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Banana

Biology Of Bananas

Plants in the banana family are superficially tree-like in appearance. However, they are actually tall, erect, perennial herbs, because after they flower and set fruit, they die Young green bananas growing in clusters. Photography by Nigel Cattlin. The National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission. back to the ground surface. Their perennating structure is a large, underground, branched rhizome or corm.

Bananas and their relatives have a pseudostem, socalled because it has the appearance of a tree trunk. However, the banana stem is actually herbaceous, and is comprised of the densely overlapping sheath and petiole bases of their spirally arranged leaves. The pseudostem contains no woody tissues, but its fibers are very strong and flexible, and can easily support the erect plant, which is among the tallest of any herbaceous plants.

Bananas can grow as tall as 19.7-23 ft (6-7 m), and typically have a crown of leaves at the top of their greenish stem. The leaves of bananas are large and simple, with a petiole, a stout mid-rib, and a long, expanded, roughly oval, leaf blade, which can reach several meters in length. The leaf blade has an entire (smooth) margin, although it often becomes frayed by the wind, and may develop lobe-like ingrowths along its edge.

The flowers of bananas are finger-shaped, with three petals and sepals, and are subtended by large, fleshy, bright reddish-colored scales, which fall off as the fruit matures. The flowers are imperfect (that is, unisexual), and the plants are monoecious, meaning individual plants contain both female and male flowers. The flowers are arranged in a group, in an elongate structure known as a raceme, with male flowers occurring at the tip of the structure, and female flowers below. Only one inflorescence develops per plant. The flowering stalk develops from the underground rhizome or corm, and pushes up through the pseudostem of the plant, to emerge at the apex. The flowering stalk eventually curves downwards, under the weight of the developing fruits. The central axis of the raceme continues to elongate during development, so that older, riper fruits occur lower down, while flowers and younger fruit occur closer to the elongating tip. The same is true of the male flowers, with spent flowers occurring lower down, and pollen-producing ones at the tip of the inflorescence.

The flowers of bananas are strongly scented, and produce large quantities of nectar. These attract birds and bats, which feed on the nectar, and pollinate the flowers. The mature fruits are a type of multi-seeded berry, with a leathery outer coat known as an exocarp, and a fleshy, edible interior with numerous seeds embedded.


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