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In the present study, an indoor potting experiment was conducted to study the effects of enhanced UV-B radiation and Magnaporthe oryzae on the growth, stomatal structure, photosynthesis, and endogenous hormone contents of a traditional rice cultivar Baijiaolaojing in the Yuanyang terraces of Yunnan Province. In addition, the relationships between these parameters and disease indices were analyzed. We aimed to clarify the response of the photosynthetic physiology of rice under the combined stress of UV-B radiation and M. oryzae. Compared with the M. oryzae infection treatment, all the treatments, including M. oryzae infection before (MBR), simultaneously with (MSR), and after (MAR) UV-B radiation significantly increased the rice height and biomass by 4%–11% and 30%–111%, respectively, and the stomatal structure and carotenoids content of leaves, while decreasing the contents of chlorophyll a and b, by 21%–41% and 63%–73%, respectively. Both the MSR and MBR treatments significantly increased the photosynthetic rate and transpiration rate of rice leaves. The MAR treatment weakened chlorophyll fluorescence parameters, including the actual photosystem II (PS II) photochemical efficiency, electron transport rate, photochemical quenching, and nonphotochemical quenching by 40%, 39%, 43%, and 24%, respectively. Moreover, the treatments of MAR, MSR, and MBR decreased the phytohormones content and the M. oryzae disease index by 27%–62% in rice leaves. Thus, the enhanced UV-B radiation contributed to suppressing the M. oryzae infection and alleviating its damage to the photosynthesis of rice leaves. This study is valuable for the control of rice blast fungus and offers important insights into plant pathology. [ABSTRACT FROM AUTHOR]

δ-MnO2 is an important component of environmental minerals and is among the strongest sorbents and oxidants. The crystalline morphology of δ-MnO2 is one of the key factors affecting its reactivity. In this work, δ-MnO2 was initially synthesized and placed in an acidic environment to react with Mn2+ and undergo a crystalline transformation. During the transformation of crystalline δ-MnO2, kinetic sampling was conducted, followed by analyses of the structures and morphologies of the samples. The results showed that at pH 2.5 and 4, δ-MnO2 nanoflakes spontaneously self-assembled into nanoribbons via edge-to-edge assembly in the initial stage. Subsequently, these nanoribbons attached to each other to form primary nanorods through a face-to-face assembly along the c-axis. These primary nanorods then assembled along the (001) planes and lateral surfaces, achieving further growth and thickening. Since a lower pH is more favorable for the formation of vacancies in δ-MnO2, δ-MnO2 can rapidly adsorb Mn2+ directly onto the vacancies to form tunnel walls. At the same time, the rapid formation of the tunnel walls leads to a quick establishment of hydrogen bonding between adjacent nanoribbons, enabling the assembly of these nanoribbons into primary nanorods. Therefore, in a solution with the same concentration of Mn2+, the structure transformation and morphology evolution of δ-MnO2 to α-MnO2 occur faster at pH 2.5 than at pH 4. These findings provide insights into the mechanism for crystal growth from layer-based to tunnel-based nanorods and methods for efficient and controlled syntheses of nanomaterials. [ABSTRACT FROM AUTHOR]

In recent years, more and more attention has been paid towards the microplastics (MPs) in soil. However, not only microplastics but also heavy metals are present in the soil. The coexistence of microplastics and heavy metals in soil will affect plants growth and plant-fungi symbiotic system. Some studies have shown that the tolerance of plants to heavy metals is enhanced by plants-arbuscular mycorrhizal fungi (AMF) symbiotic system. However, the colonization of AMF in plant roots and the abilities of AMF to filter and chelate heavy metals would be affected by microplastics, thus affecting the accumulation of heavy metals in plants. The plasticizers, stabilizers, flame retardants, and other harmful substances, which can be toxic to plants and AMF, will be released along with the microplastics as they degrade. Furthermore, the sub-micron plastics and nano-plastics directly entered plant root, stem, leaf and fruit. Microplastics adhered to plant seeds and roots to affect plant germination and seedling growth, consequently altering the colonization of AMF on plant roots. Additionally, heavy metals are adsorbed by microplastics due to their characteristics of large surface area, strong hydrophobicity, and slow degradation. However, the influence factors of adsorption included the type of microplastics, heavy metals and environmental conditions. Microplastics will affect the soil physical and chemical properties, such as the soil pH, organic carbon, cation exchange capacity. Moreover, competitive adsorption of microplastics and soil particles for heavy metal ions will change the bioavailability of heavy metals and affect heavy metal accumulation in plants. Although numerous studies have been conducted on the co-contamination of microplastics and heavy metals, there is insufficient information regarding the impacts of co-contamination of microplastics and heavy metal on the plant-AMF symbiotic system. Therefore, this article provides a summary and some suggestions about effects of co-contamination of microplastics and heavy metals on plants and AMF for further studies. [ABSTRACT FROM AUTHOR]

