Abstract
Mung bean [Vigna radiata (L.) Wilczek] was grown on a sandy loam soil under four irrigation schedules, irrigation at cumulative pan evaporation (CPE) equal to 200 mm (1-200), 300 mm (1-300), 400 mm (1-400), and no irrigation after seeding (1-0) to study the changes in plant water relations and canopy net photosynthesis (Pn) during the hot dry season (April-July, 1980) in a semiarid environment. An increase in the frequency of irrigation resulted in higher soil water content, leaf water potential (?1), osmotic potential (??), turgor potential (?p), and water loss from crop canopy (ET). The ?L recovered at later stages of growth in all irrigation treatments even with the reduction in the soil water content. Accumulation of sugars and organic acids constituted most of the ?? Lower ?? than ?L maintained positive ?p throughout the season irrespective of the irrigation schedule. Turgor potential increased with ontogeny due to the recovery in ?L and the reduction in ??· Turgor potential was linearly related to ?L · Diurnal, vapour pressure deficit (VPD) showed positive significant linear correlation with photosynthetically active radiation (PAR). In general, ET increased with the VPD but the reverse was true for stomatal diffusive conductance gs. Both gs and Pn were higher, particularly during the grain-filling stage in the 1-300 than in the more frequently irrigated 1-200. Grain yield had a positive significant correlation with Pn but the correlation was even higher with the leaf area index and gs. The study has highlighted that irrigation scheduling at 1-300 can improve physiological functions and productivity of mung bean in a semiarid environment.
