Effects of Ethylene Inhibitors on Shooting of Cymbidium sinense Rhizomes and Asymbiotic Germination of Bulbophyllum Related Species Native in Taiwan
Date Issued
2010
Date
2010
Author(s)
Ma, Ruo-Ting
Abstract
The thesis is consistent of two chapters. The first chapter describes the effects of ethylene inhibitors on shooting of Cymbidium sinense rhizomes. The second chapter elucidates asymbiotic germination of Bulbophyllum related species native in Taiwan.
Aminooxyacetic acid (AOA), silver nitrate (AgNO3), and 1-methylcyclopropene (1-MCP) were applied to indirectly clarify the ethylene effect on shoot growth and differentiation of Cym. sinense. Additionally, ethylene was supplied during culture to investigate its direct effect on organ differentiation of Cym. sinense.
Cymbidium sinense ‘Rui-Bao’ × Cym. sinense ‘Guang-Hua-Die’ rhizomes cultured in liquid rhizome propagating medium supplied with AgNO3 all developed shoots and roots. Rhizomes cultured in AgNO3-free medium (control) had more newly formed rhizomes. Liquid medium supplied with 50 μM AgNO3 had more differentiated shoots in both replicated experiments. Sheath leaf formation was observed at 10 days after culture, indicating the differentiation of shoot from rhizome. Ethylene concentrations in cultural vessels were higher in AgNO3-supplied treatments than in AgNO3-free controls.
Cymbidium sinense rhizomes cultured in solid rhizome propagating medium supplied with AOA or ethylene-inhibitor-free control did not form shoots and roots, but did differentiate some in medium supplied with 100 μM AgNO3. Thereby, ethylene perception inhibitors rather than ethylene synthesis inhibitors were more effective for Cymbidium shoot inducing.
AgNO3 was added to cultural medium at different times after subculture to test the effect of rhizome lengths on subsequent organ differentiation. When 50 μM AgNO3 were supplied in liquid rhizome propagating medium at different times after subculture, all rhizomes formed shoots compared with that no shoot formation was found in AgNO3-free controls. More shoot formation was recorded when 50 μM AgNO3 was supplied at two weeks after subculture.
Shoot differentiation of Cym. sinense. rhizomes were not induced by the fumigation of 1-MCP at 1 and 10 μL•L-1, but were induced by supplement of 100 μM AgNO3 in medium. However, combination of 1 μL•L-1 ethylene and 100 μM AgNO3 treatments did not induced the shoot differentiation of Cym. sinense rhizomes. These results indicated that ethylene inhibited shoot differentiation of Cym. sinense rhizomes.
Factors contributing to low germination of Orchidaceous plants include incompletely developed embryos, lack of endosperm, accumulation of germination-inhibiting metabolites, and seed coat impermeability. The second chapter focuses to overcome the possible difficulties in Bulbophyllum seed asymbiotic germination, so that cultural medium types, seed pretreatments, capsule maturities, fluridone (an ABA synthetic inhibitor) treatments were tested. Also, germination rates of mature seeds in different species were determind.
Seed germination of Bulb. affine and Bulb. macraei were higher in solid 1/2 MS medium than in liquid medium. Protocorm growth were also faster in solid medium; protocorms cultured in liquid medium turned vitrificated consequently.
Seeds of Bulb. aureolabellum were pretreated with sodium hyperchloride (NaOCl), sodium hydroxide (NaOH), hydrogen chloride (HCl), and ultrasonic vibration for various durations. Highest germination was recorded in control (59.3%), and treatments tested in this study did not improve germination. Moreover, germination decreased with increasing NaOCl concentration and ultrasonic vibration duration.
The lowest germination percentage (27.9%) was observed when sowing seeds on the day of Bulb. retusiusculum capsule spliting, and the highest (50.4%) was obtained by sowing seeds 85 days before capsule spliting. In another experiment, Bulb. retusiusculum capsules were harvested at 120, 150, 180, and 270 days after artificial pollination (DAP) for in vitro germination.
Fluridone application at 130 DAP did not affect the sizes and fresh weights of capsules at harvest; capsules treated with 50 and 100 μM fluridone had higher subsequent germination rates. The highest germination percentage was recorded in capsules treated with 50 μM fluridone, which was 33.4%, compared with that of 15.6% in controls.
All six species of Bulbophyllum studied had some seeds germinated, but rate in protocorm development varied. The germination percentage from high to low were Bulb. drymoglossum, Bulb. pectinatum, Bulb. albociliatum, Bulb. taiwanense, Bulb. aureolabellum, and Bulb. macraei.
Subjects
Cymbidium
organogenesis
asymbiotic germination
embryo development
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