The influence of light on germination of seeds of a number of tropical weeds was studied. The same types of light sensitivity known from seeds of plants of the temperate zone were found.In addition to the expectation that the behaviour of tropical seeds resembles that of the temperate zone, also was found that seeds of Ruellia tuberosa probably show a very fast "inverse dark reversion" and that gibberellic acid may delay or inhibit the onset of a secundary dormancy.
The wood anatomy of three related genera of the Annonaceae has been studied and described as part of a research project on the taxonomy of neotropical taxa of the family. The wood anatomy of the three genera is characterised by the occurrence of many fine apotracheal continuous concentric bands of parenchyma. The genera Desmopsis, Sapranthus, and Stenanona, restricted to Central America, can be separated on wood anatomical characters such as element length, ray height and the number of parenchyma bands per mm. A key for the genera is presented and the possible phylogenetic relationships are discussed. Finally, the wood anatomical results are correlated with data on pollen morphology, flower morphology and morphology of fruits and leaves.
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