Variability in leaf anatomical traits of <i>Quercus ilex</i> L. in Eastern Mediterranean and adaptations to the growing environment

Abstract

Adaptation of plants to different habitats correlates with variations in leaf anatomical traits. In the Quercus ilex L. populations of the Eastern Mediterranean basin, we evaluated the relationship between leaf anatomical characteristics and climate variables. Robust paired samples t-test and Spearman\"s correlation analysis were performed to compare shade and sun leaves. PCA was utilized to visualize the overall coordination of leaf anatomical traits. We analyzed the geographical variation of leaf anatomical characteristics using robust-ANOVA and investigated their relationships with climate variables using LMEs. The 14 traits in shade and sun leaves are more diagnostic. The sun leaves have thicker cuticles than shade leaves, and the adaxial surface has a thicker cuticle than the abaxial surface. The adaxial cuticle thickness at midrib, adaxial and abaxial cuticle thickness at lamina, and thickness of mesophyll, palisade, and spongy mesophyll showed significant differences between populations. Lamina cuticle thickness and stomata\"s number were mainly affected by climate variables. In both sun and shade leaves, the number of stomata was lower in semi-arid regions than in semi-humid ones. In particular, the study results reveal differences in the structural mechanisms that protect Q. ilex leaves from light in different populations. The leaf anatomical characteristics of the species exhibit wide variation in the populations of the Eastern Mediterranean region. This variation may have enabled it to thrive in both semi-humid and semi-arid areas. These findings indicate that the species\" adaptability in terms of anatomical characteristics may be quite high against stress factors that may arise from climate change.