INITIATION AND EARLY DEVELOPMENT OF THE INFLORESCENCE IN PINEAPPLE (ANANAS COMOSUS, ‘SMOOTH CAYENNE') TREATED WITH ACETYLENE

Pineapple plants 'Smooth Cayenne' were made to flower by treatment with acetylene. The organization of the vegetative shoot apex is similar to that of many investigated angiosperms in that it shows a zonate pattern, viz., apical zone, peripheral zone, and central-core rib meristem. The latter zone is weakly developed. Cytological changes at the shoot apex occur as early as 3 days after treatment.; these involve nuclear changes and an increase in ribonucleic acid (RNA) in the cytoplasm of cells of the apical zone. A marked increase in the height of the apex occurs by the 9th day; this is preceded by rib meristem activity in the central core. All component parts of the inflorescence are present and in various stages of development by the 21st day at which time vegetative scales and "crown" leaves are initiated. THE INITIATION and development of the inflorescence and collective fruit of pineapple Ananas comosus (L.) Merr. has not been studied to any great extent from the anatomical and cytohistological points of view. Cultural aspects of the pineapple have been rather thoroughly investigated to include conditions for flowering. In 1942 Clark and Kerns reported that floral initiation could be achieved in advance of the normal period by application of naphthaleneacetic acid (NAA). Low concentrations of NAA would force flowering while high concentrations inhibited floral initiation. The work of van Overbeek (1946) suggested that the pineapple 'Cabezona is a short-day plant in Puerto Rico; the flowering period coincided with the period of shortest daylength. However, the pineapple could be made to flower if chemically induced even though the plant was kept on long daylengths. NAA and