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Root : shoot ratios, optimization and nitrogen productivity.

ABSTRACT: Plants respond to nitrogen availability by changing their root : shoot ratios. One hypothesis used to explain this allocation is that plants optimize their behaviour by maximizing their relative growth rate. The consequences of this hypothesis were investigated by formulating two models for root : shoot allocation, with and without explicit inclusion of maintenance respiration. The models also took into account that relative growth rate is a linear function of plant nitrogen concentration. The model without respiration gave qualitatively reasonable results when predictions were compared with observed results from growth experiments with birch and tomato. The explicit inclusion of maintenance respiration improved considerably the agreement between prediction and observation, and for birch was within the experimental accuracy. Further improvements will require additional details in the description of respiratory processes and the nitrogen uptake function. Plants growing under extreme nutrient stress may also optimize their behaviour with respect to other variables in addition to relative growth rate.

SUBMITTER: Agren GI

PROVIDER: S-EPMC4243620 | biostudies-literature | 2003 Dec

REPOSITORIES: biostudies-literature

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Root : shoot ratios, optimization and nitrogen productivity.

Agren Göran I GI Franklin Oskar O

Annals of botany 20031017 6

Plants respond to nitrogen availability by changing their root : shoot ratios. One hypothesis used to explain this allocation is that plants optimize their behaviour by maximizing their relative growth rate. The consequences of this hypothesis were investigated by formulating two models for root : shoot allocation, with and without explicit inclusion of maintenance respiration. The models also took into account that relative growth rate is a linear function of plant nitrogen concentration. The m ...[more]

PMID: 14565938

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Project description:IntroductionMultiple studies have shown strong relationships between different nutrients in plants, and the important role of N in Zn acquisition and translocation has been recognized.ObjectivesThe aim of this study was to estimate the effect of Zn on N uptake, translocation, and distribution in rice as well as the corresponding molecular mechanisms. We also aimed to evaluate the impact of N on the Zn content in rice grains which is closely related to the Zn nutrition in humans with rice-based diets.MethodsWe conducted both field trials and hydroponic cultures of two rice cultivars to analyze the growth and yield, the uptake, translocation, and distribution of N and Zn, as well as the expression of N transport and assimilation genes, and the Zn transporter genes under different combined applications of N and Zn.ResultsZn supply promoted the root-to-shoot translocation (12-70% increasing) and distribution of N into the leaves (19-49% increasing) and brown rice (6-9% increasing) and increased the rice biomass (by 14-35%) and yield (by 13-63%). Zn supply induced the expression of OsNRTs and OsAMTs in both roots and shoots, but repressed the expression of OsNiR2, OsGS1;2, and OsFd-GOGAT in roots, whereas it activated the expression of OsNiR2, OsGS1;1, OsGS2, and OsFd-GOGAT in the shoots. Moreover, the enzyme activities of nitrite reductase, nitrate reductase, and glutamine synthetase increased and the free NO3 - concentration decreased, but the soluble protein concentration increased significantly in the shoots after Zn supply. Synergistically, N significantly facilitated the root-to-shoot translocation (1.68-11.66 fold) and distribution of Zn into the leaves (1.68-6.37 fold) and brown rice (7-12% increasing) and upregulated the expression levels of Zn transporter genes in both the roots and shoots.ConclusionsWe propose a working model of the cross-talk between Zn and N in rice plants, which will aid in the appropriate combined application of Zn and N fertilizers in the field to improve both N utilization in plants and Zn nutrition in humans with rice-based diets.

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Root : shoot ratios, optimization and nitrogen productivity.

Publications

Root : shoot ratios, optimization and nitrogen productivity.

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