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Growth and Development of the Banana Plant: II. The Transition from the Vegetative to the Floral Shoot in Musa acuminata cv. Gros Michel

W. G. BARKER and F. C. STEWARD
Annals of Botany
New Series, Vol. 26, No. 103 (JULY 1962), pp. 413-423
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/42907634
Page Count: 15
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Growth and Development of the Banana Plant: II. The Transition from the Vegetative to the Floral Shoot in Musa acuminata cv. Gros Michel
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Abstract

The changes that occur in the shoot apex of the banana, as it passes from the vegetative to the flowering stage, are described. The crucial events occur well before floral primordia are evident, and they require a redistribution of activity in the various growing regions. The vegetative shoot apex is in a central depression in the rhizome; there is virtually no internodal growth in the axis, the most active growth is in the leaf bases; vegetative buds do not form in the leaf axils but only appear adventitiously far from the tip of the shoot. With the onset of flowering this is changed; growth in the axis itself, previously suppressed, occurs and flower buds arise as primordia in the axils of subtending bracts. The bracts do not show the marked growth in their bases which is so characteristic of leaves. Thus, the shoot apex rises to the level of the rhizome and then above it; as it does so, its tip changes in shape from a broad flattened dome to a pointed cone. At the transitional stage, more activity occurs in the cells of the mantle, or tunica, which now consists of 3 to 4 layers over the central dome. Below, in the central or mother cell zone of the corpus, which was quiescent in the vegetative shoot, the cells spring into greater activity, becoming more protoplasmic and stain more deeply. Directly below this region in the rib meristem, cells show transverse divisions. Bract primordia occur high on the flanks of the apex, and, though they originate in the manner of leaves, their subsequent growth is different. Flower primordia occur even in the axils of bracts close to the shoot tip. Thus, the problem now is to designate the source, nature, and mode of action of the stimuli which initiate and control this quite different distribution of growth in the floral, as contrasted with the vegetative, shoot. The significance of the previously more quiescent central, or mother cell zone, of the apex as the source of such stimuli, is stressed. Thus, flowering first requires that the limiting controls which apply to the vegetative shoot be released, and, secondly, that the apex of the shoot, rather than the leaf base, becomes the main centre of growth and development.

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