Alginate oligosaccharides (AOS) are important components of seaweed extracts with various biological activities and have great potential for application in agricultural production, especially in promoting crop growth, increasing yield, improving quality, and enhancing crop resistance . For example, AOS can increase the levels of soluble sugars and soluble proteins in wheat leaves and improve the quality of wheat . Treatment of postharvest strawberries and kiwis with AOS maintained fruit hardness and soluble solid, organic acid, soluble sugar, and vitamin C contents. AOS spray application also increased the effective spike number and grain number of rice and increased rice yield .
In this paper, the effects of AOS spray application on the antioxidant system, photosynthesis and fruit sugar accumulation in citrus was investigated through a two-year field experiment. the results showed that 300-500 mg L-1 AOS application improved fruit quality and promoted sugar accumulation by regulating the following biological processes in citrus trees:
(1) AOS application regulated the antioxidant system of citrus leaves. Specifically, the activities of antioxidant enzymes such as SOD, POD and CAT were increased, and the expression of antioxidant-related genes such as CsFe-SOD, CsMn-SOD and CsPOD was significantly upregulated, in leaves from the first AOS spraying
(2) The activation of the antioxidant system helped the leaves maintain good photosynthetic performance and improve the accumulation of assimilated products. Starting after the 3rd AOS spray cycle, the Pn of leaves increased significantly, and the content of leaf carbohydrates increased significantly at harvest.
(3) AOS application promoted sugar metabolism and translocation in fruits.
Overall, this study found that AOS spray application may improve fruit sugar accumulation and quality by regulating the leaf antioxidant system, increasing the photosynthetic rate and assimilating product accumulation, and promoting sugar transfer from leaves to fruits.
Effect of AOS on citrus fruit quality. Citrus fruit phenogram (A)
Reference:Spraying alginate oligosaccharide improves photosynthetic performanceand sugar accumulation in citrus by regulating antioxidant system and related gene expression
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