Análise de crescimento, fisiologia e valor nutritivo de Tithonia diversifolia

• Ano de defesa: 2017
• Autor(a) principal: Mateus Neto Silva Souza
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Girassol mexicano; Análise de crescimento; Valor nutritivo; Fotossíntese; Trocas gasosas; Produção animal
• Link de acesso: http://hdl.handle.net/1843/NCAP-ARDFNB

Tithonia diversifolia (Hemsl.) A. Gray, also known as mexican sunflower, is a shrub of the Asteraceae family, originating in Central America and widely distributed in tropical regions. Due to the high nutritional value, high biomass production, low input demand and tolerance to acidic soils can be cultivated for use in animal feed. The influence of age of regrowth on the gas exchange, growth, and bromatological composition in T. diversifolia plants was evaluated. The experiment was deployed to the field in fully randomized design with four repetitions and ten rebudding ages, at 21, 28, 35, 42, 49, 56, 63, 70, 77 and 84 days. The plants were evaluated and collected at regular intervals of seven days, starting at 21 days after the cutting of uniformity. The photosynthetic rate and stomatal conductance showed a quadratic behavior throughout the regrowth ages, with relatively low values at the beginning of growth, with maximum values observed at 39 and 51 days of regrowth, respectively. The water use efficiency was higher at 45 days after the standardization cut. Sweating reduced as a function of plant age. Plants of T. diversifolia showed higher leaf area index and lower leaf area ratio, net assimilation rate and relative growth rate with increasing regrowth age. The productivity followed a logistic tendency, with values higher than 20 t ha-1 MS, while the leaf/stem ratio decreased until the 74,6 days of regrowth. The age of regrowth favored the increase of NDF and ADF, and the decline of CP, results due to the reduction of the leaf/stem ratio and lignification of the stems. The maximum crude protein production was 1,89 t ha-1. The increase in the age of regrowth promotes significant changes in the gas exchange and the photosynthetic capacity of T. diversifolia, as well as in the growth rate. It is suggested a forage harvest between 49 and 63 days of regrowth, period of high dry mass production and nutritive value that can meet the basic needs of ruminants.