ON THE APOMICTIC SEED DEVELOPMENT IN THE WALNUT (JUGLANS REGIA L.)
Some of the walnut varieties grown in Germany show the tendency of apomictic fruit development. It is not clear from which structures within the ovule the apomictic embryos develop. The investigations aimed to elucidate by histological methods the development of apomictic embryos, especially by investigating sporo-and gametogenesis and the development of the embryo sac until the beginning of the differentiation of the embryos. The embryo sac was fully differentiated only six to eight days after anthesis, and it always revealed the normal type with eight nuclei. After isolation of flowers with cloth bags embryo development originated from divisions of the egg cell. Embryo development from somatic cells of the nucellus was, with one exception, never observed. Thus, the development of the apomictic embryos in the walnut is diplosporic and not by nucellar embryony, as reported by Schanderl (1964). Embryo development started according to variety five to six weeks after anthesis, and no differences were found between isolated and open pollinated flowers.
Sartorius, R. and Stösser, R. (1997). ON THE APOMICTIC SEED DEVELOPMENT IN THE WALNUT (JUGLANS REGIA L.). Acta Hortic. 442, 225-230