RESPIRATION IN THE SOURCE-SINK SYSTEM OF PLANTS

Problems of the physiology of respiration of a plant as a whole organi sm are considered on the basis of the source-sink concept. The respira tory costs of different physiological processes in the total respirato ry expenditures are estimated for herbaceous plants adapted to growth conditions: growth and maintenance-55-65%, export from leaves-15-20%, transport and storage of assimilates-10-15%, absorption of ions by roo ts-5-10%. It is established that, in mature leaves, up to 30% of assim ilated carbon is utilized for the renewal of structure and maintenance of assimilate export. Among sinks of different types, the least respi ratory costs were attributed to specialized storage organs (tubers), w hich reflects low energy consumption by the processes of phloem unload ing and biomass growth due to the synthesis and deposition of starch. It is found that developmental changes in the respiration to photosynt hesis ratio are closely correlated with changes in source sink relatio ns, whereas their magnitude depends on the type of morphological and p hysiological organization of the source-sink system (SSS) of plants. W e conclude that plant respiration plays an important role in SSS as a powerful metabolic sink for carbon, which provides energy for substrat e conversion into biomass and for specific functions of assimilating, supplying, and utilizing organs.