On the Partitioning of Photoassimilates in Plants

Abstract

The process of photosynthesis is responsible for converting light into chemical energy and reducing power, enabling the transformation of atmospheric CO2 into organic compounds. In vascular plants, photoassimilated carbon is partitioned within and between cells. This section provides a comprehensive explanation of this process by focusing on the following aspects: (i) the exchange between chloroplasts and the cytosol of photosynthetic (source) tissues, leading to the production of starch and sucrose as temporary storage products; (ii) the transport of sucrose to non-photosynthetic (sink) tissues; and (iii) the distribution of carbon within heterotrophic cells, which takes various pathways to produce the primary storage molecules found in different types of plants. This chapter also outlines the kinetic and regulatory characteristics of the enzymes involved in the specific metabolic pathways. Particular emphasis is given to the synthesis of starch, sucrose, sugar-alcohols, raffinose, fructans, and triacylglycerides in crops that accumulate these important photosynthetic products.