Musaceae

Growth Form and Habit

Large to giant perennial herbs, often appearing tree-like but lacking true woody tissue. Growth arises from a substantial underground rhizome or corm. The aerial 'trunk' is a pseudostem formed by the tightly rolled, concentric bases (sheaths) of the leaves.

Leaves

Leaves are very large (among the largest simple leaves in the plant kingdom), simple, with entire margins that often become tattered by wind along the parallel side veins. They are arranged spirally around the pseudostem. Each leaf consists of a long, stout petiole, a massive blade with a prominent midrib, and numerous parallel veins extending perpendicularly or obliquely towards the margin (pinnate-parallel venation). Leaves are rolled longitudinally in bud.

Inflorescence

The inflorescence is large, complex, and terminal, emerging through the center of the pseudostem; it may be erect, oblique, or drooping (pendulous). It consists of a thick central axis bearing clusters (hands or cincinni) of flowers. Each cluster is subtended by a large, often colorful (red, purple, yellow, green), spathe-like bract. Typically, the basal bracts subtend female (or functionally female) flowers, while the distal bracts subtend male (or functionally male) flowers (plants are monoecious). Bracts often abscise as fruits develop.

Flowers

Flowers are unisexual (or functionally so) and zygomorphic (bilaterally symmetric). They are typically arranged in one or two rows within each bract cluster. Key features include:

• Perianth: Composed of 6 tepals in two whorls (3+3), but highly modified from the typical monocot pattern. Usually, the 3 outer tepals and 2 inner lateral tepals are fused together forming a 5-lobed or 5-toothed compound structure (often called the 'standard' or compound tepal). The remaining inner median tepal is typically free, smaller, and sometimes more membranous.
• Androecium: Stamens typically number 6 ancestrally, but usually only 5 are fertile and developed, arranged opposite the lobes of the compound tepal. The sixth stamen (opposite the free inner tepal) is either absent or present as a small staminode. Filaments are relatively thick; anthers are long and linear, opening via longitudinal slits. Female flowers possess staminodes.
• Gynoecium: Ovary is inferior, composed of 3 fused carpels forming 3 locules. Placentation is axile, with numerous ovules per locule. A single, long, slender style arises from a depression at the ovary apex, terminating in a capitate or slightly 3-lobed stigma. Male flowers possess a non-functional pistillode. Nectaries are located within the septa (partitions) of the ovary.

Fruits and Seeds

The fruit is a fleshy berry derived from the inferior ovary, commonly known as a banana or plantain. The berry wall develops from the ovary wall and surrounding receptacle tissue. In wild species, the fruit is filled with numerous hard, dark, rounded or angled seeds. However, most cultivated bananas and plantains are parthenocarpic (fruit develops without pollination/fertilization) and effectively sterile, lacking developed seeds or containing only tiny, aborted ovules.

Chemical Characteristics

Plants store starch, particularly in rhizomes and fruits (especially plantains). They contain phenolic compounds and tannins. Latex channels are sometimes present in various tissues but may not be conspicuous. Flower and bract colors are due to anthocyanins and carotenoids.