Photoinhibition of isolated mesophyll cells from cold-hardened and non-hardened winter rye |
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Authors: | L LAPOINTE N P A HUNER |
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Institution: | Department of Plant Sciences, University of Western Ontario, London, Ontario, Canada N6A 5B7 |
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Abstract: | Cold-hardened rye leaves have been shown to be more resistant to low temperature photoinhibition than non-hardened rye leaves. Isolated mesophyll cells from winter rye (Secale cereale L. cv. Musketeer) were exposed to photoinhibitory light conditions to estimate the importance of leaf morphology and leaf optical properties in the resistance of cold-hardened rye leaves to photoinhibition. Cold-hardened rye cells showed more resistance to photoinhibition than non-hardened rye cells when monitored with chlorophyll a variable to maximal fluorescence ratio (Fv/Fm). Thus, leaf morphology does not contribute to the resistance of cold-hardened rye leaves to low temperature photoinhibition. However, cold-hardened and non-hardened rye cells showed a similar extent of photoinhibition when photsynthetic CO2 fixation rates were measured. They also showed the same capacity to recover from photoinhibition. During both photoinhibition and recovery, Fv/Fm and light limited CO2 fixation rates showed different kinetics. We propose that inactivation and subsequent reactivation during recovery of some light activated Calvin cycle enzymes explain the greater extent of photoinhibition of light limited CO2 fixation and its faster recovery compared to Fv/Fm kinetics during photoinhibition. |
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Keywords: | Secale cereale cv Musketeer winter rye fluorescence carbon assimilation cold acclimation photoinhibition |
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