The local rise in urban temperature is increasingly exacerbated due to the combined effect of urban heat islands and global climate change. Numerous studies have shown that green roofs (GRs) have great potential for facilitating urban heat mitigation. However, little is known about whether such cooling effects can be achieved under extreme heat conditions. With the expected occurrence of more extreme heat events under climate change, such understanding is crucially important for the effective design of heat mitigation. This study aims to fill this gap by investigating the pedestrian-level cooling effect of GR under two weather conditions (i.e., typical summer weather conditions and extreme heat conditions). This research employed a three-dimensional simulation model, ENVI-met, to simulate pedestrian-level air temperature for three typical residential areas with different roof heights in Beijing. We conducted the simulations in two different roof scenarios, conventional roofs versus green roofs. The results showed that green roofs could provide large cooling exceeding 0.2°C on downwind sides and in the daytime, although the average cooling intensity was small. The pedestrian-level cooling intensity of GR decreased significantly under extreme heat conditions compared to typical summer weather conditions. It varied diurnally following an inverted W-shape for both weather conditions. Results also showed that the pedestrian-level cooling intensity of GR decreased with the increase in roof height in a nonlinear way and became 0 when roof height reached ∼50 m for both weather conditions. The results of our research can provide important insights for cooling-oriented urban design in the future, as we are expecting such extreme weather conditions nowadays may be the new normal in the future.

The Loropetalum chinense and Loropetalum chinense var. rubrum are typical as well as traditional ornamental and Chinese herbal medicines in Asia; however, more information is needed on the mechanisms underlying their flower coloring. Here, we profiled the flavonoid metabolome and carried out full-length sequencing in addition to transcriptome analyses to investigate the flavonoid biosynthesis and global transcriptome changes among different petal coloring cultivars of L. chinense and L. chinense var. rubrum. The total anthocyanins in addition to the RHSCC values and CIE 1976 L*a*b* values of petals were highly consistent with petal color. Moreover, a total of 207 flavonoid components were identified. Of these, 13 flavonoid compounds were considered significantly different expression compounds highly consistent with color information in the 4 samples. Meanwhile, the first reference full-length transcriptome of L. chinense var. rubrum was built, which had 171,783 high-quality nonredundant transcripts with correcting with next-generation sequencing (NGS). Among them, 52,851 transcripts were annotated in the seven databases of NR, KOG, GO, NT, Pfam, Swiss-Port, and KEGG. Combined with NGS analyses, the DETs involved in flavonoids and anthocyanins contributed greatest to the flower coloring. Additionally, the different expressions of eight LcDFRs and four LcANS genes were positively correlated with flavonoid biosynthesis, and the four LcBZ1 as well as one Lc3Mat1 were positively correlated with the content of seven anthocyanins revealed by coupling with metabolomics and transcriptomics analyses. Together, these results were used to mine candidate genes by analyzing flower coloring changes at comprehensive metabolic and transcriptomic levels in L. chinense and L. chinense var. rubrum.

Urban parks are the main place for physical activities, generating numerous benefits to enhance human well-being. Many studies have investigated the impacts of landscape features on park visitation but ignored their seasonal and diurnal variations. Taking the Hunan Martyr Park in China as an example, this study aims to assess the seasonal and diurnal variations in the impacts of landscape features on visitation density. We quantified visitation density for 109 activity zones for both daytime and nighttime in summer and winter and investigated the impacts of landscape features of the activity zone and the surrounding environments on visitation density based on 16 quantitative indicators. The results show that: (1) The impacts of ground condition, connection to water, distance to park entrances, and distance to stores were consistent in different periods. Paved activity zones, zones close to water, zones further away from the park entrances, and zones closer to the stores had significantly higher visitation density. (2) Shading degree, connected pathway, and distance to toilets had contrasting impacts between summer and winter. Zones with a higher shading degree attracted more visitors in summer and deterred visitors in winter. Zones with fewer pathways connected and zones farther away from toilets had higher visitation density in summer but not in winter. (3) Shading degree, number of trees, presence of facilities (e.g., benches, tables, pavilion, and light devices), and connected pathway had contrasting impacts between daytime and nighttime. Zones with a high shading degree, zones with benches and pavilions, and zones without trees had higher visitation density in the daytime. Zones with light devices, zones with more connected pathways, and zones without tables had higher visitation density at nighttime. These findings highlighted the seasonal and diurnal variation of the impacts of landscape features on park visitation and can help to improve urban park design, especially for cities with hot summers and cold winters.

