Discrimination against 13CO2 in leaves, pod walls, and seeds of water-stressed chickpea

The rate of photosynthesis (P-N) in leaves and pods as well as carbon isotope content in leaves, pod walls, and seeds was measured in well-watered (WW) and water-stressed (WS) chickpea plants. The P-N, on an area basis, was negligible in pods compared to leaves and was reduced by water stress (by 26%) only in leaves. WS pod walls and seeds discriminated less against (CO2)-C-13 than did the controls. This response was not observed for leaves as is usually the case. Pod walls and seeds discriminated less against (CO2)-C-13 than did leaves in both WW and WS plants. Measurement of carbon isotope composition in pods may be a more sensitive tool for assessing the impact of water stress on long-term assimilation than is the instantaneous measurement of gas exchange rates.