The effect of elevated CO2 concentration on leaf chlorophyll and nitrogen contents in rice during post-flowering phases

The effect of elevated CO2 concentration (CE) on leaf chlorophyll (Chl) and nitrogen (N) contents and photosynthetic rate (PN) was evaluated during the post-flowering stages of rice grown at CE (570+/-50 micromol/mol) in open top chamber (OTC), at ambient CO2 concentration (365 micromol/mol) in OTC and at open field. Thirty-five day old seedlings were transplanted in OTCs or in field and allowed to grow till maturity. Chl and N concentrations were highest at the time of flowering, thereafter they started to decline. Irrespective of the treatment used, flag leaf contained higher concentrations of Chl and N than penultimate and third leaves. Higher PN was observed in leaves under CE than under the two other conditions tested. Under CE treatment, PN was 40.02 micromol/square m/s at flowering and 14.77 micromol/square m/s at maturity. The beneficial effect of CE may be maintained by applying extra doses of N after flowering.