Anatomical, physiological, biochemical and molecular responses of Eucalyptus spp. under water deficit conditions and characteristics of Tunisian arid species: an overview

Abstract

The genus Eucalyptus occurs in a large range of environmental conditions, mainly arid/semi-arid areas. It includes species with high capacity to survive with extremely low water potential. For that, our review shows an important effect of drought on Eucalyptus spp. plants’ resistance mechanisms and management strategies. In fact, water stress acts directly on growth, productivity, yield, it affects also response to pests and diseases, disturbs wood formation and essential oil yield. However, the general patterns of response to water stress varied among species, genotypes, hybrids and clones. To assume, reducing water loss in eucalyptus species is manifested by reducing leaves area, reducing gas exchange, increasing water uptake thanks to a prolific and deep root systems. A greater accumulation of osmolytes that gives rise to osmotic adjustment including carbohydrates especially cyclitols and quercitol, other amino acids and organic acids, also some proteins which play a vital role in sustaining cellular functions under drought conditions. More than that, water stress increases mainly the levels of pigments, chlorophyll fluorescence parameters, malondialdehyde (MDA), abscisic acid (ABA) and the biosynthesis of triacylglycerols (TAGs) in Eucalyptus species.