The effect of UV-B radiation exposure on transgenerational plasticity, the phenomenon whereby the parental environment influences both the parent's and the offspring's phenotype, is poorly understood. To investigate the impact of exposing successive generations of rice plants to UV-B radiation on seed morphology and proanthocyanidin content, the local traditional rice variety 'Baijiaolaojing' was planted on terraces in Yuanyang county and subjected to enhanced UV-B radiation treatments. The radiation intensity that caused the maximum phenotypic plasticity (7.5 kJ·m−2) was selected for further study, and the rice crops were cultivated for four successive generations. The results show that in the same generation, enhanced UV-B radiation resulted in significant decreases in grain length, grain width, spike weight, and thousand-grain weight, as well as significant increases in empty grain percentage and proanthocyanidin content, compared with crops grown under natural light conditions. Proanthocyanidin content increased as the number of generations of rice exposed to radiation increased, but in generation G3, it decreased, along with the empty grain ratio. At the same time, biomass, tiller number, and thousand-grain weight increased, and rice growth returned to control levels. When the offspring's radiation memory and growth environment did not match, rice growth was negatively affected, and seed proanthocyanidin content was increased to maintain seed activity. The correlation analysis results show that phenylalanine ammonialyase (PAL), cinnamate-4-hydroxylase (C4H), dihydroflavonol 4-reductase (DFR), and 4-coumarate:CoA ligase (4CL) enzyme activity positively influenced proanthocyanidin content. Overall, UV-B radiation affected transgenerational plasticity in seed morphology and proanthocyanidin content, showing that rice was able to adapt to this stressor if previous generations had been continuously exposed to treatment. [ABSTRACT FROM AUTHOR]

In order to study the effects of oxalic acids on plant growth and Pb accumulation in different parts of the plants of intercropping Arabis alpina and Zea mays, pot experiment was conducted to investigate the changes of oxalic acid contents of the plants and Pb accumulation through exogenous oxalic acid addition (0, 5, 25 and 50 mmol kg−1). The results showed the root biomass of intercropped A. alpina and total biomass of Z. mays increased by 3.22 folds and 2.97 folds with 5 mmol kg−1 oxalic acid treatment. The oxalic acid contents of shoots and root secretions decreased by 86.5% and 44.3%, respectively. The BCF (bio-accumulation factor) and TF (translocation factor) of intercropping A. alpina reduced under 25 − 50 mmol kg−1 oxalic acid treatments. There were relationships between exogenous oxalic acid treatment concentrations and oxalic acid contents of A. alpina shoots, Z. mays root secretions. The Pb contents of shoots of A. alpina and Z. mays were related to exogenous oxalic acid additions and oxalic acid contents of shoots. In general, 5 mmol kg−1 oxalic acid treatment, that can improve plant growth of intercropped A. alpina and Z. mays, which Pb translocation and accumulation of A. alpina were promoted, whereas Pb accumulation of A. alpina was inhibited with 25 − 50 mmol kg−1 concentrations addition. This study will provide a basis for promoting the application of phytoremediation techniques and efficient crop production in heavy metal contaminated areas. Hyperaccumulators intercropped with crops will remediate heavy metal soils or mitigate the damage caused by heavy metals to plants through oxalic acid secretion by the root system. However, the effect of oxalic acid changes on plant growth and Pb accumulation is lacking. Our study investigated the changes in oxalic acid content at different concentrations and sites affected the ability of intercropped plants to grow and accumulate Pb. This work shown that under intercropping conditions, exogenous oxalic acid promotes intercropped plant growth as well as soil pH reduction, Pb content in shoots both Arabis alpina and Zea mays is influenced by exogenous oxalic acid content, while lower Z. mays roots Pb content is determined by a combination of exogenous addition and aboveground oxalic acid content. Low concentrations of oxalic acid promoted Pb enrichment in roots of A. alpina, while reducing the uptake of Pb content in Z. mays. This article gives us a better understanding for the response of intercropping plants to the use of organic acids under heavy metal stress and how to modify their environment so as to favor growth. [ABSTRACT FROM AUTHOR]

To clarify the effect of enhanced UV-B radiation on soil nitrogen transformation and its biological processes in paddy fields, the effects of enhanced ultraviolet-B radiation (0, 2.5, 5.0 and 7.5 kJ m−2) on soil nitrogen transformation and N2O emission, functional microbial quantity, enzyme activity, and gene expression during the growth period (tillering, jointing, booting and maturity stage) of rice were investigated in situ in a rice paddy field in the Yuanyang terraces, Yunnan Province, southwest China. The results show that UV-B radiation decreased the NH4+-N content, increased the NO3–N content in the rhizosphere, decreased N2O emissions from paddy fields, and significantly affected the properties of soil nitrogen transforming microorganisms. The 5.0 kJ m−2 UV-B radiation increased the quantity of ammonifying bacteria and ammonia oxidizing bacteria by 18–160% and 34–151%, respectively, decreased the urease activity in the rice rhizosphere by 11.9–27%; and significantly increased the expression of AOB-amoA and nosZ genes. Thus, the enhanced UV-B radiation increased the ammonia-oxidizing bacteria and AOB-amoA and nosZ gene expression, promoted the transformation of NH4+-N to NO3–N in the rice rhizosphere, and reduced N2O emissions in the paddy field. [ABSTRACT FROM AUTHOR]