Response of biochemical traits and relative water content of two bread and durum wheat cultivars to silicon spraying under water stress conditions

In order to study the effect of silicon on biochemical traits, leaf relative water content and yield of two bread and durum wheat cultivars under late season water stress conditions, a split factorial experiment in a randomized complete block design was conducted in three replicates during 2017-2018 growing season. Treatments included of water stress in two levels included normal irrigation and water stress at the end of flowering, silicon (Si) spraying at 0, 1, 2, and 3 mM and two wheat cultivars consisted of Chamran as bread wheat and Shabrang as durum wheat. The results showed that the main effects of late seasonal water stress, cultivar and silicon on leaf relative water content (RWC), total chlorophyll, carotenoid content and yield were significant. Under water stress conditions, when plants exposed to 3 mM silicon RWC increased 50% compared to no silicon application conditions. Grain protein under water stress conditions and 3 mM silicon was 59.3% higher than no silicon condition. Also, total chlorophyll content and carotenoid content under water stress conditions and application of 3 mM silicon increased 42.5 and 44.9%, respectively. In Chamran cultivar, application of silicon at 3 mM increased total chlorophyll content, carotenoid content, RWC and grain protein 40, 43, 42 and 56.4%, respectively, which caused 19.7% increase in grain yield compared to Shabrang cultivar under water stress conditions. In general, foliar application of 3 mM silicon by improving total chlorophyll content, carotenoid content and RWC can play an important role in increasing yield under water stress conditions.