Uptake kinetics and interaction of selenium species in tomato (Solanum lycopersicum L.) seedlings

Selenium and Nano-Selenium Biofortification for Human Health: Opportunities and Challenges

“…Essentiality NOT yet confirmed, but it is a beneficial nutrient at low concentrations [1] NOT yet confirmed, but may have a positive impact on levels of bio-compounds beneficial for human health in treated plants [60] Main uptake form Selenate (SeO 4 2− ) through sulfate transporter (e.g., SULTR1;1 and SULTR1;2), selenite (SeO 3 2− ) via phosphate transport (like OsPT2), and silicon transporter (OsNIP2;1) in roots [67] Unclear (may be through a passive diffusion process), Se-NPs are soluble, highly stable, have low toxicity, and high bioavailability [23] Converted form after uptake Uptake is only by roots, both selenate and selenite will be converted into organic forms like SeCys, SeMet, and MeSeCys [68]. SeMet and MeSeCys are the most dominant species in Se-enriched plants There is bioavailability of Se-NPs in plants, Se-NPs uptake could occur by roots, then transform into organic Se compounds like SeCys, SeMet, and MeSeCys, with dominance of SeMet [68] Translocation from roots to shoots Chemical Se-NPs and selenite have similar translocation of Se from roots to shoots during the longer exposure period (72 h), whereas biological Se-NPs rarely translocate to shoots [68] A few Se-NPs may transport from roots to shoots due to their rapid assimilation into selenite and organic forms [68] Main functions in plant Selenium may increase plant growth and biomass; protect plants from abiotic/biotic stresses; deter herbivores via volatile Se (dimethyl selenide) [69] Se-NPs (especially 5-200 nm), increase activities of some enzymes like GSH-Px, TrxR, and GST could scavenge free radicals, have excellent bio-availability, low toxicity, and high biological activity in plants [23] Toxicity level For agricultural crops < 50 mg Se kg −1 [23], for most angiosperm species > 10-100 mg Se kg -1 DM [70] About 100 mg kg −1 is not toxic for most cultivated crops [71], 275 mg L −1 is the toxic level for sorghum [34] Deficiency level Se content (µg kg −1 ) < 20 for severely deficient areas and 30-50 for deficient areas [72] NOT yet reported Selenium as a contaminant for plants At concentrations > 10 mg kg −1 soil, Se may cause oxidative stress for plants [73] Few publications addressed Se-NPs as a contaminant [74]. SeNPs can remove Hg in soil [69] Human Nutrition…”

“…The Se-biofortification of cereal crops depends on Se forms, method of application, the efficacy of Se-fertilizers [118], the time of application, and plant growth stage [83,135]. It also depends on soil properties, in particular soil pH, salinity content, redox potential, organic matter content, and the soil microbial community [13,69,116,[136][137][138][139]. The Se-biofortification of cereal crops including wheat, rice, and maize could be evaluated under different applied Se-forms and different growth conditions (Table 2).…”

“…The recommended Se-dose for biofortification of cereal crops mainly depends on the plant species and its variety or cultivar, the application method (seed coating and priming, foliar, or soil application), the growth media (e.g., soil, hydroponics, artificial growth media), the growth conditions (open field, controlled greenhouse, or in vitro experiment), the Se-form (inorganic, organic, or nano form), nano-Se characterization (the method of preparing, the size and color of nanoparticles), the background Se content in the soil, and the agricultural management practices [69,85].…”

“…For tomato crops, the Se-biofortification program may differ depending on the growth media. A Se concentration of 0.05 mg L −1 with selenate and selenite as dual Se sources may be optimum for tomato fruits grown under the hydroponic technique [69], but under drip irrigation this dose may be up 1.5 mg Se L −1 [151]. For potato crops, foliar applied Se at 100 g ha −1 at the tuber bulking stage led to the highest tuber Se-content [85], whereas a low Se dose (0.75 mg kg −1 as selenate) for pots filled with tropical soil (pH 4.8; clay 71%; total Se content 0.065 mg kg −1 ) was the most efficient source for potato biofortification under tropical conditions [94].…”

Effects of Selenium–Zinc Interactions on the Bioavailability of Selenium/Zinc in Soil and Its Mechanism

“…Third, Cd, Cu, Se, and Zn exposure increased the expression of sulfate transporters (Na and Salt 2011). In general, selenate enters the root of plants via S transport system (Wang et al 2019). Accordingly, the expression of sulfate transporters enhances the ability of plant roots to absorb Se (Fig.…”