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Sustainable green space is essential in urban areas to maintain and improve human well-being. However, to better understand the impact of environmental and socioeconomic changes on the sustainability of tropical urban green space landscapes, work is needed to explore the patterns of plant diversity and its drivers in urban green spaces. We explore urban floristic diversity patterns based on samples from 826 urban functional units located in five cities in the tropical coastal region of China. Field surveys were conducted to obtain data on plant diversity, land use types, socioeconomic characteristics, and environmental characteristics within these units. Plant diversity within the cities varied significantly among land use types, with high-rise housing, parks and universities exhibiting higher diversity. The diversity of cultivated plants and regional economy showed significant positive correlation, while an increase in the diversity of spontaneous plants and native species was linked to building age. Management also affected plant diversity, with watering frequency being positively associated and maintenance frequency. Urban plant diversity patterns result from a combination of multiple factors. Socio-economic factors are the primary driver of the patterns of urban plant diversity, as space management and maintenance determine what can grow in different areas. The implications of the study have important practical significance for policymakers and managers in the development and management of urban green spaces more sustainably.

The GRAS gene family is one of the most important families of transcriptional factors that have diverse functions in plant growth and developmental processes including axillary meristem patterning, signal-transduction, cell maintenance, phytohormone and light signaling. Despite their importance, the function of GRAS genes in pitaya fruit (Selenicereus undatus L.) remains unknown. Here, 45 members of the HuGRAS gene family were identified in the pitaya genome, which was distributed on 11 chromosomes. All 45 members of HuGRAS were grouped into nine subfamilies using phylogenetic analysis with six other species: maize, rice, soybeans, tomatoes, Medicago truncatula and Arabidopsis. Among the 45 genes, 12 genes were selected from RNA-Seq data due to their higher expression in different plant tissues of pitaya. In order to verify the RNA-Seq data, these 12 HuGRAS genes were subjected for qRT-PCR validation. Nine HuGRAS genes exhibited higher relative expression in different tissues of the plant. These nine genes which were categorized into six subfamilies inlcuding DELLA (HuGRAS-1), SCL-3 (HuGRAS-7), PAT1 (HuGRAS-34, HuGRAS-35, HuGRAS-41), HAM (HuGRAS-37), SCR (HuGRAS-12) and LISCL (HuGRAS-18, HuGRAS-25) might regulate growth and development in the pitaya plant. The results of the present study provide valuable information to improve tropical pitaya through a molecular and conventional breeding program.

Old, valuable trees (OVT) comprise an important urban ecological and cultural resource. Understanding their innate traits and driving factors can facilitate management, conservation and ecotourism development. This study assessed relationship between the species diversity composition, distribution, growth status, and tree-habitat of OVT in Wuzhishan City in Hainan Province, south China. We acquired tree and site data by field surveys, literature mining, interviews and laboratory tree-age determination. The results show that there are 216 OVT in Wuzhishan City, belonging to eight families and 13 genera and 21 species. Sapindaceae was the family with the largest number of species (79). Lychee was the predominant genus represented by Litchi chinensis. The overall age structure of OVT in Wuzhishan City is pyramidal, mainly concentrated in the range of 100-299a (average 163a). According to the grading norms of Chinese OVT, there are three Grade 1, 21 Grade 2 and 192 Grade 3 OVT. Tree height, trunk girth and crown width were normally distributed, mainly concentrated at ten-19 m (mean 32.1 m), 300-499 cm (mean 423 cm) and ten-20 m (mean 17 m), respectively. The overall number of individuals of OVT in Wuzhishan City was evenly distributed. The results of General Linear Model (GLM) analysis showed that the tree height of OVT in Wuzhishan City was highly significantly correlated with precipitation of wettest month (P=8.69E-04), trunk girth was highly correlated with annual mean temperature (P=9.30E-04) and precipitation of coldest quarter (P=3.06E-04), crown width was significantly correlated with mean temperature of warmest quarter (P=8.28E-03). The number of OVT in Wuzhishan City was significantly or highly significantly correlated with most environmental factors. In conclusion, Wuzhishan City has a rich variety of OVT with a uniform distribution; environmental factors have a greater impact on OVT, and it is recommended that targeted protection measures for OVT be developed in conjunction with the actual situation of the city.