Response of growth, gas exchange and PSII electron transport in greengram (Vigna radiata L., Wilczek) varieties and other pulse species to drought and re-watering

Drought resistance and recovery of greengram (Vigna radiata L. Wilczek) varieties (vars.), Kanti, Yezin-4, VC1973A and V3726, improved varieties in Myanmar, were compared in pot experiments based on the parameters related to growth and photosynthesis. At the vegetative stage (30th day after planting), the plants were subjected to four-day drought treatment during which the water supply was reduced to 20% of the control. At the end of the drought treatment, the plants were re-watered for three days as a recovery treatment. A significant varietal difference was observed in growth parameters, CO₂ exchange rate (CER), stomatal conductance (G_s), PSII electron transport (ETR) and non-photochemical quenching (NPQ) at the end of drought and re-watering treatments. Of the four varieties, vars. Kanti and Yezin-4 sustained a comparatively large value of G_s because of their relatively higher sustainability of CER and ETR and having lesser NPQ under drought condition. This result suggests that the CO₂ assimilation and PSII function in both varieties were less affected by drought, and could continue photosynthetic energy flow. Moreover, both vars. Kanti and Yezin-4 showed a better recovery in growth, gas exchange and PSII function at the re-watering treatment. There was the evidence that greengram (var. Kanti) had a high drought-resistance and quick recovery, compared with blackgram (Vigna mungo L. Hepper, var. P-11-30) and soybean (Glycine max L., var. Asoaogari).