Allocation of carbon to growth, storage and respiration in the vegetative barley plant

Abstract

Abstract. It is proposed that the growing plant can be divided into three compartments with reference to carbon: soluble, storage and structural. Experiments carried out at 10, 15, 20 and 30°C in the light followed changes in size of these compartments in barley plants 10–24 days old. The redistribution of I4 C photo‐assimilated by 10 day old plants was monitored simultaneously. The soluble and storage compartments are a higher percentage of plant weight at lower temperatures, and are turned over rapidly at all temperatures; they form the source of respired 14 C. About 30% of the 14 C fixed enters structural material; in the first 24 h after labelling, for each unit of 14 C entering the structural compartment, between 0–9 (at 15°C) and 3.2 (at 30°C) units of 14 C are lost by respiration. At 15°C in the dark, respiratory loss of 14 C is initially from soluble and storage compartments; thereafter respiration of I4 C occurs at the expense of structural material.