Effects of exogenous ABA application on stomatal regulation of gas exchange parameters and calculated water use efficiency in major pulses of Tamil Nadu, India

An experiment was conducted to study the ABA-induced changes in gas exchange parameters, in ruling varieties of soybean, green gram and black gram and to identify the crops that can show improvement in water use efficiency by maintaining higher photosynthetic rates coupled with less transpiration rates by ABA treatments. All the pulses were grown under well-watered conditions and treated with ABA. Exogenous application of 10⁻⁵M ABA solution for three consecutive days after 22^nd day from sowing showed significant variations in gas exchange parameters. Stomatal conductance declined in all pulses, while photosynthetic rate, leaf area, Total Dry Matter Production (TDMP) and photosynthetic pigments showed high stability in greengram, with the sprays of ABA. Transpiration rate were increased in soyabean and blackgram, while greengram maintained a low transpiration rate compared to its control. It is clear that ABA induced changes constitute an improvement in water-use efficiency in greengram, which may be invoked under prolonged drought conditions.