Growth and nitrogen relations in reciprocal grafts of wild-type and nitrate reductase-deficient mutants of pea (Pisum sativum L. var. Juneau)
1997
Lexa, M. | Cheeseman, J.M.
Plants growing on NO3- differ in the proportion of NO3- reduced in their roots and leaves. Using a version of a two-compartment, two-resource plant growth simulation model, the possible effects of changing the N assimilation site on plant growth were explored. Subsequently, using an experimental system designed to vary the site of NO3- reduction; chimeras (reciprocal grafts) of Pisum sativum var. Juneau and its mutant, A317, deficient in nitrate reductase. Plant growth and N metabolism at varying NO3- levels were examined in a hydroponic system. In what is thought to be the first direct plant manipulation of this kind, total dry weight, root:shoot ratio, total N and NO3- concentrations, in vitro nitrate reductase activity, NO3- in xylem exudates, and leaf chlorophyll content were compared. It was found that changing the location of nitrate reduction did not change growth significantly and caused only subtle changes in N concentration. These indifferences occurred in spite of marked changes in growth associated with NO3- availability and useability. To achieve this kind of plasticity the plants must have dramatically altered the flow and storage of NO3- and reduced N. The results are compared with existing views of biomass partitioning and regulation of N assimilation.
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