摘要:

Breakdown of gliadin during germination ofxHaynaldoticum sardoumMeletti et Onnis seeds is correlated with the appearance in the endosperms of a proteinase activity, which is absent in the quiescent seed. This activity is optimal at pH 4 and has a maximum stability at pH 4–5. Gel filtration of proteinase activity extracted from quiescent seeds indicates a molecular weight of 60–100 kDa. The proteinase can hydrolyze hemoglobin but not gliadin and is inhibited by pepstatin A and, to a lower extent, byp‐chloromercuribenzoic acid (p‐CMB). Gel filtrations of crude extracts from germinating seeds reveal two peaks (molecular weight 66 and 21 kDa) of activity against hemoglobin and a shoulder and a peak (molecular weight 21 kDa) of activity on gliadin. The first peak of activity against hemoglobin is inhibited by pepstatin A and p‐CMB; the second one is inhibited by p‐CMB and leupeptin. As for the gliadin‐eluted activity the shoulder is mainly inhibited by pepstatin A and p‐CMB, whereas the peak is inhibited by p‐CMB and leupeptin. Estimations of the ratios of total nitrogen to α‐amino nitrogen, suggest that the enzyme preparations mainly contain proteinases. It is concluded that the proteinases present in the quiescent seeds ofxH. sardoum, in particular aspartic proteinases (EC 3.4.23), could play a role as initiator endoproteases or participate in the digestion of modified proteins during the mobilization of reserve proteins. The cysteine proteinases (EC 3.4.22) appearing during the germination seem to account for the hydrolysis of the most abundant class of protein res

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02054.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Dimorphic chloroplasts ofZea maysL. cv. GH5004 from bundle sheath and mesophyll cells contained similar amounts of DNA, while bundle sheath chloroplasts contained twice the number of nucleoids compared to mesophyll chloroplasts. On average bundle sheath nucleoids were half the size of mesophyll nucleoids and contained half as much DNA. Electron microscope autoradiography of the chloroplasts showed that the nucleoid DNA is associated with the thylakoids and in the case of mesophyll chloroplasts preferentially with the grana. These observations suggest that the differences in nucleoid distribution may be due to differences in membrane morphology, with the small nucleoids of agranal bundle sheath chloroplasts being widely dispersed.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02055.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Since CO2is liberated in the conversion of ACC to ethylene, the evidence that ethylene production by plant tissues is actually promoted by CO2calls for an explanation. Accordingly, the formation of ethylene by oat (Avena sativaL. cv. Victory) leaves and by apple (Golden Delicious) and pear (Pyrus communisL. cv. Anjou) tissue in very low levels of CO2has been studied. The gas chromatograph was modified to measure CO2and ethylene at the same time, by reducing both to methane. (Response of the gas chromatograph to CO2concentrations is linear.) The work establishes a clear difference between the endogenous production of ethylene and its production from applied ACC, a difference which holds about equally for leaves and for fruit tissue. The difference is in the CO2requirement, namely, lowering the CO2level by 99% or more decreases the production of ethylene from applied ACC by 50–60%, but it does not decrease, or even slightly increases, its production from endogenous precursors. Thus, while the need for CO2has not been explained, it has at least been delimited.The responses to abscisic acid (ABA) also differ, but in the reverse direction, the endogenous production of ethylene being decreased up to 70% by ABA. while the liberation from ACC is promoted about 20%. ABA also promoted the respiratory CO2production by 30% or, in presence of 1‐aminocyclopropane‐1‐carboxylic acid (ACC), by over 50%. Inhibition of ethylene production by cobalt or EDTA shows no such differentiation, while inhibition by Na catechol‐4,6‐disulfonate (Tiron) shows a small difference. It is concluded either that endogenous ethylene is formed by an enzyme system different from that reacting with ACC, or (more likely) that when ethylene arises from endogenous precursors the reaction does not proceed by way of free ACC, but by some activated

