MUSACEAE - the banana family Systematic position

MUSACEAE - the banana family 

Systematic position

Class : Monocotyledonae

Series : Epigynae

Family : Musaceae

General characters Distribution

Musaceae includes about 6 genera and about 150 species. The members of this family are widely distributed over tropical regions of the world. In India it is represented by 2 genera and about 25 species.

Habit

Mostly perennial herbs attaining considerable height, perennating by means of rhizome (eg. Musa paradisiaca - Banana), rarely trees (eg. Ravenala madagascariensis - Traveller's palm) and watery sap is present.

Root

Generally fibrous adventitious root system is seen.

Stem

In Musa the real stem is underground called rhizome. The apparent, unbranched, errect and areal pseudostem is formed by the long, stiff and sheathy leaf bases which are rolled around one another to form an aerial pseudostem. The central axis that is concealed at the bottom of the pseudostem is called shaft. At the time of flowering, the shaft elongates, pierces through the pseudostem and produces an inflorescence terminally. Musa is a monocorpic perennial, because it produces flowers and fruits once during its life time. In Ravenala, the stem is aerial and woody.

Leaf

Simple with a long and strong petiole. The leaf blade is large and broad with sheathy leaf base. The leaf is extipulate and obtuse.

The pinnately parellel venation extends upto the leaf margin. The phyllotaxy is spiral in Musa but in Ravenala it is distichous i.e. the leaves are arranged in two rows on the same sides.

Inflorescence

In Musa, the inflorescence is branced spadix. The flowers are protected by large, brightly coloured, spirally arranged, boat shaped bracts called spathes. When the flowers open, the spathes roll back and finally fall off. In Ravenalea, the inflorescence is a compound cyme. In Musa, the flowers are polygamous i.e. staminate flowers, pistillate flowers and bisexual flowers are present in the same plant.

The male flowers lie within the upper bracts, the female flowers within the lower bracts and the bisexual flowers within the middle bracts.

Flowers

Brateate, ebractiolate, sessile, trimerous, unisexual or bisexual, when unisexual, the flowers are monoecious. The flowers are zygomorphic and epigynous.

Perianth

Tepals 6, arranged in two whorls of 3 each, free or united. In Musa, the three tepals of the outer whorl and the two lateral tepals of the inner whorl are fused by valvate aestivation to form 5 toothed tube like structure. The inner posterior tepal is alone free. It is distinctly broad and membranous.

Androecium

Basically stamens 6, in two whorls of 3 each, arranged opposite to the tepals. In Musa only 5 stamens are fertile and the inner posterior stamen is either absent or represented by a staminode. In Ravenala, all the 6 stamens are fertile. Anthers are dithecous and they dehisce by vertical slits. The filament is filiform and rudimentary ovary or pistillode is often present in the male flower.

Gynoecium

Ovary inferior, tricarpellary, syncarpous, trilocular, numerous ovules on axile placentation. The style is simple and filiform. The stigma is three lobed.

Fruit

An elongated fleshy berry without seeds eg. Musa and a capsule eg. Ravenala. 

Seed:

Non - endospermous