The effect of embryo orientation on the in vitro germination of coconut in semi-solid medium

Final EUCOST COPYTREE meeting (14-16 September, Tirana, Albania).
The coconut palm or “tree of life” is one of nature’s most useful plants and a major agricultural crop. However, the production of new coconut planting material is limited, whilst their demand is increasing. This limitation is due to coconut palms being mainly propagated via seeds and alternatives such as micropropagation methods are not yet widespread. Recently a novel propagation method has been developed, starting from zygotic embryos. This method allows for the micropropagation of hybrid disease-free elite palms, which could solve the worldwide scarcity. The first step in this production process is the in vitro germination of zygotic embryos. During the optimization of the in vitro initiation step we observed that the orientation of the embryo in the semi solid medium could have an effect on the growth. To test this, we placed embryos either vertically upright or horizontally in the medium and observed the rooting and shoot size of the embryo’s during the following months. Vertically placed embryos showed less shoot growth and less root development compared to horizontally placed ones. As the explants were reoriented during subculture after a month the long-term effect was limited. However, these results are a clear indicator that orientation plays an important role in germination.