Empirical model of nitrate metabolism regulation in the roots of wheat seedlingsстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:Abstract—The results of a study of the dependence of utilization by 12-day-old wheat seedlings (Triticum aestivum L.) on temperature and nitrogen supply are summarized. The scheme of the regulation of nitrate metabolism by compartmentation and transport into the roots and out of the roots into the shoots is elaborated. The following indices of nitrate transformation were investigated: net uptake, ratio between nitrate influx and
efflux, content in roots, nitrate reductase activity, nitrate reduction in situ, and pool sizes. In roots, total nitrate is distributed among three pools—the storage pool; metabolic pool; and mobile pool, containing nitrate translocated into shoots. Under low temperature, the net uptake of nitrate decreased, and the size of the mobile pool
increased, because nitrate translocation from roots into shoots was depressed to a higher extent than nitrate uptake by roots. The rate of nitrate uptake and nitrate content oscillated in the antiphase with a period of about 1 h, and the oscillation amplitudes decreased under low temperature. These oscillations were related to the regulation of net nitrate uptake via the influx–efflux system. Based on the empirical scheme of regulation, a mathematic model of nitrate metabolism in roots is proposed. This model is a system of ordinary differential equations predicting the appearance of nitrate uptake oscillations and describing the changes in the oscillation amplitudes as related to temperature, as observed in the experiment. The model analysis indicates the occurrence of a mobile pool in roots and the crucial role of nitrate translocation in the regulation of root nitrate metab-
olism.