media did not change during subsequent cultivation during six weeks. Also in the fungal chitosan supplemented media a very small amount of dark precipitate was formed after two days but the solutions remained clear thereafter. After eight weeks investigation, 15 ppm of fungus chitosan seemed the most effective in propagation of PLB’s as measured by the increase in their fresh weight (Fig. 5). Therefore fungus chitosan is an attractive candidate to be used as growth stimulator in VW liquid medium for orchid plant tissue culture.
3.3. Effect of various chitosan on differentiation on agar medium
In liquid media, orchid protocorm propagated only by increasing its total fresh weight. However, new plantlets of orchid can be obtained by cultivation of orchid protocorm in static cultures on the surface of solid agar media. In this system, the effect of 1 and 10 kDa shrimp chitosan and 10 kDa fungal chitosan were compared in the range of 0–25 ppm.
An important criterion in plantlet development is the formation of fresh-green differentiated tissue. Green color tissue was observed in the protocorms after two to three weeks on the medium supplied with chitosan. The green differentiated