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Selenium accumulation in the floral tissues of two Brassicaceae species and its impact on floral traits and plant performance

Hladun, Kristen R., Parker, David R., Trumble, John T.
Environmental and experimental botany 2011 v.74 pp. 90-97
Brassica juncea, Stanleya, agricultural runoff, corolla, environmental factors, greenhouses, leaves, nectar, nectar plants, plant tissues, pods, pollen, pollinators, polluted soils, reproductive traits, risk, sand, seeds, selenium, shale, soil water
Selenium (Se) is a metalloid that can occur naturally in soils from the Cretaceous shale deposits of a prehistoric inland sea in the western United States. Agricultural irrigation and runoff solubilizes Se from these shales, causing buildups of toxic levels of selenate (SeO₄ ²⁻) in water and soil. Our main objective was to investigate the accumulation of Se in two Brassicaceae species chosen for their potential as phytoremediators of Se contaminated soils. We tested the hypothesis that Se will accumulate in the pollen and nectar of two plant species and negatively affect floral traits and plant reproduction. Certain species of Brassicaceae can accumulate high concentrations of Se in their leaf tissues. In this study Se accumulation in plant tissues was investigated under greenhouse conditions. Se accumulator (Brassica juncea) and Se hyperaccumulator (Stanleya pinnata) plants were irrigated in sand culture with 0μM selenate (control), 8μM selenate, and 13μM selenate. Nectar and pollen in S. pinnata contained up to 150μgSemL⁻¹ wet weight and 12900μgSeg⁻¹dry weight when irrigated with 8μM selenate. Se levels in nectar (110μgSemL⁻¹wet weight) and pollen (1700μgSeg⁻¹dry weight) were not as high in B. juncea. Floral display width, petal area and seed pod length were significantly reduced in the 13μM selenate Se treatment in B. juncea. S. pinnata floral traits and seeds were unaffected by the Se treatments. This study provides crucial information about where some of the highest concentrations of Se are found in two phytoremediators, and may shed light on the potential risks pollinators may face when foraging upon these accumulating plants. In the field, duration of the plant's exposure, Se soil and water concentrations as well as other environmental factors may also play important roles in determining how much Se is accumulated into the leaf and floral tissues. Our greenhouse study shed light on two species’ ability to accumulate Se, as well as determined the specific plant tissues where Se concentrations are highest.