Dependence of photosynthesis intensity in Viburnum tinus L. leaves from environmental factors, leaf temperature, transpiration and their change during the growing season

Abstract

The dependence of the net photosynthesis intensity of V. tinus by environmental factors, leaf temperature, transpiration, and their change in the course of the growing period are investigated. Functions of photosynthetic response on environmental factors in the three-dimensional coordinate system is in the form of a convex surface with a peak at the top made it possible obtain numerical coefficients nonlinear regression equations relationships (models) the value of net photosynthesis for V. tinus from major environmental factors, and temperature and leaf transpiration. The data make it possible to interpret the photosynthesis rate as potential ecologo-physiological characteristic of the species, which in turn, allows you to compare different types of plants growing under similar conditions, in terms of measured using the same technique. V. tinus has a high photosynthetic capacity for acclimatization to the high temperature. When air temperature increases above of optimum value the rate photosynthesis drops sharply. The critical temperature for the leaf is 33.5°С. After stopping of period of active growing during June-October, the maximal size of speed of net-photosynthesis went down on 12%, transpiration intensity by 63.64%, temperatures of leaf - by 9.4%. Thus by comparison to June in September-October temperature-light optimums were displaced toward lowering: temperatures of air by 15.7%, deficit of humidity of air by 42.86%, and light PAR by 34.38%.