Efeito dos fatores ambientais sobre a atividade cambial em Commiphora leptophloeos – Burseraceae

Abstract

Plants exhibit adaptations to survive the changes that occur where they grow. Environmental changes not only affect phenology, but also growth, which in woody species is promoted by the action of secondary meristems. The meristems involved in secondary growth are the vascular cambium, which produces secondary xylem and phloem, and the phellogen, which produces phelloderm and suber. In seasonally dry tropical regions, it is still necessary to elucidate which factors affect cambial activity for many species, which tends not to be continuous due to hydric variations. The objective of this work was to evaluate cambial activity and phenology in relation to abiotic factors in a deciduous species with low wood density. Monthly stem samples were collected from 10 individuals of Commiphora leptophloeos, during February 2019 to January 2020 at the Fazenda Experimental do Vale do Curu (UFC). The phenological observations took place during the same collection period. The samples were dehydrated, embedded in historesin, sectioned with a rotary microtome and stained. All statistical analysis and graphics were done in RStudio. The highest number of cambial cells was present in the rainy season, as well as the mature leaves. The peak of greatest exchange rate activity occurred in the month of May, the rainy season, and also corresponds to the lowest value of the photoperiod. In the dry months, there was a large leaf fall and exchange rate activity decreased. The dry season was marked by a gradual decrease in the number of cells, absence of leaves, high temperature and photoperiod. Leaf sprouting and flowering occurred in November and December, accompanied by an increase in the number of cambial cells. The variables with an effect on the number of cambial cells were precipitation, with a negative effect (Estimates = -0.65), and mature leaves (Estimates = 0.97). Water availability is important for mature leaves and the month in which leaf regrowth begins has high luminosity, which may be acting as an initiating factor. The storage of stem water is probably responsible for the slow decrease in the number of cambial cells during the dry months. We conclude that the increase in cambial activity is related to the presence of mature leaves and the stored water helps to maintain the number of cambial cells.