Selenium (Se) enrichment of Stevia rebaudiana Bertoni can serve a dual purpose, on the one hand to increase plant biomass and stress tolerance and on the other hand to produce Se fortified plant-based food. Foliar Se spraying (0, 6, 8, 10 mg/L selenate, 14 days) of Stevia plantlets resulted in slightly decreased stevioside and rebaudioside A concentrations, and it also caused significant increment in stem elongation, leaf number, and Se content, suggesting that foliar Se supplementation can be used as a biofortifying approach. Furthermore, Se slightly limited photosynthetic CO₂ assimilation (A_N, g_sw, C_i/C_a), but exerted no significant effect on chlorophyll, carotenoid contents and on parameters associated with photosystem II (PSII) activity (F_V/F_M, F₀, Y(NO)), indicating that Se causes no photodamage in PSII. Further results indicate that Se is able to activate PSI-cyclic electron flow independent protection mechanisms of the photosynthetic apparatus of Stevia plants. The applied Se activated superoxide dismutase (SOD) isoenzymes (MnSOD1, FeSOD1, FeSOD2, Cu/ZnSOD1, Cu/ZnSOD2) and down-regulated NADPH oxidase suggesting the Se-induced limitation of superoxide anion levels and consequent oxidative signalling in Stevia leaves. Additionally, the decrease in S-nitrosoglutathione reductase protein abundance and the intensification of protein tyrosine nitration indicate Se-triggered nitrosative signalling. Collectively, these results suggest that Se supplementation alters Stevia shoot morphology without significantly affecting biomass yield and photosynthesis, but increasing Se content and performing antioxidant effects, which indicates that foliar application of Se may be a promising method in Stevia cultivation.

中文翻译：

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叶硒处理对甜叶菊叶生长，光合作用和氧化亚硝基信号的影响

富集甜叶菊的硒可以起到双重作用，一方面可以增加植物的生物量和胁迫耐受性，另一方面可以生产出以硒为基础的植物性食品。叶面喷施硒（0、6、8、10 mg / L硒酸盐，14天）导致甜叶菊甙和莱鲍迪甙A浓度略有降低，并且还导致茎伸长，叶片数和硒含量显着增加，表明叶面硒的补充可以用作生物强化方法。此外，硒稍微限制了光合作用的CO ₂同化作用（A _N，g _sw，C _i / C _a），但对叶绿素，类胡萝卜素含量以及与光系统II（PSII）活性（F _V / F _M，F ₀，Y（NO））相关的参数没有显着影响，表明Se在PSII中不引起光损伤。进一步的结果表明，Se能够激活甜叶菊植物光合装置的PSI循环电子流独立保护机制。施加的Se激活的超氧化物歧化酶（SOD）同工酶（MnSOD1，FeSOD1，FeSOD2，Cu / ZnSOD1，Cu / ZnSOD2）和下调的NADPH氧化酶表明Se诱导的甜叶菊中超氧化物阴离子水平的限制及其随后的氧化信号传导树叶。此外，S-亚硝基谷胱甘肽还原酶蛋白丰度的降低和蛋白酪氨酸硝化的增强表明硒触发了亚硝化信号。总体而言，这些结果表明，添加硒可以改变甜叶菊枝条的形态，而不会显着影响生物量的产量和光合作用，但是增加了硒的含量并具有抗氧化作用，这表明叶面施用硒可能是甜叶菊栽培中的一种有前途的方法。