Dependence of stomatal conductivity of Siberian fir needles on illuminance
Institute of Biology of the Komi Scientific Center of the Ural Branch of the Russian Academy of Sciences, Syktyvkar, Russian Federation
*E-mail: gerling@ib.komisc.ru
The dependence of transpiration of Siberian fir (Abies sibirica Ledeb.) needles on the intensity of photosynthetically active radiation (PAR) was studied. Stomatal conductance was assessed indirectly by analyzing the diffusion rates of water vapor and CO2 under controlled PAR conditions. The work was carried out using an infrared gas analyzer LI-COR LI 6400XT and an opaque chamber for conifers on intact shoots of Siberian fir in the middle subzone of the taiga of the North-East of the European part of Russia. It is shown that in the absence of soil moisture deficiency, constant leaf temperature and water vapor concentration in the atmosphere, the changes of the transpiration intensity are determined by the size of the stomatal aperture. A connection has been established between stomatal conductivity and PAR intensity: when PAR intensity is equal to zero, stomatal conductivity is minimal, but not equal to zero; when the PAR intensity increases to 15 μmole quanta∙m−2∙s−1, the conductivity increases to the maximum corresponding to the environmental conditions and remains constant for any changes in the PAR intensity; when the PAR intensity decreases to 25 μmole quanta∙∙m−2∙s−1, the conductivity decreases to a level corresponding to zero PAR intensity and given external conditions. Thus, if other environmental factors are constant, stomatal conductance is controlled by the intensity of PAR, but the control is not of a regulatory nature, in which a given intensity corresponds to a certain conductivity value, but is a factor triggering the opening and closing of stomata.
