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Peeled iron walnut kernels (Juglans sigillata Dode cv. ‘Qianhe 7’) were studied for the changes in the contents of total phenols, total flavonoids and monomeric phenols and the activities of key enzymes associated with phenolic metabolism during the development process and their relationship with antioxidant activity in vitro. The results showed that the contents of total phenols and total flavonoids and antioxidant activity in iron walnut kernels increased during the development process and reached the maximum level at maturation. The contents of total phenols and total flavonoids were 0.05 mg/g and 0.03 mg/g, respectively in the mature kernels, the ferric ion reducing antioxidant power (FRAP) was 0.019 mmol/g, and the free radical scavenging capacities against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radical were 43.57 and 16.86 mg/mL, respectively. Eight monomeric phenolics were identified in the kernels, and their contents varied greatly during the development process and decreased in general at the late stage of maturity; among these phenolics, the average content of syringic acid was the highest, followed by catechin, and the level of ferulic acid was the lowest. The contents of total phenols, gallic acid, caffeic acid, ferulic acid and quercetin were positively correlated with the FRAP value, while the contents of catechin, eugenic acid and rutin were positively correlated with the DPPH radical and ABTS cation radical scavenging capacities. The metabolic enzyme activities including chorismate mutase (CM), chorismate synthase (CS) and phenylalanine ammonia lyase (PAL) reached the highest levels at the kernel filling stage, while cinnamate 4-hydroxylase (C4H) activity showed an N-shaped trend and reached the maximum value at the late stage of maturity. The activities of 4-coumarate coenzyme A ligase (4CL), chalcone synthase (CHS) and chalcone isomerase (CHI) decreased rapidly and then increased slightly at the maturity stage. Total phenol, gallic acid, caffeic acid, ferulic acid and quercetin were positively correlated with CM, PAL and C4H, but negatively correlated with CS, 4CL, CHS and CHI. Syringic acid and rutin were positively correlated with CS. In conclusion, the polyphenols and antioxidant activity of peeled ‘Qianhe 7’ iron walnut kernels were higher during the ripening stage. This study provides a theoretical basis for the development of functional foods based on iron walnut kernels.

The escalating global climate change significantly threatens plant growth, development, and production through salinity stress. Flavonoids, a crucial category of secondary metabolites, have been extensively studied for their role in modulating plant growth and development mechanisms in the face of biological and abiotic stress. The flavonol synthetase (FLS) gene plays a key role in the biosynthesis and accumulation of flavonoids. To investigate the correlation between salt tolerance and flavonol synthesis, JsFLS5 was overexpressed in the callus of Juglans sigillata cv. "Qianhe‐7." This study shows that the upregulation of JsFLS5 significantly elevates the overall flavonoid content by modulating the expression of genes associated with flavonoid synthesis under salinity stress conditions. Additionally, the overexpressing callus exhibited enhanced resistance to salt stress compared to the wild‐type callus, as evidenced by reduced levels of reactive oxygen species accumulation, electrolyte leakage, and malondialdehyde content in the overexpressing callus relative to the wild type (WT). Moreover, the overexpressing callus showed higher antioxidant enzyme activity and a more efficient ascorbic acid‐glutathione cycle. Furthermore, the concentration of Na+ in the overexpressing callus was lower than WT, resulting in a decreased Na+/K+ ratio. These findings suggest that JsFLS5 overexpression in calli effectively mitigates the oxidative damage induced by osmotic stress and reduces Na+ toxicity by enhancing flavonoid synthesis under salt stress conditions. Consequently, this study offers a novel perspective for comprehending the role of JsFLS5 in the response to abiotic stress in J. sigillata. [ABSTRACT FROM AUTHOR]

Walnut and Rosa roxburghii are important arbor and shrub fruit trees cultivated in the southwest mountainous area of China. Furthermore, those two species are compound cultivated in this area. In this study, we investigated the growth, yield, fruit quality, photosynthesis, and soil fertility of R. roxburghii in a 7-year typical 'Qianhe 7' / 'Guinong 5' compound planting pattern in Guizhou. The results showed that compared with the monoculture, photosynthetic pigment content and photosynthetic rate of R. roxburghii leaves were significantly lower in the compound plantation. The growth and yield of R. roxburghii decreased significantly, with a 77.7% reduction of yield. Fruit quality of R. roxburghii was improved. The content of ascorbic acid (Vc), total phenol, carbohydrate, K, Ca, Mg, Fe, Mn, Zn, and other substances increased significantly. Fruit Vc and Mn content increased by 34.1% and 64.1%, respectively. The contents of total N, available N and K in the soil increased by 45.8%, 34.8% and 67.8%, respectively. The abundance of soil microorganisms and functional bacteria increased significantly, with the increase of bacteria and fungi being more than 36.0%. The increase of potassium bacteria and nitrogen fixing bacteria was 71.3% and 124.8%, respectively. However, the contents of organic matter, carbon-nitrogen ratio, total P, total K, available mineral nutrient (P, Ca, Mg, Fe, Mn, Cu, Zn) contents decreased. While the activities of soil urease and catalase were increased, the activities of other soil enzymes (sucrase, cellulase, protease, phosphatase) were significantly reduced. In summary, with continuous growth of walnuts in the walnut/R. roxburghii compound plantation, there was obvious shade and soil fertility competition for R. roxburghii, which affected its yield, but had a improvement effect on fruit quality. [ABSTRACT FROM AUTHOR]

The escalating global climate change significantly threatens plant growth, development, and production through salinity stress. Flavonoids, a crucial category of secondary metabolites, have been extensively studied for their role in modulating plant growth and development mechanisms in the face of biological and abiotic stress. The flavonol synthetase (FLS) gene plays a key role in the biosynthesis and accumulation of flavonoids. To investigate the correlation between salt tolerance and flavonol synthesis, JsFLS5 was overexpressed in the callus of Juglans sigillata cv. "Qianhe-7." This study shows that the upregulation of JsFLS5 significantly elevates the overall flavonoid content by modulating the expression of genes associated with flavonoid synthesis under salinity stress conditions. Additionally, the overexpressing callus exhibited enhanced resistance to salt stress compared to the wild-type callus, as evidenced by reduced levels of reactive oxygen species accumulation, electrolyte leakage, and malondialdehyde content in the overexpressing callus relative to the wild type (WT). Moreover, the overexpressing callus showed higher antioxidant enzyme activity and a more efficient ascorbic acid-glutathione cycle. Furthermore, the concentration of Na + in the overexpressing callus was lower than WT, resulting in a decreased Na + /K + ratio. These findings suggest that JsFLS5 overexpression in calli effectively mitigates the oxidative damage induced by osmotic stress and reduces Na + toxicity by enhancing flavonoid synthesis under salt stress conditions. Consequently, this study offers a novel perspective for comprehending the role of JsFLS5 in the response to abiotic stress in J. sigillata., (© 2023 Scandinavian Plant Physiology Society.)