Launaea

Abstract: Sequences from the internal transcribed spacer region (ITS) of nuclear ribosomal DNA were used to assess relationships among genera of subtribe Sonchinae (Lactuceae). The data suggest that Sonchinae is paraphyletic, and that the Dendroseridinae should not be recognized as a distinct subtribe. Several Macaronesian genera, along with woody Macaronesian species of Sonchus (all diploid, 2n = 18), appear to have been derived from a common ancestor. Prenanthes pendula is more closely related to this Macaronesian group than to other members of Prenanthes, suggesting that Prenanthes, like Sonchus, is polyphyletic. The Juan Fernandez Islands endemic genus Dendroseris (2n = 36) is monophyletic, but its phylogenetic relationships to other Sonchinae remain uncertain. Reichardia, which forms the sister genus of the Sonchinae, is also monophyletic. Launaea, by contrast, is considered to be paraphyletic. The monotypic genus Aetheorhiza (2n = 18) is sister to the annual weedy species of Sonchus, rather than being closely related to Launaea. Two monotypic endemic genera from New Zealand, Embergeria (2n = 36) and Kirkianella (2n = 90, 126), are sister genera, and together they form the sister clade to Sonchus arvensis-S. maritimus. This implies that these Pacific genera were derived either from section Arvenses or Maritimi of subgenus Sonchus, rather than from section Apseri.

Abstract: Essential oils (EOs) from the aerial parts of three Launaea species collected from two different habitats were extracted [Launaea mucronata collected from coastal desert (LMC) and from inland desert (LMD), Launaea nudicaulis collected from coastal desert (LNC) and from inland desert (LND), Launaea spinosa (LS)]. The EOs were analysed by gas chromatography mass spectrometry (GC‐MS) and tested for antioxidant activity as well for allelopathic activity against purslane. A total of 117 compounds were identified from all samples, including 64 from LS, 50 from LMC, 39 from LMD, 24 from LNC, and 20 from LND, representing 100% of the total oil mass. The oxygenated sesquiterpenes were the major compounds of the EOs from LS, LMC, LMD, LNC, and LND, representing 62.73, 61.02, 58.35, 43.22, and 48.33%, respectively, whereas the monoterpene hydrocarbons were minor compounds in all samples. α‐Acorenol (31.42%), trans‐longipinocarveol (12.04%), and γ‐eudesmol (6.31%) represented the major compounds of the EO from LS, whereas hexahydrofarnesyl acetone and n‐heneicosane represented the major compounds from LMC, LMD, LNC, and LND. Correlations between the EOs of the five samples were studied via principal component analysis and agglomerative hierarchical clustering, based on the chemical composition of the EOs. There was a significant variation between Launaea species regarding both the quality and the quantity of EO composition, whereas no significant difference was observed based on the habitats (coastal and inland deserts). The EOs of the five Launaea samples exhibited meaningful antioxidant activities, as follows: LND > LNC > LMD > LMC > LS. Moreover, the EOs of the five Lanaea samples exhibited significant allelopathic activity against purslane weed in a concentration‐dependent manner. LMD and LMC showed the highest effect, with germination inhibition of 96.1 and 87.9% at 250 μL L⁻¹, and radicle growth inhibition of 92.6 and 89.7%, but LS was the least effective extract. Our results showed that the variation in the quality and quantity of EO composition is mainly species specific, with a slight correlation with habitats.

Abstract: The development of the anther and pollen, megasporogenesis, female gametophyte, fertilisation, endosperm and development of the embryo ofLaunœa pinnatifida have been studied.