Family Musaceae – Banana Family

Family Musaceae – Banana Family

Diagnostic Features

•            Perennial giant herbs with pseudostems formed by leaf sheaths.

•            Leaves are large with thick midrib, parallel venation.

•            Flowers are zygomorphic, unisexual, inflorescence spadix covered by spathe.

•            Corolla 2 lipped.

•            Ovary tricarpellary, inferior.

•            Fruit elongated berry.

•            Septal nectaries are present.

Systematic Position

Note: Earlier Musaceae was a large family with 6 genera viz. Musa, Ensete, Ravenala, Strelitzia, Orchidantha and Heliconia . In APG only Musa and Ensete are retained while Ravenala, Strelitzia, Orchidantha and Heleconia are separated.

General Characters

Distribution

Musaceae includes only 2 genera (Musa and Ensete) and 81 species. The members of this family are mainly wet tropical lowlands from West Africa to Pacific (southern Japan to Queensland). (Musa is the most common plant of the family found in India).

Habit: Large perennial herbs perennating by means of rhizome ( Musa paradisiaca), raraly trees as in Ravenala madagascariensis.

Root: Fibrous adventitious root system.

Stem: In Musa the real stem is found underground called rhizomatous (dichotomously branching in atleast some spp). The apparent aerial erect, unbranched tall 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 in called shaft, which elongates and pierces through the pseudostem at the time of flowering and produces inflorescence terminally. monocorpic in Musa. (produces flowers and fruits once during its life time). Stem is aerial and woody in Ravenala madagascariensis.

Leaf: Simple with long and strong petiole the leaf blade is large and broad with sheathy leaf base. The leaf is exstipulate. Oval, obtuse or oblong with a stout midrib, entire, numerous parallel veins extending up to the margin, rolled in bud . Phyllotaxy is spiral in Musa and distichous i.e. leaves are arranged alternately in two opposite vertical rows in Ravenala.

Inflorescence: Terminal or axillary thyrse of one to many monochasial branched spadix in Musa, Usually the flowers are protected by large brightly coloured, spirally arranged, boat shaped bract called spathe. Compound cyme in Ravenala.

Flowers: Bracteate, ebracteolate, sessile, trimerours, unisexual, or bisexual or polygamous, when unisexual the flowers are monoecious. Flowers are zygyomorphic and epigynous. (In Musa flowers are polygamous i.e. staminate flowers, pistilate flowers and bisexual flowers are present in the same plant).

Perianth: Tepals 6, biseriate, arranged in two whorls of 3 each and homochlamydeous, 3 +3 syntepalous. In most of the species of Musa, the three outer tepals and two lateral tepals of the inner whorl are fused to form 5 toothed tube like structure called abaxial lip. The posterior inner median tepal alone is free, which is distinctly broad and membranous called labellum.

Androecium: Stamens 5 or 6, arranged in two whorls of 3 each opposite and adnate 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 six stamens are fertile. Filaments free, anthers linear, dithecous dehisce by longitudinal slits, and with sticky pollen.

Gynoecium:Tricarpallary,syncarpous, the median carpel is anterior in position, trilocular ovary inferior, ovules many, placentation axile, style filiform, stigma three lobed septal nectaries are present.

Fruit: Elongated berry containing numerous seeds, fruits forming compact bunches, seeds with copious and small embryo in Musa. Capsule in Ravenala.

Seed: Starch rich endosperm and starchless perisperm. Species of Ensete are distinguished from those of Musa by their larger seeds.

Botanical Description of Musa paradisiaca.

Habit: Monocarpic gigantic herb.

Root: Fibrous adventitious root system.

Stem: The real stem is underground called rhizomatous. The apparent, aerial erect unbranched pseudo stem 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. The shaft elongates, pierces through the pseudostem and produces an inflorescence terminally.

Leaf: Simple with a long and strong petiole. The leaf blade is large and broad with sheathy leaf base. Leaf exstipulate and obtuse pinnately parallel venation which extends upto the leaf margin phyllotaxy is spiral.

Inflorescence: Terminal branched spadix. Flowers are protected by large, brightly coloured spirally arranged, boat shaped bracts called spathe. When the flowers open, spathe rolls back and falls off.

Flower: Bracteate, ebracteolate, sessile, trimerous, unisexual or bisexual, flowers are zygomorphic and epigynous.

Perianth: Tepals 6, biseriate, 3+3 syntepalous, arranged in two whorls of 3 each and homochlamydeous, the three tepals of the outer whorl and the two lateral tepals of the inner whol are fused by valvate aestivation to form 5 toothed tube like structure called abaxial lip, the posterior inner median tepal is distinctly broad membrancus and free called labellum.

Androecium: Stamens 6, arranged in two whorls of 3 each, arranged opposite to the tepals. Only five stamens are fertile and the inner posterior stamen is either absent or represented by staminode. Anthers are dithecous and they dehisce by vertical slits. Filament is simple and filiform and rudimentary ovary or pistillode is often present in the male flower.

Gynoecium: Tricarpellary, syncarpous, the median carpel anterior, trilocular, ovary inferior, numerous ovules on axile placentation. Style is simple and filiform, stigma trilobed. Septal nectaries are present.

Fruit: An elongated fleshy berry and seeds are not produced in cultivated varieties.

Floral Formula

Economic Importance of The Family Musaceae