The effect of elevated CO<sub>2</sub> concentration on leaf chlorophyll and nitrogen contents in rice during post-flowering phases

Abstract

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 µmol mol-1) in open top chamber (OTC), at ambient CO2 concentration (∼ 365 µmol mol-1) 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 contents were highest at the time of flowering and thereafter it started to decline. The rate of decline in Chl and N contents was faster in plants grown under CE mostly in later part of growth. Irrespective of treatment difference, flag leaf contained the highest amount of Chl and N than penultimate and third leaf. The higher PN was observed in leaves under CE than in the leaves in other two growing conditions. Considering growth stage, PN was the highest at flowering which reduced at the later part of growth due to degradation of Chl and N content of the leaf. Under CE it was 40.02 µmol m-2 s-1 at flowering and it reduced to only 14.77 µmol m-2 s-1 at maturity stage. The beneficial effect of CE in increasing leaf PN may be maintained by applying extra dose of nitrogen at the later stages of plant growth.