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02056.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Light‐induced generator potentials were examined in the liverwortConocephalum conicumL. by applying sub‐threshold light stimuli (400–750 nm). The fluenceresponse dependence was determined for various wavelengths. At low values of quantum flux density (less than 1 μmol m−2s−1) the plant reacts to the light pulses with hyperpolarization which, with a rise in the pulse intensity, is masked by the depolarization of the transmembrane potential. The action spectrum of depolarization shares many features with the absorption specturm of photosynthetic pigments. Application of inhibitors and electron donors showed a predominant role of photosystem II in the formation of the generator potential. No significant Emerson enhancement was observed after simultaneous illumination with light beams of 650

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02057.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Changes in the excitability of the liverwortConocephalum conicumL. caused by inhibitors of ionic channels and phosphorylation uncouplers, were examined. Action potentials were triggered by electrical and light stimuli. Tetraethylammonium chloride, an inhibitor of K+channels, completely blocked the ability to generate action potentials. Excitability also disappeared under the influence of MnCl2and LaCl3, inhibitors of Ca2+channels. The participation of Ca2+and K+in the electrogenesis of action potentials inC. conicumis discussed. Treatment with phosphorylation uncouplers induced a gradual disappearance of the metabolic component of the resting potential. It was accompanied by some series of excitations, numbering from several to over a dozen impulses characterized by decreasing amplitudes, after which the organism became totally unexcitable. Dicyclohexylcarbodiimide an inhibitor of H+‐ATPase, also caused depolarization of the transmembrane potential and disappearance of excitability. The results indicated the participation of a metabolic component in the generation of action potentials inC. conicu

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02058.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Purine nucleotide and RNA synthesis have been investigated at the different growth stages of carrot (Daucus carotaL.) cells grown in suspension cultures. At the early growth stages an increase in the content of RNA was observed, although at later stages RNA was degraded. The highest rates of incorporation of [14C]‐labelled adenosine into ATP and GTP were observed at the late growth sttages. This indicated that purine slavage was more importnt at the late growth stages, while de novo synthesis was dominant during the initial growth stages. This pattern was also reflected by increased levels, in the cell dividison phase, of theenzymes glycinamide ribonucleotide synthetase (EC 6.3.1.3.) and phosphoribosylpyrophosphate amido‐transferase (EC 2.4.2.14) involved in de novo purine synthesis. The activities of the purine salvage enzymes varied little during growth. Cells in the stationary phase, that were starved for sucrose and phosphate, showed a dramatic increase in cellular metabolism, as judged from a rapid uptake and incorporation of [32P]‐labelled phosphate into nucleotides and RNA, when incubated in fresh m

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02059.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Ten of 11 supernodulating mutants of soybean [Glycine max(L.) Merr.] cv. Bragg, in which nodulation was far in excess of that in the wild type, showed pronounced tolerance of nodulation to applied nitrate. Mutant nts (nitrate‐tolerant symbiosis) 1116 had an intermediate nodulation response and also showed some inhibition by nitrate. Mutant 1029, a revertant of nts382 (an extreme supernodulator), showed a wild‐type nodulation pattern and was equally sensitive to nitrate as cv. Bragg. Grafting experiments with cv. Bragg and nts382 indicated that both supernodulation and tolerance of nodulation to nitrate were dependent on shoot factors. Total leaf nitrate reductase (EC 1.6.6.1 and EC 1.6.6.2) activity of the supernodulating mutants was similar to that in cv. Bragg. We conclude from these results that the inhibitory effect of nitrate on nodule initiation and development in soybean depends on an interaction between nitrate and the autoregulation singal. In the supernodulating mutants, the autoregulation signal is either altered or absent and cosequently nodulation in these mutants is not sensitive to nitr

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02060.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

