Response of photosynthetic performance, water relations and osmotic adjustment to salinity acclimation in two wheat cultivars

Experiment was conducted to identify the impacts of the salinity acclimation process on the photosynthetic efficiency, osmotic adjustment, membrane integrity, and yield components in two wheat cultivars differing in their salinity tolerance. The design of the experiment was factorial randomized block, where genotype is factor 1 and acclimation treatments represent factor 2. Genotypes were grown from emergence to 30 days after sowing (DAS) by irrigating with tap water [electrical conductivity (EC) of 0.776 dS m−1]. Thereafter, both the genotypes were divided into two groups and exposed to either irrigation with sublethal level of salinity EC of 2.09 or 3.76 dS m−1 for 21 days. At booting stage (65 DAS), both groups were subjected to lethal level of salinity stress EC of 12 dS m−1 for 21 days, followed by irrigation with tap water till maturity. Non-acclimated plants were irrigated with tap water from emergence to 65 days, then directly irrigated with lethal level of salinity for 21 days, followed by irrigation with tap water till maturity. The control plants were continuously irrigated with tap water from emergence until maturity. The non-acclimated plants had decreased electron transport rates at the donor and acceptor side of PSII and PSI in Giza 168, and decreased electron transport rates at PSII acceptor side in Sakha 8 compared to control plants. In both genotypes, the non-acclimated plants had decreased chlorophyll a, b, carotenoid, proline and total soluble sugar concentration, relative water content, membrane stability index, yield and yield components compared with acclimated plants. While, osmotic potential and lipid peroxidation showed an opposite trend. Overall, acclimation treatment (EC of 2.09 dS m−1) during vegetative stage alleviated the inhibitory effects of lethal level of salinity stress at booting stage through enhanced photosynthetic efficiency and osmotic adjustment, resulting in increased membrane integrity, biomass production and grain yield than in non-acclimated plants.