title: Responses of Trapa natans L. floating laminae to high concentrations of manganese.
abstract: The present study focuses on the responses of floating laminae of the Mn-tolerant hydrophyte Trapa natans L. to 1 mM Mn and their ability to accumulate the metal. Studies were carried out first on young floating laminae belonging to the second verticil of 30-day-old plants which originated from fruits that had been maintained in a 1 mM Mn-treated environment and again on the young floating laminae after 10 days of further treatment with 1 mM Mn. Mn storing was observed from the first days after germination, but only 10-day-treated laminae showed the capability to hyperaccumulate the element inside specialised cells (>20000 microg/g [dry weight]). Electron microscopy and the Folin-Ciocalteu reaction for phenolics revealed deposits of chelated material inside vacuoles of the first palisade layer and of idioblasts in the spongy tissue. X-ray microanalysis indicated that the deposits were Mn chelated with phenolic compounds. Numerous trichomes were observed at the lower epidermis of 10-day-treated laminae. They were rich in phenolics and characterised by Mn concretions at their base. As they are associated with a high concentration of the metal in culture water and sediments, trichomes may constitute a morphological differentiation for the secretion of Mn-chelating molecules into the culture water, as a probable "avoidance" mechanism. Finally, monitoring of the photosynthetic apparatus showed that photosynthetic function was not impaired, though differences in development occurred.
authors.affiliation: Laboratory of Plant Cytophysiology, Department of Natural and Cultural Resources, University of Ferrara, Ferrara, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Baldisserotto
authors.forename: L
authors.initials: L
authors.lastname: Ferroni
authors.forename: E
authors.initials: E
authors.lastname: Anfuso
authors.forename: A
authors.initials: A
authors.lastname: Pagnoni
authors.forename: M P
authors.initials: MP
authors.lastname: Fasulo
authors.forename: S
authors.initials: S
authors.lastname: Pancaldi
mesh_terms: D000872:Anthocyanins / Q000378:metabolism; D001681:Biological Assay; D018533:Biomass; D004577:Electron Probe Microanalysis; D008345:Manganese / Q000378:metabolism / Q000494:pharmacology; D010636:Phenols / Q000378:metabolism; D010788:Photosynthesis / Q000187:drug effects; D018087:Plastids / Q000648:ultrastructure; D013050:Spectrometry, Fluorescence; D013054:Spectrophotometry, Atomic; D029561:Lythraceae / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D000872:Anthocyanins; D008345:Manganese; D010636:Phenols