PHOTOSYNTHESIS, RESPIRATION, AND CHLOROPHYLLS IN PRESENESCENT, REGREENED, AND SENESCENT LEAVES OF FOREST HERB SMYRNIUM-PERFOLIATUM L. (APIACEAE)

Smyrnium perfoliatum L. (Apinceae), an endangered forest herb with onl y one main locality in South-West Slovakia (Devinska Kobyla. in the Li ttle Carpathian Mountains), is capable to recover chlorophylls at the end of the growing season. This regreening only within bracts was obse rved during two weeks before achieving the so-called ''point of no ret urn'' that leads to the last stage of ontogenesis - leaf senescence. T he effect not only of endogenous cytokinins on chlorophyll content and carbon dioxide exchange (photosynthesis, mitochondrial respiration, a nd photorespiration) is discussed but also of other factors such as st rong irradiance, high temperature or drought stress on studied paramet ers was considered.