Effect of IAA and Kinetin application on plant characteristics and chlorophyll fluorescence parameters in rice seedlings under drought stress condition

To study the effect of IAA and Kinetin phytohormones on the improvement of drought tolerance in rice seedlings (Oryza sativa L.), an experiment was carried out as factorial experiment with three factors based in completely randomized design with three replications in Agricultural Science Faculty, University of Guilan, Rasht, Iran, in 2013. The experimental factors included: 1: four rice genotypes; Gharib, Khazar, Sepidrood and Upland (IR 83750-131-1), 2: drought stress condition; control (non-stress) and drought stress from 1 to 4 of Vergara coding system and 3: hormone in three levels; control (without hormone application), IAA (5×10-5 M) and Kinetin (5×10-5 M) as foliar application. Tiller No., day to leaf rolling, leaf temperature, relative water content, electrolyte leakage, SPAD value and chlorophyll fluorescence parameters were measured. Analysis of variance indicated that all studied traits were significantly affected by all experimental factors and their interactions. Sepidrood cultivar had the highest relative water content RWC in drought condition (46.3%). The lowest relative water content (34.5%) belonged to cv. Gharib in drought stress condition. Application of IAA in both control and drought stress conditions increased RWC to 92.4% and 43.7%, respectively. In non-stress condition, Upland cultivar had the highest relative chlorophyll content (47.1%). The lowest SPAD value (30.6) belonged to Gharib in drought stress condition. IAA and Kinetin hormones increased the leaf relative chlorophyll content in Gharib cultivar to 18% and 13.7%, respectively. Drought stress without hormone application increased electrolyte leakage (32.1%). The lowest electrolyte leakage 16.3%) was observed in Sepidrood cultivar in non-stress condition. The highest photosystem II quantum efficiency (Fv/Fm) was 0.81 which belonged to Khazar cultivar in non-stress condition and IAA application. Results of this experiment indicated that the application of IAA and Kinetin hormones improved the drought tolerance related traits in rice seedlings under drought stress conditions. IAA had more effective role than Kinetin in improving drought stress tolerance in rice seedlings. Also results indicated that the Upland and Sepidrood rice cultivars were more tolerant than Gharib and Khazar. Generally, upland cultivar was more responsive to IAA application under drought stress condition.