The dynamics of phenolic compounds and soluble sugars in the leaves of the silver birch (<Emphasis Type="Italic">Betula pendula</Emphasis> Roth) after defoliation and their significance in entomological plant resistance

The dynamics of phenolic compounds, flavonols, catechines, tannins, and soluble sugars in the leaves of the silver birch Betula pendula Roth after strong (75%) and total (100%) artificial defoliation was studied. It was shown that the flavonol content in the leaves did not change after strong and total defoliation, while the amount of tannins did not change during the first 15 days but increased later on 1 and 2 years after 75% and 100% defoliation. The catechine content did not change during the first 15 days and increased later on 1 year after strong and total defoliation; however, it returned to the level of control plants 2 years after both types of defoliations. The amount of soluble sugars in the leaves increased 2 days after 75% defoliation; however, their content conformed to that in control plants after 10 days and it remained later 1 and 2 years after the damage. The amount of soluble sugars in the leaves also did not change 1 year after 100% defoliation.