摘要:

Phosphoenolpyruvate carboxylase (PEPC) from higher plants is usually assayed by using malate dehydrogenase (MDH) as a coupling enzyme. To avoid erroneous readings caused by metal ions, which convert oxaloacetate (OAA) to pyruvate, lactic dehydrogenase can be included. Reporting the total NADH used by both coupling enzymes gives the total OAA production. Microbial PEPC has been assayed by employing citrate synthase (CS) as a coupling enzyme which detects the reaction of CoA with Ellman's reagent. Comparable Kmvalues for MgPEP are found with the two assays. When MDH alone is used as the coupling system, the Vmaxvalue is about 60% larger than the one found with the CS assay. However, when MDH is added to the CS assay without the NADH cofactor, Vmaxis brought back to the same level as that with the NADH‐coupled enzyme. Malate inhibition of PEPC assayed with the CS coupling system is blocked by low concentrations of citrate in the range produced in the assay. High concentrations of citrate inhibit PEPC. Glucose‐6‐phosphate in concentrations higher than 1 mMblocks the response of PEPC to added MDH in the CS

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb05326.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Micropropagated poplar shoots rooted 100% on a rooting medium (A) containing NAA, but they did not root in the absence of auxin (NA). Putrescine, but not spermidine and spermine, promoted rooting up to 42% when added to the NA medium. Cyclohexylamine (CHA), an inhibitor of spermine synthase, also promoted (up to 36%) rooting in the absence of auxin. The inhibitors of polyamine biosynthesis DFMA (α‐difluoromethylarginine) and DFMO (α‐difluoromethylomithine), aminoguanidine (AG) and methylglyoxal‐bis‐guanylhydrazone (MGBG), inhibited rooting when applied in the presence of auxin and had no effect in its absence.The rooting inductive phase (in the presence of auxin) was determined by periodical transfer of shoots from A to NA medium, and by changes in peroxidase activity, to be 7 h. Putrescine (not spermidine and spermine) accumulated to a maximum during the inductive phase. Both putrescine and CHA promoted rooting on NA medium when applied during the first 7 h. In contrast DFMA and AG inhibited rooting during this period. The results point to the involvement of putrescine and its Δ1‐pyrroline pathway, in the inductive phase of rooting in p

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb05327.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

We examined the UV absorption spectra and the epidermal‐transmittance spectra (280–350 nm) of foliage from 42 plant species. Sun foliage was sampled from naturally growing individuals of seven species in each of six life forms comprising two evergreen groups (gymnosperms and angiosperms) and four deciduous angiosperm groups (trees, shrubs and vines, herbaceous dicotyledons and grasses). There were large differences in absorption spectra of whole‐leaf extracts among species. While absorbance declined with increasing wavelength in most woody species, there was a trough in absorbance around 300 nm in many herbaceous species. Absorption spectra were negatively correlated with epidermal‐transmittance spectra in 31 of the 42 species. Relationships between absorbance and transmittance did not follow the theoretical exponential function. Species rankings of UV‐screening effectiveness were similar when we assessed it by using epidermal transmittance at single wavelengths (300 or 320 nm) or different UV‐action spectra to weight epidermal‐transmittance spectra and estimate the levels of biologically effective UV reaching the mesophyll. Thus, differences in absolute epidermal transmittance among species appeared to overshadow spectral differences. Nevertheless, the differences we found in the internal UV spectral regime in foliage suggest that whole‐plant action spectra will differ among species. While species rankings of UV‐screening effectiveness were similar when different action spectra were used, the absolute amounts of biologically effective UV reaching the mesophyll of species varied considerably when different action

