Accumulation and Conversion of Sugars by Developing Wheat Grains. II. Light Requirement for Kernels Cultured in vitro

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Abstract
Light stimulated the incorporation of [14C]sucrose into the starch of developing wheat kernels cultured in liquid medium. The light response curve saturated at about one-tenth full sunlight. Surgical removal of the green-layer of the inner pericarp, or inhibition of its photosynthesis by 3-(3,4-dichlorophenyl)-1,1-dimethylurea, eliminated the light response. Experiments with different gases above the culture medium suggested that photosynthetic generation of oxygen by the green- layer was a possible cause of the response. Accumulation of label from [14C]sucrose into the alcohol-soluble fraction of the grain was slightly light-sensitive. This effect also saturated at about one-tenth full sunlight but there was no evidence that it was related to the photosynthetic behaviour of the green-layer. These observations are discussed in relation to in vitro culturing methodology, to the layered structure of wheat starch granules, and to the role of the green-layer of the inner pericarp of the wheat kernel.