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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]

Variations in the cadmium (Cd) accumulation and root characteristics of different genotypes of rice during three developmental periods of dry cultivation were investigated in pot experiments in which two levels of Cd were added to the soil (0 and 10 mg kg−1). The results show that the Cd concentration in each organ of the different rice genotypes decreased in both the order of roots > shoots > grains and during the three developmental periods in the order of the maturity stage > booting stage > tillering stage. The lowest bioaccumulation factor (BCF) and translocation factor (TF) were found in Yunjing37 (YJ37) under Cd stress. At maturity, Cd stress inhibited the root length of Dianheyou34 (DHY34) the most and that of Dianheyou 918 (DHY918) the least, also affecting the root volume of DHY34 and Dianheyou615 (DHY615) the most and that of YJ37 and Yiyou 673 (YY673) the least; the inhibition rates were 41.80, 5.09, 40.95, and 10.51%, respectively. The exodermis showed the greatest thickening in YY673 and the lowest thickening in DHY615, while the endodermis showed the opposite result. The rates of change were 16.48, 2.45, 5.10, and 8.49%, respectively. The stele diameter of DHY615 decreased the most, and that of YY673 decreased the least, while the secondary xylem area showed the opposite result; the rates of change were −21.50, −14.29, −5.86, and −26.35%, respectively. Under Cd stress treatment at maturity, iron plaque was extracted using the dithionite–citrate–bicarbonate (DCB) method. The concentration of iron (DCB-Fe) was highest in YJ37, and the concentration of cadmium (DCB-Cd) was lowest in DHY34. YJ37 was screened as a low Cd-accumulating variety. The concentration of available Cd in the rhizosphere soil, iron plaque, root morphology, and anatomy affect Cd accumulation in rice with genotypic differences. Our screening of Cd-accumulating rice varieties provides a basis for the dry cultivation of rice in areas with high background values of Cd in order to avoid the health risks of Cd intake. [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]

The mining of metal minerals generates considerable mining wasteland areas, which are characterized by poor soil properties that hinder plant growth. In this study, a field plot experiment was carried out in the mining wasteland of the Lanping lead–zinc mine in Yunnan Province to study the effects of applying three organic materials—biochar (B), organic fertilizer (OF), and sludge (S)—at concentrations of 1% (mass fraction), on promoting the soil of mining wasteland and the growth of two plant varieties (Huolieniao and Yingshanhong). The results showed that the amount of available nutrients in the surface soil of a mining wasteland could be considerably increased by S and OF compared to the control check (CK). In the rhizosphere soils of two Rhododendron simsii varieties, the application of S increased the available phosphorus (P) content by 66.4% to 108.8% and the alkali-hydrolyzed nitrogen (N) content by 61.7% to 295.5%. However, the contents of available cadmium (Cd) and available lead (Pb) were reduced by 17.1% to 32.0% and 14.8% to 19.0%, respectively. Moreover, three organic materials increased the photosynthetic rate and biomass of two R. simsii varieties. Specifically, OF and S were found to significantly increase the biomass of R. simsii. Organic materials have direct impacts on the increased plant height and biomass of R. simsii. Additionally, organic materials indirectly contribute to the growth of R. simsii by reducing the content of available Cd and available Pb in rhizosphere soil while increasing the content of available nutrients according to the structural equation model (SEM). Overall, S can stabilize Cd and Pb, increase soil nutrient contents, and promote the growth of R. simsii effectively, and has great potential in the vegetation reconstruction of mining wasteland. [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]

For studying the physiological response of two different Dianthus caryophyllus cultivars on Cd stress, pot experiment was carried out to measure proline and glutathione in leaves, five types of organic acids in root exudates (oxalic acid, malic acid, acetic acid, tartaric acid, citric acid), soluble sugars and free amino acids, root length, root surface area, root volume, root projected area and Cadmium content in soil, plant roots and aboveground. According to the effects of cadmium stress on the physiological and biochemical characteristics of two Dianthus caryophyllus, the results showed that: the growth of two cultivars are affected, “Master” and “Xiao Yan” are manifested as plant height, leaf, flower buds and biomass decreased, but the “Master” by the stronger inhibitory effect. The root length, total root surface area, total root projected area, and average root diameter of the “Master” increased under cadmium stress, but the root volume decreased. However, the root length, total root surface area, root volume, and root projected area of the “Xiao Yan” under cadmium stress decreased, while the average root diameter increased. The glutathione in the leaves of the two cultivars decreased, the proline content of the leaves of the “Xiao Yan” increased, while that of the “Master” decreased. In the root exudates, the free amino acid content of the two cultivars are reduced, and the secretion of organic acids is also inhibited (except for the citric acid secreted in the “Master”), while the soluble sugar content in the root exudates is expressed as “Xiao Yan” increased, and the “Master” decreased. According to the physiological response to the two cultivars under cadmium stress, the “Xiao Yan” is more suitable for soil restoration in the mining area of Lanping area.

