Underdeveloped embryos and germination in Aristolochia galeata seeds.
Aristolochiaceae have been described as having seeds with underdeveloped embryos and morphological or morphophysiological dormancy. Aristolochia galeata is a native climber found in the Cerrado biome, associated with road and gallery forest edges. The aims of this study were to investigate: embryo growth rate, morphology and seed germination parameters under different treatments. Embryos were excised to obtain embryo length at four stages: initial, seeds after coat rupture, radicle tip protrusion and cotyledon emergence from the seed coat. Germination tests were conducted at 30 °C under three nitrate concentrations (1, 10 and 20 mM), fluctuating temperature (27/20 °C) and light and dark conditions. We found that seeds have underdeveloped embryos, which take about 301 ± 178 h (±SD) to achieve seed coat rupture, another 205 ± 126 h to reach radicle protrusion and 176 ± 76 h more to the final stage of cotyledon emergence. Germinability was above 52% in all treatments, except in the dark (15%). For all treatments, average germination time was above 290 ± 123 h. Potassium nitrate increased germinability to >87%. No particular treatment was required for embryo development, but seeds in the population that continued to germinate after 1 month were probably in various states of non-deep, simple morphophysiological dormancy. Increased germinability in nitrate treatments and light requirement for germination could prevent germination under unsuitable environmental conditions and be a strategy to increase seedling establishment in the cerrado.
Departamento de Ecologia, Universidade de Brasília, Brasília (DF), Brazil.
D
D
Alves-Da-Silva
F
F
Borghetti
K
K
Thompson
H
H
Pritchard
J P
JP
Grime
D030022:Aristolochia / Q000196:embryology* / Q000502:physiology*; D018548:Cotyledon; D056625:Endosperm; D018525:Germination / Q000502:physiology*; D008027:Light; D036226:Seedlings; D012639:Seeds / Q000254:growth & development / Q000502:physiology*; D013696:Temperature