Atributos das escamas peltadas de Tillandsia que favorecem a absorção foliar de água

Abstract

Foliar water uptake (FWU) has been a strategy used by plants for at least 300 years. In the current scenario, marked by rising global temperatures, absorbing water through the leaves is important so that plants inhabiting fragile ecosystems, such as cloud forests and the epiphytic environment, can cope with the damage caused by rising environmental temperatures. Some epiphytes have leaves covered in peltate scales, a type of trichome specialized for leaf water absorption. It has been proposed that structural and chemical variations in these specialized trichomes favour leaf water absorption, and this work aimed to: (a) check whether the availability of water in the tissue influences the FWU of these species; (b) check whether characteristics such as the density of the scales and the shape of the scales affect the rate of water absorption and its speed; (c) check the distribution of lignin, suberin and pectins along the scales, trying to understand which characteristics of the wall favour apoplastic transport. It was found that the water storage capacity of the tissues positively influenced FWU and although there is a proposed trade-off between these two functions, what seems to compromise FWU is the relative water content present in the leaves of the individuals. FWU was influenced by some parameters related to the shape of the peltate scales, but many parameters did not show significant functional relationships. Individuals with a lower density of trichomes and those with a larger wing area absorbed more water through the leaves (Cmax), and significant functional relationships were established for individuals of T. pohliana, showing that investment in trichomes varies according to their interaction with water. Significant relationships were established between the deformity of the central disk and the Cmax, where individuals with more deformed central disks absorbed more water through the leaves. In the cell junctions, in the primary wall of the wings, of the cupula, of the cells that make up the stem, in the mucilaginous substance dispersed in its cytoplasm and in the primary wall of the leaf epidermis, the presence of pectins is observed which favor the transport of water via the apoplast to the interior of the leaf. This study shows that there are characteristics of peltate scales that favor leaf water absorption and some of them may have evolved by natural selection. The presence of these characteristics in organisms is important for plants that inhabit fragile ecosystems, such as epiphytes, to cope with rising global temperatures.