Germina o, biometria de sementes e morfologia de plantulas de Guizotia abyssinica Cass Germination, seed biometrics and seedling morphology of Guizotia abyssinica Cass

O niger (Guizotia abyssinica Cass.) é uma herbácea anual com potencial para produ o de biodiesel, porém com poucas informa es referentes à qualidade de suas sementes. Com isso, objetivou-se determinar as temperaturas e substratos para a germina o e desenvolvimento inicial de plantulas, além de caracterizar morfologicamente as sementes e plantulas. Foram determinados o peso de mil sementes, grau de umidade, massa, comprimento, largura e espessura das sementes. No teste de germina o foram utilizadas quatro temperaturas constantes sob luz branca constante (15 °C, 20 °C, 25 °C e 30 °C) e uma temperatura alternada (20-30 °C) sob regime de 10 horas de escuro e 14 horas de luz branca para a temperatura mais elevada e dois substratos (entre papel e sobre papel). Foram determinadas as curvas de embebi o das sementes, a germina o, o índice de velocidade de germina o, o tempo médio de germina o e o comprimento e massa seca de plantulas. As sementes de niger possuem dimens es semelhantes entre si, média de 4,54 mm de comprimento, 1,39 mm de largura, 1,15 mm de espessura e 0,0043 g de peso. As temperaturas 20-30 °C e 25 °C e ambos os substratos testados s o eficientes para a condu o do teste de germina o em sementes de niger. The niger plant (Guizotia abyssinica Cass.) is a herbaceous annual with a potential for biodiesel production but information on seed quality is scarce. The objective of this study was to determine the temperatures and substrates for seed germination and initial seedling development, besides characterizing niger seed and seedling morphology. One thousand seed weight, moisture content, weight, length, width and thickness of seeds were determined. The seed germination test was done at a constant temperature in continuous light (15 °C, 20 °C, 25 °C and 30 °C) and with an alternating temperature (20-30 °C) with 10 h dark and 14 h of white light for the highest temperature and two substrates (on paper and between paper). The seed imbibitions curves germination percentage, germination speed index, mean germination time, seedling length and dry weight were determinated. The niger seeds had similar dimensions: 4.54 mm long, 1.39 mm wide, 1.15 mm thick and a mean weight of 0.0043 g. The 20-30 °C and 25 °C temperatures and the two substrates tested are suitable for the niger seed germination test.