Yinran Huang

Ulmus pumila L. ‘Zhonghua Jinye’ is a plant variety with colourful leaves that is widely used in landscaping. In our study, the leaves of U. pumila ‘Zhonghua Jinye’ fade and turn green under light (LT, 45%), moderate (MD, 70%) and high (HG, 95%) shading treatment, reducing its ornamental value. However, the mechanism underlying this adaptation to shade is poorly understood. The objective of this study was to elucidate the mechanism of physiological, cellular microstructural and transcriptional changes involved in leaf regreening in U. pumila ‘Zhonghua Jinye’. Our results showed that the pigment content of U. pumila ‘Zhonghua Jinye’ leaves increased under shade stress, with a corresponding colour change from yellow to dark green. Thus, U. pumila ‘Zhonghua Jinye’ adapted to shade stress by increasing leaf pigment and chlorophyll content. Transmission electron microscopy showed that thylakoid stacking in the grana lamellae changed significantly from a loose state to a closely packed structure under shaded conditions. Because plant pigments were located mainly in thylakoids, this closer stacking increased photosynthetic efficiency and pigment accumulation. RNA sequencing analysis showed that Lhcb1, a key thylakoid membrane gene, was upregulated under shade, which promoted thylakoid stacking and light absorption. In the chlorophyll synthesis pathway, haeme metabolism was inhibited, increasing protoporphyrin IX flow to the chlorophyll pathway and promoting the synthesis of chlorophyll a/b. The simultaneous upregulation of plant hormone-related genes promoted an increase in plant leaf area, improving the light energy utilisation ratio. This study is the first to report the self-regulatory mechanism that leads to colour change in U. pumila ‘Zhonghua Jinye’ under shade stress and provides a theoretical basis for the cultivation of tree species with colourful leaves.

Background: Plants can retain atmospheric particulate matter (PM) through their unique foliar microstructures, which has a profound impact on the phyllosphere microbial communities. Yet, the underlying mechanisms linking atmospheric particulate matter (PM) retention by foliar microstructures to variations in the phyllosphere microbial communities remain a mystery. In this study, we conducted a field experiment with ten Ulmus lines. A series of analytical techniques, including scanning electron microscopy, atomic force microscopy, and high-throughput amplicon sequencing, were applied to examine the relationship between foliar surface microstructures, PM retention, and phyllosphere microbial diversity of Ulmus L. Results: We characterized the leaf microstructures across the ten Ulmus lines. Chun exhibited a highly undulated abaxial surface and dense stomatal distribution. Langya and Xingshan possessed dense abaxial trichomes, while Lieye, Zuiweng, and Daguo had sparsely distributed, short abaxial trichomes. Duomai, Qingyun, and Lang were characterized by sparse stomata and flat abaxial surfaces, whereas Jinye had sparsely distributed but extensive stomata. The mean leaf retention values for total suspended particulate (TSP), PM_2.5, PM_2.5-10, PM_10-100, and PM_> 100 were 135.76, 6.60, 20.10, 90.98, and 13.08 µg·cm^− 2, respectively. Trichomes substantially contributed to PM_2.5 retention, while larger undulations enhanced PM_2.5-10 retention, as evidenced by positive correlations between PM_2.5 and abaxial trichome density and between PM_2.5-10 and the adaxial raw microroughness values. Phyllosphere microbial diversity patterns varied among lines, with bacteria dominated by Sediminibacterium and fungi by Mycosphaerella, Alternaria, and Cladosporium. Redundancy analysis confirmed that dense leaf trichomes facilitated the capture of PM_2.5-associated fungi, while bacteria were less impacted by PM and struggled to adhere to leaf microstructures. Long and dense trichomes provided ideal microhabitats for retaining PM-borne microbes, as evidenced by positive feedback loops between PM_2.5, trichome characteristics, and the relative abundances of microorganisms like Trichoderma and Aspergillus. Conclusions: Based on our findings, a three-factor network profile was constructed, which provides a foundation for further exploration into how different plants retain PM through foliar microstructures, thereby impacting phyllosphere microbial communities.

Maintaining a supply–demand balance of ecosystem services (ES) is essential for enhancing the effectiveness of ecosystem restoration. However, inappropriate land use and reforestation practices can negatively impact this balance. In this study, the ES balance of the Saihanba region in China was quantified by integrating land use/cover change (LUCC) data, landscape metrics, and ES indicators. The relationship between ES balance and its driving factors was analyzed using spatial panel models. The spatiotemporal changes of landscape patterns from 2002 to 2020 were also explored. The results indicated that the overall ES supply capacity of the study region, especially in the southwestern area, increased during the research period. The ES balance and its determining factors exhibited significant spatial heterogeneity and spillover effects. Large–scale afforestation increased the local ES supply and provided economic benefits, but it also led to ecological issues, including declines in wetland area and landscape fragmentation. Our study emphasized the importance of considering the supply–demand balance in the planning and decision–making of ES, providing insight into multifunctional management and the sustainable development in the Saihanba area.