Leaf Growth, Gas Exchange and Chlorophyll Fluorescence Parameters in Response to Different Water Deficits in Wheat Cultivars

Abstract

We investigated responses of wet climate (CY17) and dry climate (XN889) Trititcum aestivum L cultivars under 85, 55 and 25% field water capacity (FC). Less decrease in grain yield, relative water content, growth, gas exchange and chlorophyll fluorescence parameters indicated that XN889 was more drought-tolerant than CY17. At 55%FC, CY17 showed a lower net photosynthetic rate (Pn) than XN889 mainly due to stomatal closure. Stomatal closure was also observed in XN889, but its Pn was higher at 55%FC than at 85%FC. The higher Pn in XN889 may be associated with a higher chlorophyll content and resulting increase in photochemical quenching (qP), apparent electron transport rate, and effective quantum yield of photosystem II (PSII). Both cultivars showed photodamage at 25%FC, but XN889 showed less photodamage in terms of maximal PSII photochemical efficiency. XN889 showed higher qP and non-photochemical quenching than CY17, further demonstrating its superior drought tolerance.