Morphological and histological observations on the induction of anther calluses and embryos in loquat (Eriobotrya japonica Lindl.)

摘要

Morphological and?histological?studies were conducted systematically for the first time on the induction ofanther?derived calluses and embryos in loquat (Eriobotrya japonica?Lindl.). The results showed that the calluses were derived from microspores?and both microspores and?capillaments,?when capillaments were not completely scraped off. Upon transfer onto the embryo differentiation medium, two types of calluses were formed within 5 to 7 days: 90%?non-embryogenic calluses?(NECs) and 10%?embryogenic calluses (ECs).?The NECs and ECs differed significantly in morphological and histological features.?NECs were compact with?a smooth?surface and there was no evidence of the formation of adventitious buds or embryos, while ECs were uneven with a crisp texture and loose structure and were beginning to form salient multicellular structures on the surface. NECs cells had little cytoplasm that stained only lightly, few large vacuoles, no or only a small nucleus and wide intercellular spaces.?NECs?had a very low cell division capability and turned brown and eventually became necrotic. EC cells were smaller, globular and abundant in cytoplasm, with one or two big nuclei located in the centre of tightly aligned heavily stained cells. They had a high capability for cell division and continued to divide and produced somatic pro-embryos which could develop further through the typical globular, heart, torpedo and cotyledon stages. Although only 10% of ECs were induced they had a high differentiation rate and produced 12.7 globular, 8.1 heart-shape, 3.8 torpedo and 10.7 cotyledonary embryos per EC after 48 days of induction.