[Effect of different nitrogen supply in soil on mineral content in the xylem sap of beechs (Fagus sylvatica L.)]

azote fagus sylvatica fertilidad del suelo fisiologia vegetal malate malates malatos nitrate nitrates nitratos nitrogen nutrient transport nutrition des plantes ph del suelo ph du sol plant nutrition plant physiology sap savia seasonal variation soil fertility soil ph transport des substances nutritives transporte de nutrientes xilema xylem