The effect of drought stress on energy dissipation and antioxidant enzyme system in two sweet sorghum inbred lines (M-81E and Roma) was investigated. Results showed that the germination indicator increased more in M-81E than that in Roma under rehydration. Under drought stress, both the maximal photochemical efficiency of PSII (F v /F m ) and oxidoreductive activity ( I/I 0 ) of Roma decreased more than those in M-81E. Relative to F v /F m , the I/I 0 decreased markedly, which indicated that PSI was more sensitive to drought stress than PSII. Increases in the reduction state of Q A (1 -q p ), nonphotochemical quenching (NPQ) and minimal fluorescence yield of the dark-adapted state (F 0 ) were greater in Roma than those in M-81E; meanwhile, the H 2 O 2 content was lower in M-81E than that in Roma. Our results suggested that the photoinhibition might be related to the accumulation of reactive oxygen species (ROS). The antioxidant enzyme system and energy dissipation of M-81E could respectively increase drought tolerance by eliminating ROS and excess energy more efficiently than that of Roma.

Green leaf volatiles play vital roles in plant biotic stress; however, their functions in plant responses to abiotic stress have not been determined. The aim of this study was to investigate the possible role of (Z)-3-hexeny-1-yl acetate (Z-3-HAC), a kind of green leaf volatile, in alleviating the salinity stress of peanut ( Arachis hypogaea L. ) seedlings and the underlying physiological mechanisms governing this effect. One salt-sensitive and one salt-tolerant peanut genotype were primed with 200 μM Z-3-HAC at the 4-week-old stage before they were exposed to salinity stress. Physiological measurements showed that the primed seedlings possessed higher relative water content, net photosynthetic rate, maximal photochemical efficiency of photosystem II, activities of the antioxidant enzymes, and osmolyte accumulation under salinity conditions. Furthermore, the reactive oxygen species, electrolyte leakage, and malondialdehyde content in the third fully expanded leaves were significantly lower than in nonprimed plants. Additionally, we found that application of Z-3-HAC increased the total length, surface area, and volume of the peanut roots under salinity stress. These results indicated that the green leaf volatile Z-3-HAC protects peanut seedlings against damage from salinity stress through priming for modifications of photosynthetic apparatus, antioxidant systems, osmoregulation, and root morphology.