| The bio-characteristics and gibberellin regulation of the semi-dwarf and premature rice mutant (B1-24) were studied in this thesis. It has stabilized inheritable traits and was derived from the variety Huiyangzhenzhuzao (Hyz) by loading in high altitude balloon and then was planted and selected continually for 6 generations. The bio-characteristics of mature mutant plants. 7-day-old seedlings that were grown in light and 3-day-old etiolated seedlings were investigated. Then, the mutant seedlings were treated with exogenous GA3 and its biosynthetic inhibitors S3307 and B9. Furthermore, the endogenous GA4 contents of buds and etiolated seedlings and tissue sections of 3-day-old etiolated seedlings were observed. The main results are as follows:1 B1-24 mutant flowers 510 days earlier than Hyz. The fact that it has less of 1 internode and 1 leaf and a shorter flag leaf results in slight decline of height of the mature mutant. The Gain of main spike of Bl-24 lessens and the length of which shortens while there is no significant difference in the weight of 100 gains between them. The elongation patterns of internodes of Bl-24 and Hyz accord with dn-type and nl-type, respectively. The 3-day-old etiolated seedlings of Bl-24 were shorter both in coleoptile and root, whereas elongate in mesocotyl. The height of 7-day-old seedlings that grown in light declines distinctly.2 Soluble protein contents in mesocotyl and root of etiolated seedlings of Bl-24 were less than that of Hyz. It was contrary in coleoptile, however.3 With increase of the exogenous GA3 concentrate(6 × 10-8 -92 × 10-8mol/L), heights of 7-day-old seedlings elongate up to that of its wild-type phenotype. However, the effects of exogenous GA3 on root of 3-day-old etiolated seedlings were much more than that in other parts of it.4 Inhibition ratio of S3307 (0.04 mg/L) on the length of coleoptile from Hyz etiolated seedling was 13.54%, while the inhibition effects on that of Bl-24 etiolated seedling were not obvious. S3307 decrease the length of mesocotylfrom Bl-24 etiolated seedling by 15.89%, while the inhibition effects on that of Hyz etiolated seedling were not evident. Treated with S3307, the root length of B1-24 and Hyz etiolated seedlings decrease by 16. 94 % and 54. 18 % , respectively. S3307 was the better inhibitor for 7-day-old seedlings in light. Inhibition ratio on the incomplete leaf, the 1st leaf sheath and blade and height of B1-24 (Hyz) is 21.58% (11.45%), 22.73% (12.73%), 11.05% (6.37%) and 15.28 % (10.34), respectively. And inhibition ratio on root length of 7-day-old seedlings is 14.24%(B1-24) or 29.41 %. (Hyz).5 Endogenous GA4 contents of B1-24 bud, mesocotyl and coleoptile in etiolated seedling were less than that of Hyz.6 Cell shape of the transverse sections of mesocotyl from B1-24 etiolated seedlings has changed, but not in size. Cell area of longitudinal sections increases about 457%. However, cell of the transverse sections of coleoptile decreased in length or width by 25.38% or 22.74%, respectively, which resulted its cell area decline about 54%. Furthermore, the length and width of longitudinal section cells decreased about 46% and 81%, respectively. Similarly, this caused its cell area decline by 1.66 times.This is the first study about the physiological and biochemical characteristics of etiolated seedling of the semi-dwarf rice mutant (B1-24), which was originated from high-altitude condition. The relationships between morphological differences and physiological- biochemical or cytological characteristics, such as soluble protein and endogenous GA4 content, the shape and size of cells, were shown here.
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