C‐Labelled Photosynthate Translocation and Utilization in Cotton Plants¹

Abstract

Cotton ( Gossypium hirsutum L.) plant organs were exposed to 14 CO 2 under field conditions to quantitatively evaluate the relative contribution of these organs to fruit development and to obtain information on photosynthate translocation rates. From 87.5 to 91.0% of the photosynthate remained in the sympodia regardless of the vertical position of the sympodia on the main stem or the lateral position of the leaf on the reproductive branch. The primary source of photosynthate for a boll was its subtending leaf with some photosynthate supplied from the associated bracts and from leaves one node removed from the boll. A more rapid rate of photosynthate export was found for main stem leaves than from sympodia leaves. The rate of photosynthate translocation from leaves to other plant parts was slow relative to rates reported for other species with high photosynthetic rates.