Soil salinity alters the sexual responses to elevated CO2 and temperature in growth and leaf traits of a dioecious plant

Abstract

This study elucidated whether the adverse effect of soil salinity is different between Populus yunnanensis Dode males and females under climate change. We hypothesized that the magnitude and direction of sexual responses to elevated CO2 and warming will be modified by soil salinity in dioecious plants. Populus yunnanensis was employed as a model species to study sexual responses in growth, photosynthesis, carbohydrate accumulation, and C and N allocation to elevated CO2 and temperature under soil salinity. Cuttings were divided into control and salt groups and were exposed to two CO2 regimes (ambient CO2 and double ambient CO2) and two temperature regimes (ambient temperature and ambient temperature + 2.2 °C) in growth chambers. Males exhibited a greater down-regulation of the net photosynthesis rate (Anet) than did females at elevated CO2, primarily due to their poorer carbon sink–source balance and lower N availability. In the salt group, unlike in the control group, warming showed a positive effect on the growth of both females and males, and elevated CO2 and temperature had a positive synergistic effect on the growth of both sexes. Sexual growth differences under soil salinity were reduced by elevated CO2, temperature, and a combination of both. These results provide evidence for sexually different responses to environmental changes in dioecious plants and support the idea that sex ratios will shift under climate change.