Gas Exchange, Chlorophyll and Growth Responses of Betula Platyphylla Seedlings to Elevated CO2 and Nitrogen

Effects of elevated [CO2] and nitrogen nutrition on leaf gas exchange, chlorophyll content and growth in Betula platyphylla seedlings were studied. The seedlings were grown in the ambient [CO2] (AC, 350????mol mol-1) and elevated [CO2] (EC, 700????mol mol-1) growth chambers, with three levels of nitrogen: LN (0mmol L-1 N), MN (1.5mmol L-1 N) and HN (3mmol L-1 N). HN increased photosynthesis (Pmax), photochemical efficiency of PSII (Fv/Fm) and intercellular [CO2] (Ci) by 120%, 8% and 11% than the LN. EC significantly increased Pmax and Ci by 37% and 57% compared to the AC. The interaction of EC and LN was significant increased by 85% than the AC+MN, and could be attributed to both inhibition of photosynthetic light reactions and carboxylation activity of Rubisco. In AC and EC, total biomass were 3.2 and 5.1 times greater in HN compared to LN. Root biomass increased significantly in HN level under both AC and EC. Chlorophyll (Chl) a and Chl b increased with increasing N availability.