3.3. Shoot bud proliferation and elongation
The regenerated shoot buds were cultured on fresh shoot bud induction
medium for one passage for further proliferation. Higher concentrations
of BAP (8.88 μM and above) and TDZ (9.29 μM and above)
produced hyper-hydrated cultures. Among all the cytokinins tested for
proliferation of regenerated shoot buds 4.44 μM BAP was found
optimum.
Subsequent subculture (after two passages) of regenerated shoot
buds on MS medium with 4.44 μM BAP produced hyper-hydrated cultures.
The clumps of proliferated shoot buds were separated and transferred
to medium with low level of cytokinins alone or in combination
with IAA for elongation (Table 2). Significant differences in elongation
were observed at different concentrations and combinations of PGRs.
Combination of BAP (1.11 μM) and IAA (0.57 μM) was found the best
for shoot bud elongation (Fig. 1B & C). Significantly lengthy (6.70 ±
0.22 cm) and viable micro-shoots were obtained on this medium formulation.
The elongation ranged from 1.97 ± 0.05 to 5.23 ± 0.02 cm.
on medium containing BAP and 2.50 ± 0.04 to 4.48 ± 0.09 on medium
with Kin. Incorporation of low level of IAA improved the shoot bud proliferation
and elongation ranged from 3.87 ± 0.12 to 6.70 ± 0.22 cm. on
medium containing BAP and IAA; and 2.68 ± 0.04 to 5.38 ± 0.12 cm. on
medium with Kin and IAA. On medium with Kin alone and in combination
with IAA, shoot buds showed poor elongation and vigor.