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- Krivosheeva, A, et al.
(författare)
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Cold acclimation and photoinhibition of photosynthesis in Scots pine
- 1996
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Ingår i: Planta. - 0032-0935 .- 1432-2048. ; 200:3, s. 296-305
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Tidskriftsartikel (refereegranskat)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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| 5. |
- Govindjee, Govindjee, et al.
(författare)
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David (Dave) Charles Fork (1929–2020) : a gentle human being, a great experimenter, and a passionate researcher
- 2023
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Ingår i: Photosynthesis Research. - : Springer Netherlands. - 0166-8595 .- 1573-5079. ; 155:1, s. 107-125
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Tidskriftsartikel (refereegranskat)abstract
- We provide here an overview of the remarkable life and outstanding research of David (Dave) Charles Fork (March 4, 1929–December 13, 2021) in oxygenic photosynthesis. In the words of the late Jack Edgar Myers, he was a top ‘photosynthetiker’. His research dealt with novel findings on light absorption, excitation energy distribution, and redistribution among the two photosystems, electron transfer, and their relation to dynamic membrane change as affected by environmental changes, especially temperature. David was an attentive listener and a creative designer of experiments and instruments, and he was also great fun to work with. He is remembered here by his family, coworkers, and friends from around the world including Australia, France, Germany, Japan, Sweden, Israel, and USA.
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| 6. |
- Greer, DH, et al.
(författare)
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Photoinhibition and recovery of photosynthesis in intact barley leaves at 5 and 20°C
- 1991
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 81:2, s. 203-210
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Tidskriftsartikel (refereegranskat)abstract
- Photoinhibition of photosynthesis and its recovery were studied in intact barley (Hordeum vulgare L. cv. Gunilla) leaves grown in a controlled environment by exposing them to two temperatures, 5 and 20-degrees-C, and a range of photon flux densities in excess of that during growth. Additionally, photoinhibition was examined in the presence of chloramphenicol (CAP, an inhibitor of chloroplast protein synthesis) and of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Susceptibility to photoinhibition was much higher at 5 than at 20-degrees-C. Furthermore, at 20-degrees-C CAP exacerbated photoinhibition strongly, whereas CAP had little additional effect (10%) at 5-degrees-C. These results support the model that net photoinhibition is the difference between the inactivation and repair of photosystem II (PSII); i.e. the degradation and synthesis of the reaction centre protein, D1. Furthermore, the steady-state extent of photoinhibition was strongly dependent on temperature and the results indicated this was manifested through the effects of temperature on the repair process of PSII. We propose that the continuous repair of PSII at 20-degrees-C conferred at least some protection from photoinhibition. At 5-degrees-C the repair process was largely inhibited, with increased photoinhibition as a consequence. However, we suggest where repair is inhibited by low temperature, some protection is alternatively conferred by the photoinhibited reaction centres. Providing they are not degraded, such centres could still dissipate excitation energy non-radiatively, thereby conferring protection of remaining photochemically active centres under steady-state conditions. A fraction of PS II centres were capable of resisting photoinhibition when the repair process was inhibited by CAP. This is discussed in relation to PS II heterogeneity. Furthermore, the repair process was not apparently activated within 3 h when barley leaves were transferred to photoinhibitory light conditions at 20-degrees-C.
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| 7. |
- Hurry, Vaughan, 1960-, et al.
(författare)
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Cold-hardening results in increased activity of enzymes involved in carbon metabolism in leaves of winter rye (Secale-Cereale L)
- 1995
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Ingår i: Planta. - 0032-0935 .- 1432-2048. ; 195:4, s. 554-562
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Tidskriftsartikel (refereegranskat)abstract
- Light- and CO2-saturated photosynthesis of nonhardened rye (Secale cereale L. cv. Musketeer) was reduced from 18.10 to 7.17 mu mol O-2.m(-2).s(-1) when leaves were transferred from 20 to 5 degrees C for 30 min. Following cold-hardening at 5 degrees C for ten weeks, photosynthesis recovered to 15.05 mu mol O-2.m(-2).s(-1), comparable to the non-hardened rate at 20 degrees C. Recovery of photosynthesis was associated with increases in the total activity and activation of enzymes of the photosynthetic carbon-reduction cycle and of sucrose synthesis. The total hexose-phosphate pool increase by 30% and 120% for nonhardened and cold-hardened leaves respectively when measured at 5 degrees C. The large increase in esterified phosphate in cold-hardened leaves occurred without a limitation in inorganic phosphate supply. In contrast, the much smaller increase in esterified phosphate in nonhardened leaves was associated with an inhibition of ribulose-1,5-bisphosphate carboxylase/oxygenase and sucrose-phosphate synthase activation. It is suggested that the large increases in hexose phosphates in cold-hardened leaves compensates for the higher substrate threshold concentrations needed for enzyme activation at low temperatures. High substrate concentrations could also compensate for the kinetic limitations imposed by product inhibition from the accumulation of sucrose at 5 degrees C. Nonhardened leaves appear to be unable to compensate in this fashion due to an inadequate supply of inorganic phosphate.
