alleviation of salinity effects by exogenous applications of salicylic acid in sugarcane (saccharum officinarum l.) seedlings

introduction abiotic stresses cause 71% reduction in crop yield around the world, from which 20% is related to salinity stress. the importance of sugarcane increases every day due to greater demand for sugar. since sugarcane has mainly grown in arid and semi-arid regions, salinity is one of the main problems for this crop due to higher evaporation in these areas. salicylic acid (sa) is classified as a phyto – hormone and belongs to a group of phenol compounds. salicylic acid can improve plant tolerance to abiotic stresses. this research aimed at studying the effect of sa on the alleviating of salinity stress in sugarcane. materials and methods the effects of salicylic acid on the growth and some physiological responses of sugarcane (saccharum officinarum l. cv. cp69-1062) were studied under salt stress. the experiment design was a factorial of two factors, based on a randomized completely design with three replications. the experiment was conducted in a greenhouse at the sugarcane research and training institute of khuzestan, iran in 2012. treatments evaluated in this study were three levels of salt stress, including (ecw results and discussion the statistical analysis showed that salinity stress above 3 dsm-1 can significantly (p ≤ 0.05) reduce plant growth and yield. this result confirmed the previous reports about low tolerance of sugarcane to salt stress. the most efficient treatment was, spraying with 1 mm sa concentration which resulted in, 10.61, 5.05, 8.24 and 46.98 % increase in total dry weight, relative water content (rwc), chlorophyll content and root k+/na+ ratio respectively, in comparison with control treatment. the enhancement of these plant traits will improve plant growth and crop yield. root k+/na+ ratio showed a significant positive correlation with total dry weight (r =0.85**), rwc, (r =0.67**), and was negatively correlated with root na+ (r =-0.87**) and root cl-, (r =-0.85**). thus increasing the amount of na+ and cl- in plant tissues, decreases the growth and yield. results also showed the positive effect of higher k+ concentration on plant growth and plant tolerance to salinity stress. the concentration of 1.5 mm sa had less positive effect in improving salt tolerance compared to 0.5 mm and 1 mm sa. this might be due to the hormonal effect of this compound at greater levels and its negative efficacy on plant growth and development. greater rwc with increasing k+/na+ ratio might be due to higher osmotic adjustment in plant tissues. conclusions this research showed that the growth and yield of sugarcane considerably reduced under salinity stress above 3 ds m-1. the results suggested that sa was useful in reducing adverse effects of salinity. under similar soil and water conditions the application of 1 mm in form of foliar spraying can be recommended for sugarcane plants.