Morphological Nature of Endosperm
The morphological nature of endosperm in angiosperms has been a subject of much discussion in evolution. The endosperm in gymnosperms is a gametophytic (haploid) tissue as it develops directly by the continued free nuclear divisions of the functional megaspore. In angiosperms, however, it develops from the primary endosperm nucleus which is normally formed by the fusion of two polar nuclei and a male nucleus and hence it is neither haploid nor diploid but generally triploid. Some workers have suggested that the endosperm in angiosperms is a gametophytic tissue just like those of gymnosperms, the only difference being that its development remains arrested till the entry of the pollen tube into the ovule.
Other embryologists have considered it as a second embryo or a maimed embryo. The most agreeable view regarding the morphological nature of the endosperm in angiosperm is that it is an undifferentiated tissue which shows different degrees of polyploidy. By suppressing the growth of the embryo in a seed, it has been possible to induce triploid shoot bud development in the endosperm. However, truly triploid plants have not been obtained so far.