the present inventors have found that 9 , 10 - dihydromethyl jasmonate , also called methyl dihydrojasmonate ( mdhj ), the general structure of which is given below in formula ( 2 ): is surprisingly effective in reducing naturally occurring leaf senescence when administered to a plant in an effective amount . this effect is contrary to what would be expected from the literature on jasmonate effects in leaf senescence . plants to which mdhj may be applied to reduce leaf senescence include , but are not limited to , angiosperms , gymnosperms , monocots , dicots , roses , tomatoes , crop plants , ornamental plants , turf plants , shrubs , trees , exotic plants , house plants , and native plants in cultivated or natural environments . mdhj may also be applied to plants grown for food , particularly where the leaves are the edible or commercially desirable portion of the plant . mdhj has been found to be particularly efficacious in roses , spinach , and corn . the mdhj may be applied alone or in a formulation comprising other elements , compounds , or substances . some examples of other compounds that may be included in the formulation include wetting agents , adjuvants , emulsifiers , dispersants , spreaders , stickers , pastes , anchorage agents , fixatives , extenders , coating agents , buffering agents , plant nutrients , absorptive additives , and disintegrants . the formulation may also include acids , bases , or other compounds that adjust or maintain the final ph of the formulation in order to increase solubility of certain compounds in the formulation or for other reasons . those of skill in the art will recognize that a single ingredient may perform multiple functions , and may thus be classified or grouped in different ways . particular examples of formulation ingredients include ionic , non - ionic , and zwitterionic surfactants , such as triton ® x - 100 , triton ® x - 114 , np - 40 , silwet , and sodium dodecyl sulfate ; alcohols ; synthetic or natural oils , such as castor oil , canola ( rapeseed ) oil , and soybean oil ; soaps ; and adjuvants derived from natural sources , such as lecithin , saponin , cocodiethanolamide , and extracts from yucca , coconut , and pine . additionally , for example , citric acid may be used to acidify a formulation , and compounds such as dipotassium phosphate , calcium carbonate , and potassium silicate may be used to raise the ph . in some embodiments , it may be beneficial to use ingredients that are high in compounds that play a role in the octadecanoic pathway . for example , canola oil is high in linoleic and linolenic acids , compounds that play a role in the octadecanoic pathway . soaps of linoleic , linolenic , and cis - 7 , 10 , 13 - hexadecatrienoic acids may also be desirable formulation ingredients in some embodiments . an mdhj formulation used in embodiments of the invention may also include fixative and extender compounds , in order to reduce volatility and evaporation of the active ingredient or ingredients , so as to increase exposure of the plant to the active ingredient . exemplary fixatives include canola oil , castor oil , benzoyl benzoate , benzyl salicylate and synthetic musks , and sandalwood . gums , waxes , and other carbohydrates , such as carnauba wax , carob gum , dextrins , dextrose , gellan gum , guar gum , paraffin wax , sorbitol , xanthan gum , polyvinylpyrrolidone , and glycerin , may also be used as fixatives . absorptive additives may also be included for extending the release and exposure time . exemplary absorptive additives include , but are not limited to , silica gel ; precipitated crystalline - free silica gel ; amorphous , fumed , crystalline - free silica ; amorphous , precipitated gel silica ; silica hydrate ; vitreous silica ; silicic acid ; and silicon dioxide . alone or in combination with other ingredients , the mdhj may be delivered in the form of emulsions , suspensions , powders , hydrates , solutions , granules , pastes , aerosols , and volatile formulations . if mdhj is delivered in the form of a solution , it may be in solution with any compatible solvent , including aqueous ( water ) solutions , alcohol ( e . g ., ethanol ) solutions , or in combinations of solvents ( e . g ., water / ethanol .) in general , a “ compatible solvent ,” as the term is used here , refers to any solvent in which mdhj is at least slightly soluble and which is not phytotoxic in the amounts or concentrations used to apply the mdhj . forms of mdhj may be adapted for application to the plant &# 39 ; s foliage , roots , stems , and flowers . particularly advantageous forms include foliar sprays , root solutions , and pellet - based root preparations . as a root solution or preparation , jasmonates such as mdhj may be formulated and applied to plants grown in soil , non - soil , artificial growing media , and / or hydroponic systems . in some embodiments , the mdhj formulations may be combined with other active compounds that can be administered in the same fashion as the mdhj formulation . examples include fertilizers , seaweed , kelp , humic acid , and microbes . an mdhj foliar spray may be combined with a foliar fertilizer , and a root solution may be combined with a fertilizer that is applied to the roots . specific fertilizer and plant nutrient elements include , but are not limited to , nitrogen , potassium , phosphorus , calcium , magnesium , which may be compounded in any known manner so as to be absorbable by the plant . for example , plant nutrients may include monobasic potassium phosphate ( kh 2 po 4 ) and magnesium sulfate ( mgso 4 ). in addition to the above ingredients , formulations according to embodiments of the invention may also include preservatives . suitable preservatives may include potassium sorbate , sodium benzoate , sulfites , sodium nitrite , edta , and calcium propionate , to name a few . as was noted above , the mdhj is applied in an “ effective amount ” to reduce leaf senescence . for purposes of this description , an effective amount of mdhj is any amount of mdhj that produces a noticeable decrease in leaf senescence as compared with untreated plants . effective amounts of mdhj will vary from species to species and cultivar to cultivar , and will depend on the manner of application , the environmental conditions around the plant or plants , the form in which the mdhj is administered , and the nature and type of additive compounds , if any , present in the formulation with the mdhj . for example , if an mdhj formulation is applied over a substantial portion of a plant &# 39 ; s foliage , or is applied using a formulation that includes wetting agents , fixatives , and / or other additives intended to increase the level of exposure of the plant to the mdhj , the formulation itself may contain a smaller amount or lower concentration of mdhj than if an mdhj formulation is applied over only a small portion of a plant &# 39 ; s foliage , or without additives intended to increase the plant &# 39 ; s exposure to the mdhj . similarly , if the mdhj is administered in a form that tends to dwell on the plant &# 39 ; s foliage , or in proximity to another part of the plant , then it may be administered in a lower concentration or amount . as one example , an effective amount of mdhj for reducing leaf senescence may comprise an aqueous solution with an mdhj concentration in the range from about 0 . 15 mm to about 6 mm , inclusive . however , for some purposes , and in some species , concentrations up to or greater than 20 mm may be used . as those of skill in the art will realize , in general , mdhj may be used in even higher concentrations for some applications , provided that the total dose of mdhj that is absorbed by the plant is not phytotoxic . similarly , lower concentrations may be adequate in some situations , for example , in an enclosed environment or greenhouse . one example of an aqueous mdhj foliar spray formulation is given below in table 1 : in addition to liquid and aqueous preparations , mdhj may be formulated for use in a slow - release application and provided in a granular - or pellet - based form , including fertilizer and / or pesticide components . mdhj may be present in those formulations in weight / weight ratios of mdhj to other ingredients in the range of 0 . 008 % to 0 . 8 %, and in some cases an effective ratio could be greater than 1 . 0 % or less than 0 . 008 %. other inert or nutritive ingredients included in the pellets or granules can include binding agents and polymers , such as polysaccharides and polyvinylpyrrolidone , at 5 - 95 %, a surfactant at 0 . 001 - 10 %, and other absorptive ingredients , such as acrylamide and acrylamide polymers . formulations including mdhj may be applied once or repeatedly , depending on the circumstances and the type of formulation , to treat a plant . for example , mdhj formulations according to embodiments of the invention may be applied to the roots , foliage or some other part of a plant once or , alternatively , two or more times at defined intervals of time , such as every 2 - 14 days , every 30 days , or 1 - 2 times per month . the intervals at which the mdhj is applied may vary . a plant may be treated with mdhj whether or not it has senescing leaves at the time of treatment . additionally , plants may be treated with mdhj for purposes of reducing leaf senescence whether they are healthy or not . ( for example , work by the present inventors has also shown that mdhj is effective in reducing biotic attack and disease in plants ; see , for example , u . s . patent application publication no . 2009 / 0082453 , the contents of which are incorporated by reference herein in their entirety . therefore , a plant may be treated with mdhj for multiple reasons .) among other factors , the environmental conditions around the plant or plants may influence the manner in which the mdhj is applied or its frequency . for example , if the plants are field - grown or otherwise exposed to the elements , rain showers , excessive wind gusts , or other environmental factors shortly after an application , it may be desirable to reapply it . under some circumstances , a more dilute formulation or solution may be used if repeated applications are to be performed . optionally , in at least some embodiments , a plant treated with mdhj , or a portion thereof , may be harvested some time after the plant is treated with mdhj . harvesting may occur shortly after ( e . g ., several days after ) treatment , or it may occur after sustained , relatively long - term treatment with mdhj ( e . g ., several weeks or several months of treatment at regular intervals ). treatment with mdhj may reduce the levels of chlorosis and necrosis seen in plant leaves , and / or it may reduce the total number of senescing leaves , thus potentially improving the appearance of the plant and , consequently , its perceived health and / or commercial value . the following examples serve to illustrate the efficacy of mdhj in reducing leaf senescence . unless otherwise noted , in the following examples , the mdhj was obtained from bedoukian research , inc . ( danbury , conn ., united states ; product no . 398e ). as supplied , the mdhj solution was specified as having a minimum purity of 92 . 5 %, of which 25 - 40 % was the “ epi ” or “ cis ” isomer of mdhj , shown as formula ( 3 ) below : unless otherwise noted , percentages , for example , percentages of additional or inert formulation ingredients , are given as percentages by volume . potted miniature parade ® roses were evaluated for the effect on leaf senescence of foliar spray treatment with an mdhj formulation . one group of four plants acted as an untreated control group and did not receive any foliar spray . another group of four plants was sprayed with a formulation comprising 1 . 