Search

Elevated temperatures severely affect plant growth, reducing yield and quality. Melatonin (MT), a plant biomolecule, is known to enhance stress tolerance, but its role in heat resistance and underlying mechanisms require further exploration. This study investigates MT's regulatory effects on chlorophyll metabolism and photosynthesis in tomato seedlings under high-temperature stress (40°C). Tomato seedlings treated with 100 μmol MT showed improved physiological and photosynthetic performance under heat stress. MT application increased osmolytes (proline and soluble sugar), enhanced antioxidant enzyme activities [catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX)], and reduced oxidative damage markers (H2O2, O2−, malondialdehyde, and conductivity). Photosynthetic parameters, including key enzyme activities [sedoheptulose-1,7-bisphosphatase (SBPase), ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), and NADP-dependent glyceraldehyde-3-phosphate dehydrogenase (NADP-GAPDH)], photochemical efficiency [Fv/Fm and Y(II)], and photochemical quenching (Qp), were significantly improved, restoring the OJIP curve and enhancing photosynthesis. MT also regulated chlorophyll metabolism by promoting synthesis [increasing chlorophyll a and b , 5-aminolevulinic acid (ALA), Mg-protoporphyrin (Mg Proto), and protochlorophyllide (Pchlide) levels] and upregulating synthesis genes (SlHEMA1 , SlPORB , SlPORC , and SlCHLI) while inhibiting degradation genes (SlCLH1 , SlCLH2 , SlPAO , SlPPH , and SlRCCR). These findings demonstrate that MT enhances tomato heat tolerance by protecting chlorophyll metabolism and photosynthesis, offering a theoretical basis for improving crop resilience to heat stress. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) are commonly found in heavy metal-contaminated environments and form extraradical mycelium (ERM), but knowledge of their ecological functions is limited. In the present study, a soil column was filled with sterilized cadmium (Cd)-contaminated soil and contained an in-growth core for AMF-inoculated maize seedling growth. The in-growth core was static to maintain or rotated to disrupt ERM growth. Compared with the static treatment, the rotation treatment caused significant decreases in the content of glomalin-related soil protein (GRSP), the photosynthetic physiology of leaves, and maize growth, while increasing the Cd content in shoots and roots by 64 and 82%, respectively; additionally, the rotation treatment resulted in increases in the Cd concentration of the soil solution inside and outside the growth core by 30–38 and 17–52%, respectively, and Cd leaching loss by 29–39%. Moreover, the rotation treatment significantly altered the Cd forms in the soil solution and leachate, increasing the proportion of free Cd2+ by 0.8–2.1% and decreasing the proportions of CdSO4(aq) and CdOH+ by 6.1–56.1% and 26.1–48.7%, respectively. The structural equation model indicated that AMF directly and indirectly reduced maize Cd uptake and Cd leaching loss by decreasing Cd availability in the soil and soil solution through the GRSP secreted by ERM. Thus, AMF plays a crucial role in inhibiting Cd migration in soil through mycelial exudates. [ABSTRACT FROM AUTHOR]

In arid areas, water shortage has become a major bottleneck limiting the sustainable development of agriculture, necessitating improved water use efficiency and the full development of innovative water-saving irrigation management technologies to improve quality. In the present study, tomato (Solanum lycopersicum cv. Micro Tom) fruits were used as materials, and different irrigation frequencies were set during the fruit expansion stage. The normal treatment (CK) was irrigated every three days, while the water deficit treatments were irrigated at varying frequencies: once every 4 days (T1), 5 days (T2), 6 days (T3), 7 days (T4), and 8 days (T5). These corresponded to 80%, 70%, 60%, 50%, and 40% of the maximum field moisture capacity (FMC), respectively, with CK maintaining full irrigation at 90% of the maximum FMC. The water deficit treatment T3, with less stress damage to plants and the most significant effect on fruit quality improvement, was selected based on plant growth indices, photosynthetic characteristics, chlorophyll fluorescence parameters, and fruit quality indices, and its effects on carotenoids, glycolic acid fractions, and volatile compounds during tomato fruit ripening were further investigated. The outcome indicated that moderate water deficit significantly increased the carotenoid components of the tomato fruits, and their lycopene, lutein, α-carotene, and β-carotene contents increased by 11.85%, 12.28%, 20.87%, and 63.89%, respectively, compared with the control fruits at the ripening stage. The contents of glucose and fructose increased with the development and ripening of the tomato fruits, and reached their maximum at the ripening stage. Compared to the control treatment, the moderate water deficit treatment significantly increased the glucose and fructose levels during ripening by 86.70% and 19.83%, respectively. Compared to the control conditions, water deficit conditions reduced the sucrose content in the tomato fruits by 27.14%, 18.03%, and 18.42% at the mature green, turning, and ripening stages, respectively. The moderate water deficit treatment significantly increased the contents of tartaric acid, malic acid, shikimic acid, alpha ketoglutaric acid, succinic acid, and ascorbic acid, and decreased the contents of oxalic acid and citric acid compared to the control. The contents of total soluble sugar and total organic acid and the sugar–acid ratio were significantly increased by 48.69%, 3.71%, and 43.09%, respectively, compared with the control at the ripening stage. The moderate water deficit treatment increased the fruit response values to each sensor of the electronic nose, especially W5S, which was increased by 28.40% compared to the control at the ripening stage. In conclusion, during the ripening process of tomato fruit, its nutritional quality and flavor quality contents can be significantly improved under moderate (MD) deficit irrigation treatment. The results of this experiment can lay the foundation for the research on the mechanism of water deficit aiming to promote the quality of tomato fruit, and, at the same time, provide a theoretical basis and reference for tomato water conservation and high-quality cultivation. [ABSTRACT FROM AUTHOR]

5‐Aminolevulinic acid (ALA) can not only improve fruit yield and quality, but also increase the lycopene content in tomato fruits. Furthermore, ALA has been shown to promote system‐2 ethylene production in tomato fruits. However, the specific interactions between ALA and ethylene during fruit ripening remain unclear. In this study, we treated tomato fruits with ALA, 1‐aminocyclopropane‐1‐carboxylic acid (ACC), aminooxyacetic acid (AOA) + AgNO3, and AOA + AgNO3 + ALA and analyzed ethylene emissions, carotenoid contents, and the relative gene expression levels related to fruit ripening, carotenoid contents, ethylene synthesis, and signal transduction. The ALA treatment significantly enhanced ethylene bursts and carotenoid accumulation, and significantly upregulated the expression of ethylene and carotenoid‐related genes, such as SlACS2, SlACS4, SlACO1, SlPSY1, and SlPDS. We also observed that the gene expression levels associated with carotenoid synthesis were downregulated in fruits treated with a combination of ethylene inhibitors (AOA + AgNO3). However, there was a significant upregulation in the gene expression levels associated with carotenoid synthesis and an increase in carotenoid content when fruits were treated with AOA + AgNO3 + ALA. After silencing SlACO1 expression, the total carotenoid content and SlPSY1 expression decreased significantly, while this effect was reversed after exogenous application of ALA. These results indicated that ALA promotes carotenoid accumulation in tomato fruits by promoting ethylene biosynthesis. In conclusion, our results highlighted the role of ALA in promoting carotenoid accumulation and ripening in tomato fruits by regulating ethylene synthesis, thereby providing a novel strategy for improving fruit quality. [ABSTRACT FROM AUTHOR]

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]

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]