Dynamics of phenolic compounds in leaves Fragaria ananassa Duch. after treatment with different forms of chitosan

The article considers the effect of chitosans of different origin, molecular weight, and degree of deacetylation on the dynamics of phenolic substances in the leaves of Fragaria ananassa Duch. These substances potentially act as agents in plant responses to biotic stresses. We showed that the daily variations in individual phenolic compounds are most pronounced in the group of ellagitannins and kaempferol-3-b-D-[6-O-(E)-coumaroyl]-glucopyranoside. The most stable indicators were concentrations of kaempferol glycoside and ellagic acid pentoside. The strongest plant response to leaf treatment with low- and high-molecular-weight chitosans was a significant increase in the concentration of hexahydroxydiphenyl (HHDP)-glucose in leaves, peaking at 12 h after treatment. Treatment of F. ananassa with various forms of chitosans resulted in different concentrations of the basic phenolic substances. In particular, the plant response to a single treatment with 0.4% low-molecular-weight chitosan (LMC) was accompanied by a significant decrease in the ellagic acid concentration, after a slight increase in the first hour after treatment. The opposite effect was observed in plants after treatment with high-molecular-weight chitosan (HMC). We also determined the daily dynamics for the quantitative and qualitative composition of phenolic compounds in the control group of plants. By using the Biplot analysis, we showed a clear difference between phenol concentrations in the evening (0, 24, and 48 h) and in the morning (12 h). The strongest difference was an increase in the concentration of HHDP-glucose, galloylquinic acid, ellagic acid pentoside, kaempferol glycoside, and ellagic acid in leaves in the morning, followed by a decrease in the evening and nighttime, due to the physiological reactions of plants to external abiotic and biotic factors