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Eucalyptus has become one of the most widely planted genera in the world because of its tolerance to a wide range of soil types and climates, as well as for its many industrial, commercial and medicinal uses. Eucalyptus torquata Luehm. is a plantation species frequently planted in semi-arid and arid regions for its ecological, forestry, ornamental and melliferous interests. Based on literature, drought tolerance of this species was mostly directed to adaptation mechanisms. Physiological investigations reveal the importance of stomatal closure and increased solute contents suggesting that osmotic adjustment is one of the main responses to drought in E. torquata. On the other hand, it showed low sensitivity to salt stress. This paper also highlights the immense benefits of E. torquata which contains essential oils with variable chemical composition and rich essentially in 1,8-cineole, torquatone, α-pinene, trans-myrtanol, α-eudesmol, β-eudesmol, globulol, trans-pinocarveol and aromadendrene. These oils, as well as the methanol and aqueous extracts possess a wide variety of bioactivities of great importance which are particularly valuable as antibacterial and antifungal agents also have a strong toxicity against insects and mites in addition to antiproliferative and cytotoxic effects against different types of cancer cells.

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.