The extensive applications of graphene oxide (GO) inevitably lead to entry into the natural aquatic environment. However, information on its toxicity to emergent plants is still lacking. In this study, an emergent plant, Iris pseudacorus, was exposed to GO (1, 20, 80, and 140 mg·L⁻¹) under hydroponic conditions for 15 weeks. Changes in plant growth were assessed by analyzing plant biomass and photosynthetic pigment contents; the photosynthesis response was verified by measuring chlorophyll a fluorescence; and the nutrient levels of the plant were evaluated. Results showed that GO at 20–140 mg·L⁻¹ significantly increased plant dry weight by 37–84% and photosynthetic pigment contents by 26–178%, and 80 mg·L⁻¹ was the optimal concentration. PSII activity, adjustment capacities of electron transport in PSII, the grouping or energetic connectivity between PSII units, light energy conversion efficiency, photosynthesis performance indexes (by 11–51%), and contents of several nutrient elements (N, Fe, and Cu) were increased by 49–69%, 34–84%, and 11–38%, respectively. These findings indicate that GO can enhance plant growth by promoting plant photosynthesis performance and improving plant nutrient levels, and has great application potential in promoting the growth and development of this emergent plant as a phytoremediation agent.

The bioenergy crop switchgrass (Panicum virgatum L.) has been recognized as friendly to the soil of cultivated land depending on the previous land use types and management practices. However, the effects of switchgrass establishment on soil properties at a broader depth when it is harvested annually without any fertilization in northern China largely remain unknown. To explore the impacts of unfertilized switchgrass on soil physical and chemical properties, 0–100 cm soil samples were collected from 7-year cropland-to-switchgrass conversion and the bare land (control). The results showed that switchgrass establishment increased soil total and capillary porosity, CFU numbers of the microbial communities (fungi, bacteria, and actinomycetes), contents of microbial biomass (carbon, nitrogen, and phosphorus), and water-soluble organic carbon, and decreased soil bulk density, mostly at 0–60 cm depths, compared to the control values. Notably, the annual harvest of switchgrass insignificantly increased soil total and available nitrogen contents and slightly reduced available phosphorus and potassium contents. In conclusion, long-term cropland conversion to unfertilized switchgrass could ameliorate soil properties and does not cause soil depletion. The output of this study could inspire governments and farmers to make large-scale use of switchgrass in the ecological restoration of abandoned cropland in north China.

This study focused on three drought-tolerant grasses, namely Miscanthus sinensis ‘Gracillimus’ (Mis), Pennisetum alopecuroides ‘Ziguang’ (Pen), and Elytrigia repens (L.) Nevski ‘Jingcao No. 2′ (Ely), selected from nine species. Despite limited knowledge regarding their tolerance to submergence and responses to this stress, these three grasses were chosen for investigation. The three grass species were exposed to varying durations of submergence (0, 1, 3, 5, 7, 9, and 11 days) in a greenhouse setting. Subsequently, their growth characteristics, physiological traits, and nitrogen accumulation were evaluated. The study found that all three grass species exhibited flood tolerance, with Mis showing the strongest resistance. Under an 11-day flooding treatment, there was no significant trend in the above-ground biomass of Mis. Flooding significantly reduced the root-to-stem ratio, with Pen and Ely exhibiting more pronounced declines than Mis. The chlorophyll content in Mis decreased by 38%, compared to 41% in Pen and 60% in Ely. The root activity of the most affected species dropped by 88.6%, and nitrogen accumulation was inhibited with longer flooding durations. Pen’s nitrogen levels decreased significantly across treatments, while no significant changes were observed in Mis. Ely’s nitrogen assimilation initially increased until T4, after which it began to decline, reflecting similar trends in above-ground biomass. These findings suggest that flood tolerance is linked to nutrient uptake and photosynthetic capacity, highlighting Mis as the most suitable grass species for flood-prone areas and recommending its use in ecological ditch construction in China. This study provides material selection for the construction of ecological ditches.

Interactions between weeds and crops often occur by resource competition or allelopathy. However, it is still unknown how local weed species influence artificially introduced switchgrass. In this study, four experiments were conducted to evaluate the inhibitory effects of redroot pigweed (Amaranthus retroflexus) and crabgrass (Digitaria sanguinalis) on germination and growth of switchgrass, the lowland tetraploid cultivar ‘Alamo’ (Panicum virgatum cv. Alamo). Switchgrass germination was inhibited significantly in Petri dishes, with 48.1% and 33.9% inhibition on germination rate by redroot pigweed and crabgrass root aqueous extracts at 0.1 g·mL^− 1 concentration, respectively. Significant inhibitory effects on switchgrass seedling biomass were observed at 5:5 proportion with redroot pigweed and crabgrass in glass jars, with 61.6% and 53.4% inhibition on plant biomass, respectively. Under the same root segregation, redroot pigweed had a stronger inhibitory effect on switchgrass seedling growth than crabgrass. Growth of transplanted switchgrass seedlings was inhibited significantly by local weeds in the field, with 46.2% and 11.7% inhibition on shoot biomass during the first and second growing seasons, respectively. However, no significant growth reduction in switchgrass was detected in the third growing season.