In crude extracts ofChlorella kessleriFott and Novákóva cells grown autotrophically in white light the activity of phosphofructokinase (PFK, EC 2.7.1.11) is 62.9 ± 1.5 nmol (mg protein)−1min−1under optimized test conditions. It is greatly increased in red [88.3 ± 1.8 nmol (mg protein)−1min−1], but somewhat decreased [57.0 ± 0.5 nmol (mg protein)−1min−1] in blue light of equal productivity. Mixtures of blue and red light yield the low activity as long as blue light represents at least 35% of the total quantum fluence rate. The rough wavelength dependence of the counteracting effect of short wavelength light on the increasing effect of red light exhibits a broad peak at 460 nm, reminiscent of action spectra of the blue/UV photoreceptors(s). Upon transfer of red light‐grown cells to blue light, the decrease develops slowly within 72 h; it cannot be prevented by 3‐(3,4‐dichlorophenyl)‐1,1‐dimethyl urea (DCMU). Since there is less carbohydrate in blue than in red light‐exposed cells, correlations between biosynthesis of PFK and level of carbohydrate are discussed, based on the assumption that red light decreases and/or blue light increases the transport of metabolites acr

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02061.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Cellular and compositional changes related to tissue growth and assembly of the photosynthetic apparatus were established with reference to the developmental gradient along the expanding fourth leaf ofLolium temulentumL. Ba 3081. The number of cells and the fresh weight per leaf segment fell with increasing cell age (distance from the leaf base). Components of the photosynthetic apparatus increased in concentration towards the more mature part of the leaf. Appreciable levels of chlorophyll and carotenoid could be detected in basal tissue enclosed in the sheaths of previous leaves prior to emergence into full light. The distributions of NADPH‐protochlorophyllide oxidoreductase (PCR. EC 1.6.99.1) and cytochromefalong the age gradient were visualized by Western blotting. Leaf base tissue contained two forms of PCR, 41 and 39 kDa, the smaller of which diminished with increasing cell age and proximity to full light. Cytochromefcomprised a 52 kDa species, which also declined with distance from the base, and a group of polypeptides at around 30–33 kDa which greatly intensified with tissue maturity. The significance of multiple forms of plastid proteins and the role of the light gradient penetrating the leaf sheath in regulating growth and plastid assembly processes are discus

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02062.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Jack pine (Pinus banksianaLamb.) seedlings were inoculated with either one of the ectomycorrhizal (ECM) fungi,Laccaria bicolor(Maire) Orton orPisolithus tinctorius(Pers.) Coker and Couch, and grown for 16 weeks in a growth chamber along with non‐ECM controls. Five enzymes involved with the assimilation of nitrogen or the synthesis of amino acids were measured in the 3 jack pine root systems as well as in the pure fungal cultures.Pisolithus tinctoriusin pure culture had no detectable activity of nitrate reductase (NR. EC 1.6.6.1), glutamate dehydrogenase (GDH. EC 1.4.1.2), glutamate decarboxylase (GDCO. EC 4.1.1.15) or glutamate oxoglutarate aminotransferase (GOGAT, EC 1.4.1.13) but did have some glutamine synthetase (GS, EC 6.3.1.2) activity.Laccaria bicolorin pure culture had no NR activity, small levels of GDCO activity, and high GS, GDH and GOGAT activity. The high levels of enzymatic activity present inL. bicolorindicate that it may play a greater role in the nitrogen metabolism of its host plant thanP. tinctorius.ECM infection clearly altered the enzymatic activity in jack pine roots but the nature of these changes depended on the fungal associate. Non‐ECM root systems had higher specific activities than ECM root systems for NR, GS, GDH and GDCO but GOGAT activites were the same for both the ECM and non‐ECM roots. Root systems infected withL. bicolorhad significantly greater NR and GDCO activity than those infected withP. tinctorius. Differences in the GS activity of the two fungi in pure culture corresponded to the GS activity of jack pine roots in symbiotic association with these fungi. While the free amino acid profiles in roots were significantly affected by ECM infection, the profile of free amino acids exported to the stem was the same for all treatments. High asparagine and low glutamine in roots infected withP. tinctoriusindicates that asparagine synthetase (EC x.x.x.x) activity should be higher within this symbiotic association than in theL. bicolorassociation or in the non‐mycorrhiza

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02063.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY