Physiological responses of radish (Raphanus sativus L.) to controlled water limitations - potential effects on tuber quality and shelf life

Radish (Raphanus sativus L.) is very sensitive to inadequate water supply. Controlled mild water deficits during growth are assumed to induce various acclimation processes in plants. This, in turn, may positively affect overall performance of produce and potentially improve their shelf life. The effects of various soil water conditions were evaluated in relation to plant physiological activity (photosynthesis and gas exchange), tuber yield, and plant water relations (incl. transpiration) during growth and postharvest. Experiments were performed on potted climate chamber-grown radish plants. While controls were continuously watered (15-17 mL plant(-1)), deficit irrigation was simulated by gradually reduced watering to 6 mL plant(-1) during a 12 d growth period. Reducing soil water content by 50% only insignificantly affected photosynthesis by limiting stomatal conductance. Thus plant development and tuber growth were not affected. Limited water availability only slightly reduced tuber water content and water and osmotic potential, but not pressure potential. It eventually increased the sugar content and proline concentration. This is indicative of some osmotic acclimation, which is also manifested by a lowered osmotic potential at turgor loss point. In addition, overall tuber conductance to water vapour diffusion significantly declined in deficit-irrigated plants. This may reflect improved postharvest quality and prolonged shelf life of radish due to lower water losses during sales. Comprehensively evaluating the effects of preharvest conditions on postharvest behaviour potentially provides solutions to improve overall postharvest quality of highly perishable vegetables such as radish.