Chitosan is a deacetylated derivative of chitin that is derived from the cell walls of fungi, crustacean exoskeletons, cuticles of insects and
some algae. It is considered environmental friendly for agricultural uses as it is easily degradable and non toxic to humans. Chitosan and
its derivatives have been reported to elicit natural defence responses in plants and it has been used as a natural compound to control preand
postharvest pathogenic diseases. Chitosan application has also been shown to increase yields of some agricultural crops. Chitosan has
recently been reported to act as a plant growth promotor in some species including orchids. The degree of deacetylation and concentrations
of chitosan have varying effects on the growth and development of orchid cultured in vitro. Spraying with chitosan has been shown
to significantly reduce the severity of leaf spot disease in orchids. Also, it has been shown that application of chitosan to Dendrobium
orchid plants tended to increase the size of open florets and length of the inflorescences, but did not affect the display-life of cut orchids