Relações hídricas, trocas gasosas e anatomia foliar de Vochysia divergens Pohl., espécie invasora no Pantanal mato-grossense

Abstract

Considered one of the major floodplains of the planet, the Pantanal of Mato Grosso is subject to changes in rainfall that are characteristic of wetlands with periods of flooding and drought. Characteristic rainfall function as filters for the establishment and development of the species that co-exist there and are characteristic of the adjacent biomes. There is growing concern regarding the establishment and dominance of V. divergens Pohl. in the wetland by scientists as this species decreases the biodiversity of occupied areas, modifies the chemistry of the soil and tends to encroach on areas used for agriculture, the basis of the local economy. Ecological studies have shown that the areas occupied by V. divergens expand in more humid conditions and retract in drier periods. The present study investigated the hypothesis that V. divergens reduce their metabolic rates in the dry season, which would contribute to a decrease in their population. To determine the effects flooding and drought on metabolic rate we evaluated water relationship (Ψω and PV curve), gas exchange (AxCC and AxDFFA curves) and chlorophyll fluorescence parameters, as well as leaf structure ( anatomy of photosynthetic pigment concentration and N partitioning) of five young individuals of V. divergens in Pantanal during flood and drought periods. The period of drought contributed to reduction of the values of Ψω, and showed marked effects on biochemical parameters with a decrease in Vcmax and Jmax being the most severe effects observed on the photochemistry, evidenced by chlorophyll fluorescence parameters with a decrease in ΦPSII , and increase in F0 and ΦNPQ . However, the biochemical and photochemical damage were not severe enough to cause changes in the gas exchange rates. These rates were maintained due to: the increased bulk modulus of elasticity of the cell wall,. The maintenance of positive values of potential net photosynthetic rate, despite biochemical and photochemical limitations, and non-critical values of water potential indicate that the species has plasticity and is adapted to the period of drought. These results suggest that the decrease in physiological parameters of young individuals are not decisive for the species decline.