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- Krivosheeva, A, et al.
(author)
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Cold acclimation and photoinhibition of photosynthesis in Scots pine
- 1996
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In: Planta. - 0032-0935 .- 1432-2048. ; 200:3, s. 296-305
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Journal article (peer-reviewed)abstract
- Cold acclimation of Scots pine did not affect the susceptibility of photosynthesis to photoinhibition. Cold acclimation did however cause a suppression of the rate of CO2 uptake, and at given light and temperature conditions a larger fraction of the photosystem Il reaction centres were closed in cold-acclimated than in nonacclimated pine. Therefore, when assayed at the level of photosystem II reaction centres, i.e. in relation to the degree of photosystem closure, cold acclimation caused a significant increase in resistance to photoinhibition; at given levels of photosystem II closure the resistance to photoinhibition was higher after cold acclimation. This was particularly evident in measurements at 20 degrees C. The amounts and activities of the majority of analysed active oxygen scavengers were higher after cold acclimation. We suggest that this increase in protective enzymes and compounds, particularly superoxide dismutase, ascorbate peroxidase, glutathione reductase and ascorbate of the chloroplasts, enables Scots pine to avoid excessive photoinhibition of photosynthesis despite partial suppression of photosynthesis upon cold acclimation. An increased capacity for light-induced de-epoxidation of violaxanthin to zeaxanthin upon cold acclimation may also be of significance.
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| 2. |
- Tao, D L, et al.
(author)
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Active oxygen scavengers during cold acclimation of Scots pine seedlings in relation to freezing tolerance
- 1998
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In: Cryobiology. - 0011-2240 .- 1090-2392. ; 37:1, s. 38-45
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Journal article (peer-reviewed)abstract
- Freezing injury of plants may be caused by the deleterious reactions of active oxygen species, and free-radical scavenging systems may be important in the alleviation of freezing stress. To test the feasibility of this hypothesis, enzymes and metabolites that cooperatively scavenge O-2(-) and H2O2 were analyzed in Scots pine (Pinus sylvestris L.) seedlings during a stepwise cold acclimation procedure. Elevated levels of enzymatic scavengers such as ascorbate peroxidase, glutathione reductase, monodehydroascorbate reductase, and dehy droascorbate reductase were found, along with increased freezing tolerance during cold acclimation, supporting the hypothesis. Induction of the scavenging systems during acclimation is discussed in relation to freezing tolerance. (C) 1998 Academic Press.
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