5 mm mdhj , 0 . 5 % triton ® x - 100 , and 0 . 125 % canola oil . the treated plants were sprayed on six occasions , on days 1 , 3 , 12 , 29 , 31 , and 58 , by spraying foliage to the point of drip . the number of leaflets exhibiting senescence was analyzed 65 days after the first treatment . senescence was indicated by chlorosis and necrosis affecting greater than 50 % of an individual leaflet . the results of example 1 are shown in table 2 . specifically , mdhj treatment reduced leaf senescence normally associated with the end of the growing season . sixty - five days after treatment , mdhj - treated roses showed no senescing leaves , while untreated roses exhibited leaf senescence in up to 9 . 4 % of their leaflets . potted yellow dwarf roses were grouped into one of four groups , and each of the groups received one treatment . the four groups are set forth in table 3 below . one group was an untreated control ( utc ), while the other three groups were treated with aqueous solutions of mdhj that differed only in the concentration of mdhj . there were three plants in each group . before the trial began , naturally senescing leaves were visible on all plants ; these were removed at the time that the trial began . the rose leaves received one foliar spray treatment by applying spray until the point of drip . evaluation for leaf senescence , without any additional treatment , occurred on days 3 , 7 , 10 , 14 , and 31 by counting the number of leaves on each plant exhibiting senescence . senescence was indicated by chlorosis and necrosis affecting greater than 50 % of an individual leaf . after each evaluation , senescing leaves were removed . the results of example 2 are shown in table 4 below . in general , mdhj treatment reduced the rate of naturally senescing leaves of yellow dwarf rose compared to the untreated control group . in table 4 below , treatment groups indicated by the same letter did not significantly differ ( p = 0 . 5 , student = newman - keuls ). greenhouse - grown spinach seedlings , cultivar ‘ merlo nero ,’ were divided into two groups , with eight plants per group . one group was left untreated , while the other group was treated with 0 . 5 mm mdhj in 0 . 1 % ethanol by spraying leaves until the point of drip . treatments occurred on days 1 , 4 and 8 of the experiment . on day 6 , senescence was noted on some leaves , defined by chlorosis and / or necrosis . senescence began at the leaf tip and spread towards the petiole . on day 8 , the number of plants exhibiting senescence was counted . all leaves from each plant were then harvested and combined for each treatment . the total number of senescing leaves were counted and taken as a percentage of the total number of leaves per treatment . senescence was indicated by chlorosis and necrosis affecting greater than 50 % of an individual leaf . in the untreated spinach group , 87 . 5 % of the plants exhibited signs of senescence compared to 37 . 5 % in the treated group . in the untreated group , 34 . 6 % of the leaves exhibited senescence . in the treated group , 8 . 6 % of the leaves showed senescence . the full results of example 3 are set forth below in table 5 below . seeds of corn (‘ kandy korn ’, extra sweet ) were planted in 2 - inch pots . seedlings were germinated under 16 - hour day / 8 - hour night greenhouse conditions . plants were placed outdoors and received 5 - 6 hours of natural , direct light . eighteen days after planting , seedlings received one of two treatments . treatment 1 ( n = 11 ): foliar spray with water — control treatment 2 ( n = 12 ): foliar spray of 1 mm mdhj in water . plant leaves from both treatments were sprayed until the point of drip and allowed to air dry before being randomly combined into the same growing tray ( to provide plants from both treatments with identical growing conditions ). because mdhj has relatively low solubility in water , the mdhj treatment solution / suspension was shaken vigorously before the mdhj was applied to the plants . plants were observed and visible leaf senescence recorded 6 days after the single treatment . plants were scored according to presence or absence of senescence on any leaf of the plant . table 6 contains the results . as shown in table 6 , 64 % of control plants ( treatment 1 ) exhibited visibly senescing leaves as indicated by yellowing of the leaf , whereas only 27 % of the plants that received foliar mdhj treatment ( treatment 2 ) exhibited yellowing . of the plants with senescing leaves , only one leaf per plant had senescence ( 10 %) in the treatment 2 group . in treatment 1 , three of the seven ( or 43 %) plants showed yellow leaves on two leaves per plant . the remaining four plants showed senescence on one leaf ( table 1 ). in addition to the presence or absence of senescence , the severity of senescence , as indicated by the average percent leaf area that is yellow , was greater in plants in treatment 2 than treatment 1 . senescing leaves in treatment 2 plants showed a mean of 15 % yellow per leaf . in contrast , senescing leaves in the treatment 1 group had a mean of 43 % of the leaf area exhibiting senescing . while the invention has been described with respect to certain embodiments and examples , the description is intended to be illustrative , rather than limiting . modifications and changes may be made within the scope of the invention , which is defined by the appended claims .
methods for reducing leaf senescence in plants or portions thereof by treating them with a solid preparation of methyl dihydrojasmonate are disclosed , as are appropriate solid preparations of methyl dihydrojasmonate . the solid preparations may be applied , for example , to the roots or to the growth medium of the plants .