Fluorescência da clorofila e emissões de isopreno em função do aumento da temperatura em indivíduos de Vismia guianensis na Amazônia Central

Abstract

Climate models indicate an average increase in global temperature that can affect tropical forests. This increase may reflect in consequence to the metabolic processes of plants such as, for example, photosynthesis. Although all plants may be affected in the future by average increase in global temperature, pioneer species are naturally more resistant as a result of natural selection mechanisms and occupation of specific niches where the incidence of solar radiation is predominant, besides presenting a shorter life cycle. Therefore, it is necessary to understand the effects of temperature increase on the photochemical processes and carbon assimilation in higher resistant species to radiation and temperature as the pioneer plants. Thus, the focus of this study was to evaluate how leaf temperature variation affects photochemical performance and carbon metabolism of Vismia guianensis (Aubl.) Pers. (Hypericaceae) in central Amazonia. Temperature curves were made from light and dark adapted leaves in three individuals of Vismia guianensis. As well, for each temperature, fluorescence, photosynthesis and volatile organic compounds (VOCs) data were collected in order to verify isoprene emissions. Collects were made with infrared gas analyzer (LI 6400 - XT). At higher temperatures, the highest values of the electron transport rate (ETR) parameters, the operational efficiency of photosystem II (ɸPSII), the ratio and open reaction centers (qP) and isoprene emissions were found, in contrast, the stomatal conductance (gs) was the lowest. However, net photosynthesis (Pn) and transpiration (E) presented optimal temperature followed by a decline. The results of this work indicate that individuals of the species Vismia guianensis have energy and carbon distribution strategies for the maintenance of photosynthetic processes as a function of temperature increase, since the ETR, ɸPSII, qP parameters increased as well as the isoprene emissions, while the parameters Pn, gs and E decreased. Isoprene emissions presented a strong positive correlation with the ETR, ɸPSII and qP parameters, and a negative correlation with Pn, that apparently, isn’t dependent on atmospheric carbon and acting as a drain of energy and protection at high temperatures. Results obtained by this study may also feed on current climate models such as the Earth System Model and, more specifically, the E3SM-FATES (Energy Exascale Earth System Model-Functionally Assembled Terrestrial Ecosystem Simulator) model which is being developed by the NGEE - tropics project (Next Generation Ecosystem Experiment) in which this dissertation is inserted.