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ABA to Enhance Stress Tolerance of Vegetable Transplants

High air temperatures coupled with dry winds and rapid soil drying conditions encountered in southern regions of the USA can greatly reduce stand establishment or impair early growth of vegetable transplants. Understanding the morphological and physiological responses during the transplant shock period can provide a basis for elucidating the complex mechanisms underlying transplant stress tolerance. The development of antitranspirant compounds aimed to reduce transpiration and/or to improve plant growth has broadened opportunities for research in vegetable species. We investigated the influence of plant growth regulators [abscisic acid (ABA) and aminoethoxyvinylglycine (AVG)], physical antitranspirants [AntiStress (AS), Transfilm (TS), and Vapor Gard (VG)] and method of application on the growth and physiology of pepper (Capsicum annuum), tomato (Lycopersicon esculentum) and artichoke (Cynara scolymus) seedlings exposed to one or two cycles of desiccation. In pepper, root application of ABA enhanced desiccation tolerance compared to foliar application. Leaf photosynthesis and conductance decreased upon ABA foliar application (up to 2000 mg L-1) ; however, photosynthesis rates recovered within a few days of application. Throughout two cycles of desiccation on pepper seedlings, ABA had a stronger effect in reducing stomatal conductance while increasing leaf water potential compared to AVG or physical antitranspirants. Plant water status was also significantly improved with ABA applied to tomato seedlings. Similar physiological responses were measured for artichoke seedlings following foliar ABA (1000 mg L-1) treatments. Our results suggest that exogenous ABA treatments are superior to AVG and film-forming antitranspirants. Abscisic acid can be an effective physiological tool to mitigate the negative effects of transplant shock and improve stand establishment of vegetable transplants.

abscisic acid; antitranspirants; pepper; photosynthesis; stand establishment; stomatal conductance; tomato

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