| Autor: |
Newsham, K. K.1, Hodgson, D. A.1, Murray, A. W. A.1, Peat, H. J.1, Smith, R. I. Lewis1 |
| Předmět: |
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| Zdroj: |
Global Change Biology. Oct2002, Vol. 8 Issue 10, p972-983. 12p. |
| Abstrakt: |
Abstract We report a study which measured changes to the radiative environment arising from stratospheric O3 depletion at Rothera Point on the western Antarctic Peninsula (67°S, 68°W) and subsequent associations between these changes and the pigmentation and maximum quantum yield of photochemistry (F v /F m ) of two Antarctic bryophytes, the liverwort Cephaloziella varians and the moss Sanionia uncinata . We found a strong relationship between O3 column depth and the ratio of UV-B to PAR irradiance (F UV-B /F PAR ) recorded at ground level. Weaker, but significant, associations were also found between O3 column depth and noon irradiances and daily doses of unweighted and biologically effective UV-B radiation received at ground level. Regression analyses indicated that F UV-B /F PAR and daily dose of unweighted UV-B were best predictors for concentrations of total carotenoids and UV-B screening pigments extracted from bryophyte tissues. Concentrations of these pigments were loosely but significantly positively associated with O3 -dependent irradiance parameters. HPLC analyses of carotenoids also suggested that both species increased the synthesis of neoxanthin during periods of O3 depletion. Violaxanthin, lutein, zeaxanthin and b,bββ-carotene concentrations were also apparently influenced by O3 reduction, but not consistently across both bryophyte species. Concentrations of chlorophylls a and b were apparently unaffected by O3 depletion. No direct associations between F v /F m and O3 -dependent irradiance parameters were found. However stepwise multiple regression analyses suggested that the production of UV-B screening pigments conferred protection from elevated F UV-B /F PAR on F v /F m in both species and that carotenoids... [ABSTRACT FROM AUTHOR] |
| Databáze: |
GreenFILE |
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