Effect of salinity on photosynthesis and leaf carbohydrate content in two wheat (Triticum aestivum L.)‎ cultivars

الملخص EN

Plant growth is the result of many integrated and regulated physiological processes.

Salinity, which is one of the major abiotic stresses, causes alterations in a wide range of physiological, biochemical and molecular processes in plants.

Therefore, a factorial pot experiment was conducted based on randomized complete blocks design in green house condition to investigate the effect of salt stress on photosynthesis, leaf carbohydrate concentration and daytime leaf carbon budget of two wheat cultivars (CR and Ghods) over photoperiod.

Plants were exposed to 0, 50, 150 and 250 mM salinity (NaCl and CaCl2 in 5:1 molar ratio) for 60 days.

Measurements were done on fully youngest expanded leaves.

Salinity caused a significant reduction in leaf net photosynthesis consequently total carbon fixed in both cultivars.

Plants grown at low (50 mM) and high (250 mM) levels of salinity had net photosynthesis rates of 78.9 and 20.6% respectively compared to the control.

However, salt stress significantly increased soluble carbohydrate concentration in both cultivars from 50 mM in the control to 150 mM at highest salt treatment.

Starch concentration of leaves also increased with increasing salinity.

As salinity had inverse effect on photosynthesis process, the total carbon fixed decreased with increasing salinity.

At control condition the total carbon fixed by leaves of cultivars CR and Ghods were 255.2 and 225.3 mmol C m-2 leaf respectively, while at high level salt concentration (250 mM) only 95.4 (CR) and 63.1 (Ghods) mmol C m-2 fixed.

Daytime amount of carbon translocated from leaf was reduced by salinity.

However, CR exported greater amount of carbon from leaf than Ghods.