Dynamics of bioavailable rhizosphere soil phenolics and photosynthesis of Arum maculatum L. in a lime-beech forest

In this article, the dynamics of phenolics in the soil originated from dominant trees and the photosynthetic performance and growth of the forest floor species Arum maculatum is firstly reported. Assimilation of CO2, chlorophyll fluorescence and chlorophyll concentration in the leaf tissue of A. maculatum as well as natural concentrations of total bioavailable phenolics and phenolic acids in the rhizosphere of this herb were estimated simultaneously during the growing season. Additionally, growth dynamics of A. maculatum were assessed by determination of instantaneous growth rate and leaf area index. The dominant species Fagus moesiaca and Tilia tomentosa were the main sources of the total phenolics and phenolic acids in plant litter and soil. The amounts of bioavailable phenolics and phenolic acids in rhizosphere soil were several times lower than in the litter or in freshly fallen leaves of lime and beech. In the rhizosphere soil of A. maculatum, the amount of total phenolics decreased rapidly from March to May. All of five phenolic acids present in leaves of dominant trees were identified in the A. maculatum rhizosphere soil, with characteristic turnover dynamics shown by ferulic and vanillic acid. Dynamics of the photosynthetic performance of A. maculatum was assessed as net photosynthetic rates and chlorophyll fluorescence, which had opposite courses. PN decreased continuously during the growing season (from 9.91±1.41 μmol m−2 s−1 at the beginning of March to 4.36±0.86 μmol m−2 s−1 at the end of May). Photosynthetic rate, growth rate and chlorophyll a:b ratio were positively correlated with total soil phenolics, and also with the available derivatives of cinnamic and benzoic acids (p<0.05). Photosynthetic efficiency, total chlorophyll content and leaf area index were negatively correlated with total soil phenolics and derivatives of benzoic acid, and positively correlated with the derivatives of cinammic acid (p<0.05). These results indicate that there was a high correlation between total bioavailable rhizosphere soil phenolics and phenolic acids originated from dominant trees on one side, and the photosynthetic performance and growth parameters of A. maculatum on the other side.