Short-term responses of stomatal conductance for screening wheat cultivars (Triticum aestivum L.(differing in salt tolerance for osmotic stress tolerance

Salinity affects plant growth by the osmotic stress of salt around the roots as well as by toxicity caused by excessive accumulation of salt in leaves. An investigation was set up to study the effects of salt stress on stomatal conductance, growth rate and the relation between them.Six selected wheat cultivarsthat were previously identified as contrasting in salt stress tolerance (Roshan, Kavir, Bam, Gaspard, Shiraz and Qods) with three salinity levels (0, 100 and 200 mM NaCl) were used in a pot experiment, using a factorial experiment based on completely randomized design with three replications. Stomatal conductance was reduced at 1, 10 and 20 days after plants were exposed to salinity, and a similar result was obtained for relative growth rate at 10 and 20 days after exposure to salt. However, the reduction was greater in salt sensitive cultivars as compared with tolerantones. Results showed that stomatal conductance acts as a tool for screening of osmotic stress tolerance which was reduced immediately after the onset of salinity, while relative growth rate was declined in the first 10 days exposure to salt. Cultivars with high stomatal conductance maintained a higher growth rate under salt stress. High stomatal conductance in short-term salinity exposure was related to high growth rate over a long period of time. A positive relationship between stomatal conductances with relative growth rate indicated that stomatal conductance can be a reliable indicator of the photosynthesis and growth rate and can be considered as a sensitive indicator of the osmotic stress toleranceand other abiotic stresses.