z-logo
Premium
Selenium in Plants: Uptake, Functions, and Environmental Toxicity
Author(s) -
Läuchli A.
Publication year - 1993
Publication title -
botanica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 0932-8629
DOI - 10.1111/j.1438-8677.1993.tb00774.x
Subject(s) - selenate , selenium , bioaccumulation , chemistry , environmental chemistry , algae , sulfate , selenocysteine , botany , biochemistry , biology , cysteine , enzyme , organic chemistry
Selenium (Se) has chemical properties similar to sulfur, but slight differences can lead to altered tertiary structure and dysfunction of proteins and enzymes, if selenocysteine is incorporated into proteins in place of cysteine. In some areas of California with irrigation agriculture elevated Se concentration in drainage and shallow groundwaters caused bioaccumulation of Se in wetlands and Se toxicity to wildlife. Among higher plants Se accumulators are tolerant to high Se concentrations whereas non‐accumulators are Se‐sensitive. Algae show a requirement of Se for growth and development, but no Se essentiality has been demonstrated for higher plants, possibly with the exception of Se accumulators. Higher plants take up Se preferentially as selenate via the high affinity sulfate permease. Contents of Se in agricultural crops are usually below 1 mg kg −1 DW, and hence such crops are considered safe for human and animal consumption even when grown on moderately high Se soils. Sulfate salinity inhibits uptake of selenate by many plant species. Assimilation of selenate by non‐accumulators leads to synthesis of selenocysteine and selenomethionine; Se‐cysteine is readily incorporated into proteins. High Se can interfere with S and N metabolism in non‐accumulators. In contrast, Se accumulators sequester Se mainly in non‐protein selenoamino acids. Among several selenoenzymes identified in bacteria and mammals, Se‐dependent glutathione peroxidase which catalyses the reduction of organic peroxides and H 2 O 2 has been demonstrated convincingly in algae; in higher plants, however, the experimental evidence regarding its occurrence is controversial. All organisms including higher plants contain Se‐cysteyl‐tRNAs that decode UGA. Selenocysteine is proposed to function as 21st proteinaceous amino acid and thus is suggested to have a biological role in higher plants. Biogeochemical cycling of Se involves significant volatilization of methylated selenides such as dimethyl selenide to the atmosphere from higher plants as well as freshwater algae, but Se exchange between oceans and the atmosphere appears to proceed as net flux to the oceans.

This content is not available in your region!

Continue researching here.

Having issues? You can contact us here