Carbohydrate, Nitrogen and Dry Matter Accumulation and Partitioning of Maize Hybrids Under Drought Stress

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Abstract
Maize (Zea mays L.) productivity under drought stress depends to some extent upon a hybrid's capacity to produce and translocate assimilate to its developing kernels during the stress period and/or after the stress is relieved. The objective of this study was to evaluate differences in carbon and nitrogen accumulation and partitioning under drought stress among maize hybrids that differ in yield potential and/or physiological metabolism during reproductive development. The hybrids B73 × LH38, FS854, B73×Mol7 and US13 were subjected to drought stress from the 7th leaf stage until pollination was completed, at which time the soil of the stressed plots was replenished with water. For d. wt and chemical constituent determinations, plants of each hybrid were harvested from the irrigated and drought stressed plots at silking, mid-grain fill, and physiological maturity. Averaged over hybrids, vegetative biomass at silking was reduced 25% as a result of the drought stress treatment, with B73 × LH38 and FS854 accumulating more total biomass during the later portion of grain fill than the other two hybrids under both soil moisture treatments. At silking, the total non-structural carbohydrate content of the hybrids' vegetative tissue was not changed as a result of drought stress, whereas their reduced nitrogen (N) contents were decreased by an average of 33%. B73 × LH38 and FS854 had greater grain carbohydrate and reduced N contents under irrigation and smaller decreases in those variables as a result of soil moisture deficit than did the other two hybrids. These results indicate that the greater drought tolerance of B73 × LH38 and FS854 to stress imposed during vegetative and early reproductive development resulted from their more active N uptake and assimilation and sugar production during the later portion of grain fill and from their more efficient partitioning of assimilate to the developing kernels.