AN EVALUATION OF THE ROLE OF CYTOKININS IN THE DEVELOPMENT OF ABNORMAL INFLORESCENCES IN OIL PALMS (ELAEIS-GUINEENSIS JACQ) REGENERATED FROM TISSUE-CULTURE

Tissue cultures and regenerant plants from cell lines producing palms with normal and abnormal flowers were analyzed for cytokinin content a nd compared with zygotic embryos and seedlings. Immature inflorescence s at the critical stage of flower development dissected from normal an d abnormal palms were also analyzed, High performance liquid chromatog raphy (HPLC)/radioimmunoassay and HPLC/enzyme-linked immunosorbent ass ay methods were used over a period of several years to measure the iso prenoid cytokinins. The results of analyses of endogenous aromatic cyt okinins, present at comparable levels, will be reported separately. Oi l palm cultures and regenerant plants contained relatively high concen trations of the 9-glucosides of isopentenyladenine ([9G]iP) and zeatin ([9G]Z), The predominant biologically active isoprenoid cytokinin pre sent was zeatin riboside ([9R]Z), with lesser amounts of isopentenylad enine (iP) and isopentenyladenosine ([9R]iP). There was evidence of sm all amounts of dihydrozeatin compounds, but high concentrations (mainl y as dihydrozeatin-9-glucoside ([9G]DHZ)) were confined to the haustor ium of the zygotic embryo. Callus tissue contained very low concentrat ions of cytokinin. Frequently only [9G]iP could be detected, at about 1 pmol . g(-1) fresh weight, with [9R]Z at less than 0.05 pmol . g(-1) . In comparison, nodular embryogenic tissues in vitro contained betwee n 30 and 1,500 pmol . g(-1) of [9G]iP, 5-50 pmol . g(-1) of [9G]Z, and up to 12 pmol . g(-1) of [9R]Z. Shoots of regenerant plantlets and se edlings contained lower concentrations of [9G]iP (3-30 pmol . g(-1)), although this was still the predominant cytokinin. [9R]Z and [9G]Z wer e present at between 2 and 15 pmol . g(-1), with iP at 1-5 pmol . g(-1 ) and [9R]iP at between 1 and 12 pmol . g(-1). Seedlings contained sim ilar amounts with the exception of a lower [9G]iP content (5-10 pmol . g(-1)) and more [9R]iP (10-20 pmol . g(-1)). Root tissues of ramets c ontained significantly higher concentrations of [9G]iP than shoots. Co mparison of two isogenic lines of one clone giving rise to normal and abnormal palms showed significantly higher concentrations of [9R]Z and [9G]Z in the normal than in the abnormal line and, in embryoids only, higher [9G]iP in the normal line. In all other cases the between-clon e differences were greater than any normal/abnormal differences. There was a general tendency for increased concentrations of [9G]iP in abno rmal lines and for this compound to be in a higher concentration in em bryoids and plants derived from culture than in zygotic embryos and se edlings. Analysis of cytokinins in immature female inflorescences of n ormal and abnormal palms of a single clone showed the abnormal inflore scences to have higher concentrations of [9R]Z and [9R]DHZ and less [9 G]Z than the normal inflorescences at comparable stages of development .