PubMed · 14833396
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R K S WOOD. 1951-05-12. Pectic enzymes produced by Bacterium aroideae.. https://doi.org/10.1038/167771a0
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PREMISE: The evolutionary history of morphologically variable plant groups is often obscured by cryptic diversity, morphological convergence, and limited genetic data. Arisaema, a diverse genus within Araceae, exemplifies these challenges. Although some taxonomic treatments recognize only two species of North American Arisaema (A. dracontium and A. triphyllum), other studies have identified morphologically distinct groups within both taxa. Here, we reconstructed evolutionary relationships in North American Arisaema, assessed genetic structure and admixture, and tested the monophyly of proposed species. METHODS: We used 2b-RAD sequencing to generate genome-wide SNP data for 146 samples from 31 populations across the eastern United States. Phylogenetic relationships were inferred using maximum-likelihood and Bayesian approaches. Population structure and admixture were assessed using the program structure and principal component analysis (PCA). RESULTS: Both the Arisaema triphyllum and A. dracontium complexes formed well-supported monophyletic groups. Within the A. dracontium complex, we recovered three monophyletic lineages: A. dracontium, A. calciphilum, and A. macrospathum. In the A. triphyllum complex, A. quinatum, A. stewardsonii, and A. allegheniense consistently formed distinct groups. Relationships between A. pusillum and A. acuminatum, and among A. triphyllum s.s., A. purpurascens, and A. striatum were less clearly resolved, likely due to recent or incomplete divergence, gene flow, or polyploidy. CONCLUSIONS: The results support the monophyly of multiple newly proposed taxa within North American Arisaema, but additional sampling across the species' ranges is needed to fully resolve species boundaries. Our study provides the first evolutionary framework for this group, providing a foundation for future ecological, taxonomic, and conservation research in the genus.
The section Alatae of genus Lemna of the monocotyledonous aquatic duckweed family (Lemnaceae) consists of rather diverse accessions with unknown phylogeny and unclear taxonomic assignment. In contrast to other duckweeds, some Alatae accessions, in addition to mainly vegetative propagation, produce readily flowers and viable seeds. We analyzed the genomic diversity and phylogenetic relationship of 52 Alatae accessions. For this purpose, we applied multiple molecular and cytogenetic approaches, including plastid and nuclear sequence polymorphisms, chromosome counting, genome size determination, and genomic in situ hybridization in combination with geographic distribution. We uncovered ploidy variation, recurrent hybridization, and backcrosses between species and their hybrids. The latter successfully spread over three continents. The results elucidate the evolution of Alatae accessions and explain the difficult taxonomic assignment of distinct accessions. Our study might be an example for analogous studies to resolve the hitherto unclear relationships among accessions of the duckweed genera Wolffiella and Wolffia.
BACKGROUND AND AIMS: Plants from the family Lemnaceae are widely used in ecological engineering projects to purify wastewater and eutrophic water bodies. However, the biology of nutrient uptake mechanisms in plants of this family is still poorly understood. There is controversy over whether Lemnaceae roots are involved in nutrient uptake. No information is available on nitrogen (N) preferences and capacity of Landoltia punctata (dotted duckweed), one of the best prospective species in Lemnaceae for phytomelioration and biomass production. The aim of this study was to assess L. punctata plants for their ability to take up NH4+ and NO3- by both roots and fronds. METHODS: NO3- and NH4+ fluxes were estimated by a non-invasive ion-selective microelectrode technique. This technique allows direct measurements of ion fluxes across the root or frond surface of an intact plant. KEY RESULTS: Landoltia punctata plants took up NH4+ and NO3- by both fronds and roots. Spatial distribution of NH4+ and NO3- fluxes demonstrated that, although ion fluxes at the most distal parts of the root were uneven, the mature part of the root was involved in N uptake. Despite the absolute flux values for NH4+ and NO3- being lower in roots than at the frond surface, the overall capacity of roots to take up ions was similar to that of fronds because the surface area of roots was larger. L. punctata plants preferred to take up NH4+ over NO3- when both N sources were available. CONCLUSIONS: Landoltia punctata plants take up nitrogen by both roots and fronds. When both sources of N are available, plants prefer to take up NH4+, but will take up NO3- when it is the only N source.