摘要:

Two cultivars of wheat (Triticum aestivumL.), a winter wheat, Kharkov, and a spring wheat, Glenlea, were acclimated under controlled conditions at 2 temperatures, 5°C and 25°C with a 12‐h photoperiod. Water content, protein and proline concentrations were determined. Enzymatic properties (activity and apparent energy of activation) were investigated for enzymatic systems involved in 2 pathways of proline metabolism, the glutamic acid and ornithine pathways. Four enzymes were studied, proline dehydrogenase (PDH, EC 1.5.1.2), glutamate dehydrogenase (GDH, EC 1.4.1.2‐4), glutamine synthetase (GS, EC 6.3.1.2) and ornithine transaminase (OT, EC 2.6.1.13). Cold acclimation led to an accumulation of proline, a decrease in water content and an increase in soluble protein, especially in winter wheat. For both cultivars, cold acclimation modulated enzyme properties of PDH and GDH. Increased activities of GS and OT were observed as a result of cold acclimation in both cultivars, with the greatest increase in Kharkov. The apparent energy of activation of these 2 enzymes decreased, particularly for Kharkov, which accumulated proline in cold condi

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb04391.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A sucrose gradient fraction was used to characterize the tonoplast ATPase from storage tissue of the sugarcane plant (Saccharumsp. var. H57–5175). Marker enzyme analyses and characterization of low‐density vesicles isolated on a sucrose gradient were consistent with a highly enriched tonoplast fraction. ATPase and proton transport activities were both substantially inhibited by nitrate (80%), but very little by vanadate (10%), indicating a high titer of tonoplast compared to plasma‐membrane vesicles in the fraction. Sensitivity toward other inhibitors, as well as ion effects, correlated closely among ATPase and proton translocation activities. Although the vesicles in this fraction showed good proton translocating activity there was no indication that ATP stimulated sucrose uptake in this tonoplast popul

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb04392.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

It is well known in short‐day plants that a leaf held in non‐inductive photoperiods inhibits flowering when interposed between the induced leaf and the apical meristem, in an analogous manner to the basal half of a leaf induced by short‐day in its distal half. This has often been explained by the inhibiting leaf or basal part of an induced leaf becoming the major source of carbohydrates to the apex, rather than the induced leaf itself; i.e. by preventing thus the co‐transported stimulus from reaching the apex. Experiments withKalanchoe blossfeldianaPoellniz andXanthium strumariumL. in which carbon dioxide levels were lowered or increased, or 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea injected, or sugar fed to the petioles of a debladed interposed leaf, or night‐breaks given as well as other photoperiodic treatments, all pointed to ‘carbohydrate diversion’ not being the major cause of failure of the short‐day stimulus reaching the target apex. It is tentatively concluded that instead an inhibitory action occurs in the vascular passage of the stimulus preventing co‐transport

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb04393.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Plants of lucerne (Medicago sativaL. cv. Aragón) inoculated with several strains ofRhizobium melilotiwere supplied with a low level of nitrate (5 mM). After 1 week, normalised nodule mass, obtained by dividing nodule weight by shoot weight, was decreased by one‐fourth. This result closely paralleled the bacteroid protein content of nodules, whereas the cytosolic content remained constant. Nitrate reductase activity (NRA, EC 1.7.99.4) of bacteroids increased rapidly after nitrate supply, with actual rates being highly dependent on theRhizobiumstrain. The expression of cytosolic NR (EC 1.6.6.1) also varied depending on the bacterial strain but was largely insensitive to nitrate feeding. Nitrite reductase activity (NiRA, EC 1.7.2.2) of either bacteroid or plant origin was independent of theR. melilotistrain. Activation occurred after 3 and 7 days, respectively, of nitrate feeding. Significant amounts of nitrite were obtained throughout the experimental period from buffered extracts of both bacteroids and cytosol of nodules. However, when these nodules were ground in the presence of inhibitors of enzyme activity, nitrite was only found in nodules containing strain 102‐F‐51 after 1 week of treatment. These results agree with the recent hypothesis that nitrite plays a role in a secondary stage of nodule damage by nitrate. We propose that NiRA rather than NRA can be used as an internal probe of nitrate access to the infected region of n

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb04394.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Oscillatory changes in electrical parameters of cells ofNitellopsis obtusa(Desv. in Lois) J. Gr. andNitella flexilisf. Atkahensis R. D. W., particularly in the membrane potential, were investigated with external Ag/AgCl electrodes. Three main types of oscillations were observed. The measurements were carried out on 30 cells with the application of an inhibitor of cytoplasmic streaming (procaine) and revealed that there was no direct correlation between cytoplasmic streaming and oscillations in the membrane potential.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb04395.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

