Ultrastructural aspects of adaptation of 'Asli' local grapevine cultivar (Vitis vinifera L.) to arid environments
'Asli' autochthonous Tunisian cultivar native to Kerkena islands (South of Tunisia) represents a specific genotype regarding its singularity among Tunisian grapevine accessions and aromatic potential expressed by juicy white berries with a high brix degree. Therefore, 'Asli' cultivar is characterized by a low transpiration rate (1.5 mm j-1), justifying its adaptation to drought. Linking the traditional monoculture of 'Asli' grapevine cultivar in Kerkena to the arid climatic conditions prevailing in this region (5<IDM<10), ultrastructural investigations were carried out in order to determine the leaf cellular modifications involved in the adaptation of this cultivar. This study was based on leaf surface and section observations using scanning and transmission microscopy. Comparisons were done between 'Asli' vines cultivated in northern Tunisia (semi-arid climate) and Kerkena islands. Scanning electron microscopy (SEM) of leaf surfaces and sections from 'Asli' cultivar revealed abundant epicuticular wax deposits on Kerkena grapevine leaves as dense crusts and plates. Further details on the crystalloid structure of epicuticular wax deposits were investigated using atomic force microscopy (AFM). SEM showed also a markedly higher density of lanate and pilose trichomes on the abaxial leaf surface in Kerkena-cultivated grapevines in comparison to those grown in the North. On the other hand, a significant cell wall thickening was observed by transmission electron microscopy (TEM) on the adaxial epidermis of leaves sampled in Kerkena. This study, carried out for the first time on grapevines native to arid environments, evidenced some adaptation features in 'Asli' cultivar. In fact, epicuticular wax accumulation and cell wall thickening observed on the leaves represent effective barriers to cell and tissue desiccation, while an increased trichome density on the abaxial leaf surface has an anti-transpiring and a boundary layer thickening effects under arid conditions.
Ben Salem-Fnayou, A., Ghorbel, A., Mliki, A. and Jemaa, R. (2017). Ultrastructural aspects of adaptation of 'Asli' local grapevine cultivar (Vitis vinifera L.) to arid environments. Acta Hortic. 1157, 197-202
leaf, epicuticular wax, scanning microscopy, TEM, cuticle, trichomes