Abstract:
The present invention describes a method for increasing the drought tolerance of selected ornamental plants comprising administering abscisic acid (ABA) or its salts to said plants.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method of delaying the wilting of drought stressed ornamental plants. 
     BACKGROUND OF THE INVENTION 
     Abscisic acid (ABA) is a natural occurring hormone found in all higher plants (Cutler and Krochko. 1999. Trends in Plant Science. 4: 472-478.; Finkelstein and Rock. 2002. The  Arabidopsis  Book. ASPB, Monona, Md., 1-52). ABA is involved in many major events of plant growth and development including dormancy, germination, bud break, flowering, fruit set, growth and development, stress tolerance, ripening, abscission and senescence. One of the roles of ABA is the regulation of water relations in plants through the control of stomata opening and closure. 
     Most plants have improved drought tolerance following application of ABA, but plants differ in their sensitivity to applied ABA. Different types of ornamental plants differ in both the extent of increased drought tolerance and potential for undesirable side effects from ABA treatment. Others have reported ABA effects on transpiration of whole plants or excised plant parts and yellowing of excised plant parts. Foliar application of ABA reduced the transpiration of potted Poinsettia plants (Krizek, et al., 1986, Influence of soil moisture and ABA acid pretreatment in modifying SO 2  sensitivity in poinsettia, J. Amer. Hort. Sci. 111:446-450). ABA applied through the petiole of excised Coleus leaves reduces their transpiration rate compared to excised leaves standing in water (Rajapakse, et al., 1988, Transpiration and water use of potted floricultural plants under low light conditions, J. Amer. Hort. Sci. 113:910-914). Treatment of Geranium cuttings causes the undesirable effect of leaf yellowing (Mutui et al., 2005, Journal of Horticultural Science &amp; Biotechnology 80: 453-550). There are no previous reports that could be used to determine which ornamental plants benefit from ABA application in terms of reduced transpiration rates without unacceptable risk of ABA-induced leaf yellowing or abscission. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to the treatment of an ornamental plant selected from the group consisting of Celosia, Chrysanthemum, Coleus, Cosmos, Cuphea, Dianthus, Euryops, Hydrangea, Impatiens, Lantana, Marigold, New Guinea Impatiens, Pentas, Petunia, Salvia and Snapdragon to improve drought tolerance with only slight potential for undesirable side effects comprising applying an effective amount of ABA or a salt thereof to said plants. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The applied concentration of ABA can vary widely depending on the water volume applied to plants as well as other factors such as the plant age and size, and plant sensitivity to ABA, but is generally in the range of about 1 ppm to about 10,000 ppm, preferably from about 10 to about 1000 ppm. 
     It is also contemplated that salts of ABA may be utilized in accordance with the present invention. 
     As used herein, the term “salt” refers to the water soluble salts of ABA. Representative such salts include inorganic salts such as the ammonium, lithium, sodium, calcium, potassium and magnesium salts and organic amine salts such as the triethanolamine, dimethylethanolamine and ethanolamine salts. 
     Other ingredients such as surfactants can be used in compositions useful in the present invention. 
     The presently preferred surfactant for ABA performance is Brij 98 (polyoxyethylene (20) oleyl ether) available from Uniqema (Castle, Del.). Other surfactants that are also useful in the present invention, including but not limited to other surfactants in the Brij family (polyoxyethylene fatty alcohol ether) from Uniqema (Castle, Del.); surfactants in the Tween family (Polyoxyethylene sorbitan esters) from Uniqema (Castle, Del.); Silwet family (Organosilicone) from Union Carbide (Lisle, Ill.); Triton family (Octylphenol ethoxylate) from The Dow Chemical Company (Midland, Mich.); Tomadol family (ethoxylated linear alcohol) from Tomah3 Products, Inc. (Milton, Wis.); Myrj family (Polyoxyethylene (POE) fatty acid esters) from Uniqema (Castle, Del.); Span family (Sorbitan ester) from Uniqema (Castle, Del.); Trylox family (Ethoxylated Sorbitol and Ethoxylated Sorbitol Esters) from Cognis Corporation (Cincinnati, Ohio). These surfactants, commercially available for agricultural use, are also useful in the present invention: Latron B-1956 (77.0% modified phthalic/glycerol alkyl resin and 23.0% Butyl alcohol) from Rohm &amp; Haas (Philadelphia, Pa.); Caspil (Blend of Polyether-polymethylsiloxanecopolymer and nonionic surfactant) from Aquatrols (Paulsboro, N.J.); Agral 90 (Nonyl phenol ethoxylate) from Norac Concept. Inc. (Orleans, Ontario, Canada); Kinetic (99.00% proprietary blend of polyalkyleneoxide modified polydimethylsiloxane and nonionic surfactants) from Setre Chemical Company (Memphis, Tenn.); and Regulaid (90.6% 2-butoxyethanol, poloxalene, monopropylene glycol) from KALO, Inc. (Overland Park, Kans.). 
     Many different commercial ornamental crops were obtained from local retailers, or from wholesale nurseries, and transported to a greenhouse for testing. Plants were watered to saturation and allowed to stand and drain for about one hour. Plants were selected for uniformity based on leaf area and arranged in a randomized complete block design, or a completely randomized design, on the greenhouse bench. The plants were sprayed or drenched with water or treatment solution equaling about 5-10% of the pot volume. The plants were held without irrigation until all the plants wilted to a point when they were determined to be unmarketable. The plants were rated daily for the extent of wilting on a scale from 1 for no wilting to 4 for complete wilting. A rating of 2.5 was the point at which a plant was determined to be unmarketable and the previous day was recorded as the marketable life of that plant in days. The plants were rated for the extent of lower leaf yellowing or leaf or flower abscission on a scale from 1 for no yellowing or abscission to 4 for complete yellowing or abscission. A rating of 2.5 was the point at which a plant was determined to be unmarketable. 
     The present invention may be illustrated by the following representative example. 
     Example 1 
     Ornamental bedding plants were treated (sprayed or drenched) with water or 250 ppm abscisic acid (S-ABA; ABA; S-(+)-abscisic acid; +-ABA, (+)-(S)-cis,trans-abscisic acid,(+)-(S)-cis,trans-ABA; S-ABA; (S)-5-(1-hydroxy-2,6,6,-trimethyl-4-oxo-2-cyclohexen-1-yl)-3-methyl-(2Z,4E)-pentadienoic acid; CAS no. 21293-29-8) and then irrigation was withheld until all the plants wilted. Plants were individually rated on a daily basis for degree of wilting and other undesirable characteristics like leaf yellowing. 
     In Table 1, plants were drenched with water or a 250 ppm ABA solution, and held in a greenhouse without irrigation. 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Classification of ornamental plants by ABA effects on drought 
               
