Original paper

Observations on the development of the placentas and closing bodies in the fruit capsules of some Mesembryanthema (Aizoaceae)

Kurzweil, Hubert


The development of the placentas and closing bodies of the fruit capsules of selected species of Aizoaceae — subfamily Ruschioideae is described and discussed, and particular attention is paid to the early stages of the ontogeny. It is shown that, expectedly, the main portions of the ridge-shaped placental primordia form the ovule-bearing placental tissue on their surface. The closing bodies of the study species originate from the distal portions of the same parenchymatic ridge as visible in early ontogeny, and their first traces can already be detected in the small flower bud. The closing bodies are thus derived from the same primordia as the ovule-bearing placental surface tissue. In late ontogeny this placental tissue (conventionally simply termed 'placenta') and the closing bodies are very distinct both in their gross-morphology and ultrastructure. According to their mode of development and late ontogenetic/mature structure it is suggested that the closing bodies are products of the endocarp and not the placentas. This supports recent theories but is in sharp contrast to older interpretations.