Full text
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| Author(s): |
Lucas Macedo Felix
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) |
| Defense date: | 2013-03-18 |
| Examining board members: |
Gilberto Barbante Kerbauy;
Marcilio de Almeida;
Luciano Freschi
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| Advisor: | Gilberto Barbante Kerbauy |
| Abstract | |
In vitro multiplication has been used for some time in order to improve multiplication rate, eliminate pathogens and reduce the production costs. This working tool has been routinely used in our laboratory for over than two decades of basic research in plant physiology and enhancement of cloning technique, especially orchids, aiming to obtain greater genetic stability of regenerants in long term crops. Genus Catasetum present indeterminate shoot apical meristem activity when incubated in the dark, resulting, in a short period of time, long stolons with indeterminate growth: rare behavior in the plant kingdom. Each etiolated steam node has a lateral bud that, when isolated and incubated in light, quickly forms a complete plant, facilitating micropropagation. Other species of valued orchids in floriculture, such as genus Dendrobium (Orchidaceae), have no such facility in multiplication, being recalcitrant to micropropagation. The goals of this study were to gain a better understanding of the physiological mechanisms involved in plant etiolation in Dendrobium \"Second Love\", which has limited stem growth when in dark: and to understand the effects of dark, gibberellin and ethylene (plant hormones), as well as the free radical nitric oxide and carbon dioxide in the activity of apical and lateral meristems of the orchid. As a complementary objective, we tried to stimulate etiolation, aiming to potentially increase lateral buds formation and to break apical dominance with a subsequent stolons growth. Dendrobium plants used in this work were part of our in vitro germplasm stock. After 120 days of incubation in light, the plants were transferred to dark and treated with different concentrations of gibberellic acid (GA), paclobutrazol (PA - gibberellin biosynthesis inhibitor), ethylene, 1-methylcyclopropene (1-MCP - ethylene action inhibitor) and nitric oxide (NO). During a three months period, monthly analyzes of the accumulated levels of ethylene and CO2 in the flasks were performed using gas chromatography. After 30, 60 and 90 days of dark treatment the number of lateral buds presented in stolons, the number of developed lateral and apical buds, the size of formed stolons, and the respective amounts of fresh and dry mass were quantified. Finally, we evaluated the importance of incubation to steam growth in low light and in the dark, and the number of lateral buds and their development after three months of incubation. The Dendrobium \"Second Love\" steam growth in dark is extremely slow and limited when compared to Catasetum fimbriatum plants. However, after three months of treatment with 1.000 μM nitric oxide it was found to have five times more lateral buds than the respective control treatment plants. The treatment with 10 ppm ethylene showed a significant increase in the number of buds and lateral stolons compared to the control treatment from the second month of incubation. Treatments with 5 and 50 μM of GA had no promoting effect on the apical stolon stem elongation. Although not presenting the resumption of apical meristem activity, 5 μM of PA treatment has released a greater number of lateral stolons than the control treatment. Plants treated with 1000 ppm of NO, from the second month of incubation, showed a higher number of lateral stolons, moreover they were significantly larger. Treatment with 100 ppm 1-MCP had the same phenotype as plants treated in light: in other words, they did not etiolate even in light absence. Regarding the ethylene emission, we observed that the treatment with 1-MCP caused a significant increase in the emission of this gas by the plant, reaching values twenty times higher than the control treatment. CO2 emission was lower in light treatment when compared to most of the other treatments in dark. Treatments at higher concentrations of NO and GA seemed to foster some sort of plant stress (evidenced by tissue necrosis), demonstrating that the specie in question may be sensitive to high levels of these substances (AU) | |
| FAPESP's process: | 09/12568-6 - Establishment of a new strategy for in vitro cloning of Oncidium and Dendrobium (Orchidaceae) using etiolated stems. |
| Grantee: | Lucas Macedo Félix |
| Support Opportunities: | Scholarships in Brazil - Master |