Search Results (6)

Background/Objectives: Crassula aquatica (L.) Schonl. is a very small annual plant growing along riverbanks. Chloroplast (cp) genomes, crucial for photosynthesis, are highly conserved and play a key role in understanding plant evolution. In this study, we conducted cp genome analysis of C. aquatica, aiming to elucidate its phylogenetic position and structural variations. We analyzed and described the features of the complete cp genome of C. aquatica and conducted comparative analysis with the cp genomes of closely related taxa. Rsults: The cp genome was 144,503 bp in length and exhibited the typical quadripartite structure, consisting of a large single-copy region (LSC; 77,993 bp), a small single-copy region (SSC; 16,784 bp), and two inverted repeats (24,863 bp). The cp genome of C. aquatica comprised 113 unique genes, including 79 protein-coding genes (PCGs), 30 tRNAs, and 4 rRNA genes. Comparative genomic analysis of 13 other Crassula species and six outgroups demonstrated highly conserved gene content and order among Crassula species. However, notable differences were observed, including the complete loss of the rpoC1 intron in C. aquatica and several closely related species, which may serve as a synapomorphic trait supporting the monophyly of the subgenus Disporocarpa. We analyzed the nucleotide diversity among 14 Crassula cp genomes and identified five highly variable regions (pi > 0.08) in the IGS regions. Phylogenetic analysis based on 78 PCGs confirmed the monophyly of Crassula and its division into two subgenera: Crassula and Disporocarpa. Although the phylogenetic tree supported the subgeneric classification system, the sectional classification system requires reassessment. Conclusions: In this study, we conducted a comparative analysis of the cp genome of the genus Crassula. We inferred evolutionary trends within the Crassula cp genome and provided molecular evidence supporting the integration of the genus Tillaea into the genus Crassula. However, as this study does not represent all species within the genus Tillaea, further comprehensive phylogenetic analyses are requrired. Full article

On a global scale, wetlands are suffering from a steady decline in surface area and environmental quality. Protecting them is essential and requires a careful spatialisation of their natural habitats. Traditionally, in our study area, species discrimination for floristic mapping has been achieved through on-site field inventories, but this approach is very time-consuming in these difficult-to-access environments. Usually, the resulting maps are also not spatially exhaustive and are not frequently updated. In this paper, we propose to establish a complete map of the study area using remote sensors and set up a long-term and regular observatory of environmental changes to monitor the evolution of a major French wetland. This methodology combines three dataset acquisition technologies, airborne hyperspectral and WorldView-3 multispectral images, supplemented by LiDAR images, which we compared to evaluate the difference in performances. To do so, we applied the Random Forest supervised classification methods using ground reference areas and compared the out-of-bag score (OOB score) as well as the matrix of confusion resulting from each dataset. Thirteen habitats were discriminated at level 4 of the European Nature Information System (EUNIS) typology, at a spatial resolution of around 1.2 m. We first show that a multispectral image with 19 variables produces results which are almost as good as those produced by a hyperspectral image with 58 variables. The experiment with different features also demonstrates that the use of four bands derived from LiDAR datasets can improve the quality of the classification. Invasive alien species Ludwigia grandiflora and Crassula helmsii were also detected without error which is very interesting when applied to these endangered environments. Therefore, since WV-3 images provide very good results and are easier to acquire than airborne hyperspectral data, we propose to use them going forward for the regular observation of the Brière marshes habitat we initiated. Full article

Australian swamp stonecrop (Crassula helmsii (Kirk) Cockayne) is invasive in Western Europe. Its small size and high potential for regeneration make it difficult to eliminate. Short-term experiments have demonstrated that the growth of C. helmsii depends on nutrient availability and resource competition. In order to confirm those mechanisms in the field, we studied the abundance of C. helmsii in Northern Europe over a longer period of time in relation to nutrient availability and co-occurring plant communities and plant species. C. helmsii impacted native species mainly by limiting their abundance. The native plant species present indicated that previous or periodic elevated nutrient availability were likely responsible for the proliferation of C. helmsii. When growing in submerged conditions, the dominance of C. helmsii depended on a high availability of CO₂. A series of exceptionally dry summers allowed C. helmsii to increase in cover due to weakened biotic resistance and a loss of carbon limitation. Only Littorella uniflora (L.) Asch. and Juncus effusus L. were able to remain dominant and continue to provide biotic resistance. Based on our findings, minimizing nutrient (C and N) availability and optimizing hydrology provides native species with stable growth conditions. This optimizes resource competition and may prevent the proliferation of C. helmsii. Full article

