Effect of limited supply of assimilates on the relationships between their sources and acceptors

Abstract

Sink activity in young sunflower and bean plants was determined mainly by their growth rate. The organ with higher RGR (stem in sunflower and apical part with expanded trifoliate leaf- in bean plant) was the dominant acceptor even in conditions of limited supply of assimilates.Specific activity of root - donor of phosphorus, depends on the roofs metabolic and physiological activity only in the case, when supply of P to the aerial parts is not a factor limiting photosynthesis. If the activity of the whole root system is relatively low (like in preshaded series of sunflower) the photosynthetic compensation observed in plants replaced into better conditions coincides with compensation of P-absorption (both calculated per g of dry matter). It may explain the existence of a functional balance between shoot and root activity in the case of a changed proportion between their sizes.