Accumulation and turnover of abscisic acid in osmotically stressed cotton leaf tissue in relation to temperature

Abstract

Leaf discs of cotton ( Gossypium hirsutum L. cv. Deltapine 70) were osmotically stressed by floating them on solutions of polyethylene glycol 8000. The tissue produced copious amounts of abscisic acid (ABA) when stressed. Accumulation of ABA depended strongly upon temperature during the incubation, displaying a maximum at 20°C. At 35°C, the amount of ABA accumulated after 24 h was 45–80% less than at 20°C. Temperature did not affect leakage of ABA into the medium. Turnover rate of [ 14C]ABA was more than 3 times greater at 35°C than at 20°C. This rapd turnover at 35°C could account for the decreased ABA accumulation. Three 14C-containing metabolites of ABA were extracted from the tissue. At 20°C, two of these accumulated and retained substantial 14C over 16 h. At 35°C, though, the 14C in one of these compounds was almost completely lost during the last 8 h of the incubation. Although the metabolites are not identified, the results show some specific effects of temperature on ABA metabolism. The strong effect of temperature on ABA accumulation may contribute to patterns of ABA-dependent processes (such as stomatal closure) during water stress.