PHYSIOLOGICAL FEATURES OF THE TERRESTRIAL ORCHIDS CEPHALANTHERA LONGIFOLIA AND PLATANTHERA BIFOLIA THAT GROW IN THE PEDO-CLIMATIC CONDITIONS FROM OLTENIA REGION OF ROMANIA

Abstract

For studying the physiology of terrestrial orchids, plants from the species Cephalanthera longifolia and Platanthera bifolia have been used. The experiences were carried out directly on the field, in Mehedinţi County, Comanesti Hills. In both species of orchids, the seasonal dynamics of photosynthesis registers a peak during the flowering period that corresponds to a maximum content of assimilating pigments and also a maximum leaf surface. In terrestrial orchids, the seasonal dynamics of leaf transpiration intensity is highest during spring, when the water content in the soil is high and minimal in summer. The graphs showing the diurnal variation of photosynthesis for the two species indicate that Cephalanthera longifolia prefers semi-shaded and sunny habitats, while the plants of Platanthera bifolia that are found in the studied areas prefer a more shaded environment