Abscisic Acid Application Increases the Water Use Efficiency of Potted Lettuce Plants

As water for agricultural irrigation becomes less available, the importance of water use efficiency (WUE) of crops is increasing.  There may soon be a paradigm shift in regard to yield considerations from yield per acre to yield per unit of water consumed to grow the crop.  Valent BioSciences Corporation recently commercialized abscisic acid (S-ABA) for the enhancement of color development of red table grapes with a product called ProTone®.  S-ABA has long been known to reduce transpiration of treated plants.  The objective of this research is to determine the effect of S-ABA on WUE.  In our studies, we have investigated the use of foliar application of S-ABA can improve the WUE of potted Red Romaine Lettuce plants.  Lettuce seedlings were grown in a greenhouse in 2.1-L pots filled with Promix BX that were watered to saturation, allowed to drain for one hour, and then weighed.  Evapotranspiration (ET) was determined gravimetrically twice a week, and the plants were irrigated with 25%, 50%, 75%, or 100% of the average ET for that treatment.  On the day after each irrigation, six plants from each irrigation level were sprayed with 2.5 ml of 0.05% Latron B 1956 surfactant per plant and six plants from each irrigation level were sprayed with 2.5 ml of 100 ppm S-ABA plus 0.05% Latron B 1956.  After 3 weeks, the lettuce shoots were excised and weighed.  Fresh shoot weight was directly related to irrigation level.  WUE (fresh shoot weight per irrigation volume) increased with decreasing irrigation level.  As irrigation decreased from 100 to 25% ET, WUE increased from 17.2 to 25.5 grams fresh shoot weight per liter of irrigation.  At each irrigation level, application of S-ABA increased WUE.  These results demonstrate the potential for the use of foliar S-ABA treatments to reduce water needed to grow lettuce under a wide range of irrigation levels.