Dioecious plants play an important role in terrestrial ecosystems. Because of different resource demands, and different resource strategies, males and females may exhibit sexual segregation and environment-related sex ratio bias. Male plants are more responsive to an elevated CO₂ concentration and less sensitive than females when grown under various stresses including those due to salinity. However, the sex-dependent responses of dioecious plants to stress at an elevated CO₂ concentration are less well documented.

Populus yunnanensis Dode.,a native dioecious woody plant in southwestern China, the majority of are males and females are rare in the field, was employed as a model species to study sex-specific morphological, physiological and biochemical responses to elevated CO₂ and salinity by Prof. LI CHUNYANG’ team from Chengdu Institute of Biology recently. The cuttings of different sexes were exposed to two CO₂ regimes (ambient CO₂ and double ambient CO₂) and two salt treatments (0 and 50 mm NaCl) in growth chambers at the Maoxian Field Ecological Station.

While, they found that males exhibited greater down-regulation of net photosynthesis rate (Anet) and carboxylation efficiency (CE) than females at elevated CO₂, whereas these sexual differences were lessened under salt stress.

On the other hand, salinity induced a higher decrease in Anet and CE, more growth inhibition and leaf Cl- accumulation, and more damage to cell organelles in females than in males, whereas the sexual differences in photosynthesis and growth were lessened at elevated CO₂. However, elevated CO₂ exacerbated membrane lipid peroxidation and organelle damage in females but not in males under salt stress.

Their results provide evidence for different adaptive responses between plants of different sexes exposed to elevatedCO₂and salinity, and infer as the global CO₂ concentration increases, although the sexual biasofP. yunnanensis is likely to decrease but the populations will degenerate as a result of photosynthesis acclimation and aggravated salt stress. More results entitled " Sex-specific responses of Populus yunnanensis exposed to elevated CO2 and salinity " have been published in PHYSIOLOGIA PLANTARUM in April of 2013.