THE CONTENT OF SOLUBLE SUGARS IN TRUNK TISSUES OF BIRCH, ALDER AND ASPEN IN AN EXPERIMENT WITH EXOGENOUS SUCROSE

Abstract

Previously it was shown that formation of parenchyma tissue inclusions in the wood of Karelian birch ( Betula pendula Roth var. carelica ) was associated with the high activity of apoplastic invertase. In our experiments with injection of sucrose solutions (1.0%, 2.5%. 5.0%, 10%) into the cambial zone of silver birch ( B. pendula var. pendula ) the activity of apoplastic invertase in the zone of experimental treatment also rose. Activity of that enzyme gradually increased with the rise of concentration of sucrose solution from 1% to 5% and sharply increased in the variant with 10% of sucrose. Sucrose concentration in tissues coincided with the enzyme activity: its level rose with the increase in sucrose concentration from 1% to 5% and sharply decreased in the variant with 10% of sucrose. At this concentration of exogenous sucrose the growth in parenchyma volume was observed: in the phloem the proportion of parenchyma cells significantly increased, in the xylem thick parenchyma layer was formed. Similar experiments performed on the trunks of alder ( Alnus incana (L.) Moench) and aspen ( Populus tremula L.) have shown that reaction of that tree species differed from the birch reply. In alder tissues no signs of structural or functional changes were detected. In aspen tissues the percentage of structural elements in conducting tissues remained the same but their functional state changed as evidenced by the increase in the proportion of parenchyma cells with large vacuole. Sucrose in tissues of aspen and alder in the experiment was mostly absent. Glucose was represented in minor amounts, fructose levels were significantly higher. The data indicate the ability of alder and aspen tissues to utilize large amounts of sucrose, not allowing its accumulation in the trunk tissues. This may be the possible reason for the absence of structural deviations in phloem and xylem of these species in the variants with the high concentration of sucrose. The causes of quick sucrose utilization in aspen and alder would be the subject of further investigations.