## 2 Taxonomy and Morphology  
_Ailanthus altissima_ is an accepted name with original publication details in J. Wash. Acad. Sci. 6: 495 (1916) and many synonyms [11]. It belongs to the family Simaroubaceae [6], which consists mainly of trees and shrubs, distributed in tropical and warm regions, comprising 30 genera and 150 species. The term for the genus _Ailanthus_ is an Ambonese word derived from ailanto, meaning \"tree of heaven\" [12]. About 5-10 species of trees from this genus are known and characterised by being deciduous with rapid growth, large spreading branches, pinnate leaves with pointed leaflets, where the terminal leaflet is usually present, small yellow to greenish flowers, and the fruits samaras stretched into a long wing, where the seed lies in the middle (Figure 1C). In the root sprouts, the emerging leaves vary in the number of divisions (from unifoliate to compound pinnately) and are yellowish-green at first. In addition, the genus _Ailanthus_ has a fine, satiny wood and is known for its medicinal values [12].  
Regarding the morphology of the species in the study, _A. altissima_ (Figure 1) is described as a tree growing up to 30 m in height with a trunk of greyish, smooth, or cracked bark, and in the oldest specimens and branches, a reddish-brown colour. Its leaves (30-100 cm) are alternate, compound, odd-pinnate (on the shoots) and paripinnate (arranged at the ends of the branches), and glabrous or with scattered hairs on the upper side of the margin. Each leaf can have 5-12 pairs of leaflets (or 4 to 35 leaflets [13]) of very variable size, petiolate, from narrowly lancelate to ovate-lanceolate, with gradually narrowed apex, and an entire margin. Each of these leaflets has two to four glandular teeth near the base, with 1-8 openings as extra-loral nectaries--an important characteristic to identify _A. altissima_[6; 13; 14].  
_A. altissima_ is a tree with both female and male terminally located infloresences, where the latter are larger, pluriflor, and emit an unpleasant scent. In addition, unlike the female flowers, the male flowers have 10 well-functioning stemens, each with a fertile anther; the female flowers have abortive anthers. It is due to these facts that _A. altissima_ is considered a dioiceous tree [7; 13; 15]. Flowers have a tiny cupular and five-lobed calyx, a corolla with five sepals, lanceclate and green, five distinct petals that are hairy at the base, greenish to yellowish-green, and an annular and lobed gland disc (different types of nectaries); female flowers have five free carpels that generally develop into five separate winged fruits. The fruits (samaras) can vary from greenish-yellow to reddish-brown, and are arranged in clusters and dispersed by the wind [6; 7; 13; 14]. In the samaras, the seeds are found and these, depending on the location of the trees, vary considerably in colour, size, weight, and thickness [6].  
Concerning roots, the main root can develop several lateral roots, from pre-existing primordia or root sprouts. The root system has a highly variable and asymmetric spatial extent, in which lateral roots have been reported to reach a length of 27 m from the parent  
Figure 1: Some examples of _A. altissima_ in the Castelo Branco region (Portugal); (**A**) an old plant; (**B**) a younger plant; (**C**) the samaras with seeds in the middle; (**D**) the trunk of the first plant and (**E**) part of a leaf with its leaflets.  
tree. The nectaries' primary function is to eliminate excess sugar from the plant. _A. altissima_ has floral and extrafloral nectaries, which excrete different forms of sugar until October. These nectaries are located on the leaves, pseudostipules, and cataphylls. Trees of the genus _Ailanthus_ have a rapid stem elongation, which leads to the fact that these trees can grow to heights of 25-45 m [7; 12].