the effect of silicon on some morpho-physiological characteristics and grain yield of sorghum (sorghum bicolor l.) under salt stress

introduction nowadays, salinity is one of the limiting factors for crop production in arid and semi-arid regions. on the other hand, sorghum (sorghum bicolor l.) is a self-pollinated and short-day plant, which partly has been adapted to salinity and water stress conditions; also play an important role in humans, livestock and poultry nourishments. all studies have showed the positive effects of silicon on growth and yield of plants in both normal and stress conditions. the aim of this experiment was to improve salinity tolerance of sorghum by application of silicon. materials and methods a split plot experiment based on randomized complete block design with three replications in both normal and salt stress conditions was carried out at research farm of shahid bahonar university of kerman in 2013. silicon treatments (0 and 6 mm) were considered as main plot and various sorghum genotypes (payam, sepideh, tn-4-70, tn-04-71, tn-04-39, tn-04-107, tn-04-100, tn-04-37, tn-04-68, tn-04-83, tn-04-62 and tn-04-95) were assigned to sub plots. the sodium silicate was used as silica source. the data were analyzed by sas software using combine analysis. means comparisons were accomplished by duncan multiple range test at 5% probability level. some of the measured traits were as follow: relative water content (ritchie and nguyen, 1990), relative permeability (33), leaf area index and chlorophyll index (by spad). results and discussion according to the results, use of silicon led to increase of rwc under salinity stress, while rwc decreased by 13% when no silicon applied. salinity significantly decreased 1000-grain weight. maximum grain yield obtained from tn-04-37 (987.6 g m-2) under normal condition with foliar application of silicon. application of silicon under stress condition led to 38% increase in grain yield of sepideh compared to control. under salt stress, silicon also increased shoot dry weight in tn-04-107, tn-04-70, tn-04-37, payam and sepideh genotypes in comparison with control. sepideh and payam showed the lowest sensitive to salinity. in the other genotypes, harvest index decreased more than 50%. the minimum rate of harvest index was recorded for payam genotypes under salinity stress and silicon treatments. under stress conditions, silicon significantly increased leaf area index in sepideh, payam, tn-04-83, tn-04-68, tn-04-37, tn-04-100 and tn-04-62. chlorophyll index also increased under salinity stress using silicon treatments. the highest chlorophyll index belonged to tn-04-68 and was significantly different from the others genotypes. use of silicon improved the membrane stability in tn-04-37, tn-04-107, tn-04-100, tn-04-71, tn-04-70, tn-04-95 and sepideh. conclusions the results showed that the use of silicon improved the physiological characteristics, yield and yield components of sorghum. most of the genotypes showed a positive reaction to the applied silicon especially under stress condition. according to the results the maximum yield obtained from sepideh (540 g m-2) and payam (475 g m-2), respectively. it seems that among the studied genotypes, sepideh, payam and tn-04-100 had the best response to the silicon and showed the minimum sensitivity to the salinity stress. the most sensitive genotypes were tn-04-39, tn-04-68, and tn-04-62. in general it can be said that either under normal condition or salinity stress, silicon is able to improve yield production of grain sorghum and its components.