The Role of Cotyledons in Growth and Photosynthesis of Radish Plants

Abstract

When cotyledons of radish plants were excised at an early stage of growth, decrease in plant growth was observed. To understand this phenomenon, the role of cotyledons in radish growth was examined.
Dry weight of cotyledons decreased and that of the other organs increased in the dark, whereas dry weight of every organ increased in the light. Furthermore, dry weight of hypocotyls and that of roots decreased in decotylized plants grown in the light, but decrease in dry weight of foliage leaves was not observed. From these results, it was concluded that cotyledons were the source and the other organs were the sink. Especially, the foliage leaves could be regarded as the strongest sink.
In Rapid Red cultivar, the growth phase could be divided into two periods (Phase 1 and Phase 2). In Phase 1, the growth of foliage leaves was enhanced by the supply of reserve materials and photosynthetic products from cotyledons. In Phase 2, activet hickening growth of hypocotyls was caused by a sufficient supply of photosynthetic products from foliage leaves. Therefore, it is concluded that the decrease in radish growth by decotylization is due to the resulting decrease in the growth of foliage leaves.