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- Author or Editor: Stephen F. Chandler x
Abstract
Shoot cultures were initiated from seedling shoot tips of Brassica campestris ssp. pekinensis (Lour.) Olsson (Chinese cabbage, cv. Kimjung) on Murashige–Skoog medium supplemented with 46.5 μm kinetin and 1.5 μm IBA. Proliferation was a result of growth from axillary buds. Adventitious shoots could not be induced on a wide range of culture media. The effects of cytokinin and auxin type and concentration, nitrate : ammonium ratio, sucrose concentration, and other additives on shoot multiplication and growth were determined. Only adenine sulfate was beneficial. Expiants were rooted on hormone-free medium, but addition of 2.5 or 5.0 μm IAA or IBA increased rooting and enhanced shoot growth. Regenerated plants were morphologically normal and exhibited flowering during both root initiation in vitro and after establishment in soil. Chemical names used: N-(2-furanylmethyl)-1H-purin-6-amine (kinetin); 1H-indole-3-butanoic acid (IBA); 1H-indole-3-acetic acid (IAA).
Ethylene is essential for the senescence process in many fruit and flowers. In the last two steps in the biosynthesis of ethylene in plants ACC synthase converts S-adenosyl methionine to 1-aminocyclopropane-1-carboxylic acid(ACC). ACC oxidase (ACO) then degrades ACC to ethylene. Inhibitors of ethylene synthesis, such as amino-oxyacetic acid, and of the response to ethylene, such as silver thiosulphate, delay or prevent senescence. By expression of an antisense version of ACO RNA, we have generated two varieties of transgenic carnation which produce flowers with an extended vase life. These were produced using the cultivars Red Sim and White Sim. Flowers from these plants produce very little ethylene and normally fail to display the inrolling phenotype typical of senescence in this species. At the time after harvest when inrolling would normally lake place (5 days), the antisense ACO flowers produce only barely detectable levels of endogenous ACO mRNA or ACS (ACC Synthase) mRNA. Exposure to exogenous ethylene(100ppm) induces inrolling and production of ACS and ACO mRNA species. Such carnations will be valuable both as a commercial product and as a tool for further exploring the role of ethylene in carnation flower senescence and leaf wound response.