Leaf gas exchange and δC in cowpea and triticale under water stress and well-watered conditions.

Leaf gas exchanges play a critical role in determining crop productivity as they control both CO gain and water loss. CO gain and water loss influence water use efficiency (WUE) and carbon isotope composition (δC). Responses in leaf gas exchanges to water stress are species-specific. However, the extent of this variation in C3 crops is less studied. A field study was carried out to investigate the influence of water stress on leaf gas exchanges of triticale and cowpea. Crops were grown under water stress and well-watered conditions and leaf gas exchanges were determined at flowering. The results showed that triticale maintained a higher stomatal conductance (), transpiration rate() and intercellular CO concentration () compared to cowpea but did not differ in photosynthetic rate(). As a result, triticale discriminated against C more than cowpea. These results suggest a higher influence of on δC than . Despite triticale maintaining higher rates of , and , it had lower WUE compared to cowpea. Consequently, triticale grain yield was more sensitive to water stress than cowpea. The findings of this study showed significant variation in leaf gas exchanges and δC between two drought-tolerant C3 crops suggesting differences in their response mechanism to water stress.