used by Tan et al. (2007), obtained even less hybrids, suggesting that the zygotic embryos require better development to be able to germinate and grow into seedlings.
In this study, the hybrids were only obtained from large- to medium-sized embryos, which was the same as those observed by Andrade-Rodrígue et al. (2004). There was no hybrid seedling derived from the small embryos. However, it cannot be sure if there was any zygotic embryo existing within the small embryos, because most of small embryos did not germinate. It was reported that the zygotic embryo was consistently located at the micropylar end of the seed (Thakur and Bojwa, 1971). In more recent study, Andrade-Rodrígue et al. (2004) found that the embryos located at the micropylar end were the smallest ones, and could not develop into seedlings under greenhouse or nursery conditions due to dehydration or lack of reserved nutrition. The alternative location of zygotic embryo was also observed in large to medium size. Those embryos can develop into health seedlings