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.

Effect of Water Deficits on Seed Development in Soybean

“…Maintenance of a favorable water status within the seed may be an important prerequisite for conserving seed growth rate under adverse environmental conditions. Observations similar to those reported here have been made in maize, wheat, barley, and rice (2,7,19,22). The breadth of these observations suggests that the apparent independence of seed water status from that of the maternal tissues may be a phenomenon common to all seeds.…”

“…They also suggested that the developing seed of soybean might be buffered from water deficits experienced by maternal plant tissues as has been observed for caryopses of several grass species (2,7,19,22). To investigate this possibility, we measured the *', of leaf, pericarp, and seed tissues of soybean plants from which water was withheld during the period of rapid seed growth.…”

Soybean Seed Water Relations during in Situ and in Vitro Growth and Maturation

“…In developing bean (Phaseolus vulgaris L.) seeds, water and osmotic potentials ofembryo tissues changed independently of maternal tissues (25). Maize (Zea mays L.) kernel water relations were unaffected by imposed water deficits that caused significant declines in water and osmotic potentials of leaves (12,22 and osmotic potentials declined during late growth and maturation in both wheat (1) and maize (21).Increasingly, evidence is pointing to the regulation of solute availability to developing embryos and endosperm by water relations of the embryo itself and the surrounding medium (2, 13, 18, 19, 23) (and others). Although solute unloading rates from seed coats varied considerably with the osmolality of the receiving medium in P. vulgaris L. (13), faba bean (Vicia faba L.), and pea (Pisum sativum L.) (23), sucrose unloading rates from attached soybean seed coats were reduced only at trap solution concentrations over 500 mM (18).…”

“…In developing bean (Phaseolus vulgaris L.) seeds, water and osmotic potentials ofembryo tissues changed independently of maternal tissues (25). Maize (Zea mays L.) kernel water relations were unaffected by imposed water deficits that caused significant declines in water and osmotic potentials of leaves (12,22). Similarly, a lack of response of grain water relations to imposed severe water deficits was observed in wheat (Triticum aestivum L.) (1).…”

Effects of Irrigation on the Flowering and Maturity of Chickpea Genotypes

“…Other work of Ouattar et al, (1987) concluded that sifting period for drought stress tolerance could extend until the grain development phase. (Table 5).…”