DISTRIBUTION AND UTILIZATION OF ASSIMILATED CARBON IN RED-CLOVER DURING THE 1ST YEAR OF VEGETATION

The pattern of distribution of 14C labelled assimilates and translocation with time was measured in red clover during one reproductive cycle. Measurements were made on whole plants grown outdoors in pots by exposing the aerial parts of 14CO2 during one photoperiod. Simultaneously, root, respiration and N2 fixation were recorded. At the beginning of the vegetative period, 2/3 of the assimilates remained in the leaves (BASAL LEAVES), and 1/3 were directed to the root system. Then the development of branches required as much as 40% of the C and the root allocation decreased. Reproductive structures diverted 17% of the current photosynthates. Nitrogen fixation was optimal during the maximum extension of the basal leaves and decreased during the devleopment of branches. During this period, C allocation to the nodulated roots was high with an estimated amount of 3.2 mg of C per mg of N fixed. With time, translocation occurred within the foliage, from basal leaves to the levels of the branches and to the new basal leaves developed after senescence of the branches. Remobilization to the reproductive structures remained minimal indicating that flower and seed growth was supported by current photosynthesis.