Ontogenesis, Differentiation and Precocious Germination in Anther-derived Somatic Embryos of Grapevine ( Vitis viniferaL.): Proembryogenesis

Histological steps of callogenesis and proembryogenesis in anther cultures of Vitis viniferaL. ‘Grenache noir’ are described. Embryogenic calli were obtained on Nitsch and Nitsch medium supplemented with 1mgl -12,4-dichlorophenoxyacetic acid (2,4-D) and 0.25mgl -1benzylaminopurine (BAP). Calli were initiated from anther connective cells only and no division of microspores occurred. The embryos were hence of somatic origin. Proembryos developed either directly (i.e. without intervening callus) from the endothecium, or indirectly from the connective-derived callus. In both cases, proembryos originated from single cells. They developed from starchy differentiated cells of a predetermined type. The polarity of the somatic proembryo was established from the first divisions and it was marked by precocious development of an easily recognizable suspensor. Other analogies with the development of the zygote are also emphasised.