The role of the transport system in the control of the source-sink relations in Pinus sylvestris

Morphophysiological correlations were studied in medium-aged (20- to 60-year-old) Scots pine trees under the northern taiga conditions. Under various ecological conditions, pine trees developed a well-balanced structure, with close linear relationships between needle and root weight and their cross-section areas in all components of the continuous transport network (the coefficient of determination was between 0.88 and 0.999). When the annual cycle of soluble and insoluble carbohydrate contents was followed in various pine tissues, the total concentrations of soluble and insoluble carbohydrates were maintained at constant and tissue-specific levels, except in the growth period. The maximum level of carbohydrates was observed in all tissues at the beginning of rapid growth, and the minimum, at growth cessation. The qualitative composition and amount of carbohydrates matched the phenological phases of development and were not affected by the ecological growth conditions pertinent to the particular environment. The authors conclude that assimilate synthesis and partitioning are related to structural development, and the state of sink centers determines the attracting capacity, whereas the transport network, from roots to needles, and its conducting capacity are essential for the realization of systemic relationships and the control over growth and development in Pinus sylvestris L.