Hormonal and histological studies related to in vitro banana bud formation

Shoot apices of Musa subgroup AAA 'Grande Naine' were used for in vitro cul ture establishment. The endogenous hormone levels and their effects on bud formation were evaluated during a 75-day period. Cytokinins, IAA and ABA we re separated by HPLC and quantified by means of ELISA. Enzymatic degradatio n of IAA was determined by the colorimetric method. Explants were maintaine d on establishment medium for 60 days. The endogenous cytokinins were highe r in the basal portion of the explant. Subculture to proliferation medium ( 65 to 75 days) resulted in a substantial increase of cytokinins in the basa l portion and in a decline in the apical portion. 2iP was the predominant c ytokinin in the tissue. The endogenous level of IAA and the IAA/cytokinin r atio decreased after the 65th day of culture. The level of ABA was reduced from the time of inoculation up to the 75th day of culture. Histological an alysis indicated that buds formed at the leaf base at the 65th day of cultu re.