Abstract:
A study was undertaken in the Department of Plantation Crops and
Spices, College of Horticulture, Vellanikkara, during 1995 to 1997 to find out the in
vitro response and causes of recalcitrancy in coconut (Cocos nucifera L.). Young
palms of 0 x T parentage were used as source of explants in the present study.
Direct and indirect organogenesis and embryogenesis were tried in various explants
like zygotic embryo, immature inflorescence rachillae, anther and tender leaves.
Coconut tissues usually turn brown under in vitro condition due to
polyphenol interference. Addition of 0.25 per cent activated charcoal reduced the
phenolic exudation effectively and was found superior to the addition of ascorbic
acid or polyvinyl pyrrolidone. The phenolic exudation was considerably reduced
under dark condition.
Y 3 medium was found to be superior for zygotic embryo culture and
growth of inflorescence tissues whereas, Blaydes medium was found suitable for
anther culture. Y3 medium supplemented with 2.0 mg -1 NAA and 1.0 mg -1
kinetin was found the best for zygotic embryo culture. Immature zygotic embryos
produced friable, nodular callus with higher embryogenic potential. White globular
structures were produced when concentration of 2,4-0 was gradually reduced but
regeneration was not obtained. Immature inflorescence rachillae explants produced
friable callus when high levels of 2,4-0 was supplemented. Callusing was observed
from microspores when L-glutamine 500 mg 1-1,2,4-02 mg l-1, coconut water 15
per cent v/v and 9 per cent sucrose were added to the Blaydes medium. But repeat-
ability of callus induction was not obtained.
Total phenol content, polyphenol oxidase activity and protein content
were different in different plant parts and these factors indirectly affected the
response of tissues under in vitro condition.
Coconut is admittedly a recalcitrant material as far as tissue culture is
concerned. Hence much more concerted efforts are required to develop a viable
protocol for the micropropagation of coconut (Cocos nucifera) L. Nevertheless, the
above mentioned observations on biochemical attributes points, in part, to the
possible factors related to the recalcitrant behaviour of coconut in vitro.
