Water storage and transport in leaves of vesselless trees in the temperate rainforest of south-central Chile

Abstract

According to a common hypothesis, some of the epidermal structural features in the leaves of tracheid- bearing plants “offset” low specific conductivity of vesselless wood. The data concerning this issue is contradictory, which can be explained by the fact that leaf water relations depend not only on the epidermis structure, but also on the structure of other leaf tissues. In the current study we aimed to evaluate the diversity of water transport systems in the leaves of tracheid-bearing woody plants in the temperate rainforest of south-central Chile. For this purpose, we collected leaves of four Podocarpaceae and two Winteraceae species in natural habitats, examined their leaf anatomy using light and transmission electron microscopy, measured the quantitative characters and analyzed the data using principal component analysis. Leaves of the studied species differ in the mesophyll and xylem anatomy. Four species have features that accelerate water transport through the leaf tissues via the apoplast (Prumnopitys andina), accessory transfusion tissue (Podocarpus saligna) and a network of veins (Drimys species). On the contrary, the leaves of Saxegothaea conspicua and Podocarpus nubigena accumulate water in water-storage tissue (hydrenchyma), but their ecology suggest that hydrenchyma is not an adaptation to environmental conditions. The obtained data indicate the existence of different ways of water delivery to the photosynthetic tissue in the leaves of vesselless plants. In the case of insufficient water supply through the tracheids, hydrenchyma is likely to maintain hydration of the leaves.