Scientific publications

The effect of exogenous nitrate on photosynthetic activity, content of sucrose and starch, and activity of sucrose metabolic enzymes, sucrose synthase (SS ) and cell-wall invertase (Cw-Inv), in leaves on long (auxiblasts) and short (brachyblasts) shoots were studied in silver birch (Betula pendula Roth var. pendula) and Karelian birch (B. pendula var. carelica). L eaves on brachyblasts in experimental birch plant demonstrated an increase in the total content of pigments and the share of chlorophyll in the light-harvesting complex. A dditional application of potassium nitrate did not modify the level of sucrose – the main transport sugar in birch, but had a negative effect on starch content. Its amounts in silver birch decreased 1.4-fold in leaves on brachyblasts, and in Karelian birch the reduction was 2.6- and 3.1-fold in leaves on auxiblasts and brachyblasts, respectively. A pplication of potassium nitrate to silver birch inhibited SS activity and promoted C w-Inv activity, indicating increased utilization of sucrose in leaves. T he effect in Karelian birch leaves was a rise in SS activity, pointing to increased synthesis of sucrose and its greater transport to sink organs.