Nitrogen Partitioning Within the Potato (Solarium tuberosum L) Plant in Relation to Nitrogen Supply

Abstract

Nitrogen uptake and partitioning have been studied in field-grown potato crops which were subjected to N deficiency (no fertilizer N applied), or received large applications of N (20 g N m−2) at planting. Isolation of part of the root system of the plants allowed pulses of 1SN to be applied at three different stages of crop development. Partitioning of 15N throughout the plants was followed during a subsequent chase, to distinguish between the use in tuber growth of recently absorbed N, and redistribution of N from the existing N capital of the plant. When a pulse of 15N was applied 26 d after emergence (DAE), the distribution of 15N within the plant closely followed that of total N for the duration of the chase, which finished 110 DAE. Application of fertilizer N decreased the proportion of 15N recovered in the tubers, while increasing that found in the canopy, because of an increase in leaf growth, particularly at the top of the canopy, after 69 DAE. When fertilized plants were supplied with 18N 69 DAE, a greater proportion of 15N was recovered in new leaf growth during the subsequent chase, than when the 15N was supplied earlier in the season. It appears that current uptake of N is used to augment N pools within the canopy and, where appropriate, support leaf growth at the end of the season. In contrast, transfer of N into the tubers is by remobilization of the existing N capital, as leaves senesce. The results are discussed in relation to studies of N partitioning in potatoes and other crops.