A great deal of effort has been made to clear invasive alien plants in South Africa, yet it remains unclear if the clearing efforts are yielding positive soil and vegetation recovery trajectories. A few short-term studies have been conducted to monitor soil and vegetation recovery after alien plant removal in South Africa, but convincing, long-term monitoring studies are scarce yet needed. We investigated topsoil and vegetation recovery following Eucalyptus grandis removal 14 years ago by Working for Water in Makhanda, Eastern Cape province of South Africa. The detailed topsoil and vegetation surveys were conducted on forty 10 m × 10 m plots that were in paired cleared and natural sites. The results show no significant differences for the measured soil pH, total N, total C, K, Ca, and Na between the cleared and natural sites, an indication that the two sites are becoming similar. Similarly, the gravimetric soil moisture content shows no significant differences between the two sites, although monthly variations are observed. The topsoils in the cleared sites are hydrophobic as compared to those in the natural sites, which are wettable. We observed no significant vegetation diversity differences between the two sites, with native woody species, such as Crassula pellucida and Helichrysum petiolare, frequently occurring in the cleared sites. We recorded low reinvasion by E. grandis and other secondary invaders like Acacia mearnsii and Rubus cuneifolius in the cleared sites. Based on these results, we conclude that 14 years after E. grandis clearing, both topsoil and vegetation recovery are following a positive trajectory towards the natural sites. However, both reinvasion and secondary invasion have the potential to slow down soil and native vegetation recovery. Recommendations such as timeous follow-up clearing and incorporating restoration monitoring in the WfW clearing programme are discussed. Full article

The genus Crassula is the second-largest genus in the family Crassulaceae, with about 200 species. As an acknowledged super-barcode, plastomes have been extensively utilized for plant evolutionary studies. Here, we first report 10 new plastomes of Crassula. We further focused on the structural characterizations, codon usage, aversion patterns, and evolutionary rates of plastomes. The IR junction patterns—IRb had 110 bp expansion to rps19—were conservative among Crassula species. Interestingly, we found the codon usage patterns of matK gene in Crassula species are unique among Crassulaceae species with elevated ENC values. Furthermore, subgenus Crassula species have specific GC-biases in the matK gene. In addition, the codon aversion motifs from matK, pafI, and rpl22 contained phylogenetic implications within Crassula. The evolutionary rates analyses indicated all plastid genes of Crassulaceae were under the purifying selection. Among plastid genes, ycf1 and ycf2 were the most rapidly evolving genes, whereas psaC was the most conserved gene. Additionally, our phylogenetic analyses strongly supported that Crassula is sister to all other Crassulaceae species. Our findings will be useful for further evolutionary studies within the Crassula and Crassulaceae. Full article

Aspergillus sp., an endophytic fungus isolated from Crassula arborescens, displayed potent inhibitory activity against the seed germination of Arabidopsis thaliana. The bioactivity-guided fractionation of the culture extract of Aspergillus sp. MJ01 led to the isolation of nine compounds, including one previously undescribed furanone, namely aspertamarinoic acid (1), and eight known compounds, (−)-dihydrocanadensolide (2), kojic acid (3), citreoisocoumarin (4), astellolide A (5), astellolide B (6), astellolide G (7), cyclo-N-methylphenylalanyltryptophenyl (8) and (−)-ditryptophenaline (9). In the evaluation of the phytotoxic activities of compounds 1–9, the results suggested that 1 and 5 showed significant inhibitory activity on the seed germination of A. thaliana. This is the first report to disclose the phytotoxic activity of these compounds. Full article