Embryo origin and development in Crocus sativus L. (Iridaceae)

Abstract

Fruit and seed set were obtained in the triploid Crocus sativus (saffron) either by hand crossing with pollen of the diploid C. cartwrightianus or by free pollination. The morphology of the capsules and seeds was similar in both Crocus species. The embryo is comparatively small, whereas the endosperm is formed of numerous layers of cells with hemicellulose-thickened walls and a cytoplasm containing few lipid and protein reserves. Seed germination gave rise to a white prophyll from which a green leaf emerged. At the base of this leaf, a small corm without tunics developed, which, after leaf desiccation, became dormant. These corms sown separately in pots were again capable of growth and emitted a single long green leaf. Vegetative development of new corms was similar in the diploid and hybrid saffron plants. In sites of past saffron cultivation the beds were found to contain degenerated corms and corms at different development stages. The absence of fruit and seed set in emasculated and self- and out-pollinated plants suggests that saffron does not form apomictic embryos.