When illuminated leaf discs and detached leaves of spinach (Spinacia oleraceaL. cv. Estivato) were exposed to 0.4 and 0.25 μl 1‐1H2S, respectively, pool sizes of cysteine and glutathione increased. In the dark, apart from these compounds, the level of γ‐glutamyl‐cysteine also increased. Incubation of leaf discs with 1.0 mMbuthionine sulfoximine (BSO) resulted in the accumulation of cysteine only, both in the light and in darkness. When glycine was supplied to the petioles of detached leaves exposed to H2S in the dark, the accumulation of glutathione was stimulated, while γ‐glutamyl‐cysteine accumulation was prevented completely. Glycolate and glyoxylate, precursors of glycine in the glycolate pathway, had nearly the same effect as glycine. Although other amino acids were apparently taken up equally well as glycine when supplied to the petiole, they were much less effective, or not effective at all, in restoring glutathione synthesis in the dark. These results provide evidence, that H2S‐induced glutathione accumulation in spinach leaves in the dark is limited by the availability of glycine, giving rise to the accumulation of the metabolic precursor γ‐

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb04396.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Continuous recordings of the effect of red light on the over‐all and zonal growth responses were made on intact, dark‐grown wheat (Triticum aestivumL., cv. Hatri) seedlings selected 70 or 90 h after sowing. The over‐all growth response of intact coleoptiles induced by bilateral continuous red light (660 nm, 17 W m−2) was complex and resulted from the overlapping of different zonal growth responses. During a 5 h investigation period, these responses can be divided into two phases. The first phase (short‐term response) was a transient growth inhibition. After a lag period of ca 15 min, the rate of extension decelerated to a minimum value at ca 60 min, after which an acceleration was seen. This response was qualitatively the same in all coleoptile zones investigated (tip, subapical zone, base) and independent of coleoptile age. The second phase (delayed response) became measurable between 1.8 and 3 h after onset of red light irradiation and exhibited zonal‐specific growth promotion or inhibition, dependent on the coleoptile age. A persistent growth promotion was observed only in the tip region of coleoptiles selected 70 h after sowing and became detectable about 3 h after the onset o

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb04397.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

ATPase activity was studied in plasma membrane‐enriched fractions prepared from culturedCitrus sinensisL. cv. Osbeck cells. In general, properties of the plasma membrane ATPase from cultured cells, such as optimal pH and temperature. Vmaxand Kmwere similar to those already observed in higher plants. The effects of high salt concentrations on ATPase activity were studied in membrane fractions derived from salt‐sensitive and salt‐tolerant cells grown in the presence or absence of salt. NaCl did not have an in vivo effect on Vmaxand the apparent Kmvalue for ATP. However, high concentrations of NaCl, or KCl, added in vitro, induced cooperativity in the enzyme and reduced the affinity of the enzyme for its substrate. Isoosmolar concentrations of sucrose or choline chloride failed to do so. Our results suggest that the plasma membrane ATPase ofCitruscells has more than one substrate‐binding site on the native form of the enzyme which interact in the presence of salt and act independently in its

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb04398.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Transcripts for thylakoid proteins encoded in the chloroplast genome that show decreased synthesis in senescing primary leaves of bean (Phaseolus vulgaris) have been examined by Northern and dot blot analyses. In young, 7‐day‐old leaves pulse‐labelled with35S‐methionine, all of the major chloroplast DNA‐encoded thylakoid proteins become radiolabelled, including the 68 kDa protein of PSI encoded bypsaAlandpsbA2, the D‐1, D‐2, CP47 and CP43 proteins of PSII encoded bypsbA,psbD,psbB, andpsbC, respectively, and cytochromefand cytochromeb6encoded bypetAandpetB, respectively. By contrast, in pulse‐labelled, senescent 28‐day‐old leaves, the only chloroplast‐encoded thylakoid protein showing active synthesis is the D‐1 protein of PSII. Total RNA levels decline by ≅ 9 fold between 7 and 28 days on a fresh weight basis. Dot blot analyses using gene‐specific hybridization probes indicate that steady state transcript levels for all of the chloroplast DNA‐encoded proteins examined maintain the same proportion of total RNA over this period. This means that these transcripts also decline by =9 fold between 7 and 28 days. Thus, reduced synthesis of the 68 kDa protein of PSI, the CP47 and CP43 proteins of PSII, cytochromefand cytochromeb6can presumably be attributed, at least in part, to a decline in steady state levels of corresponding message. It is apparent from Northern blot hybridizations that there are also qualitative changes in transcript pattern forpetA,psbCandpsbDbetween 7 and 28 days that perhaps reflect alterations in post‐transcriptional processing. These alterations may also contribute to the decreased synthesis of the CP43 protein and cytochromef. The continued active synthesis of the D‐1 protein of PSII in the senescent 28‐day‐old leaves, despite the =9 fold decrease in the steady state level of its transcript, suggests that the psbA transcript is preferentially translated relative to transcripts for other

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb04399.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Isolated potato (Solanum tuberosumL. cv. Dansyaku) tuber mitochondria showed a significant loss in respiratory activity when treated withtert‐butyl hydroperoxide (BHP), especially in the presence of microsomes. The following alterations appeared in parallel with the gradual decrease in the respiratory activity: The outer membrane became leaky, probably due to peroxidation of phospholipids. The level of sulfhydryl (SH) groups in mitochondrial proteins decreased in contrast to non‐protein SH groups. A considerable amount of phospholipids was degraded and lost. A mechanism of the mitochondrial damage induced by BHP and microsomes is discussed with respect to a significant role of free radicals which may be formed at the onset of senescence or physiological disord

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb04400.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY