title: Photoprotection by foliar anthocyanins mitigates effects of boron toxicity in sweet basil (Ocimum basilicum).
abstract: Boron (B) toxicity is an important agricultural problem in arid environments. Excess edaphic B compromises photosynthetic efficiency, limits growth and reduces crop yield. However, some purple-leafed cultivars of sweet basil (Ocimum basilicum) exhibit greater tolerance to high B concentrations than do green-leafed cultivars. We hypothesised that foliar anthocyanins protect basil leaf mesophyll from photo-oxidative stress when chloroplast function is compromised by B toxicity. Purple-leafed 'Red Rubin' and green-leafed 'Tigullio' cultivars, grown with high or negligible edaphic B, were given a photoinhibitory light treatment. Possible effects of photoabatement by anthocyanins were simulated by superimposing a purple polycarbonate filter on the green leaves. An ameliorative effect of light filtering on photosynthetic quantum yield and on photo-oxidative load was observed in B-stressed plants. In addition, when green protoplasts from both cultivars were treated with B and illuminated through a screen of anthocyanic protoplasts or a polycarbonate film which approximated cyanidin-3-O-glucoside optical properties, the degree of photoinhibition, hydrogen peroxide production, and malondialdehyde content were reduced. The data provide evidence that anthocyanins exert a photoprotective role in purple-leafed basil mesophyll cells, thereby contributing to improved tolerance to high B concentrations.
authors.affiliation: Department of Agriculture, Food and Environment, Via del Borghetto 80, 56124, Pisa, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Landi
authors.forename: Lucia
authors.initials: L
authors.lastname: Guidi
authors.forename: Alberto
authors.initials: A
authors.lastname: Pardossi
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Tattini
authors.forename: Kevin S
authors.initials: KS
authors.lastname: Gould
mesh_terms: D000872:Anthocyanins / Q000378:metabolism*; D001895:Boron / Q000378:metabolism* / Q000633:toxicity; D002734:Chlorophyll / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D008027:Light; D008315:Malondialdehyde / Q000378:metabolism; D058503:Mesophyll Cells / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D018613:Microscopy, Confocal; D018649:Ocimum basilicum / Q000378:metabolism* / Q000502:physiology / Q000528:radiation effects; D018384:Oxidative Stress / Q000528:radiation effects; D010788:Photosynthesis / Q000528:radiation effects; D018515:Plant Leaves / Q000378:metabolism* / Q000502:physiology / Q000528:radiation effects; D011523:Protoplasts / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D013053:Spectrophotometry
chemical_list: D000872:Anthocyanins; D002734:Chlorophyll; D008315:Malondialdehyde; D006861:Hydrogen Peroxide; D001895:Boron