Effect of Drought on Water Relations of Developing Maize Kernels1

Abstract

Although considerable information exists concerning the effect of drought on the water relations of maize (Zea mays L.) leaves, little has been published about the water relations of maize grain, or on how the process of grain filling is affected by a limited water supply. We had previously observed that the maize plant sustained normal rates of kernel growth for long periods in spite of severe water deficit during grain filling. The objective of this study was to investigate the nature of that response. Plants were grown outdoors in Rabat, Morocco, in large pots. Severe water deficit was imposed during either early or mid grain filling, and was maintained until maturity in each case. Grain water status (water potential, osmotic potential, and turgor pressure) was independent of whole‐plant water status, particularly leaf status. Photosynthesis decreased as judged by leaf water potential, diffusive resistance, leaf senescence, and total plant dry weight. Kernel growth was relatively unaffected by a water deficit that completely inhibited net photosynthate production. Kernel growth was maintained by a remobilization of stored assimilates from nongrain parts to the grain. The main source of assimilates was the stem as judged by dry weight loss and soluble sugar content. The maintenance of a high stalk moisture content in spite of severe leaf dehydration may have facilitated translocation from the stalk to the grain.