Leaf morphology, wax composition, and residual (cuticular) transpiration of four poplar clones

Paul Grünhofer,Lena Herzig,Lukas Schreiber

doi:10.1007/s00468-021-02236-2

Abstract

Key messageWe identified two poplar clones of the same species as highly comparable, yet clones of two further species of the same genus to be distinctly different regarding multiple morphological and ecophysiological traits.Leaf morphology, wax composition, and residual (cuticular) transpiration of four poplar clones (two clones of the hybrid species P. × canescens, P. trichocarpa, and P. euphratica) were monitored from the beginning to end of the growing season 2020. A pronounced epicuticular wax coverage was found only with P. euphratica. As the most prominent substance classes of cuticular wax primary alcohols, alkanes and esters were identified with P. × canescens and P. trichocarpa, whereas esters and alkanes were completely lacking in P. euphratica. Wax amounts were slightly decreasing during the season and significantly lower wax amounts were found for newly formed leaves in summer compared to leaves of the same age formed in spring. Residual (cuticular) transpiration was about five to tenfold lower for P. × canescens compared with the two other poplar species. Interestingly, with three of the four investigated species, newly formed leaves in summer had lower wax coverages and lower rates of residual (cuticular) transpiration compared to leaves of exactly the same age formed in spring. Our findings were especially surprising with P. euphratica, representing the only one of the four investigated poplar species naturally growing in very dry and hot climates in Central Asia. Instead of developing very low rates of residual (cuticular) transpiration, it seems to be of major advantage for P. euphratica to develop a pronounced epicuticular wax bloom efficiently reflecting light.

Highlights

Due to its considerably fast growth and ease of vegetative propagation, the genus of Populus became an increasingly interesting taxon for short-rotation agroforestry (Sannigrahi and Ragauskas 2010), even despite its generally high needs for a constant water supply caused by low water-use efficiencies (Blake et al 1984; Souch and Stephens 1997)
We report on a subset of four commonly researched Populus clones covering two intra-sectional hybrids and two true species, belonging to three sections in total: two clones of the hybrid species P. × canescens (Aiton) Sm., P. trichocarpa Torr. & Gray ex Brayshaw, and P. euphratica Oliv
In terms of leaf morphology, wax composition, and residual transpiration both clones of P. × canescens are not very different, which ensures good comparability of ecophysiological data acquired with either clone

Summary

Introduction

Due to its considerably fast growth and ease of vegetative propagation, the genus of Populus became an increasingly interesting taxon for short-rotation agroforestry (Sannigrahi and Ragauskas 2010), even despite its generally high needs for a constant water supply caused by low water-use efficiencies (Blake et al 1984; Souch and Stephens 1997). Its main function is the protection of the living tissues inside the leaf from environmental stress factors This includes (i) the restriction of uncontrolled water loss (cuticular transpiration) under drought conditions (Riederer and Schreiber 2001), (ii) protection from microbial pathogens (Andrews and Harris 2000) and herbivores (Alfaro-Tapia et al 2007), and (iii) reflection of UV light (Shepherd and Griffiths 2006). When measuring cuticular transpiration using intact leaves instead of isolated astomatous cuticles, it has been suggested to use the term”residual transpiration” (Burghardt and Riederer 2003; Kerstiens 1996). This considers the fact that incomplete stomatal closure after leaf abscission can not always be excluded. In the following, we will use the term “residual (cuticular) transpiration” to indicate that the transpiration was measured with intact leaves and not with isolated astomatous cuticles

Methods

Results

Discussion

Conclusion