STIMULATION BY AUXIN AND SUCROSE OF BULBIL FORMATION IN-VITRO BY SINGLE LEAF CULTURES OF NARCISSUS

Bulbil formation in vitro by single leaf explants from shoot clump cul tures was investigated for Narcissus cultivars St Keverne and Hawera. Single leaf explants (30-50 mm leaf with attached basal plate tissue) formed bulbils very infrequently unless cultured on media containing b oth auxin and a high concentration of sucrose whereas auxin was not ne cessary for bulbil formation by shoot clump cultures. As well as she-w ing much stronger stimulation by auxin, bulbil initiation and developm ent were more strongly inhibited by BA in single leaf cultures than in shoot clump cultures. Partitioning of dry matter into bulbils was gen erally lower in single leaf cultures than in shoot clump cultures but was more sensitive to growth regulators. Optimal sucrose and auxin con centrations for bulbil development by single leaf cultures were invest igated. Bulbil formation in the presence of NAA was strongly stimulate d by 176 mM sucrose for both cultivars but there were genotypic differ ences in auxin responses, St Keverne showing good bulbil development w ith 0.54 mu M NAA, 5.4 mu M IAA and 5.4 mu M IBA and Hawera responding only to 27 mu M IAA. It is concluded that single leaf cultures could provide a simple system for investigation of the regulation of Narciss us bulb initiation and development.