Sex-related differences of two ecologically divergent Salix species in the responses of enzyme activities to atmospheric CO2 enrichment

Sex-related differences in the responses of plants to CO2 enrichment are still rarely studied. In this study, we examined the effects of elevated atmospheric CO2 (720 μmol mol−1) on the activities of polyphenoloxidases (PPOs) and guaiacol peroxidases (PODs) in male and female plants of two ecologically divergent willow species Salix repens and S. phylicifolia. We detected that females invested more in PPO-based defence than did males, whose PPO activity decreased as a result of CO2 enrichment. Moreover, we found that the inherently slow-growing S. repens had markedly higher POD activity than did the more rapid-growing S. phylicifolia. The PODs of these two species also differed in their biochemical properties.