Tropical Plant Research
An International Journal by Society for Tropical Plant Research
Contribution of environmental factors on in vitro culture of an endangered and endemic mangroves Heritiera fomes Buch.-Ham. and Bruguiera gymnorhiza (L.) Lam.
Importance and destruction of mangroves have appeared in some recent surveys. So their restoration through tissue culture study is urgently required because in vivo propagation is plagued with unforeseen obstacles. This study describes for the first time in vitro approach for threatened species Heritiera fomesand Bruguiera gymnorhiza through callus. For initiation of callus modified MS medium was formulated for each species which correlated with soil conditions of Sundarban mangrove forest. For both species the auxin NAA, nodal or shoot tip explants and rainy season were found to be most suitable for callusing. NaCl at the concentration of 20 mM and 60 mM promoted growth for H. fomes and B. gymnorhiza callus respectively which was found to be comparative for their growth in vivo as in Sundarban. Histological study indicated morphogenicity of callus. Previous in vitro studies on mangroves were mostly based on the effect of variety of hormones and different sea salts. However this present study clearly indicates that the in vitro studies of mangroves not only depend on these factors but greatly influence by soil condition of their habitual environment, seasonal condition etc. From this study it seems that more and more in vitro studies of mangroves are possible if researchers focus on their habitual environmental conditions as many mangrove species remains recalcitrant for in vitro study. The present research clearly indicated that the species may be restored in low saline or non-saline land as land destruction is another vital reason for mangrove extinction.
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Fig.: Callus initiation, in vitro sprouting of different explants, histological section and media discoloration of Heritiera fomes: A, Callus initiation site after 10 days of explants inoculation using NAA and BAP combination of H. fomes; B, Yellow and light brown callus formation after 2 weeks of inoculation of explants of H. fomes; C, General view of 3 week old protuberance produced at the proximal part of the explant (Vetical section), VC- Large vaculated cells, Black arrow indicates calli at inner region containing both small meristematic cells with highly-stained nucleus in mitotic cells zone (MCZ), Green arrow indicates embyogenic cells where red arrow indicates non embryogenic cells; D, Close view of embryogenic cells on callus where black arrow shows the embryogenic cells; E, Media discoloration caused by secretion of tannin or phenolic compounds after five days of inoculation; F, In vitro sprouting of leaf using NAA and BAP in combination; G, Deep brown small callus formation in combination of 2, 4-D and BAP.
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