Light acclimation maintains the redox state of the PS II electron acceptor Q2 within a narrow range over a broad range of light intensities |
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Authors: | Eva Rosenqvist |
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Institution: | (1) Department of Horticulture, Danish Institute of Agricultural Sciences, Kirstinebjergvej 10, P.O. Box 102, DK-5792 Aarslev, Denmark |
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Abstract: | Chrysanthemum inducum-hybrid `Coral Charm', Hibiscus rosa-sinensis L. `Cairo Red' and Spathiphyllum wallisii Regel `Petit' were grown in natural light in a greenhouse at three levels of irradiance using permanent shade screens. Light
acclimation of photosynthesis was characterized using modulated chlorophyll a fluorescence of intact leaves. A close correlation was found between the degree of reduction of the primary electron acceptor
QA of Photosystem II (PS II) approximated as the fluorescence parameter 1−qP, and light acclimation. The action range of 1−qP was 0–0.4 from darkness to full irradiance around noon, within the respective light treatments in the greenhouse, indicating
that most PS II reaction centres were kept open. In general, the index for electron transport (ETR) measured by chlorophyll
fluorescence was higher for high-light (HL) than intermediate-(IL) and low-light (LL) grown plants. However, HL Chrysanthemum showed 40% higher ETR than HL Hibiscus at light saturation, despite identical redox states of QA. The light acclimation of the non-radiative dissipation of excess energy in the antenna, NPQ, varied considerably between
the species. However, when normalized against qP, a strong negative correlation was found between thermal dissipation and ETR measured by chlorophyll fluorescence. To be
able to accommodate a high flux of electrons through PS II, the plants with the highest light-saturated ETR had the lowest
NPQ/qP. The possibility of using chlorophyll fluorescence for quantification of the energy balance between energy input and utilization
in PS II in intact leaves is discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | Chrysanthemum inducum-hybrid Hibiscus rosa-sinensis light acclimation modulated chlorophyll fluorescence non-photochemical quenching photosynthesis redox state of QA Spathiphyllum wallisii the photosynthetic electron transport chain |
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