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ToolsFernández-Baco, L., Figueroa, M. E., Luque, T. and Davy, A. J. (1998) Diurnal and seasonal variations in chlorophyll fluorescence in two Mediterranean grassland species under field conditions. Photosynthetica, 35 (4). pp. 535-544. ISSN 1573-9058
Full text not available from this repository. (Request a copy)Abstract
Seasonal and daily variations in chlorophyll (Chl) fluorescence were studied in two representative species of Mediterranean grasslands, Tuberaria guttata (an annual) and Chamaemelum nobile (a perennial), in order to assess physiological responses to climatically induced stresses during the growing season. The photochemical efficiency of photosystem (PS) 2 in dark-adapted leaves was measured by the Chl fluorescence ratio Fv/Fp. This ratio decreased progressively from December to July, as the effects of increasing solar radiation and summer drought became more severe. The seasonal decline was observed particularly as a depression of morning and midday values, when photoinhibition was more evident. In both species, the extent of this diurnal depression increased with midday irradiance throughout winter and spring. After sunset, there was complete recovery to optimum values. Towards the end of the life cycle, increased irradiance did not affect the midday decline further but Fv/Fp measurements in the morning and evening never regained their optimum values, indicating the accumulation of photodamage in the reaction centres of PS2. The half-rise time of Fp (T1/2), used to estimate the size of the plastoquinone pool, showed little daily variation in C. nobile throughout the most important part of its seasonal cycle. However, towards the end of its life cycle (June and July) T1/2 values ranged from ca. 200 ms before sunrise to near zero at midday on the same day. The annual species, T. guttata, showed similar disregulation in energy transmission rate both at the seedling stage and at end of its life cycle. Thus seedlings and reproductive plants in particular are sensitive to environmental conditions (extremes of temperature and drought) and cannot maintain consistent electron flow throughout the day.
| Item Type: | Article |
|---|---|
| Faculty \ School: | Faculty of Science > School of Biological Sciences |
| UEA Research Groups: | Faculty of Science > Research Centres > Centre for Ecology, Evolution and Conservation Faculty of Science > Research Groups > Organisms and the Environment |
| Depositing User: | Users 2731 not found. |
| Date Deposited: | 07 Apr 2011 13:06 |
| Last Modified: | 28 Mar 2025 05:00 |
| URI: | https://ueaeprints.uea.ac.uk/id/eprint/28435 |
| DOI: | 10.1023/A:1006926923293 |
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