Ageing and irradiance enhance vitamin E content in green edible tissues from crop plants.
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.
Lizarazo
Karol
K
Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), Aptdo 644, E-48080 Bilbao, Spain.
Fernández-Marín
Beatriz
B
Becerril
José María
JM
García-Plazaola
José Ignacio
JI
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*
D000975:Antioxidants; D014810:Vitamin E