Water and fertilizer coupling is a high-efficiency technology for the development of facility agriculture. However, the interaction effect of nitrogen (N) and air carbon dioxide (CO2) on hydroponic purple cabbage, especially on its leaf anthocyanins under hydroponic solution systems, remains unexplored. In this study, six treatments were set as C0N0, C0N2, C0N4, C1N0, C1N2 and C1N4, with N0, N2 and N4 being 0.0 g/L, 0.2 g/L and 0.4 g/L exogenous urea-N to hydroponic solution dilution, respectively. C0 and C1 were set as with and without CO2 fertilizer (i.e., 800 g CO2 agent added one week after transplanting and 600 g CO2 agent added when the plant reached 15 cm in height), respectively. Pot experiments were conducted to investigate the interaction effect of N and air CO2 (N×CO2) on the growth, photosynthesis, yield and anthocyanin content of hydroponic purple cabbage Brassica campestris ssp. chinensis. The results showed N×CO2 extremely significantly influenced plant height (H), net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular oxidation concentration (Ci), transpiration rate (Tr), leaf water use efficiency (LWUE) and yield. The C1N0 treatment had the largest yield at 262.5 g/plant, with higher values for root length, root weight, plant height and leaf number than the other treatments. The Pn, Ci and Tr of C1N4 were the highest at 3.05 μmol CO2/m2•s, 352.8 μmol CO2/m2•s and 2.31 mmol H2O/m2•s, respectively. The C1N2 treatment received the largest Gs value of 0.70 mol H2O/m2•s and the largest Tr of 2.31 mmol H2O/m2•s. There was the highest LWUE for C0N2 (1.41) and the highest anthocyanin content for C1N2 (1.35 mg/kg). There was a significant negative correlation between leaf number and anthocyanin (r = –0.414, p<0.05). The findings demonstrated that adding CO2 fertilizer and 0.2 g/L exogenous urea-N to hydroponic solution dilution is a potential N×CO2 coupling strategy to increase anthocyanin and the yield of purple cabbage. Keywords: nitrogen concentration, carbon dioxide, purple cabbage, hydroponic solution, anthocyanins DOI: 10.25165/j.ijabe.20231605.7638 Citation: Chen D Y, Feng Y Y, Liu Y, Hu J, Li S L, Ma J Z, et al. Effects of urea-N and CO2 coupling fertilization on the growth, photosynthesis, yield and anthocyanin content of hydroponic purple cabbage Brassica campestris ssp. chinensis. Int J Agric & Biol Eng, 2023; 16(5): 123–131.

The Mediator complex (MED) functions as a co-activator in plants, transmitting transcriptional signals to regulate gene expression, including responses to environmental stresses. While the MED gene family has been identified in several species, it has not yet been reported in cassava. In this study, we identified 32 members of the MeMED gene family in cassava (Manihot esculenta Crantz) distributed across 13 chromosomes. These genes were categorized into distinct Mediator subunits based on their similarity to Arabidopsis modules. Promoter analysis revealed the presence of various cis-regulatory elements, which likely play key roles in regulating plant growth, development, and stress responses. RNA-seq data showed tissue-specific expression patterns for the MeMED genes, with significant expression observed in leaves, roots, petioles, stems, friable embryogenic callus, and shoot apical meristems. Further RT-qPCR analysis under various abiotic stress conditions—including drought, exogenous hydrogen peroxide, cold, heat, and salt—demonstrated that 10 selected MeMED genes exhibited significant differential expression, indicating their potential functional involvement in stress adaptation. These findings offer insights into the biological roles of the MeMED gene family in cassava, with implications for improving stress tolerance in future breeding programs.

Leaf angle is a key agronomic trait that determines plant architecture and grain yield in rice. Although brassinosteroids (BRs) are known to play a central