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb05328.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Ethylene enhances senescence of carnation (Dianthus caryophyllusL.) flowers. Sephacryl S‐200 gel filtration followed by SDS‐PAGE of extracts of petals exposed to ethyiene revealed the increase or appearance of proteins with molecular masses of 70, 60, 35 and 33 kDa, and a concomitant decrease in proteins with molecular masses of 62. 45. 34. 30 and 26 kDa.The 70‐kDa protein, which was not detected in untreated flowers, was isolated and polyclonal antibodies were prepared against it. Its N‐terminal sequence (20 amino acids) was identical to that of a portion of the deduced protein encoded by cDNA clone pSR 12. recently isolated by others from carnation petals. Western blot analyses of petal extracts after various exposure times to ethylene alone or in the presence of translation or transcription inhibitors suggested that accumulation of the 70‐kDa protein is due primarily to ethylene‐induced synthesis. The apparent induction by ethyiene was further supported by data indicating that the protein is not formed in flowers pre‐treated with silver thiosulfale. an inhibitor of ethylene action, prior to exposure to ethylene. Ethylene induction of the protein was found only in petal tissue, and the protein was not detected in other carnation plant organs. Immunological studies revealed that the protein is specifically expressed in carnation petals and not in petals of several other flowers. Southern and northern analyses using an SRI2 cDNA probe indicated that the genomic DNA of petunia, carnation, and gerbera contain fragments homologous to SRI2. Gene expression products were however, only detected in petals of ethylenetreated carn

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb05329.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Superoxide dismutases (SOD; EC 1.15.1.1) in chestnut (Castanea sativaMill., cv. 431) leaves were characterized by native polyacrylamide gel electrophoresis. The three molecular forms of SOD were distinguished from each other by their different sensitivity to cyanide and H2O2Three CuZn‐containing SODs were detected (CuZn‐SOD I, II. and III), and all the isozymes had a molecular mass of 33 kDa. CuZn‐SOD III was the most abundant isozyme. whereas CuZn‐SOD II was present in a minor amount. In leaves showing typical symptoms of senescence increases of 2.5‐. 7‐ and 4‐fold in the specific activities of CuZn‐SODs I, II, and III. respectively, were found. In addition, the pattern of the three isozymes was modified by the age of leaves, a rise in the CuZn‐SOD II and a decrease in the CuZn‐SOD 1 percentages being found in senescent leaves compared to green leaves. As to other activated oxygen‐related enzymes, an increase in the superoxide‐generating xanthine oxidase activity and a decline in both catalase and peroxidase activities during natural senescence of chestnut leaves were observed. Results obtained suggest that in natural senescence of chestnut leaves activated oxygen species are involved, and an overproduction of hydrogen peroxide and superoxide radica

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb05330.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

A 42 kDa anionic peroxidase (EC 1.11.1.7) having a pl of 3.6 was purified from suspension cultures of cells of sycamore maple (Acer pseudoplatanusL.) grown in the dark by a combination of lectin‐affinity, anion‐exchange and gel permeation chromatography. The enzyme had an amino acid composition similar to that found for other anionic plant peroxidases, but the protein was blocked to amino‐terminal protein sequencing. Commercially available antibodies against horseradish peroxidase were shown to cross‐react with the sycamore maple enzyme on immunoblots. The purified peroxidase displayed differences in its affinity for each of the three monolignols, and these differences were compared to those found for a commercial preparation of horseradish peroxidase, as well as a laccase (p‐diphenol:O2oxidoreductase: EC 1.10.3.1) purified from sycamore maple cell suspension cultures. These results are discussed with respect to the role played by peroxidases in lignin deposition and host‐pathog

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb05331.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Cytokinin free bases, ribosides and 9‐glucosides were measured in stem node cultures of potato (Solanum tuberosumL. cv. Ulster Sceptre) in the presence or absence of 1 μMjasmonic acid (JA) to examine whether or not their changed levels were part of the JA‐induced growth response. The enhanced growth response in JA‐treated plantlets included: expanded root systems, extended leaf areas, increased number of nodes, and enlarged stem diameters. The protein analysis revealed a substantial decrease in a 62‐kDa polypeptide. On a dry weight basis, the levels of ribulose‐1,5‐biphosphate carboxylase/oxygenase (RuBP carboxylase, EC 4.1.1.39) and chlorophyllsaandbwere constant. The total concentration of endogenous cytokinins remained virtually the same in control and treated plantlets; but in JA‐treated plantlets the amount of cytokinin free bases and cytokinin 9‐glucosides decreased. In addition, the level of cytokinin ribosides was elevated. The ratio between active and inactive cytokinins increased from 1.2 to 2.1, which correlates with the enhanced growth of potato plantlets grown on 1 μMJA. Thus the observed growth and developmental changes may be a consequence of the measured altered cytokinin level. However, significant morphological alterations of the potato plantlets treated with JA may also be a result of the changed critical cytokinin concentration or critical ratios of cytokinins to auxins and JA, rather than their absolu

