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| Author(s): |
Carla Elisa Alves Bastos
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2013-01-22 |
| Examining board members: |
Francisco Antonio Monteiro;
Helio Grassi Filho;
Ana Cláudia Ruggieri
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| Advisor: | Francisco Antonio Monteiro |
| Abstract | |
Nitrogen is the major determinant of pasture production and sustainability, and the uptake of nitrate and ammonium by the roots can result in changes in growth, morphogenesis and structural characteristics of plants. Thus, it is essential to know the response of recently developed cultivars to nitrogen availability forms and rates. Accordingly, the objective was to evaluate the nutritional, productive and morphological modifications of Brachiaria brizantha cv. Xaraés in initial growth and regrowth. The experiment was conducted in a greenhouse, where three nitrogen rates (3, 15 and 27mmol L-1) and three ratios of nitrate/ammonium (30/70, 85/15 and 100/0) in nutrient solution were evaluated. The plants were cultivated in two growth periods in which growth analysis was done and the leaf appearance rate, phyllochron, number of living leaves per tiller, final length of the leaf blades, number of tillers, total nitrogen, nitrate and ammonium concentration in the shoot and total nitrogen in the diagnostic leaves and SPAD readings were evaluated. At the end of the regrowth period dry weight of roots, roots length and surface and total nitrogen were assessed. The lowest nitrogen rate and the 30/70 nitrate/ammonium ratio reduced growth, dry matter production and leaf area of plants on both growth periods. The number of living leaves and tillers increased by increasing nitrogen rates and by nitrate and ammonium in the proportion 85/15, while there was a reduction in the phyllochron when the intermediate and high nitrogen rate and nitrate/ammonium ratios of 85/15 and 100/0 were applied. The highest ammonium proportion in the nutrient solution increased the activity of the nitrate reductase enzyme and total nitrogen concentration in the diagnostic leaves and shoots, while it reduced SPAD value, length and root surface. SPAD reading was not a good estimation of total nitrogen content in the diagnostic leaves of Xaraés palisadegrass supplied with high ammonium proportions. (AU) | |
| FAPESP's process: | 11/03866-3 - Forms and doses of nitrogen on nutrition, production and morphogenetics aspects of xaraes grass |
| Grantee: | Carla Elisa Alves Bastos |
| Support Opportunities: | Scholarships in Brazil - Master |