in biology, structure is the basis of function. for plants, changes in their physiological and ecological functions are usually caused by structural changes. to understand how shading conditions change the plant structures, thereby providing structural insights into the improved yield and quality, oilseed tree peony were shaded with different densities of polyethylene nets from 28 days after pollination (DAP) until harvesting. The thickness of the leaf (LT), vein (VT), upper epidermis (UET), lower epidermis (LET), palisade tissue (PT), sponge tissue (ST), as well as the accumulation and distribution of starch, protein, and fat, were observed at 14-day intervals. The results showed that shading had a significant effect on the anatomical structure of the leaves. In the rapid growth period (before 70 DAP), the LT, ET, and VT under shading were significantly lower than under non-shading. During this period, the accumulation of starch and protein under shading was lower than that under non-shading. At the maturation period (99-112 DAP), the LT and PT under shading were higher than under non-shading, indicating that light shading delayed leaf senescence and increased photosynthetic capacity. Shading delayed the degradation of the integument cells and prolonged seed development and nutrient accumulation.Tree peony (Paeonia section Moutan DC.) is indigenous to China, and its wild germplasms are mainly distributed in mountainous shrublands and secondary broad-leafed forests in the provinces of Henan, Gansu, and Shanxi 1 . In the transplantation process of oilseed tree peony from mountainous shrublands to the field, their leaves usually turn yellow, senescence prematurely, or even fall off due to the high light intensity and temperature, which seriously reduces the yield and quality of the tree peony seeds 2 . Shading is the preferred method for providing a suitable environment during the growth period since high light intensity and temperature are detrimental to ornamenta shrubs growth 3 . For example, when kiwi fruit plants were shaded, the canopy microclimate was significantly optimized, the temperature was lowered, and the humidity was increased, which effectively alleviated the physiological stress of the leaves and fruits and reduced the fallen fruit 4 . Under shading, Trollius chinensis Bunge grew relatively better and exhibited an extended viewing life 5 .Light is a primary factor of the physical environment. Shading changes the microenvironment, which consequently alters leaf physiological characteristics 6 as well as leaf structure 7-9 . Shading increases leaf area and reduces leaf thickness 7 and reduces palisade tissue and stomatal density 8 . It also increases the intercellular space between the palisade tissue and spongy tissue, as well as the numbers of vascular bundles 5 . Shading has also been found to reduce the palisade tissue thickness, stomatal density, and the ratio of palisade tissue to sponge tissue 10 . Shading www.nature.com/scientificreports www.nature.com/scientificreports/ than that under non-s...
