Fruit harvesting time and corresponding morphological changes of seed integuments influence in vitro seed germination of Dendrobium nobile Lindl.

Abstract

In vitro asymbiotic seed germination of Dendrobium nobile varied significantly with fruit harvesting time and growth medium used for culturing seeds. Seeds harvested 129 days after pollination (DAP) possessing globular shaped embryos and a discontinuous cuticle layer showed a substantially greater germination on P668 medium. Alternatively, immature seeds harvested 96 and 116 DAP displayed a significantly lower germination response on various growth media. Most of the ovules at 96 DAP are in archesporial and megaspore mother cell stages, whereas the majority of ovules are mature and fertilized at 116 DAP. Mature seeds harvested 158 DAP also germinated at a higher frequency at Stage 5 (emergence of the first leaf) after 8 weeks of culture on different growth media indicating the absence of testa imposed dormancy in this endangered epiphytic orchid.

Asymbiotic seed germination and multiplication of an endangered orchid – Paphiopedilum venustum (Wall. ex Sims.)

“…formosa showed positive correlation between the germination abilities of immature seeds with their internal organization such as discontinuous cuticle layer enveloping the embryo, presence of gaps which are caused by the cellular degeneration of the inner integument, and the absence of secondary wall thickenings in the outer integument. All these features of the seed integuments contribute to maximizing the percentage of germination of immature seeds [28,29].…”

“…Literature survey indicates a correlation between maturity related progressive decline of germination percentage to the biochemical changes, which induce dormancy in the seeds, by accumulating inhibitory substances leading to the rapid loss of viability [18,[29][30][31][32][33][34]. As the embryo matures, it dehydrates due to the development of hydrophobic carapace sheath and lignification of the cell walls of testa layer.…”

Asymbiotic in vitro seed propagation of Dendrobium

“…ex Lindl., D. hookerianum Lindl., D. longicornu Lindl., D. nobile, D. parishii Rchb.f.) are also flamed(Dohling et al 2008;Hajong et al 2010;Vasudevan and Van Staden 2010;Dutta et al 2011;Kaewduangta and Reamkatog 2011;Parthibhan et al 2012;Paul et al 2012;Hossain 2013;Nongdam and Tikendra 2014)…”

Enzymatic scarification of Anacamptis morio (Orchidaceae) seed facilitates lignin degradation, water uptake and germination

“…This has a number of implications for our understanding of both dormancy mechanisms and the ecology of dormancy release during germination in soil. Lignins are hydrophobic and extremely resistant to degradation, and thus probably contribute to the capacity of integuments to exclude water (Baskin ) and have been directly implicated in ‘testa imposed dormancy’ (Vasudevan & van Staden ). Degradation in nature is usually catalysed by lignin modifying enzymes, or ligninases, a general class of polyphenol oxidases catalysing the oxidation of aromatic compounds.…”

“…The outer integuments of Dendrobium nobile Lindl. seeds are lignified whereas the inner integuments are cutinised, which has been suggested as a water exclusion mechanism (Vasudevan & van Staden ). Phloroglucinol staining of Cephalanthera falcata (Thunb.)…”