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

Key message We 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.