CAMBIAL ACTIVITY AND CO2 EXCHANGE IN PINUS-SYLVESTRIS TRUNK

The rate of CO2 evolution from trunks of Pinus sylvestris L. was monit ored at various heights during three growing seasons. The seasonal dyn amics of phloem and xylem development and cell differentiation were st udied. The dependence of trunk respiration on temperature and humidity was not always apparent. It is supposed that changes in CO2 evolution from the pine trunk during the growing season are related to the cont ent of living cells in the developing annual ring. During the period o f radial growth, the evolution of carbon dioxide occurred faster in th e upper trunk parts than in the lower ones, owing to higher cambial ac tivity in upper regions.