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb05332.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Three invertase forms (EC 3.2.1.26) were identified in soluble extracts from developing flower buds of Lilium longiflorum Thunb. cv. Nellie White. The enzymes were separable on a diethylaminoethyl (DEAE)‐Sephacel column and designated invertase I.II or III according to the order of elution from Sephacel. To determine tissue specificityof these floral invertases, anthers were separated from tepal. pistil and filament tissue, and analyzed for invertase activity. Invertase I was localized primarily in anthers, with invertases II and III being present in much smaller amounts (less than 5% of the invertase I activity). Much higher levels of invertases II and III were found in the nonanther organs of the flower, where essentially no invertase 1 was detectable. Further purification of each form (using gel filtration. Con‐A‐Sepharose affinity chromatog‐raphy and hydrophobic interaction chromatography on phenyl‐agarose) resulted in 135‐ 189‐ and 202‐fold purification of pooled fractions from DEAE‐Sephacel. respectively, and established that each invertase form is a glycoprotein. Each was an acid invertase. with pH optima between 4.0 and 5.0 and an apparent molecular mass of 77 500 Da (as determined by Sephadex gel filtration). The invertases had sucrose Kmvalues of 1.0. 6.4 and 6.6 mM. and temperature optima of 40. 50 and 45°C. respectively. A temperature stability study revealed that invertase III was the most thermostable, followed by II and I. Invertases II and III had lower affinity to raffinose and stachyose than invertase I. All three enzymes were completely inhibited by Hg2+or Ag+ions at 1.7 mM. At this concentration. Cu2‐showed differential partial inhibition. Although fructan was shown to be present in both anther and nonanther tissues ofLiliumflower buds, these invertases showed no sucrose:sucrose fructosyltransferase (E

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb05333.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The effect of blue and red light on the adaptation to low CO2conditions was studied in high‐CO2grown cultures ofChlorella Pyrenoidosa(82T) andChlamydomonas reinhardtii(137+) by measuring O2exchange under various inorganic carbon (Ci) concentrations. At equal photosynthetic photon flux density (PPFD), blue light was more favourable for adaptation in both species, compared to red light. The difference in photosynthetic oxygen evolution between cells adapted to low Ciunder blue and red light was more pronounced when oxygen evolution was measured under low Cicompared to high Ciconditions. The effect of light quality on adaptation remained for several hours. The different effects caused by blue and red light was observed inC. pyrenoidosaover a wide range of PPFD with increasing differences at increasing PPFD. The maximal difference was obtained at a PPFD above 1 500 μmol m−2s−1. We found no difference in the extracellular carbonic anhydrase activity between blue‐ and red light adapted cells.The light quality effect recorded under Ci‐limiting conditions inC. reinhardtiicells adapted to air, was only 37% less when instead of pure blue light red light containing 12.5% of blue light (similar PPFD as blue light) was used during adaptation to low carbon. This indicates that in addition to affecting photosynthesis, blue light affected a sensory system involved in algal adaptation to low Ciconditions. Since the affinity for CiofC. PyrenoidosaandC. reinhardtiicells adapted to air under blue light was higher than that of cells adapted under red light, we suggest that induction of some component(s) of the Ciaccumulating mechanism is regulated by the lig

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb05334.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Modifications of cytoplasmic pH has biological significance in animal and plant cell development. Many observations suggest an important function of cytopiasmic pH in mitotic signalling in animal ceils. InBidens pilosacultivated under white light, acidification of cytoplasm, observed after mechanical trauma, is associated with an inhibition of DNA synthesis and a decrease in mitotic frequency. In contrast, inBidens pilosacultivated under blue light, mechanical stimulation induces an increase of cytoplasmic pH and stimulation of DNA duplication and mitotic activity. A correlation has been established between transient variations of cytoplasmic pH and rapid modification in cell development. The critical role of cytoplasmic pH in the regulation of the cell cycle in plants is discussed.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb05335.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY