Abstract
To assess the effects of IAA and Kinetin plant growth regulators in order to improve the drought tolerance in rice seedlings (Oryza sativa L.), a factorial experiment was carried out based on complete randomized design with three replications. The experimental factors included different rice genotypes [‘Gharib’, ‘Khazar’, ‘Sepidrood’ and ‘IR83750 -131-1’ (‘IR83750’ )], drought stress from 1 to 4 code of the Vergara coding system and control (normal irrigation) and growth regulators in three levels (IAA and Kinetin through foliar spraying and non-application as control). The results indicated, under normal irrigation condition together with IAA application, ‘IR83750’ rice had the highest number of tillers and leaf greenness, with mean of 18.27 and 49.46, respectively. The highest amount of leaf relative water content) 95.11 percent) was related to ‘Sepidrood’. Under drought stress condition, the highest electrolyte leakage (36.59 percent) was observed in ‘Gharib’. In drought condition, the highest leaf drying score was related to ‘Gharib’ in both years, but the highest score of leaf rolling index (9) was observed in ‘Gharib’ and ‘Khazar’. The present findings showed that drought stress had harmful effects in all examined genotypes and the impact in susceptible genotypes (‘Gharib’ and ‘Khazar’) was more than ‘IR83750’ and ‘Sepidrood’. Application of growth regulators (IAA and Kin) improved conditions for the growth of all genotypes. Therefore, using the tolerant genotypes along with growth regulators can improve the rice growth traits.
Highlights
Abiotic stresses, such as drought and salinity are primary factors that limit crop and rice production (Farooq et al, 2009)
Abscisic acid (ABA) has been introduced as hormone regarding to different stresses, the cytokinins (CK), brassinosteroids (BR) and auxin should not be ignored during environmental stresses (Peleg and Blumwald, 2011)
Chlorophyll fluorescence is one of the most important ways for assaying environmental stress impacts, and it has been suggested to determinate the tolerance of crops facing drought stress (Moffatt et al, 1990)
Summary
Abiotic stresses, such as drought and salinity are primary factors that limit crop and rice production (Farooq et al, 2009). Chlorophyll fluorescence is one of the most important ways for assaying environmental stress impacts, and it has been suggested to determinate the tolerance of crops facing drought stress (Moffatt et al, 1990). Environmental stresses such as drought and low temperature induce plants stomatal closure and reduce photosynthetic rate. Regarding the importance of drought stress in vegetative stage of different plant genotypes, this research has been carried out to examine some of the physiological and morphological traits of tolerant and sensitive rice genotypes under drought stress, as well as the effect of IAA and Kinetin in improving drought tolerance of the plants
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