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The Effect of Elevated Co2 Concentration on Leaf Chlorophyll (chl)and Nitrogen Contents in Rice During Post-flowering Phases

M. Moynul Haque
Department of Agronomy, BSMR Agricultural University, Salna, Gazipur, Bangladesh

A. Hamid
Plant Physiology Division, BRRI, Joydebpur, Gazipur, Bangladesh

M. Khanam
Plant Physiology Division, BRRI, Joydebpur, Gazipur, Bangladesh

D. K. Biswas
Agronomy Division, BARl, Joydebpur, Gazipur, Bangladesh

M.A. Karim
Agronomy Division, BARl, Joydebpur, Gazipur, Bangladesh

Q.A. Khaliq
Agronomy Division, BARl, Joydebpur, Gazipur, Bangladesh

M.A. Hossain
Agronomy Division, BARl, Joydebpur, Gazipur, Bangladesh

D.C. Uprety
Plant Physiology Division, lARl, New Delhi, lndia

Abstract/ Executive Summary:

The effect of elevated CO₂ concentration (CE) on leaf chlorophyll (Chl) and nitrogen (N) contents and photosynthetic rate (P_N) 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 P_N was observed in leaves under CE than in the leaves in other two growing conditions. Considering growth stage, P_N 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 P_N may be maintained by applying extra dose of nitrogen at the later stages of plant growth.

Keywords: Open top chamber, Photosynthesis, Oryza sativa L.

Location: Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur

Start Date: 00-00-2000

End Date: 00-00-2000

Program Area: Crop-Soil-Water Management

Commodity: Rice

Objectives:

To evaluates the effect of CE on the changes in leaf Chl and N concentrations in relation to P_N during the post- flowering phases in rice plants.

Methodology:

An experiment was conducted at the Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur (Bangladesh) during the wet season of 2000. 35-d-old seedlings of rice (Oryza sativa L. cv. BRRldhan39) were transplanted in OTC placed on a previously prepared lowland. Details of the construction and operation of OTC have been provided elsewhere. In one chamber CO₂ concentration was raised to 570 ± 50 µmol mol^-1 while in another chamber ambient CO₂ concentration, i.e., ~360 µmol mol^-1 was maintained. Single seedling per hill was used. Seedlings were also transplanted in a plot of similar dimension in the open field close to the OTC's as control treatment. The diameter of the chamber was 3 m and 280 hills of rice were accommodated maintaining a planting configuration of 25 x 10 cm. A fertilizer dose of 90 kg , 20 kg P, 60 kg K, 20 kg S and 3.5 kg Zn was used. Entire amount of all the fertilizers excepting N was applied prior to transplanting while N was applied in three split doses at 4, 21, and 52 d after transplanting. Adequate measures were taken to keep the insect pest infestation and weed growth to a minimum. Leaf Chl and N concentrations were determined non- destructively using SPAD meter. SPAD values were transformed into Chl and N contents based on standard curves determined previously analyzing a large number of leaf samples representing wide ranges of Chl and N contents. Leaf samples were analyzed for Chi content and N contents using Kjeldahl procedure. SPAD values were taken on flag leaf, penultimate leaf and the third leaf during the post-flowering period until maturity. P_N of flag leaves were determined on four occasions during post- flowering stages with a portable photosynthesis device. Measurements were taken on clear sunny days between 10:00 and 13 :00. Replicated data were analyzed statistically and mean values were used with ± standard errors.

Source of Information: BIOLOGIA PLANTARUM 50 (I): 69-73, 2006

Article Link (Online Journal):

Funding Source:

1.

Budget:

Total Budget (Tk.) :

Achievement/Findings:

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^-2S^-1 at flowering and it reduced to only 14.77 µmol m^-2 S^-1at maturity stage. The beneficial effect of CE in increasing leaf P_N may be maintained by applying extra dose of nitrogen at the later stages of plant growth.

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