Different morpho-anatomical strategies against desiccation in five species of Xerophyta genus in relation to their ecophysiological aspects

Although many works deal with different aspects of some Xerophyta plants individually as the typical model species of desiccation tolerant resurrection species, they do not deal with comparing species within the genus. In our study we mainly focus on different histo-anatomical characters which can play a special role in the mechanism of desiccation tolerance. Differences are shown among five species of Xerophyta genus which derive from three tropical African regions. On the leaf surface of X. scabrida glands are involved in the regulation of water uptake. Epidermal papillae of X. villosa can also reduce water loss by decreasing the stomata number. Special palisade cells of X. nandrasanae and X. scabrida take part in the water transport between the adaxial epidermis and the vascular bundles. In addition to retaining water, furrows of the leaf margins play an essential role in the folding of leaves during desiccation. Aquiferous parenchyma cells of X. scabrida, X. spekei and X. villosa can play a similar role due to their characteristic arrangement. Because of the considerable folding of parenchyma, Xerophyta species need extensive sclerenchyma tissue, which can help maintain leaf consistency in a desiccated state. The main photosynthetic pigments (chlorophylls and carotenoids) content, the net photosynthesis and the Fv/Fm fluorescence parameter of five Xerophyta species also reflect their unique adaptation to their proper microhabitat.