Physiology of Cereal Grain III. Photosynthesis in the Wheat Ear During Grain Development

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Abstract
Cereal ears are important as photo-synthetic organs in contributing to grain yield and, since ear tissues are the last to yellow, their relative activity may increase during grain development. Glume surface exposed to light has been observed to increase as grains swell, and thus actual photosynthetic capacity of ears may also increase. The contribution of ear photosynthesis to grain growth has now been measured for wheat (Triticum vulgare cv. Gabo) over intervals between anthesis and maturity, by a technique involving stem shading and grain removal. In the first 3 weeks after anthesis, when grains grew slowly, florets contributed about 0.2 mg per day to the enclosed grain, representing 50% of grain dry weight increment. During the latter half of grain growth, when grain weight increased more rapidly, florets contributed more than 0.6 mg per day per grain, representing 60% of the weight increment. The technique used is discussed and it shown that certain precautions must be taken if reliable measurements are to be obtained.