Effects of short-term heat stress on oxidative damage and responses of antioxidant system in Lilium longiflorum

This paper aims to determine the changes in reactive oxygen species (ROS) and the responses of the lily (Lilium longiflorum L.) antioxidant system to short-term high temperatures. Plants were exposed to three levels of heat stress (37 degrees C, 42 degrees C, 47 degrees C) for 10 h when hydrogen peroxide (H2O2) and superoxide (O-2(-) production rate along with membrane injury indexes, and changes in antioxidants were measured. Compared with the control (20 degrees C), electrolyte leakage and MDA concentration varied slightly after 10 h at 37 degrees C and 42 degrees C, while increased significantly at 47 degrees C. During 10 h at 37 degrees C and 42 degrees C, antioxidant enzyme activities, such as SOD, POD, CAT, APX and GR, were stimulated and antioxidants (AsA and GSH concentrations) maintained high levels, which resulted in low levels of O-2(-) and H2O2 concentration. However, after 10 h at 47 degrees C, SOD, APX, GR activities and GSH concentration were similar to the controls, while POD, CAT activities and AsA concentration decreased significantly as compared with the control, concomitant with significant increase in O-2(-) and H2O2 concentrations. In addition, such heat-induced effects on antioxidant enzymes were also confirmed by SOD and POD isoform, as Cu/ZnSOD maintained high stability under heat stress and the intensity of POD isoforms reduced with the duration of heat stress, especially at 47 degrees C. It is concluded that in lily plants, the oxidative damage induced by heat stress was related to the changes in antioxidant enzyme activities and antioxidants.