferred compound to use in the methods is 1-phenyl-3-(1,2,3-thiadiazol-5-yl)urea, referred to as thidiazuron. Other preferred compounds include N-(2-chloro-4-pyridyl)-N′-phenylurea and 1,3-diphneyl urea.
The compositions of the invention may contain other constituents such as plant nutrients and surfactants, depending upon the particular use. The methods are useful with all plants, particularly cut flowers and potted plants.
DEFINITIONS
The term “plant” includes whole plants, and plant parts including shoot vegetative organs/structures (e.g. leaves, stems and tubers), roots, flowers and floral organs/structures (e.g. bracts, sepals, petals, stamens, carpels, anthers and ovules), seed (including embryo, endosperm, and seed coat) and fruit (the mature ovary). For example, the term refers to cut flowers or other organs. The class of plants that can be used in the method of the invention includes the class of higher and lower plants, including angiosperms (monocotyledonous and dicotyledonous plants), gymnosperms, ferns, and multicellular algae. It includes plants of a variety of ploidy levels, including aneuploid, polyploid, diploid, haploid and hemizygous.
The term “alkyl,” by itself or as part of another substituent, means, unless otherwise stated, a straight or branched chain, or cyclic hydrocarbon radical, or combination thereof, which may be fully saturated, mono- or polyunsaturated and can include di- and multi-valent radicals, having the number of carbon atoms designated (i.e. C
1
-C
10
means one to ten carbons). Examples of saturated hydrocarbon radicals include groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isobutyl, sec-butyl, cyclohexyl, (cyclohexyl)ethyl, cyclopropylmethyl, homologs and isomers of, for example, n-pentyl, n-hexyl, n-heptyl, n-octyl, and the like. An unsaturated alkyl group is one having one or more double bonds or triple bonds. Examples of unsaturated alkyl groups include vinyl, 2-propenyl, crotyl, 2-isopentenyl, 2-(butadienyl), 2,4-pentadienyl, 3-(1,4-pentadienyl), ethynyl, 1- and 3-propynyl, 3-butynyl, and the higher homologs and isomers. The term “alkyl,” unless otherwise noted, is also meant to include those derivatives of alkyl defined in more detail below as “heteroalkyl,” “cycloalkyl” and “alkylene.” The term “alkylene” by itself or as part of another substituent means a divalent radical derived from an alkane, as exemplified by —CH
2
CH
2
CH
2
CH
2
—. Typically, an alkyl group will have from 1 to 24 carbon atoms, with those groups having 10 or fewer carbon atoms being preferred in the present invention. A “lower alkyl” or “lower alkylene” is a shorter chain alkyl or alkylene group, generally having eight or fewer carbon atoms.
The term “alkoxy,” refers to those groups having an alkyl group attached to the remainder of the molecule through an oxygen, atom.
The term “alkyl mercapto,” refers to those groups having an alkyl group attached to the remainder of the molecule through a sulfur atom.
The terms “cycloalkyl” and “heterocycloalkyl”, by themselves or in combination with other terms, represent, unless otherwise stated, cyclic versions of “alkyl” and “heteroalkyl”, respectively. Additionally, for heterocycloalkyl, a heteroatom can occupy the position at which the heterocycle is attached to the remainder of the molecule. Examples of cycloalkyl include cyclopentyl, cyclohexyl, 1-cyclohexenyl, 3-cyclohexenyl, cycloheptyl, and the like. Examples of heterocycloalkyl include 1-(1,2,5,6-tetrahydropyridyl), 1-piperidinyl, 2-piperidinyl, 3-piperidinyl, 4-morpholinyl, 3-morpholinyl, tetrahydrofuran-2-yl, tetrahydrofuran-3-yl, tetrahydrothien-2-yl, tetrahydrothien-3-yl, 1-piperazinyl, 2-piperazinyl, and the like.
T

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