Physiological changes of purslane (Portulaca oleracea L.) after progressive drought stress and rehydration

Purslane (Portulaca oleracea L.) is a herbaceous fleshy plant, which is relatively more tolerant to drought than other species. So far, there is little information on the combined response of this plant to drought and rehydration. In this study, physiological changes were measured under drought stress and rehydration conditions in purslane. Soil water content (SWC), leaf water content (LWC), malondialdehyde (MDA), proline, electrolyte leakage (EL), chlorophyll content, O-2(center dot-), SOD and POD activities were determined at designated time periods (5 d, 10 d, 15 d, 22 d after drought and 3 h, 1 d, 3 d after rehydration). Progressive drought treatment for 10 d significantly increased MDA, proline, EL, O-2(center dot-), and activities of SOD and POD, while rehydration for 1-3 d caused decline of these parameters. Conversely, drought stress decreased LWC and chlorophyll content, while rehydration increased LWC quickly and chlorophyll content gradually. The present study indicated that the purslane has a great capability to cope with drought stress and activate many physiological mechanisms, which allow more efficient recovery during rehydration. These results provided the first physiological evidences that the harvest time for purslane was within 5-10 d of drought or 1-3 d after rehydration. (C) 2015 Elsevier B.V. All rights reserved.