Influence of abiotic factors on CO₂-gas exchange of Pinus pallasiana, Juniperus excelsa and Arbutus andrachne

Abstract

The complex interactions among environmental factors as incident light, temperature and soil water content create the need for used physiology-based models which describe plants performance under current and changing climatic conditions. In the present work the net photosynthetic rate of Pinus pallasiana D. Don, Juniperus excelsa M.Bieb. and Arbutus andrachne L. was modeled as a function of light irradiance using the modified rectangular hyperbola model, which is capable of describing the photoinhibition by the non-rectangular hyperbola function. A comparative assessment of the adaptive response of the photosynthetic apparatus plants on the effect of abiotic factors and their strategies in maintaining an optimal water balance in accordance with environmental conditions has been performed. The parameters of light curves of photosynthesis under conditions of full sunlight, moderate shading and drought are determined. In relation to light, Pinus pallasiana is characterized by wider ecological amplitude compared to Juniperus excelsa and Arbutus andrachne. Inefficient use of low-intensity of photosynthetically active radiation by immature plants Pinus pallasiana and Juniperus excelsa indicates poor shade tolerance and inability to resume in shade-type forests. Due to the low plasticity to changes in the light regime, Arbutus andrachne L. may experience a significant lack of light in strong shading. Arbutus andrachne has the highest ability to actively rearrange water regime in accordance with its external moisture supply, which causes the highest drought resistance, and Juniperus excelsa has a slightly lower capacity. Tolerance to hydrothermal stress in Pinus pallasiana is significantly lower than in Arbutus andrachne and Juniperus excelsa.