Correlation between Photoinhibition Sensitivity and the Rates and Relative Extents of Xanthophyll Cycle De-epoxidation in Chlorina Mutants of Barley (Hordeum vulgare L.) |
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Authors: | Peng Chang-Lian Duan Jun Lin Guizhu Gilmore AM |
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Institution: | (1) South China Institute of Botany, Chinese Academy of Sciences, Guangzhou, 510650, P. R. China;(2) Australian National University, Canberra, ACT, 0200, Australia |
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Abstract: | We compared photoinhibition sensitivity to high irradiance (HI) in wild-type barley (wt) and both its chlorina f
104-nuclear gene mutant, that restricts chlorophyll (Chl) a and Chl b synthesis, and its f
2-nuclear gene mutant, that inhibits all Chl b synthesis. Both Fv/Fm and PS2 decreased more significantly in f
2 than f
104 and wt with duration of HI exposure. Chl degraded more rapidly in the f
2 than in either f
104 or wt. Most sensitivity to photoinhibition was exhibited for f
2, whereas there was little difference in response to HI between the f
104 and wt. The highest de-epoxidation (DES) value at every time point of exposure to HI was measured for f
2, whereas the wt had the lowest value among the three strains. There were two lifetime components resolved for the conversion of violaxanthin (V) to zeaxanthin plus antheraxanthin (Z + A). The most rapid lifetime was around 6 min and the slower lifetime was >140 min, in both the mutants and wt. However, the wt and f
104 both displayed larger amplitudes of both de-epoxidation lifetimes than f
2. The difference between the final de-epoxidation state (DES = Z + A]/V + A + Z]) in the light compared to the dark expressed as DES for wt, f
104, and f
2 was 0.630, 0.623, and 0.420, respectively. The slow lifetime component and overall larger DES in the wt and f
104 correlated with more photoprotection, as indicated by relatively higher Fv/Fm and PS2, compared to the f
2. Hence the photoprotection against photoinhibition has no relationship with the absolute DES value, but there is a strong relationship with de-epoxidation rate and relative extent or DES. |
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Keywords: | antheraxanthin chlorophyll a fluorescence chlorosis global kinetic analysis non-photochemical quenching photoprotection violaxanthin zeaxanthin |
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