Foliar ABA Sprays Controlled Growth and Improved Survival and Desiccation Tolerance of Vegetable Transplants

In most vegetable production systems, transplanting with containerized transplants or plugs is the most common practice used to maximize stand establishment, shorten the growing period and enhance earliness in production. Under field conditions of high evapotranspiration demand commonly present in many southern regions of the USA, transplants are exposed to transient drought stress, even under well-irrigated conditions. Our previous research documented the efficacy of foliar application of abscisic acid (ABA) in mitigating the negative effects of drought stress on pepper. In these experiments we evaluated spray ABA concentrations and frequency of application as a growth-controlling agent for 'mature' (ready-to-go) watermelon and pepper transplants in the greenhouse and its effect on survival after transplanting. We also evaluated the effects of ABA concentration on growth and physiological responses of melon transplants subjected to a short (3-day) desiccation period. Overall, there was a trend for ABA to reduce undesirable excess shoot growth with an increase in root: shoot ratio. Positive survival trends were measured after field transplanting of watermelon in two field environments and pepper in one environment. In melon transplants, foliar ABA application at 500 mg.L-1 was effective in maintaining plant water status and enhancing drought stress tolerance. Understanding how ABA differentially affects seedling growth, physiology and stand establishment is crucial to develop hormonal conditioning treatments to mitigate post transplanting stress.