To explore the effects of Cd and As composite contaminated soils on the element contents and effectiveness in rhizosphere soils of different forages, the root morphology, rhizosphere soil elements and their availability of 21 forages were studied and analyzed. The results showed: The 21 cultivars showed significant differences in root morphological characteristics. Root length is an index of root morphology that has the highest correlation with other elements and availability. And the correlation between the availability of each element and root morphology was higher than that of element content. Among them, Fe availability was significantly correlated with root morphological characteristics (P

Field experiments were conducted with peach (local variety)-soybean intercropping system as an agro-forestry community. The results showed that the reduction rate of CODcr losses were 24.31%, 50.50% and 65.19% respectively under the precipitation strength between 25mm d-1 and 100 mm d-1 with treatments of 36 kg plot-1, 54 kg plot-1 and 72 kg plot-1 straw mulching. The reduction rate of NH4+-N losses were 12.56%, 49.38% and 58.60%, respectively; The reduction rate of NO3--N losses were 27.78%, 9.55% and 58.61%, respectively; The reduction rate of TN losses were 3.85%, 31.67% and 56.01%, respectively. The reduction rate of TP losses were 23.02%, 30.19% and 42.65%, respectively. The yields of soybean increased by 24.09%, 47.46% and 93.84%, respectively. Peach-soybean intercropping with straw mulching could decrease the runoff losses of nitrogen and phosphorus with time effect for reducing non-point sources pollution losses.

Under different concentrations of cadmium treatments (Cd2+ concentration: 0, 0.6, 6.0, 12.0 mg/kg, prepared with CdCl2•2.5H2O), pot experiments were conducted to study the application of two calcium-containing substances (Ca2+ concentration: 0, 180, 360 mg/kg, prepared with calcium chloride CaCl2 and lime Ca(OH)2) on the yields of flavonoids and saponins of P. notoginseng. The results showed that the application of calcium chloride and lime could increase the biomass of the main root of P. notoginseng and significantly reduce the cadmium contents. Under 0 and 0.6 mg/kg cadmium treatment, the cadmium content in the main root of P. notoginseng did not exceed the standard value (Cd≤0.5 mg/kg1, GB/T 19086–2008). Under 0.6 mg/kg cadmium treatment, the application of calcium chloride increased the yield of flavonoids in the main root of P. notoginseng. The yield of flavonoids in the main root of P. notoginseng decreased under the treatment of 360 mg/kg Ca2+ lime and 0.6 mg/kg Cd2+. Under the treatments of 6.0 mg/kg and 12.0 mg/kg cadmium stress, calcium chloride and lime reduced the yield of flavonoids in P. notoginseng by 14.2%-35.2%. There was a significant positive logarithmic function correlation between flavonoid yield and ratio of Ca/Cd treatment concentration (P < 0.05). Under the treatment of 0.6 mg/kg Cd2+ with 180 mg/kg Ca2+ (calcium chloride), yields of Rg1, Rb1 and total saponins of P. notoginseng reached the highest and were increased by 114.9%, 323.0% and 172.4%, respectively, compared with no calcium chloride treatment. Under different Cd treatment levels and lime application, the yields of Rg1, Rb1 and total saponins of P. notoginseng decreased and the yield of R1 remained relatively stable. Under a certain concentration of cadmium treatment, appropriate calcium chloride and lime application could increase or maintain the biomass, saponin and flavonoid yields of the main root of P. notoginseng. Yields of R1, Rg1, Rb1 and SPN were influenced due to interaction of Cd2+ and Ca2+. In order to ensure the cadmium content of P. notoginseng less than the standard value and optimal yields of flavonoids and saponins, it could be recommended to apply calcium chloride or lime 1125 kg/hm (180 mg/kg Ca2+) under 0.6 mg/kg Cd2+ treatment. [ABSTRACT FROM AUTHOR]