Effect of different levels of sodium chloride and photosynthetic photon flux density on some physiological traits of two barley cultivars

In majority of southern provinces of Iran, soil salinity is a growing problem particularly in the irrigated agricultural areas and has been found to reduce barley yields. In order to investigate the effect of various levels of sodium chloride (Nacl) on some physiological characteristics of two barley (Hordeum vulgare L.) cultivars viz., Afzal (a salt tolerant variety) and Reyhan (a salt sensitive variety), an experiment was conducted with salinity levels of 0, 4, 8 and 12 dS m–¹ in four replications in a controlled environment of the greenhouse during 2007–2008. The physiological parameters measured were Photosynthetic Photon Flux Density (PPFD) incident on leaf surface, photosynthesis rate (A), sub-stomatal CO₂(Ci), transpiration rate(E) and stomatal conductance of CO₂ (gs). The results showed that PPFD increased during the period between 8 to 14 O'clock. At both stem elongation and anthesis stages photosynthesis rate, transpiration rate, stomatal conductance and intercellular CO₂ content increased consistently between 8 to 12 O'clock periods. However, the above mentioned traits were found to decline from 12 to 14 O'clock due to the increasing leaf temperature. The decreasing in photosynthesis in saline conditions was attributed to excess Na⁺ and K⁺ ions. The increasing of these ions in vacuole has led to the increase in cytoplasm and declining photosynthesis processes. A substantial reduction in photosynthesis, stomatal conductance and transpiration rate was detected due to exposure to salt stress. In general, the photosynthesis rate, transpiration rate, stomatal conductance and intercellular CO₂ of salt tolerant Afzal variety were found to be higher than salt sensitive Reyhan variety. Thus, it can be stated from the investigation that due to its less adverse effect on salinity, Afzal cultivar is found more suitable for cultivation in the saline soils of the Iran province.