Micropropagation and medicinal properties of Barleria greenii

different plant species (GILL et al., 1995; GOGATE and NADGAUDA, 2003;
PAREEK and KOTHARI, 2003; GOMES et al., 2006; RAI et al., 2007; AZAD et
al., 2009; OTHMANI et al., 2009).
2.1.5 Stage III: Preparation of propagules for transfer to soil
Regenerated shoots or plantlets produced during the immediate previous stage
(stage II) are often too small or of low vigour to be able to survive in soil. The
objective of this third micropropagation stage is therefore to prepare regenerated
shoots or plantlets for successful transfer to soil (MURASHIGE, 1978). This stage
involves the in vitro rooting of individual regenerated shoots, hardening of plants to
impart some disease resistance and tolerance to moisture stress, as well as
rendering the plants capable of autotrophic development (MURASHIGE, 1978).
Although in vitro rooting is generally an expensive, labour-consuming process,
especially from a commercial perspective, it may be the only practical method of
rooting plantlets in some species (TORRES, 1989). DE KLERK (2002) reported
that in vitro rooting of apple microcuttings strongly increased plantlet size during
the rooting treatment, enhanced acclimatization by improved water uptake during
early acclimatization and facilitated the addition of extra nutrients and protective
compounds that may strongly improve performance. In vitro rooting is often
achieved by culturing shoot cuttings on medium with half-strength concentrations
of macro- and micronutrients, with or without auxins (TORRES, 1989;
MONCOUSIN, 1991). This however, is often dependent on the plant species. SUN
et al., (2008), for example, observed a significantly higher rooting frequency in
Zygophyllum xanthoxylon shoots cultured on full-strength MS medium compared
to those cultured on half-strength medium. On the other hand, PATIL (1998)
reported an inverse relationship between media strength and rooting frequency in
three different species of Ceropegia. Indeed, many other researchers have
reported better in vitro rooting on low-strength media compared to full-strength
(SAXENA and BHOJWANI, 1993; PUROHIT et al., 1994; ANDRADE et al.,
1999; BEENA et al., 2003). The beneficial effect of low medium strength on
rooting has been reported to be possibly due to a reduced requirement of nitrogen
by the plantlets for root formation (HYNDMAN et al., 1982). In some plant species,
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