JOURNAL OF PLANT PHYSIOLOGY, cilt.146, ss.355-360, 1995 (SCI İndekslerine Giren Dergi)
JOURNAL OF PLANT PHYSIOLOGY
The effect of varied light intensity on seasonal changes in levels of chlorophyll, ascorbic acid, lipid peroxidation and mineral nutrients was studied in leaves of 5-year-old <> grapefruit (Citrus paradisi Macf.) and 12-year-old <> mandarin (Citrus reticulata Blanco) trees in orchards in Southern Turkey. In the leaf canopy, light intensity was reduced by partial shading of trees from the south and southeast sides by using a green plastic screen. Measurements were carried out in spring-cycle and autumn-cycle leaves between August 1992 to April 1993 at about monthly intervals. Concentration of chlorophyll remained more or less constant in shaded parts of trees between August and April, whereas in light exposed parts during this period (winter month) the chlorophyll concentration markedly declined and severe, mainly interveinal chlorosis developed. During the winter months, levels of ascorbic acid and lipid peroxidation increased in light-exposed leaves, but not in shaded leaves. There was a close relationship between chlorosis and levels of ascorbic acid and lipid peroxidation.