Résumé
Nothapodytes nimmoniana is an endangered medicinal tree and regarded most convenient natural source for large scale isolation of anticancer alkaloid camptothecin. In order to meet pharmaceutical market demand for camptothecin and conserve natural population of the species, in vitro culture techniques can be employed for mass propagation and production of the alkaloid. Seed germination is one of the difficult challenges in the establishment of the aseptic in vitro cultures. Pre-germination treatments of soaking in water, GA3 solution and aseptic excision of the embryo axis were employed to enhance seed germination and seedling recovery respectively for further in vitro studies. Seed soaking in water or GA3 solution for 24 hours enhanced the germination capacity with better response obtained when seeds were soaked in GA3 (2.6 μM) solution and germinated on half strength MS medium supplemented with the GA3. Removal of the outer, inner seed coat and inoculation of the embryo axis on medium amended with or without GA3 reduced seedling recovery time to 3-4 weeks. Seedlings obtained on medium fortified with GA3 showed vigorous growth with complete plantlet development than on PGR-free medium. The strategy can be employed to reduce seedling recovery time to within 3-4 weeks compared to 7-10 weeks required for germinating the seeds in vitro.
Résumé
The present study describes the incidence of somatic embryo (SE) irregularities in Catharanthus roseus (L.) G. Don. In this ornamental and anti-cancerous medicinal plant, SEs were developed at a very high rate from hypocotyl callus on MS medium, amended with 1.0 mg l-1 naphthalene acetic acid (NAA) and 1.5 mg l-1benzylaminopurine (BA). But at high (1.5 mg l-1) plant growth regulators (PGRs) levels severe embryo developmental abnormalities were caused. The major aberrant SE types have been described in the present communication. In several cases, the in vitro raised SEs had underdeveloped root ends or with aborted root axis. These irregularities in embryo structure appreciably reduced embryo germination rate and plantlet recovery. Here, we evaluated the effect of various PGRs, activated charcoal (AC), and various levels of sucrose in order to improve SE quality and germination. Medium added with 4.0 % sucrose improved rooting ability and growth. The addition of AC improved plantlet conversion significantly by promoting rooting.