Variations in internal water distribution and leaf anatomical structure in maize under persistently reduced soil water content and growth recovery after re-watering

Episodes of regional drought are increasing and are frequently associated with increased duration and intensity. However, relatively little is known about effects of long-lasting drought on leaf microscopic structure and physiological metabolism of plants. In this study, we investigated internal water re-distribution and leaf anatomical structure of maize (Zea mays L.) grown under persistently reduced soil water content. Meanwhile, the threshold of soil water content at which maize cannot recover growth vitality after re-watering was determined. Our results showed that during persistent reductions in the field water capacity from 75 to 25 %, plant growth declined, while the water content in maize decreased following the order from the lower to upper leaves and their leaf sheathes to the stem and roots. At 20 % of field water capacity, the volume of bulliform cells declined, accompanied by an inward shrinkage of cell walls. Under field water capacity below 20 %, the number of chloroplasts in bundle-sheath cells decreased, chloroplasts in mesophyll cells deformed from oval to round, concomitant of a near to zero net photosynthetic rate. It was demonstrated that the growth vitality of maize plants could be recovered by re-watering even if field water capacity reduced to 15 %, but not to 10 %.