ESTRATÉGIAS DIFERENCIAIS DE RESPOSTA À SECA SAZONAL EM ESPÉCIES DECÍCUAS E SEMPRE-VERDES DO CERRADO: UMA ANÁLISE DOS MECANISMOS DE SEGURANÇA HIDRÁULICA E ESTOQUE DE CARBONO

Abstract

The Cerrado is one of the world's largest biodiversity hotspots and the most threatened savannah in the world due to its low legal protection. Climate projection models predict, in the coming years, an increase in the intensity and frequency of drought events, which could compromise the growth and survival of several species, exceeding the threshold even for species acclimatized to drought conditions. As a survival strategy, Cerrado plants have different levels of deciduousness, being classified as deciduous or evergreen species, a strategy often associated with the hydraulic security of these plants during drought. The objective of the work was to evaluate the plasticity of water status maintenance in evergreen and deciduous species in the Cerrado during the drought and rainy seasons. For this, 10 plant species were studied in the Botanical Garden of the Instituto Federal Goiano Campus Rio Verde. Five evergreen and five deciduous species were chosen, with four replications. Samplings were carried out over 3 months, including May (the beginning of the drought), August (the end of the drought), and December (the rainy season). Analyzes of water relations were carried out (water potential, gcanopy, gstem, and PLC); gas exchange; morphoanatomical characteristics (TC_Ramos); biochemical analyses (determination of starch and total sugars), and plasticity index. The species had different strategies between the seasons. Evergreen species decreased gcanopy during the drought season, which is believed to result from greater plasticity in the leaves, enabling continuous growth of leaves and branches, with consequent greater consumption of carbohydrates; while the deciduous plants showed greater leaks and less plasticity, as well as lower growth. Even with different strategies, both groups managed to achieve the same objective: prevent lethal hydraulic failure during drought. It is noteworthy that although these strategies are efficient, with climate change, even well-adapted plants can reach a threshold and suffer drastic effects such as the replacement and extinction of species in the Brazilian Cerrado.