Lemna sect. Uninerves Hegelm. consists of three species, Lemna minuta Kunth (synonym L. minuscula), L. valdiviana Phil. and L. yungensis Landolt. Lemna yungensis was discovered growing on rocks in the Yungas in Bolivia by E. Landolt and was described just 20 years ago. In the original description, Landolt reported that this species is closely related to L. valdiviana and that it is difficult to distinguish the three species on a morphological basis. Therefore, the taxonomic position and status of L. yungensis remained controversial. Here, we carried out a detailed taxonomic study, integrating approaches that include quantitative morphometry, metabolomic profiling by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) as well as molecular genetic analysis using amplified fragment length polymorphism (AFLP), and barcoding of plastidic sequences. We also investigated genome sizes of clones of the three species. Whereas L. minuta can easily be differentiated from L. valdiviana and L. yungensis, it was not possible to distinguish L. valdiviana from L. yungensis with any of the methods used. These data imply that L. yungensis is identical to L. valdiviana. Thus, the name L. yungensis should be synonymised with the name L. valdiviana, since this is the older name.
Lemnaceae are being exploited to remediate a variety of different wastewaters. Dairy processing waste is produced in large amounts, and contains a range of valuable plant nutrients, for example, nitrate, ammonium, phosphate, iron and calcium. Our aim was to remediate dairy processing waste with the duckweed plant Lemna minor. However, initial trials failed to establish growth of L. minor on this medium. A lack of growth can be due to a lack of essential plant micro-and macro-nutrients, or the presence of phytotoxic ingredients. In this study we show that not just nutrient concentrations, but also the ratios between them can be important in facilitating growth. Using lab-scale experiments in which L. minor were grown on 100 mL of synthetic wastewater, we demonstrated that the skewed Ca:Mg ratio in synthetic dairy industry wastewater is a key obstacle to good growth. Experiments showed that a ratio which favours magnesium over calcium negatively affects L. minor growth and photosynthetic yield, leading to RGRs as low as 0.05 day -1 . A change in this ratio to favour calcium, through the addition of calcium sulphate, leads to RGRs of 0.2 -0.3 day -1 . Experiments lead us to conclude that a Ca:Mg ratio of 1:1.6 (by molar concentration) or greater is necessary for Lemna minor growth, and therefore phytoremediation of dairy industry processing wastewater.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.