A comparative assessment of C02/H20 gas exchange in evergreen woody and shrubby plants under favorable and stressful environmental conditions

Abstract

A comparative assessment of the adaptive response of the photosynthetic apparatus and water regime in 6 evergreen tree and shrub plant species to the effect of abiotic factors and their strategies in supporting optimal water balance in accordance with environmental conditions was carried out. Parameters of photosynthesis light response curves under conditions of full sunlight and moderate shading were determined. It is shown that due to the low plasticity to changes in the light regime Arbutus andrachne L. may have a significant lack of light in strong shading. Important adaptive features of Laurus nobilis L., Aucuba japónica Thunb. and Viburnum tinus L. is the ability of the photosynthetic apparatus to effectively use low light and maintain a positive carbon balance in conditions of strong shading. Three types of plant response to water deficit have been identified. Drought- resistant type of water balance regulation by closing stomata is characteristic of Nerium oleander L. and Laurus nobilis. In Aucuba japónica and Prunus laurocerasus L. a reaction aimed at preserving the water balance in the plant by maintaining a high level of transpiration has been identified. The third type of plant response to water deficit which combines both types of reaction provides high adaptive ability to drought Viburnum tinus and Arbutus andrachne. Drought tolerance of Arbutus andrachne was the highest among the studied species.