Foliar senescence in maize plants grown under different water regimes

The leaf ontogeny of potted maize plants subjected to severe water stress w as carried out in a greenhouse. The water stress cycle started at the onset of the vegetative stage (five-leaf stage). Control and water-stressed plan ts received 100 and 50 % of the water evapotranspired, respectively. After 30 days half of the water-stressed plants were fully irrigated to control l evels. Water stress lowered osmotic potentials of all leaves along the plan t profile as well as their chlorophyll concentration and photosynthetic rat e. Leaf area of stressed plants was reduced, while leaf nitrogen concentrat ion was higher than in control plants at the end of the vegetative stage. A fter re-watering, recovered plants increased their leaf photosynthetic rate and leaf turgor, although they remained lower than in control plants. At t he end of the vegetative stage, leaf nitrogen concentration of re-watered p lants was similar to that of the stressed plants, while leaf growth was not resumed though relative death rate was slowed to that of the control treat ment. This suggests that severe water-stressed plants, when fully re-irriga ted, were able to re-establish good physiological processes although at a l evel lower than in the control, because chlorophyll concentration was not f ully recovered. ((C) 1999 Inra/Editions scientifiques et medicales Elsevier SAS.)