In vitro direct rhizogenesis from Gerbera jamesonii Bolus leaf

The present report describes an original protocol for in vitro direct induction of roots from leaf explants of gerbera for the first time. Since gerbera has immense potential as a premium cut-flower, the major attempts were made on in vitro mass propagation chiefly through in vitro multiple shoot proliferation or callus regeneration. Nevertheless, rhizogenesis could be impending an unattempted method with its yet-to-be known advantages. In our study, the optimum conditions for direct root induction from leaf explants were assessed employing tissue culture technique. Leaves were inoculated to MS medium containing no or variable auxin sources and concentrations namely, 2,4-dichlorophenoxyacetic acid, indole-3-acetic acid (IAA), indole-3-butyric acid or α-naphthaleneacetic acid for root induction. It was evident that the maximum root induction (with a frequency of 92.6 %) occurred on MS media fortified with 1.5 mg l−1 IAA, wherein root induction was observed as early as 11 days of culture and an average of ~19 roots with ~13 mm length was obtained from 4 cm2 leaf segment after 45 days of culture. Stereo microscopic observation revealed the induction of roots and gradual developmental stages of rhizogenesis. The efficiency of direct root induction without any interim growth stages (such as, callus or shoots) in our study offers a reproducible system that could provide a model protocol for more comprehensive developmental studies on root growth

Influence of auxin and its polar transport inhibitor on the development of somatic embryos in Digitalis trojana

The present study reports the role of auxin and its transport inhibitor during the establishment of an efficient and optimized protocol for the somatic embryogenesis in Digitalis trojana Ivan. Hypocotyl segments (5 mm long) were placed vertically in the Murashige and Skoog medium supplemented with three sets [indole-3-acetic acid (IAA) alone or 2,3,5-triiodobenzoic acid (TIBA) alone or IAA-TIBA combination] of formulations of plant growth regulators, to assess their differential influence on induction and proliferation of somatic embryos (SEs). IAA alone was found to be the most effective, at a concentration of 0.5 mg/l, inducing similar to 10 SEs per explant with 52% induction frequency. On the other hand, the combination of 0.5 mg/l of IAA and 1 mg/l of TIBA produced significantly fewer (similar to 3.6 SEs) and abnormal (enlarged, oblong, jar and cup-shaped) SEs per explant with 24% induction frequency in comparison to that in the IAA alone. The explants treated with IAA-TIBA exhibited a delayed response along with the formation of abnormal SEs. Our study revealed that IAA induces high-frequency SE formation when used singly, but the frequency gradually declines when IAA was coupled with increasing levels of TIBA. Eventually, our findings bring new insights into the roles of auxin and its polar transport in somatic embryogenesis of D. trojana