ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Photoinactivation of photosystem II (PSII) and energy dissipation at low leaf temperatures were investigated in leaves of glasshouse-grown grapevine (Vitis vinifera L. cv. Riesling). At low temperatures (〈 15°C), photosynthetic rates of CO2 assimilation were reduced. However, despite a significant increase in the amount of light excessive to that required by photosynthesis, grapevine leaves maintained high intrinsic quantum efficiencies of PSII (Fv/Fm) and were highly resistant to photoinactivation compared to other species. Non-photochemical energy dissipation involving xanthophylls and fast D1 repair were the main protective processes reducing the ‘gross’ rate of photoinactivation and the ‘net’ rate of photoinactivation, respectively. We developed an improved method of energy dissipation analysis that revealed up to 75% of absorbed light is dissipated thermally via pH- and xanthophyll-mediated non-photochemical quenching at low temperatures (5–15°C) and moderate (800 µmol quanta m−2 s−1) light. Up to 20% of the energy flux contributing to electron transport was dissipated via photorespiration when taking into account temperature-dependent mesophyll conductance; however, this flux used in photorespiration was only a relatively small amount of the total absorbed light energy. Photoreduction of O2 at photosystem I (PSI) and subsequent superoxide detoxification (water-water cycle) was more sensitive to inhibition by low temperature than photorespiration. Therefore the water-water cycle represents a negligibly small energy sink below 15°C, irrespective of mesophyll conductance.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.0031-9317.2004.0324.x
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