The early stages of grain development in wheat: Response to water stress in a single variety

Abstract

In wheat (Triticum aestivum cv. Gabo) a temporary water deficit in the first 7 days following anthesis significantly reduced the final grain weight per ear. A reduction in seed set in response to stress was associated with an initially greater rate of development of the remaining grains, with an enhanced rate of cell division in the endosperm. Relative turgidity measurements indicated that the stress applied did not significantly reduce grain water content, although the ear structure showed some water loss, and the stem and flag leaf blade were quite severely stressed. This greater desiccation of the leaf and stem in comparison with the ear was reflected in the lower rate of photosynthesis of these organs under stress conditions. With the reduction in net photosynthesis, both during and subsequent to the period of water deficit, there was a marked reduction in the storage of dry materia in the stem of stressed plants, a temporary cessation of tiller development, and an almost complete inhibition of net root growth in dry weight. However, estimates of net photosynthesis by the upper parts of the plant indicated that this was probablyin excess of that required for grain growth in the stressed plants. Also, experiments in which additional grains were removed from the ears of stressed plants 10 days after anthesis gave no indication of a substrate limitation to grain growth. Thus the interaction between a temporary water deficit during the early stages of grain development and final grain yield would appear to be an indirect one. © 1971 CSIRO.