Mechanisms of energy dissipation in peanut under water stress

Effect of drought on the mechanisms of energy dissipation was evaluated in two-month-old Arachis hypogaea cvs. 57-422, 73-30, and GC 8-35. Plants were submitted to three treatments: control (C), mild water stress (S I), and severe water stress (S2). Photosynthetic performance was evaluated as the Hill and Mehler reactions. These activities were correlated with the contents of the low and high potential forms of cytochrome (cyt) b(559), plastoquinone, cyt b(563), and cytf Additionally, the patterns of carotenoids and chlorophylls (Ch1s), as well as the alterations of Chl a fluorescence parameters were studied. Under mild water stress the regulatory mechanism at the antennae level was effective for 57-422 and GC 8-35, while in the cv. 73-30 an overcharge of photosynthetic apparatus occurred. Relative to this cv., under S I the stability of carotene and the dissipative cycle around photosystem (PS) 2 became an important factor for the effective protection of the PS2 reaction centres. The cyclic electron flow around PSI was important for energy dissipation under S 1 only for the cvs. 57-422 and 73-30.