To explore replacement control of the invasive weedIpomoea cairica, we studied the competitive effects of two valuable natives,Pueraria lobataandPaederia scandens, on growth and photosynthetic characteristics ofI. cairica, in pot and field experiments. WhenI. cairicawas planted in pots withP. lobataorP. scandens, its total biomass decreased by 68.7% and 45.8% and its stem length by 33.3% and 34.1%, respectively. The two natives depressed growth of the weed by their strong effects on its photosynthetic characteristics, including suppression of leaf biomass and the abundance of the CO₂-fixing enzyme RUBISCO. The field experiment demonstrated that sowing seeds ofP. lobataorP. scandensin plots where the weed had been largely cleared produced 11.8-fold or 2.5-fold as much leaf biomass of the two natives, respectively, as the weed. Replacement control by valuable native species is potentially a feasible and sustainable means of suppressingI. cairica.

Ipomoea cairica is a perennial creeper that has been widely introduced as a garden ornamental across tropical, subtropical, and temperate regions. Because it grows extremely fast and spreads easily, it has been listed as an invasive species in many countries. Here, we constructed the chromosome-level reference genome of Ipomoea cairica by Pacific Biosciences HiFi and Hi-C sequencing, with the assembly size of 733.0 Mb, the contig N50 of 43.8 Mb, the scaffold N50 of 45.7 Mb, and the Benchmarking Universal Single-Copy Orthologs complete rate of 98.0%. Hi-C scaffolding assigned 97.9% of the contigs to 15 pseudo-chromosomes. Telomeric repeat analysis reveals that 7 of the 15 pseudo-chromosomes are gapless and telomere to telomere. The transposable element content of Ipomoea cairica is 73.4%, obviously higher than that of other Ipomoea species. A total of 38,115 protein-coding genes were predicted, with the Benchmarking Universal Single-Copy Orthologs complete rate of 98.5%, comparable to that of the genome assembly, and 92.6% of genes were functional annotated. In addition, we identified 3,039 tRNA genes and 2,403 rRNA genes in the assembled genome. Phylogenetic analysis showed that Ipomoea cairica formed a clade with Ipomoea aquatica, and they diverged from each other 8.1 million years ago. Through comparative genome analysis, we reconfirmed that a whole genome triplication event occurred specific to Convolvulaceae family and in the ancestor of the genus Ipomoea and Cuscuta. This high-quality reference genome of Ipomoea cairica will greatly facilitate the studies on the molecular mechanisms of its rapid growth and invasiveness.

Changes in the proportions of male and female flowers in monoecious plants in response to external environmental conditions are directly related to the reproductive fitness of plants. The monoecious cucumber (Cucumber sativus) plant was used in this study to assess the responses of sex differentiation and the breeding process to nutrient supply and the degree of artificial pollination using pollen solutions of different concentrations. We found that the nutrient supply significantly improved the number of female flowers, while pollination treatments did not obviously increase the number of male flowers. Continuous pollination changed the number of female flowers especially in the later stage of the pollination experiment. Therefore, pollination changed the ratio of male and female flowers in the flowering stage of cucumber. Pollination treatment affected the fruit growth, seed set, and fruit yield. The number of fruit, fruit set percentage, and total seeds per plant did not increase with the pollination level, but individual fruit weight and seed number in one fruit did increase. The differentiation of male and female flowers in the flowering stage of cucumber is a response to nutrient and pollination resources, but this response is not the optimal resource allocation for subsequent fruit development and seed maturity, which suggests that the response of plants to external environment resources is short-term and direct.

Selecting native species for restoration is often done without proper ecological background, particularly with regard to how native and invasive species interact. Here, we provide insights suggesting that such information may greatly enhance restoration success. The performance of the native vine, Pueraria lobata, and that of the invasive bitter vine, Mikania micrantha, were investigated in South China to test how priority effects (timing and rate of germination and seedling growth) and competition (phytochemical effects and competitive ability) impact invasive plant performance. We found that, in the absence of competition, the germination rate of M. micrantha, but not of P. lobata, was significantly affected by light availability. P. lobata seedlings also performed better than those of M. micrantha during early growth phases. Under competition, negative phytochemical effects of P. lobata on M. micrantha were strong and we found M. micrantha to have lower performance when grown with P. lobata compared to when grown by itself. Relative interaction indexes indicated that, under interspecific competition, P. lobata negatively affected (i.e., inhibited) M. micrantha, whereas M. micrantha positively affected (i.e., facilitated) P. lobata. Higher photosynthetic efficiency and soil nutrient utilization put P. lobata at a further advantage over M. micrantha. Field trails corroborated these experimental findings, showing little recruitment of M. micrantha in previously invaded and cleared field plots that were sown with P. lobata. Thus, P. lobata is a promising candidate for ecological restoration and for reducing impacts of M. micrantha in China. This research illustrates that careful species selection may improve restoration outcomes, a finding that may also apply to other invaded ecosystems and species.