Lauric acid improves the growth of zygotic coconut (Cocos nucifera L.) embryos in vitro

Coconuts (Cocos nucifera L.) germinating in situ make use of both sucrose and fatty acids, notably lauric acid, as sources of energy and carbon, but current tissue culture methods routinely include only sucrose in the culture medium. The aim of the experiments was to establish whether lauric acid could improve the growth and development of zygotic coconut embryos in culture. The culture medium of zygotic embryos was adjusted to give various concentrations of sucrose and lauric acid. The concentration of free lauric acid was increased at specific times of the culture. At the end of the experiments, plantlet growth was measured. Added at day zero, lauric acid inhibited germination. Added at 60 or 75 days, lauric acid (75 mu M, unbound concentration) showed a marked stimulation of plantlet growth and development. When C-14-labelled lauric acid was used, radioactivity was incorporated mainly into longer chain fatty acids of complex lipids, notably of the phospholipid fraction. Supplementation at these times may mimic conditions in situ and suggests that the supply of fatty acids may represent a physiological requirement for continued growth. The experiments with radioactive lauric acid confirm that it provides carbon for the synthesis of new structural lipids. The method may provide a means of improving the development of coconut somatic embryos in future.