Young leaf segments from plants growing both in vivo and in vitro were cultured on Murashige and Skoog (MS) medium supplemented with auxins [naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D)], cytokinins [kinetin (KN) and N 6 -benzyladenine (BA)] and coconut liquid endosperm (CW). The explants from mature leaves did not show any growth and turned necrotic, while those obtained from juvenile leaves growing in vitro developed protocorm-like bodies (PLBs) at their cut surfaces within 4±8 wk depending on the growth medium. An optimum of 18 PLBs developed from leaf explants on medium supplemented with 2.0 mg l 21 (8.87 mM) BA. Upon subculture in basal MS medium, the PLBs differentiated into plantlets within 6±8 wk. The resulting plantlets were successfully transferred to vermiculite initially and subsequently to potting mixture; 84% of the plantlets survived after 3 mo. of transplantation.

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An attempt was made to in vitro seed germination and plantlet regeneration in Aerides ringens, a threatened, endemic and epiphytic orchid. Five basal media Knudson C (KC), Vacin and Went (VW), Burgeff’s (N3f), half strength MS, MS were examined for their effectiveness. Germination occurred in all the media. However, KC medium proved to be the best for seed germination (70.8%) and half strength MS was superior for the differentiation of protocorm like bodies (PLBs) into seedlings. The seeds were also cultured on various plant growth regulators (PGRs) to evaluate their effectiveness on seed germination and further differentiation. Among the PGRs tested, 0.57 μM IAA (IAA 89.3%), 4.64 μM Kn (88.6%) and 2.21 μM BAP (90.7%) and 0.57 μM IAA + 0.55 μM BAP (96.5%) were stimulated the germination and further differentiation of PLBs into seedlings. The concentrations of 2.21 μM BAP and combination of 0.57 μM IAA + 0.55 μM BAP stimulated the formation of MPLBs, which later differentiated into shoots and roots. Four potting substrates were evaluated for Ex vitro seedling survivability of which brick: charcoal: decaying litter: coconut husk (1 : 1 : 1 : 1) gave maximum survival rate (89.0%). Plant Tissue Cult. & Biotech. 29(1): 49-62, 2019 (June)

In vitro regenerative potential of protocorm like bodies (PLBs) of Dendrobium barbatulum were assessed. The formation of secondary PLBs from the primary PLBs that formed from the callus, it is derived from a few larger injured protocorm like bodies. The injured larger PLBs were cultured on half strength MS supplemented with different concentrations of BAP (0.32, 1.62, 3.23 and 16.15 μM), Zn (0.46, 2.28, 4.56 and 22.80 μM) and Kn (0.47, 2.33, 4.65 and 23.25 μM). The highest percentage of secondary PLBs (66.33%) were obtained on half strength MS medium supplemented with BAP 3.23 μM, after 5 weeks of culture. Then these clumps of PLBs were subcultured on half strength MS fortified with coconut water (CW), cane juice (CJ), peptone (P) and casein hydrolysate (CH) for regeneration. Among the complex organic additives 20% CW and 2.0 g/l P to half strength MS resulted in the development of plantlet 78.31 and 62.60%, respectively. Well developed plantlets were successfully acclimatized in the community pots having brick pieces, charcoal, decaying litter and coconut husk (1 : 1 : 1 : 1) gave maximum survival rate of 87.03%. Plant Tissue Cult. & Biotech. 30(2): 243-252, 2020 (December)