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

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.