Studies on Hollarrhena floribunda (G. Don) Durand Schinz: Germination and seedling growth, and preliminary investigations on callus induction and plant regeneration

Seed germination, seedling growth and in vitro regeneration studies were conducted on H. floribunda(Apocynaceae), a potential reforestation candidate. The seeds germinated readily with 96.0 ± 2.5% germination in 10 days. The seedlings exhibited a slow growth rate, attaining a shoot height of 35.5 ± 4.46 cm and a leaf area of 23.86 ± 3.89 cm2 in 12 weeks. Murashige and Skoog (MS) medium supplemented with various concentrations of 2, 4-dichlorophenoxyacetic acid, (2, 4-D) alone or combined with Benzyladenine induced callus formation in leaf, internode and node explants. Massive callus production was generally observed with explants cultured on MS media supplemented with 4.5 µM 2, 4-D alone or combined with 2.2 µM BA. The highest frequency of shoot regeneration was induced by a combination of 4.5 µM 2, 4-D and 2.2 µM BA; no complete plantlets were however produced.   Key words: Callus, germination, H. floribunda, plant regeneration, seedling growth.