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| 8. |
- Hurry, Vaughan, 1960-, et al.
(författare)
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Effect of cold hardening on the components of respiratory decarboxylation in the light and in the dark in leaves of winter rye
- 1996
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Ingår i: Plant Physiology. - 0032-0889 .- 1532-2548. ; 111:3, s. 713-719
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Tidskriftsartikel (refereegranskat)abstract
- In the dark, all decarboxylation reactions are associated with the oxidase reactions of mitochondrial electron transport. In the light, photorespiration is also active in photosynthetic cells. In winter rye (Secale cereale L.), cold hardening resulted in a P-fold increase in the rate of dark respiratory CO2 release from leaves compared with nonhardened (NH) controls. However, in the light, NH and cold-hardened (CH) leaves had comparable rates of oxidase decarboxylation and total intracellular decarboxylation, Furthermore, whereas CH leaves showed similar rates of total oxidase decarboxylation in the dark and light, NH leaves showed a 2-fold increase in total oxidase activity in the light compared with the dark. Light suppressed oxidase decarboxylation of end products of photosynthesis 2-fold in NH leaves and 3-fold in CH leaves in air. However, in high-CO2, light did not suppress the oxidase decarboxylation of end products. Thus, the decrease in oxidase decarboxylation of end products observed in the light and in air reflected glycolate-cycle-related inhibition of tricarboxylic acid cycle activity. We also showed that the glycolate cycle was involved in the decarboxylation of the end products of photosynthesis in both NH and CH leaves, suggesting a flow of fixed carbon out of the starch pool in the light.
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| 9. |
- Hurry, Vaughan, 1960-, et al.
(författare)
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Effects of a short-term shift to low-temperature and of long-term cold hardening on photosynthesis and ribulose-1,5-bisphosphate carboxylase oxygenase and sucrose-phosphate synthase activity in leabves of winter rye (Secale-Cereale L)
- 1994
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Ingår i: Plant Physiology. - 0032-0889 .- 1532-2548. ; 106:3, s. 983-990
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Tidskriftsartikel (refereegranskat)abstract
- The effect of a short-term (hours) shift to low temperature (5 degrees C) and long-term (months) cold hardening on photosynthesis and carbon metabolism was studied in winter rye (Secale cereale L. cv Musketeer), Cold-hardened plants grown at 5 degrees C exhibited 25% higher in situ CO2 exchange rates than nonhardened plants grown at 24 degrees C. Cold-hardened plants maintained these high rates throughout the day, in contrast to nonhardened plants, which showed a gradual decline in photosynthesis after 3 h. Associated with the increase in photosynthetic capacity following cold hardening was an increase in ribulose-1,5-bisphosphate carboxylase/oxygenase and sucrose phosphate synthase activity and 3- to 4-fold increases in the pools of associated metabolites. Leaves of nonhardened plants shifted overnight to 5 degrees C required 9 h in the light at 5 degrees C before maximum rates of photosynthesis were reached. The gradual increase in photosynthesis in leaves shifted to 5 degrees C was correlated with a sharp decline in the 3-phosphoglycerate/triose phosphate ratio and by an increase in the ribulose bisphosphate/3-phosphoglycerate ratio, indicating the gradual easing of aninorganic phosphate-mediated feedback inhibition on photo-synthesis. We suggest that the strong recovery of photosynthesis in winter rye following cold hardening indicates that the buildup of photosynthetic enzymes, as well as those involved in sucrose synthesis, is an adaptive response that enables these plants to maximize the production of sugars that have both cryoprotective and storage functions that are critical to the performance of these cultivars during over-wintering.
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| 10. |
- Hurry, Vaughan M., 1960-, et al.
(författare)
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Cold hardening of spring and winter-wheat and rape results in differential-effects on growth, carbon metabolism, and carbohydrate content
- 1995
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Ingår i: Plant Physiology. - 0032-0889 .- 1532-2548. ; 109:2, s. 697-706
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Tidskriftsartikel (refereegranskat)abstract
- The effect of long-term (months) exposure to low temperature (5 degrees C) on growth, photosynthesis, and carbon metabolism was studied in spring and winter cultivars of wheat (Triticum aestivum) and rape (Brassica napus). Cold-grown winter rape and winter wheat maintained higher net assimilation rates and higher in situ CO2 exchange rates than the respective cold-grown spring cultivars. In particular, the relative growth rate of spring rape declined over time at low temperature, and this was associated with a 92% loss in in situ CO2 exchange rates. Associated with the high photosynthetic rates of cold-grown winter cultivars was a P-fold increase per unit of protein in both stromal and cytosolic fructose-1,6-bisphosphatase activity and a 1.5- to 2-fold increase in sucrose-phosphate synthase activity. Neither spring cultivar increased enzyme activity on a per unit of protein basis. We suggest that the recovery of photosynthetic capacity at low temperature and the regulation of enzymatic activity represent acclimation in winter cultivars. This allows these overwintering herbaceous annuals to maximize the production of sugars with possible cryoprotective function and to accumulate sufficient carbohydrate storage reserves to support basal metabolism and regrowth in the spring.
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