CARACTERIZAÇÃO DOS DETERMINANTES DA MANUTENÇÃO DO STATUS HÍDRICO EM PLANTAS DECÍDUAS E SEMPRE-VERDES NO CERRADO BRASILEIRO

Abstract

The Cerrado is characterized as a seasonally dry tropical domain, with two well-defined seasons – the rainy season and the intense dry season. Although the species in this domain are acclimatized to the occurrence of seasonal drought, climate change models predict an increase in the frequency and intensity of droughts for Cerrado region in the coming years, which may result in water restriction events that exceed the thresholds of plants tolerance, causing the death and replacement of species. Tree species in this domain show different patterns of deciduousness, being defined as evergreen or deciduous. These phenological patterns are indicated as strategies for acclimatization to environmental conditions and deciduousness is often pointed out as a crucial mechanism for maintaining water potential. Therefore, the objective of this study was to evaluate the main determinants of water potential in deciduous and evergreen species from the Brazilian Cerrado during the dry and rainy seasons. The study evaluated 10 plant species in the Botanical Garden of the Instituto Federal Goiano Campus Rio Verde, being 5 evergreen and 5 deciduous species, with 4 adult replicates for each species. The collections were carried out over 3 months, two months during the dry season (May and August) and one during the rainy season (December). The month of May was defined as the beginning of the drought, August as the end of the drought and December as the rainy season. Environmental (soil moisture, air humidity and temperature, and rainfall) and plant analyzes were carried out, being these physiological (gas exchange) and water relations (water potential; residual transpiration - gcopae gstem, hydraulic conductivity of the leaf, curves pressure-volume and stem capacitance). Evergreen and deciduous species showed different survival strategies to seasonal drought and reflected in a differential capacity to maintain water potential. The deciduous strategy consisted of decreasing gs, and with that, they decreased photosynthesis, demonstrated ability to transport water and release stored water, maintaining greater Kleaf, CFT, CTLP and Cacaulinar. Evergreens maintained gs and photosynthesis. While evergreens prioritized the maintenance of the photosynthetic process and invested in non-stomatal strategies to reduce water loss, deciduous plants invested in processes related to the transport and release of water.