INITIATING CULTURES OF HALESIA AND MALUS - INFLUENCE OF FLUSHING STAGE AND BENZYLADENINE

Shoot tips of Halesia carolina L. and Malus domestica Borkh. 'Golden D elicious' collected at various times during the spring growth flush va ried considerably in their ability to initiate shoot proliferating cul tures. Shoot tips collected during, or at the end of, the period of mo st rapid shoot elongation exhibited weak shoot proliferation potential , while shoot tips collected before or after this period were capable of strong shoot proliferation in vitro. Benzyladenine concentrations i n the culture media above 22.5 muM (Halesia) or 44.5 muM (Malus) were inhibitory during the period between bud break and rapid shoot elongat ion. Benzyladenine concentrations of 22.5 or 44.5 muM were useful in e nhancing shoot proliferation potential in shoot tips collected after t he period of rapid shoot elongation, but before the onset of summer do rmancy. Benzyladenine concentration did not affect the shoot prolifera tion potential of shoot tips collected during the rapid shoot elongati on phase of the spring growth flush. Halesia and Malus shoot tips beha ved similarly in this study. For deciduous woody perennials, the time of explant collection for culture initiation could be refined on the b asis of these results.