| 1. |
- Hurry, Vaughan, 1960-, et al.
(författare)
-
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
-
Ingår i: Plant Physiology. - 0032-0889 .- 1532-2548. ; 106:3, s. 983-990
-
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.
|
|
| 2. |
- Igamberdiev, Abir U, et al.
(författare)
-
Respiration of barley protoplasts before and after illumination
- 1997
-
Ingår i: Physiologia Plantarum. - : John Wiley & Sons, Inc.. - 0031-9317 .- 1399-3054. ; 99:1, s. 15-22
-
Tidskriftsartikel (refereegranskat)abstract
- Respiratory O-2 consumption was investigated in dark-adapted barley (Hordeum vulgare L. cv. Gunilla) protoplasts and after illumination for 10 min at high and very low CO2 in the presence of respiratory and photorespiratory inhibitors. In dark-adapted protoplasts no difference was observed between inhibitor treatments in high and very low CO2. The respiratory rate increased somewhat after illumination and a difference in responce to inhibitors was in some cases observed between high and very low CO2. Thus, the operation of the mitochondrial electron transport chain is affected following a period of active photosynthesis. In all situations tested, oligomycin inhibited respiratiory O-2 uptake indicating that respiration of mitochondria in protoplasts is not strictly ADP limited. Antimycin A inhibited respiration more in dark-adapted protoplasts than after illumination whereas SHAM gave the opposite response. Rotenone inhibited respiration both in dark adapted protoplasts (about 30%) and after illumination where the inhibition was much greater in very low CO2 (50%) than in high CO2 (10%). After iilumination in very low CO2, SHAM + rotenone inhibited respiration almost completely (70%). Photorespiratory inhibitors had very small effect on O-2 consumption in darkness. After illumination the effect of aminoacetonitrile (AAN) was also very low whereas a-hydroxypyridine-2-methane sulphonate (HPMS) in photorespiratory conditions inhibited O-2 uptake much stronger (35%). The addition of glyoxylate enhanced respiration in the presence of HPMS up to the control level suggesting that alternative pathways of glyoxylate conversion might be operating. The differences in inhibitor responses may reflect fine mechanisms for the regulation of energetic balance in the plant cell which consists of switching from electron transport coupled to ATP production to non-coupled transport. Photorespiratory flux is also very flexible, and the suppression of glycine decarboxylation can induce bypass reactions of glyoxylate metabolism.
|
|
| 3. |
- KROMER, S, et al.
(författare)
-
MITOCHONDRIAL CONTRIBUTION TO PHOTOSYNTHETIC METABOLISM - A STUDY WITH BARLEY (HORDEUM-VULGARE L) LEAF PROTOPLASTS AT DIFFERENT LIGHT INTENSITIES AND CO2 CONCENTRATIONS
- 1993
-
Ingår i: Plant Physiology. - 0032-0889 .- 1532-2548. ; 102:3, s. 947-955
-
Tidskriftsartikel (refereegranskat)abstract
- An oligomycin concentration that specifically inhibits oxidative Phosphorylation was added to isolated barley (Hordeum vulgare L.) leaf protoplasts at various irradiances and carbon dioxide concentrations. At saturating as well as low light intensities, photosynthetic oxygen evolution was decreased as a result of the oligomycin treatment, whereas no effect was observed at intermediate light intensities. This was the same for photorespiratory and nonphotorespiratory conditions. These results were confirmed by measurements of fluorescence quenching under the same conditions. Metabolite analysis in the presence of oligomycin revealed a drastic decrease in the mitochondrial and cytosolic ATP/ADP ratios, whereas there was little or no effect on the chloroplastic ratio. Concomitantly, sucrose phosphate synthase activity was reduced. Under high irradiances, this inhibition of sucrose synthesis by oligomycin apparently caused a feedback inhibition on the Calvin cycle and the photosynthetic activity. Under low irradiances, a feedback regulation compensated, indicating that light was more limiting than the activity of regulative enzymes. Thus, the importance of mitochondrial respiratory activity might be different in different metabolic situations. At saturating light, the oxidation of excess photosynthetic redox equivalents is required to sustain a high rate of photosynthesis. At low light, the supply of ATP to the cytosol might be required to support biosynthetic reactions.
|
|
| 4. |
- Larsson, Kjell, et al.
(författare)
-
Hyaluronic acid (hyaluronan) in BAL fluid distinguishes farmers with allergic alveolitis from farmers with asymptomatic alveolitis
- 1992
-
Ingår i: Chest. - : Elsevier BV. - 1931-3543 .- 0012-3692. ; 101:1, s. 109-114
-
Tidskriftsartikel (refereegranskat)abstract
- Pulmonary function measurements, bronchoalveolar lavage (BAL), and analyses of precipitating antibodies in blood were performed in 12 farmers wtih no symptoms from the airways and 12 farmers who were admitted to the hospital due to acute symptoms of alveolitis (all nonsmokers). In addition, a bronchial methacholine provocation test was performed in the asymptomatic farmers. In 11 of the 12 symptomatic farmers but in none of the asymptomatic farmers, precipitating antibodies against one or more of the microorganisms which usually occur in a farmer's environment were found. In the farmers with symptomatic alveolitis, a restrictive impairment of pulmonary function was found, while pulmonary function was normal in all asymptomatic farmers. Findings in the BAL fluid showed increased concentrations of total cells, lymphocytes, and neutrophils and elevated levels of albumin, fibronectin, and angiotensin-converting enzyme in asymptomatic farmers compared with our own reference group. The same analyses in BAL fluid from the symptomatic farmers revealed a further increase in all parameters compared with the asymptomatic farmers. The BAL fluid from asymptomatic farmers had normal levels of hyaluronic acid (hyaluronan) and procollagen 3 N-terminal peptide, while these levels were significantly increased in the symptomatic group. We conclude that inflammation in the alveolar space and signs of activation of alveolar macrophages are present in farmers regardless of respiratory symptoms, although these findings are more pronounced in the presence of symptoms of acute alveolitis; however, the findings of impaired pulmonary function and the occurrence of precipitins and elevated levels of hyaluronic acid and procollagen 3 N-terminal peptide in BAL fluid were exclusively found in the farmers with airways symptoms. We postulate the hyaluronic acid, due to its pronounced ability to immobilize water, may be of importance in the development of the pulmonary function impairment observed in farmer's lung disease.
|
|
| 5. |
|
|
| 6. |
- Meurling, Birgitta, Malmberg, Per & Serritzlew, Carina
(författare)
-
Indledning (Introduction)
- 1998
-
Ingår i: Nord Nytt. Nordisk tidskrift för etnologi och folkloristik. - : NEFA, København. ; :71/72, s. 3–5-
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
