| Asparagus (Asparagus officinalis L.) is one of the most celebrated and precious vegetables with good taste and abundant nutrition and high medical value. It's very popular among consumers and regarded as one of the ten most precious vegetables. UC800 which shares plenty of good properties is a good strain of asparagus. It is planted with large-scale in producing area and is one of the most important vegetables for export in China. This study set up a high efficient and stable somatic embryogenesis system using the UC800 burgeon as material, and researched on their characters in cytology and physiology and biochemistry of somatic embryogenesis. The results are as follows:1 The conditions for somatic embryogenesis of UC800 were optimized. The burgeon in May and June was the most perfect explant for primary callus induction. And the burgeon of 10 cm length and 0 =0.2-0.5 cm was most efficiency for callus initiation. The most suitable medium were: MS+NAA 1mg · L-1+BA 0.5mg · L-1 for primary callus induction, MS+2,4-D10mg · L-1+NAA 0.5mg · L-1 for embryogenic callus induction. 30 days and 60 days were primary and embryogenic callus induction periods respectively, and in 25 and 50 they should be propagated. Primary callus was green and its surface was smooth, character was compact and stiff, while the embryogenic callus was yellow, granule and incompact. 2,4-D was the key substance for embryogenic callus induction, and high concentration of 2,4-D needed for UC800 embryogenic callus induction. BA promoted callus growth but inhibited embryogenic callus induction. The somatic embryos induction medium were MS or MS+NAA 0.3mg · L-1+KT0.2 mg · L-1. While somatic embryos can't germination in these medium and they should be transferred to 1/2MS. The mature embryos first generated roots then shoots, and the regenerating plantlets can grow after transplant to soil.2 It's showed by cytology method that asparagus embryogenic callus consisted of regular shaped cells with dense cytoplasm, large nucleus while the non-embryogenic callus cells with large volume, small nucleus and thin cytoplasm. The UC800 somatic embryogenesis underwent several phases: 2-cell, 4-cell, embryogenic cell mass, proembryogenic masses, early globular embryo, globular embryo, pear-shaped embryo, club-shaped embryo and banana-shaped embryo. Proembryogenic masses formed in 5 days, and globular embryo in 10 days, pear-shaped embryo, club-shaped embryo in 20 days, and banana-shaped embryo in30 days. Embryogenic callus, embryogenic cell masses and globular embryo accumulated large number of starch grains, which might supply energy for cell division and differentiation.3 As showed as followed by SEM asparagus primary callus owned smooth surfaces and there was little gap among cells, which shared silk-shaped attachment in the cell surface. On the contrary, embryogenic callus had rough surfaces, and the embryogenic cells were closely conjuncted to form cell masses in which loosely connection and large empty were observed. The cells of cell masses were regular-shaped, and many of them exposed on the surface of the calli. Non-embryogenic callus surface shape was irregular and covered with plenty of lamellar or snow-shaper tectums. The non-embryogenic cells had different shape with large volume. It was showed by TEM that the primary callus cells had large central vacuole, which squeezed its cytoplasm to a thin layer around the brim of cell. Chloroplasts and liposomes distributed in cytoplasm. The cells of embryogenic callus had dense cytoplasm, which was full of the whole cell, big nucleus with obvious nucleolus. Many starch grains, liposomes and chloroplasts including starch grains distributed on the districts near cell membrane. The cells of non-embryogenic callus were almost occupied by large central vacuole, and its cytoplasm was extruded. Nucleus and other organelles were hardly observed.4. There were close relationship between somatic embryogenesis and changes of soluble protein contents and its constitution...
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