Morphologie des trichomes foliaires chez Quercus spp.

Abstract

The genus Quercus in Algeria is characterized by a high morphological diversity, particularly in the foliar trichomes. This study focuses on five oak species (Q. afares, Q. suber, Q. canariensis, Q. ilex, and Q. coccifera), distributed across three bioclimatic zones in northeastern Algeria: humid (Skikda, Annaba), sub-arid to semi-arid highlands (Batna), and upper semi-arid (Constantine). Through microscopic observation (optical microscope with Optika camera) of leaves, the shape, number, and length of the trichomes were analyzed. The results show significant variations in trichome density depending on the species and sites studied. Q. afares from Skikda exhibits a high density of trichomes on the upper surface of the leaves, indicating an adaptive strategy even in a humid environment. In contrast, the leaves of Q. coccifera from Annaba lack trichomes due to their maturity (deciduous trichomes). Q. suber, also from Skikda, shows a moderate density, lower than that of Q. afares. The samples from Batna and Constantine exhibit a high density of trichomes, reflecting adaptation to harsh environmental conditions. Foliar trichomes appear to be adaptive structures sensitive to ecological variations.