Germination of Aristolochia Seeds (Aristolochiaceae)

Resumo

We studied the seed morphology and germination of 17 Aristolochia species (A. arborea, A. baetica, A. inflata, A. gigantea, A. gracilis, A. clematitis, A. contorta, A. fimbriata, A. labiata, A. littoralis, A. macrophylla, A. manshuriensis, A. maxima, A. rotunda, A. sempervirens, A. tomentosa, A. trilobata). The seeds of A. clematitis, A. contorta, A. trilobata, A. labiata, and A. maxima, as well as all species of Siphisia section (seeds with no wings), have the higher seed morphometric parameters. The seed weight characteristics of species typical of tropical climatic zones (the Gymnolobus section) were lower by ten or more times than those of the species of the other two sections, which are typical of a temperate climate. The greater weight of seeds studied for the species of Siphisia and Diplolobus sections is associated with the presence of a voluminous endosperm, which is required for the embryo development after a long period of time between dissemination and seedlings emergence. The period from sowing to the beginning of germination and the length of the germination period differ between species; the duration of germination is from 1 month to 3.5 years. The seeds of the species from temperate climatic zones (sections Diplolobus and Siphisia) have a non-deep simple morphophysiological dormancy, and the germination starts 1–11 months after seed sowing. We observed intervals in germination from 2 to 12 months in the species of the Diplolobus section; after the intervals, the germination process was continued. The seeds of most of the Gymnolobus section species from tropical zones have a morphological type of dormancy and germinate without intervals. The prolonged germination period and the type of morphophysiological dormancy of seeds have an adaptive value for the species conservation and survival in situ and ex situ.