Dendrobium officinale Kimura et Migo, a highly valued Chinese herbal medicine, is on the verge of extinction in the wild, and is not cultivated efficiently. In this study, we explored the possibility that orchid mycorrhizal fungi (OMF) might improve the growth and cultivation of D. officinale. Serendipita sp., Tulasnella calospora and Tulasnella asymmetrica isolated from three different orchids were co-cultured with sterile seedlings of D. officinale. The seedlings were found to stably coexist with fungi after 60 days of co-culture. The co-culture of T. calospora with plants upregulated the activity of antioxidant enzymes, stimulated the production of osmoregulatory substances and reduced electrical conductivity. Plants with T. calospora had longer roots (141.2%), thicker leaves (58.3%), increased root number (71.4%) and leaf number (11.1%), and increased weight (155.2%) and photosynthetic pigment content (99.6%), relative to controls. The content of total medicinal polysaccharides increased by 42.69 % due to the addition of T. calospora. T. asymmetrica was less effective, followed by Serendipita sp. When T. calospora established a symbiotic relationship with D. officinale, resistance indicators increased. The content of functional components was significantly increased. This study contributes to the protection and commercial reproduction of endangered orchid plants with mycorrhizal technology.

The WRKY gene family plays important roles in plant growth and development, as well as in the responses to biotic and abiotic stresses. Loropetalum chinense var. rubrum has high ornamental and medicinal value. However, few WRKY genes have been reported in this plant, and their functions remain unknown. To explore the roles that the WRKY genes play in L. chinense var. rubrum, we identified and characterized 79 LcWRKYs through BLAST homology analysis and renamed them (as LcWRKY1–79) based on their distribution on the chromosomes of L. chinense var. rubrum. In this way, according to their structural characteristics and phylogenetic analysis, they were divided into three groups containing 16 (Group I), 52 (Group II), and 11 (Group III) WRKYs, respectively. LcWRKYs in the same group have similar motifs and gene structures; for instance, Motifs 1, 2, 3, 4, and 10 constitute the WRKY domain and zinc-finger structure. The LcWRKY promoter region contains light response elements (ACE, G-box), stress response elements (TC-rich repeats), hormone response elements (TATC-box, TCA-element), and MYB binding sites (MBS, MBSI). Synteny analysis of LcWRKYs allowed us to establish orthologous relationships among the WRKY gene families of Arabidopsis thaliana, Oryza sativa, Solanum lycopersicum L., Vitis vinifera L., Oryza sativa L., and Zea mays L.; furthermore, analysis of the transcriptomes of mature leaves and flowers from different cultivars demonstrated the cultivar-specific LcWRKY gene expression. The expression levels of certain LcWRKY genes also presented responsive changes from young to mature leaves, based on an analysis of the transcriptome in leaves at different developmental stages. White light treatment led to a significant decrease in the expression of LcWRKY6, 18, 24, 34, 36, 44, 48, 61, 62, and 77 and a significant increase in the expression of LcWRKY41, blue light treatment led to a significant decrease in the expression of LcWRKY18, 34, 50, and 77 and a significant increase in the expression of LcWRKY36 and 48. These results enable a better understanding of LcWRKYs, facilitating the further exploration of their genetic functions and the molecular breeding of L. chinense var. rubrum.

The basic helix–loop–helix (bHLH) transcription factor family is the second-largest transcription factor family in plants. Members of this family are involved in the processes of growth and development, secondary metabolic biosynthesis, signal transduction, and plant resistance. Loropetalum chinense var. rubrum is a critical woody plant with higher ornamental and economic values, which has been used as ornamental architecture and traditional Chinese herbal medicine plants. However, the bHLH transcription factors in Loropetalum chinense var. rubrum (L. chinense var. rubrum) have not yet been systematically demonstrated, and their role in the biosynthesis of anthocyanin is still unclear. Here, we identified 165 potential LcbHLHs genes by using two methods, and they were unequally distributed on chromosomes 1 to 12 of the genome of L. chinense var. rubrum. Based on an evolutionary comparison with proteins from Arabidopsis and Oryza sativa, these bHLH proteins were categorized into 21 subfamilies. Most LcbHLHs in a particular subfamily had similar gene structures and conserved motifs. The Gene Ontology annotation and Cis-elements predicted that LcbHLHs had many molecular functions and were involved in processes of plant growth, including the biosynthesis of flavonoids and anthocyanins. Transcriptomic analysis revealed different expression patterns among different tissues and cultivars of L. chinense var. rubrum. Many LcbHLHs were expressed in the leaves, and only a few genes were highly expressed in the flowers. Six LcbHLHs candidate genes were identified by bioinformatics analysis and expression analysis. Further Real-time quantitative PCR analysis and protein interaction network analysis showed that LcbHLH156, which is one of the candidate proteins belonging to the IIIf subfamily, could interact with proteins related to anthocyanin synthesis. Therefore, LcbHLH156 was transiently expressed in L. chinense var. rubrum to verify its function in regulating anthocyanin synthesis. Compared with the control group, red pigment accumulation appeared at the wound after injection, and the total anthocyanin content increased at the wound of leaves. These results lay a foundation for the research of the regulation mechanism of leaf colors in L. chinense var. rubrum and also provide a basis for the function of the LcbHLH family.