Photosynthesis, Respiration and Stomatal Conductance in Two Species of Brassica Under Water Stress

The effect of water stress on photosynthesis and respiration was studied in two species of Brassica. Water stress was created by withholding irrigation at different growth and developmental stages. Under controlled conditions, photosynthetic rates were higher in Brassica juncea fraya) than in Brassica campestris (brown sarson). However, the redaction in photosynthesis was more in raya than in brown sarson with decreasing leaf water potential and it was more daring later growth stages. Stomatal conductance also followed similar trends. Decreasing leaf water potential resulted in increased rates of dark respiration in both the species. Carbon dioxide compensation point was also found to increase with the decrease in leaf water potential, which was more during later growth and developmental stages in both the species. The recovery in photosynthesis, dark respiration and CO₂ compensation point was better in brown sarson than in raya which could be one of the reasons for better performance of brown sarson under limited moisture conditions.