The gum arabic tree (Acacia senegal (L.) Willd. or Senegalia senegal (L.) Britton) is a legume tree from the dry tropics and subtropics. It is valued for the production of gum arabic, the only acacia gum evaluated as a safe food additive. The leaves and pods are browsed by livestock.
The gum arabic tree is a low branching, small, and spiny tree, which grows up to 7-15 m in height with a girth of about 1.3 m (Kew Gardens, 2016; Duke, 1983). It has a rounded, flat-topped crown (Orwa et al., 2009). The tree is deciduous, dropping its leaves during the dry season. Under dry conditions, the taproot develops to a great depth allowing the tree to become larger than usual. The trunk is about 30 cm in diameter and is covered by a greyish-white bark that becomes dark, scaly and thin in old trees (Kew Gardens, 2016; Orwa et al., 2009; Bekele-Tesemma, 2007). The tree bears prickly branches, armed with three hooked thorns, up to 7 mm long, just below the nodes. The leaves are pinnately compound, 3.5-8 cm long. Their rachis may be spiny. The leaflets are linear to oblong, 1-9 mm long and 0.5-3 mm wide. They may be sparsely hairy and a pale glaucous green in colour (Kew Gardens, 2016; Bekele-Tesemma, 2007). The yellowish-white and fragrant flowers are borne on cylindrical spikes, 5-10 cm long. The fruits are straight, hairy, flat, dehiscent papery pods, about 7 cm long x 2 cm wide. Green and pubescent when young, they become a shiny bronze with maturity. They contain 3-6 smooth, flat shiny seeds (Kew Gardens, 2016; Bekele-Tesemma, 2007).
The most important use of the gum arabic tree is the harvest of gum arabic, an exudate from the bark that is tapped for this purpose during the dry season (Orwa et al., 2009). Several thousand tons of gum arabic are internationally traded every year, mainly in Europe and the USA (Kew Gardens, 2016). Gum arabic has many commercial uses: food (flavour fixative, emulsifier, stabilizer of dairy products), pharmaceutics (these two sectors representing 60-75% of the use of gum arabic), and industrial products (inks, pigments, polishes) (Kew Gardens, 2016). Gum arabic was reported to have antidotal effects as it can destroy many alkaloids (Duke, 1983). Acacia senegal seeds are traditionally used for human nutrition in Rajasthan (Ram et al., 2014). The wood is valued as firewood, and can be used to produce charcoal. The wood is also used to make utensils, poles and fence-posts. The bark and the roots provide fibre and make strong ropes and fishing nets (Orwa et al., 2009; Duke, 1983). Gum arabic trees provide valuable fodder to sheep, goats and camels. Leaves and pods are browsed by domestic and wild ruminants. Flowers provide valuable nectar to bees for honey production (Orwa et al., 2009).