Gamma-tocopherol dominates in young leaves of runner bean (Phaseolus coccineus) under a variety of growing conditions: the possible functions of gamma-tocopherol.
It has been shown that young leaves of runner bean (Phaseolus coccineus) plants grown under natural conditions have an unusually high content of gamma-tocopherol, accounting for up to 90% of all tocopherols and 50% of the chlorophyll content. The level of gamma-tocopherol gradually decreased during the first two weeks of leaf development. The high content of gamma-tocopherol in young leaves was not significantly influenced by growth conditions. In contrast to seeds, gamma-tocopherol was also the main tocopherol found in light-grown and etiolated primary leaves of runner bean. The obtained results suggest that gamma-tocopherol decline during leaf development is not only due to conversion of gamma- to alpha-tocopherol but probably also due to degradation of gamma-tocopherol to non-tocochromanol compounds. We have also shown that gamma-tocopherol found in young leaves is mainly localized in thylakoid membranes within chloroplast. In the primary leaves subjected to different abiotic stresses, only during simultaneous drought and light stress, gamma-tocopherolquinone, an oxidation product of gamma-tocopherol, was preferentially accumulated. Since one of the other possible functions of gamma-tocopherol could be its action as a nitric oxide scavenger, young leaves were analyzed for the presence of nitro-gamma-tocopherol. However, despite the use of a sensitive detection method, it was not found. The possible physiological function of the increased level of gamma-tocopherol in the young leaves was discussed.
Szymańska
Renata
R
Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland.
Kruk
Jerzy
J
D002734:Chlorophyll / Q000378:metabolism; D007536:Isomerism; D027805:Phaseolus / Q000254:growth & development* / Q000378:metabolism*; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D024504:gamma-Tocopherol / Q000031:analogs & derivatives / Q000378:metabolism*
D002734:Chlorophyll; D024504:gamma-Tocopherol