Effect of Salicylic acid and Selenium application at different growth stages on some physiological traits of chickpea under rainfed conditions

Introduction  Chickpea (Cicer arietinum L.) is one of the important pulse crops in the world. Also it is valued through high protein content in seeds (23.5-28.9%). In Iran, chickpea produced under arid and semi-arid zones and usually chickpea plants during flowering and maturity stages are exposed to increasing water deficit stress. Different methods are existed in agriculture to increase plants tolerance to abiotic and biotic stresses. Seed priming and foliar application by amino acids, proline, glycinebetaine, Salicylic acid as well as zinc, Selenium and Silicon have been considered in recent years. Selenium is not an essential nutrient for plants. Reports showed that selenium could protect the plants under abiotic stresses such as salinity, high temperature and drought. Selenium protected the plants from abiotic stresses by participate in several physiological and biochemical process such as water condition retain, increasing plant pigments and photosynthesis apparatus regulation. Salicylic acid (SA) is a plant-produced nature phenolic compound which plays an important role in the abiotic stresses tolerance. Growth and production of crops will affect by SA application. Several studies showed that salicylic acid application increased the plant tolerant to drought stress. Increasing proteins, photosynthesis pigments and sugars indicated on the role of salicylic acid in increasing the plant resistance to stress. Therefore, this experiment carried out to study the influence of foliar application of salicylic acid and selenium at different growth stages on some physiological traits of chickpea under rainfed condition.   Material & Methods To evaluate the response of some physiological traits of chickpea at different growth stages to foliar application of salicylic acid and selenium under rain fed condition, an experiment was conducted as split plot based on Randomized Complete Block Design with four replications during 2013-2014 cropping season. Experimental factors were salicylic acid in three levels (0,100 and 200 mg L-1) and foliar selenium spraying in two levels (0 and 18 gr ha-1) that applicated in different growth stages (vegetative, reproductive growth and vegetative growth along with reproductive). According to the soil analysis results, 50 kg ha-1 urea and 40 kg ha-1 triple superphosphate fertilizers were applied at planting time. Each experimental plot included 30 cm distanced rows with 10 cm spacing between plants in rows. The chickpea cultivar was ‘Azad’. The seeds were sown at 6 cm depth in end of February 2013. Physiological traits measured from three replications. Relative water content was determined from five leaflet from leaves at flowering stage that were prepared immediately and weighed to measure fresh leaf weight in the laboratory at 25°C. Then, leaflet were placed in distilled water for 24 h until completely saturated. At the end of this stage, leaflet were dried with dry paper towels and reweighed. Samples were placed in the oven for 48 h at 72°C until dried and then weight of the dried leaves was recorded. Relative water content was calculated using the following relation. where RWC is the relative water content, Wf is the leaf fresh weight, Wd is the leaf dry weight and Ws is the leaf saturated weight. Photosynthetic pigments were calculated by the method presented by Arnon (1949). Samples collected from five leaflet, 0.5 gr leaves were ground in 80% acetone for determination and absorbance of the resulting extracts, recorded at 480, 510, 645 and 663 nm with a spectrophotometer. Biological and seed yield harvested from 2 m2 of middle in each plots. Data were subjected to analysis of variance using SAS program. Means were compared using the Least Significant Diffrence test (LSD) Multiple Range Test at 5% probablity level.   Results & Discussion Results showed that the highest leaf relative water content observed from foliar application of selenium and salicylic acid at vegetative along with reproductive stages. Salicylic acid appli­cation at the rate of 100 and 200 mg L-1 and selenium at the rate of 18 gr ha-1 increased the leaf relative water content by 18, 42.7 and 31%, respectively as compared with control. There were reports that, application of salicylic acid improved vegetative growth rate, chlorophyll a, b and total chlorophyll, leaf relative water content and resistance to water deficit in lawn. The highest ion leakage (82.57%) and the lowest (75.86%) recorded from treatments of without application of selenium and foliar application of 18 gr ha-1 selenium, respectively. Foliar application of 100 and 200 mg L-1 salicylic acid along with 18 gr ha-1 selenium increased chlorophyll a content compared with control, significantly. Foliar application of 100, 200 mg L-1 salicylic acid and 18 gr ha-1 selenium alone increased chlorophyll b content by 29.4%, 32.3% and 26.4% as compared with control, respectively. The highest carotenoids content belonged to foliar application of 200 mg L-1 salicylic acid. There were reports that application of selenium decreased chloroplast damage and help to retain of photosynthesis pigments. Foliar application of 100 and 200 mg L-1 salicylic acid along with 18 gr ha-1 selenium increased productivity index at different growth stages as compared with control. The treatments interaction effects showed that the maximum biological yields (1528.86 and 1628.40 kg ha-1) obtained from treatment of 100 and 200 mg L-1 salicylic acid along with 18 gr ha-1 selenium at different growth stages, respectively. The results showed that foliar application of salicylic acid and selenium could be increased chickpea seed yield.   Conclusion The positive role of application of salicylic acid and selenium under rainfed condition exerted by the effects on physiological process such as water retain in plant, membrane stability retain and improve of photosynthesis pigments. Therefore, foliar application of 100 mg L-1 salicylic acid and along with 18 gr ha-1 selenium at vegetative growth along with reproductive growth could obtain optimum yield.