Dinâmica de crescimento em Tabebuia rosea (Bertol.) Bertero ex A.DC. (Bignoniaceae): fenologia apical e cambial caulinar

Abstract

The study of growth dynamics in tree species allows better understand the adaptation of a species to the environment in which it develops. Such data are still scarce in Brazil considering the diversity of species and vegetation types. This type of study has been considered of great importance especially under the current situations of deforestation and climate change, requiring reclamation and prospect with native species survive on this rapidly changing environment. In this perspective, the objective of this study was to investigate the dynamics of growth of Tabebuia rosea, through monthly monitoring and apical and cambial shoot phenology and yield of photosynthetic pigments: chlorophyll a, b, total and carotenoids. The results were correlated with each other and with the seasonality of environmental variables: temperature, precipitation and photoperiod. With regard to the content of photosynthetic pigments, was also evaluated the oscillations observed in the leaves obtained in the geographical directions: north, south, east and west. The study was conducted on the campus of the State University of Rio de Janeiro, RJ, Brazil. Apices shoot phenology was accompanied monthly from qualitative and quantitative observations on 15 individuals. Samples containing cambial zone were obtained by non-destructive method and processed according to the usual techniques in plant histology. The extraction of photosynthetic pigments was performed in 80% acetone, followed by centrifugation and analysis by spectrophotometer at different wavelengths. Tabebuia rosea showed an increase in the width of the cambial zone in number of cell layers and micrometers, decreased radial diameter of the fusiform initial cell and increased in micrometers of the cell layer in the process of stretching and differentiation of secondary xylem in the same period in which the canopy of trees was occupied by adult leaves and with the highest levels of chlorophyll in the leaves, which is the period in which environmental variables showed up high, corroborating the results obtained for other species native to the Atlantic Forest developing in the state of Rio de Janeiro. The highest concentration of carotenoids was observed in the period in which environmental factors had high levels and the plants were more exposed to light radiation, possibly due to increased investment in photoprotection. It should be noted that the west side of the canopy of trees showed a tendency to have higher concentrations of the studied photosynthetic pigments, results not yet reported in the literature to date, which can be a kind of strategy to compensate for low levels of solar radiation accumulation chlorophylls