Association of the effects of elevated temperature and co2 on plant growth and leaf photosynthesis with changes in stomatal traits, leaf anatomy, and foliar carbohydrates in winter wheat (triticum aestivum l.)

We examined the effects of elevated CO2 concentration (e[CO2]), experimental warming (warming) and the two combined environmental factors (e[CO2] x warming) on plant biomass, stomatal characteristics, gas exchange, leaf anatomy, as well as the Rubisco activity and gene express of winter wheat with environmental growth chambers, where the temperature was set at 21/16 degrees C (day/night) or 26/21 degrees C and the [CO2] was controlled at 400 mu mol mol(-1) or 800 mu mol mol(-1), respectively. We found that the plant biomass and leaf photosynthesis were dramatically decreased by e[CO2] x warming (all p<0.05), although elevated temperature and [CO2] were not significantly altered biomass accumulation and leaf photosynthesis (all p>0.05). This down-regulated net photosynthetic rates (P-n) at e[CO2] x warming partially attributed to the limited effect of CO2 diffusion processes relating to the declined regularity of stomata distribution, as evidenced by the decrease of stomatal conductance (G(s)) at e[CO2] x warming. Additionally, accumulation of nonstructural carbohydrates in leaves of winter wheat can also contribute to the declines of plant biomass and P-n at e[CO2] x warming. These results indicate that the fertilization effect from CO2 enrichment can be lowered by experimental warming, and thus the potential risks of global change on the net primary productivity of agricultural ecosystems may be underestimated by current process-based ecological models.