Sexual differences in defensive and protective mechanisms ofPopulus cathayanaexposed to highUV‐B radiation and low soil nutrient status

Abstract

Previous studies have indicated thatPopulus cathayanaRehder females are more sensitive and less tolerant to stressful environments than males, but it is still unknown whether there are sexual differences in defensive and protective traits under highUV‐B (HUVB) radiation and low soil nutrient status. In this study,P. cathayanawas employed as a model species to investigate sex‐related physiological and biochemical responses toUV‐B radiation under different soil nutrient conditions. Cuttings were exposed to twoUV‐B radiation regimes (ambientUV‐B radiation and decreasedUV‐B radiation) under two soil nutrient status (topsoil and deep soil) for 100 days over one growing season. Both HUVB radiation and low soil nutrient status induced greater decreases in plant growth, dry mass accumulation, gas exchange and leaf nitrogen use efficiency in females than in males, and greater increases in lipid peroxide and antioxidant enzyme activities, and secondary defense capacities in males than in females. Moreover, sexually different responses happened also in organelle ultrastructure. Our results showed that: (1) females suffered greater negative effects and exhibited lower defense capacities than did males under HUVB radiation, low soil nutrient status and their combination; (2) low soil nutrient status reduced plant's sensitivity to HUVB radiation by increasing allocation to defense and decreasing allocation to growth compared with high soil nutrient status. These results provide evidence that sexually different tradeoffs happen between growth and defense inP. cathayanaunder HUVB radiation and low soil nutrient status.