title: Ageing and irradiance enhance vitamin E content in green edible tissues from crop plants.
abstract: BACKGROUND
  Tocopherol (vitamin E) is an antioxidant essential in human nutrition. Several approaches have aimed to enhance tocopherol content in crops by the genetic modification of plants, a practice that generates some social concern. As tocopherol accumulates with leaf age in some wild plants and the antioxidant mechanisms respond with flexibility to stress conditions, it is hypothesised that tocopherol content can be increased in edible plants by the manipulation of harvesting time and growth conditions, in particular irradiance.
  
  
  RESULTS
  Ontogenic changes in tocopherol concentration have been studied in photosynthetic tissues of edible leaves (lettuce, spinach, corn salad and dandelion) and green fruits (cucumber and pepper). In all species, tocopherol content increased with tissue age. Spinach showed the fastest rate of tocopherol accumulation, and growth at higher irradiance had a synergistic effect on the rate of accumulation. The same irradiance dependence of this accumulation was observed in fruits, but a final decrease with senescence occurred in cucumber.
  
  
  CONCLUSIONS
  This study demonstrates that the content of tocopherol in vegetables can be notably enhanced (or reduced) by simply selecting the appropriate harvesting time and/or by manipulating the environmental conditions during the growth period.
authors.affiliation: Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Aptdo 644, E-48080 Bilbao, Spain.
authors.forename: Karol
authors.initials: K
authors.lastname: Lizarazo
authors.forename: Beatriz
authors.initials: B
authors.lastname: Fernández-Marín
authors.forename: José María
authors.initials: JM
authors.lastname: Becerril
authors.forename: José Ignacio
authors.initials: JI
authors.lastname: García-Plazaola
mesh_terms: D000383:Agriculture / Q000379:methods*; D000975:Antioxidants / Q000032:analysis*; D018556:Crops, Agricultural / Q000737:chemistry* / Q000254:growth & development / Q000528:radiation effects; D005638:Fruit / Q000737:chemistry / Q000254:growth & development / Q000528:radiation effects; D006801:Humans; D008027:Light; D019684:Magnoliopsida / Q000737:chemistry* / Q000254:growth & development / Q000528:radiation effects; D009753:Nutritive Value; D017785:Photons; D018514:Plant Structures; D013312:Stress, Physiological; D013997:Time Factors; D014675:Vegetables / Q000737:chemistry* / Q000254:growth & development / Q000528:radiation effects; D014810:Vitamin E / Q000032:analysis*
chemical_list: D000975:Antioxidants; D014810:Vitamin E