               
                 tolerance and potential for undesirable side effects of 
               
               
                 lower leaf yellowing or leaf or flower abscission. 
               
             
          
           
               
                   
                   
                   
                   
                 Leaf or 
               
               
                 Classifica- 
                   
                 Market life 
                 Lower leaf 
                 flower 
               
               
                 tion 1   
                 Plant 
                 extension 2   
                 yellowing 3   
                 abscision 4   
               
               
                   
               
             
          
           
               
                 Favorable 
                 
                   Celosia 
                 
                 2.3 
                 1 
                 1 
               
               
                 Favorable 
                 
                   Chrysanthemum 
                 
                 2.0 
                 1 
                 1 
               
               
                 Favorable 
                 
                   Coleus 
                 
                 2.3 
                 1 
                 1 
               
               
                 Favorable 
                 
                   Cosmos 
                 
                 1.4 
                 1 
                 1 
               
               
                 Favorable 
                 
                   Cuphea 
                 
                 2.3 
                 1 
                 1 
               
               
                 Favorable 
                 
                   Dianthus 
                 
                 1.6 
                 1 
                 1 
               
               
                 Favorable 
                 
                   Euryops 
                 
                 3.3 
                 1 
                 1 
               
               
                 Favorable 
                 
                   Hydrangea 
                 
                 3.4 
                 1 
                 1 
               
               
                 Favorable 
                 
                   Impatiens 
                 
                 2.0 
                 1 
                 1 
               
               
                 Favorable 
                 
                   Lantana 
                 
                 2.4 
                 1 
                 1 
               
               
                 Favorable 
                 Marigold 
                 1.9 
                 1 
                 1 
               
               
                 Favorable 
                 New Guinea 
                 3.3 
                 1 
                 1 
               
               
                   
                 
                   Impatiens 
                 
               
               
                 Favorable 
                 
                   Pentas 
                 
                 2.8 
                 1 
                 1 
               
               
                 Favorable 
                 
                   Petunia 
                 
                 3.5 
                 1.9 
                 1 
               
               
                 Favorable 
                 
                   Salvia 
                 
                 1.9 
                 1 
                 1 
               
               
                 Favorable 
                 Snapdragon 
                 1.5 
                 1.3 
                 1 
               
               
                 Unfavorable 
                 
                   Agapanthus 
                 
                 0 
                 2 
                 1 
               
               
                 Unfavorable 
                 Alyssum 
                 0 
                 3.5 
                 1 
               
               
                 Unfavorable 
                 
                   Calibrachoa 
                 
                 0 
                 3 
                 1 
               
               
                 Unfavorable 
                 
                   Gazania 
                 
                 0 
                 3 
                 1 
               
               
                 Unfavorable 
                 
                   Lobelia 
                 
                 2.5 
                 3 
                 2.5 
               
               
                 Unfavorable 
                 Pansy 
                 1.6 
                 3 
                 1 
               
               
                 Unfavorable 
                 Poinsettia 
                 2.0 
                 3 
                 2.5 
               
               
                 Unfavorable 
                 Rose 
                 0 
                 4 
                 1 
               
               
                 Unfavorable 
                 
                   Vinca 
                 
                 2.5 
                 2.5 
                 3 
               
               
                   
               
               
                   1 Classification: Favorable = increased market life due to delayed wilting without the occurrence of unmarketable lower leaf yellowing or abscission, Unfavorable = presence of unmarketable lower leaf yellowing or abscission. 
               
               
                   2 Market life extension = days of additional market life compared to control plants due to delayed wilting. 
               
               
                   3 Lower leaf yellowing = average rating where 1 = no yellowing, 2.5 = unmarketable due to lower leaf yellowing, and 4 = severe lower leaf yellowing. 
               
               
                   4 Leaf or flower abscission = average rating where 1 = no leaf or flower abscission, 2.5 = unmarketable due to leaf or flower abscission, and 4 = severe leaf or flower abscission. 
               
             
          
         
       
     
     Many bedding plants like New Guinea Impatiens are very favorable candidates for ABA application because treated plants have much greater drought tolerance without any noticeable undesirable side effects. Other plants like Pansy are not favorable candidates for ABA application because even though the treated plants are more drought tolerant the undesirable effect of ABA-induced leaf yellowing often occurs. Other plants like Vinca are not favorable candidates for ABA application because even though the treated plants are more drought tolerant the undesirable effect of flower abscission often occurs. Still other plants like Calibrachoa are not favorable candidates because undesirable side effects like severe leaf yellowing occur before wilting symptoms develop in the control and treated plants.