Ambiol Preconditioning Can Induce Drought Tolerance in Abscisic Acid-deficient Tomato Seedlings

Abstract

Ambiol, a derivative of 5-hydroxybenzimidazole, has been well documented to function as a growth promoter, an antistress compound, and an antioxidant when applied as a seed preconditioning agent. However, evidence suggests that Ambiol decreases transpiration and promotes root growth similar to the phytohormone abscisic acid (ABA), leading to the development of the hypothesis that Ambiol promotes drought resistance through an ABA-dependent pathway. The effect of 0 mg·L−1 and 10 mg·L−1 was tested on wild-type tomato seedlings (Lycopersicon esculentum Mill. var. Scotia), ABA-deficient flacca tomato seedlings, and ABA-inhibited (with fluridone) tomato seedlings. In both fluridone-treated and flacca seedlings, Ambiol preconditioning resulted in significant increases in shoot growth, root growth, leaf area, and plant height consistent with gains experienced by wild-type tomatoes. In addition, flacca tomatoes experienced increases in photosynthesis and water use efficiency consistent with wild-type tomatoes. Ambiol was able to confer benefits to drought-stressed tomatoes in ABA-deficient and ABA-inhibited conditions, suggesting that Ambiol functions through an ABA-independent pathway.