A stay‐green mutation of Lolium perenne affects NO3− uptake and translocation of N during prolonged N starvation

Publisher Website
Google Scholar
Abstract
SUMMARY: Apparent Km and Vmax for net NOS″ uptake and short‐term translocation patterns of recently absorbed N were compared in a stay‐green mutant and wild‐type selection line of Lolium perenne L. by means of a series of depletion studies using 18NO3, performed over 12 d under conditions of progressively increasing N deprivation. In view of the greater retention of N in senescent leaves of the stay‐green phenotype, it was predicted that NOS″ uptake would be up‐regulated relative to the normal line, and that a proportionally higher fraction of recently absorbed N would be allocated to young leaves. It was shown that the stay‐green trait had significant phenotypic consequences for plant N relations, with higher ‘sink strength‘ of shoots for recently absorbed N, and higher Vmaxfor NO3 uptake compared with those of normal plants. The stay‐green mutation had no effect on the Km of the nitrate uptake system. Although the N‐use efficiency might he expected to be lower in stay‐green than in normal plants, there were no differences in rates of dry matter production.