Regulation of Physiological and Biochemical Processes in an Intact Plant Is Determined by Interaction of Flows of Substance Bulk Transfer

The analysis of characteristic features of photosynthesis alterations, assimilate transport, growth function, and plant leaf ultrastructure under the changes in sink-source relations (SSR) between photosynthetic and sink organs is carried out, as well as the level of nitrogen (nitrate) nutrition. Under modeling conditions, there is shown NO-triggering mechanism of inhibition of assimilate export from leaves which becomes involved with the increase in the plant apoplast nitrate level. The concept that the plant metabolism regulation under the changes of environmental conditions is realized through the interaction of counter flows of nitrates and photoassimilates. This interaction involves changing in the degree of reduction of absorbed nitrates resulting in NO formation. By activating the callose synthesis, NO plugs pores in sieve tubes and inhibits sugar transport along the phloem. Numerous genes are activated under the effect of NO signal system. Out of all enzymes synthesized due to the expression of these genes, there function and change the metabolism only the ones for which cofactors and substrates resulting from SSR disturbance exist. Such reorganization of metabolism occurs every new photoperiod in accordance with new levels of assimilates and nitrates in plants.