Abstract
Aim: As water is crucial for survival, growth and yield of plants, it is highly desirable to devise strategies for enhancing drought tolerance in plants. This study investigates the impact of foliar application of indole acetic acid (IAA) on plant growth and leaf characteristics of faba bean (Vicia faba L.) under normal and water-deficit conditions in order to determine its role in drought resistance of plants.
Methodology: In a pot experiment, 4-week-old seedlings were sprayed daily with IAA(0, 15, 30 and 45 mg1(-1)) for 15 days. These seedlings were then maintained under (a) regular watering with 100% field capacity, and (b) water stress created by stopping watering for 5 days. Fifty-day-old seedlings were sampled for analyzing the growth, water content and photosynthetic parameters by standard methods.
Results: Water-deficit condition reduced plant growth, dry mass production, pigment concentration, maximum quantum yield of PSII (Fv/Fm), stomatal conductance (gs), net photosynthetic rate (Pn), transpiration rate (E) and relative water content (RWC). IAA application enabled the plants to withstand water stress and reduced the expected loss by about 18% in root length, 7% in shoot length, 10% in basal stem diameter, 11% in number of branches, 3% in number of leaves, 20% in leaf length, 22% in leaf area, 48% in root dry mass, 34% in stem dry mass and 26% in leaf dry mass. The loss was also mitigated by 44% in chl a, 39% in chl b, 60% in carotenoids, 9% in Fv/Fm, 36% in gs, 63% in Pn; 35% in E and 52% in RWC of the leaf.
Interpretation: Water-deficit hindered the vegetative growth of seedlings by affecting adversely the dry-mass production, photosynthetic pigments, gaseous exchange, photochemical efficiency and water status of plants, while IAA application promoted these parameters not only in normal but also in water stressed conditions. The 45 mg IAAl(-1) dose proved to be most effective.