Crescimento geotrópico positivo do pecíolo cotiledonar em Butia capitata e implicações ecológicas e filogenéticas em palmeiras

Abstract

Palm trees have great ecological and economic importance in the tropical and subtropical regions of the world. Seedlings of several species of Arecaceae have positive geotropic growth of the cotyledonary petiole (CGP), which promotes the burial and protection of the vegetative axis. Information on the anatomical aspects of this process, as well as on the influence of environmental and evolutionary factors on its establishment, is scarce. This work aimed to evaluate anatomical aspects of the CGP of palm trees and to relate its occurrence to evolutionary and environmental aspects. For the anatomical study, Butia capitata, a palm tree endemic to the Cerrado in Brazilian central area, was used as a model species. Biometric, anatomical, micromorphometric and histochemical evaluations were performed on the embryos and seedlings of the species, throughout development. Based on a literature review, phylogenetic and environmental aspects of the cotyledonary petiole growth patterns in the Arecaceae family were discussed. The elongation of the cotyledonary petiole in B. capitata is due to meristematic activity (M zone and petiole meristem) and cellular expansion, mainly in the distal region. These processes are associated with the intense mobilization of carbohydrate and protein reserves. Differential elongation of the cotyledonary petiole cells promotes their curvature, initially in the distal region and later in the median region. CGP is a derived trait in Arecaceae, being an important strategy for the establishment of palm trees in seasonal and arid environments.