Family Solanaceae

Family Solanaceae: An Overview Through Its Key Characters

Family Solanaceae is placed under the subclass Gamopetalae in Bentham and Hooker's classification, since its petals are united into a single fused corolla, unlike the free-petalled condition of Fabaceae. The family is conveniently summarised through twelve key characteristics spanning habit, vegetative structure, floral organisation, pollination, fruit, and economic uses.

Habit and vegetative features: the family consists mostly of herbs and shrubs, with a small tree occurring only rarely; the stem is generally herbaceous, though it may become somewhat woody at the base in older plants; the leaves are arranged alternately, are simple (undivided), and are exstipulate, lacking stipules — a useful point of difference from the stipulate compound leaves of Fabaceae. The inflorescence is either a solitary axillary flower or a cyme.

The flower itself is bisexual, actinomorphic (radially symmetrical, in contrast to the zygomorphic Fabaceae flower), and pentamerous, its parts arranged in fives. The calyx has five sepals fused together and, notably, is persistent — it remains attached to the fruit as it develops, which is why a small green cap of fused sepals is still visible at the base of a ripe tomato or brinjal. The corolla likewise has five petals fused together into a rotate shape, spreading out flat like a wheel from a very short tube.

Androecium and gynoecium: there are five stamens, epipetalous (attached to the corolla tube) and positioned alternating with the petal lobes rather than opposite them. The gynoecium is bicarpellary and syncarpous (two carpels fused into one compound pistil), with a superior, bilocular ovary showing axile placentation. A particularly diagnostic detail of the family is that the two carpels — and so the two locules — are not set along the flower's ordinary median plane but are oriented obliquely, at roughly forty-five degrees to it, a subtle feature that distinguishes the Solanaceae ovary from other superficially similar bicarpellary ovaries.

Pollination, fruit, and economic importance: pollination is mostly entomophilous. The fruit is a fleshy berry (as in tomato and brinjal) or a dry capsule (as in Datura). Economically, the family is highly significant: as food it gives tomato, potato, and brinjal; as medicine it gives belladonna and ashwagandha; as an ornamental it gives petunia; and as a narcotic source it gives tobacco.

Floral Diagram, Floral Formula, and the Representative Example …