摘要:

The effect of the 5 calmodulin (CaM) antagonists trifluoperazine (TFP). compound 48/80, N‐(6‐aminohexyl)‐naphthalenesulfonamtde (W‐5), N‐(6‐aminohexyl)‐5‐chloro‐1‐naphthalenesulfonamide (W‐7), and calmidazolium on auxin‐dependent medium acidification was investigated in abraded segments ofAvena sativaL. cv. Victory I. Buffering capacity, Asn content, and changes in pH of bathing solutions were measured in the presence of these inhibitors. When coleoptiles were treated with TFP or compound 48/80, the Asn content and the buffering capacity increased, thus suggesting that plasma membrane permeability was modified. On the contrary. the effect of calmidazolium, W‐5. and W‐7 on Asn release and buffering capacity was rather low; only small effects being observable at the highest concentration employed. Calmidazolium and W‐7 strongly inhibited auxin‐dependent medium acidification. W‐5 did not affect medium acidification. The specificity of these CaM antagonists and their effects on medium acidification are discussed. The data adduced is consistent with the working hypothesis which postulates an essential role for the Ca2+‐CaM system on a

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb08792.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The isoenzymatic pattern of Superoxide dismutase (SOD; EC 1.15.1.1) was studied in the symbiosis ofGlomus mosseae(Nicol. and Gerd.) Gerd. andTrappe‐Trifolium prarenseL A Cu.Zn‐SOD (M, 40500) was found in spores of G.mosseae. while one Mn‐SOD (Mn‐SOD I) and two Cu.Zn‐SODs (Cu.Zn‐SOD 1 and Cu.Zn‐SOD II) were present in both roots and leaves ofT. pratense. Molecular masses for Cu.Zn‐SOD I and Cu.Zn‐SOD II were 31000 and 34300. respectively. However, whenT. pratemeandG. mosseaewere associated, mycorrhizal roots showed two new iso‐zymes, Mn‐SOD II and mycCu.Zn‐SOD, which have relative molecular masses of 37 800 and 33 300, respectively. The mycCu.Zn‐SOD was found to be specific for this association, whereas Mn‐SOD II was also present in nodules ofRhizobium‐T. pra‐tense. Results suggest that both enzymes are induced in theT. praienseroots in response to invasion by mycorrhizal fungi, perhaps as a result of an increase in the generatio

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb08793.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Sucrose and fructan metabolism were studied in wheat (Triticuin aotiirumL. cv. Tribal 800) roots during a period at chilling temperature. Enzyme activities related to fructan and sucrose metabolism were measured. Sucrose‐sucrose fructosyl transfer‐ase (EC 2.4.1.99) activity increased more than 25‐fold when plants were cooled to 4°C. Sucrose synthase (EC 2.4.1.13) and sucrose‐phosphate synthase (EC 2.4.1.14) activities also increased, but low temperatures had no significant effect on invertaso (EC 3.2.1.26) or on fructan hydrolase (EC 3.2.1.26) activities. The accumulation pattern of fructan in roots was different to that in leaves. In roots chilling stimulated the synthesis of fructans of high degree of polyme

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb08794.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Measurements of the short‐term response of nodulated roots of soybean (Glycine maxL. Merr, cv. Harosoy:Bradyrhizobium japonicumUSDA 16) to rapid changes in surrounding pO2indicate that their ability to reversibly adjust gaseous diffusive resistance is retained whether plants are cultured in rhizospheres of very low (2.8%) or very high (61.2%) pO2. Thus the capacity for reversible short‐term diffusion adjustment is additional to structural changes in the fixed diffusional barriers of nodules which allow their continued fixation of N2in unfavourably high or low external pO2. Anatomical evidence, involving quantitative measurement of intercellular spaces in the cortical tissues using electron microscopy of thin sections, indicates that the major fixed diffusional barrier is a boundary layer of cells in the inner cortex which may be as small as one cell thick in nodules from 2.8% O2to 5 or 6 cells thick, and almost completely devoid of intercellular spaces, in those from 61.2% O2. The data are interpreted to indicate that the variable diffusion harrier is distinct from the boundary layer and is most likely to be a property of cells and/or intercellular spaces inside the boundary layer of the nodule cor

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb08795.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Stomatal phosphoenolpyruvate carboxylase (PEPCase EC 4.1.1.31), extracted from abaxial epidermal peels ofVicia fabaL. cv. Frühe Weiβkeimige, was partially purified by ammoniumsulfate precipitation, and molecular sieve (Sepharosc S‐400) and ion exchange (DEAE‐Sepharose) chromatography. The partially purified enzyme, essentially free of a PEPCase isoform existing in mesophyll and epidermal cells, had a specific activity of 300 nkat mg‐1protein at 25°C. Western immunoblot analysis revealed that the stomatal enzyme had two bands (M:of 110000 and 112000), crossreacting with PEPCase antibodies raised against PEPCase fromKa‐lanchoe daigremontiana. The native molecular mass of the enzyme (467000) points to a tetrameric subunit structure. The temperature optimum was found to be 35°C; cold treatments of PEPCase before assaying were accompanied by inactivation. The energy of activation was calculated to 51 kJ mol‐1. The kinetic behaviour of the enzyme at fixed MgCl2concentrations is characterized by a pH optimum between pH 8.0–8.2 with or without 1 mMmalate or 5 mMglucose‐6‐phosphate (Glc‐6‐P), but a combination of both effectors resulted in a shift of the optimum to pH 7.6. The enzyme showed a pH sensitive inhibition by 1 mMmalate and an activation by Glc‐6‐P. At low pH (6–7), Glc‐6‐P was able to compensate for the malate induced inhibition of the enzyme. Malate and Glc‐6‐P both affected Km(PEP), drastically and influenced Vmaxat pH 7, but not at pH 8.3. The inhibition constant of malate was determined to be 1.2 mMat pH 7. From the Dixon plot, a competitive inhibition of malate was a

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb08796.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Incubation of plant tissues at a constant elevated temperature greatly inhibits both basal and wound ethylene production. However, recovery from heat treatment is relatively rapid and is followed by stimulated ethylene production. The present investigation examines the kinetics of ethylene production after short‐term heal treatment and the regulation of heat‐altered ethylene production. Subapical stem segments of 7‐day‐old etiolated pea L. cv. Alaska) seedlings were analyzed for ethylene production, 1‐aminocyclopropane‐l‐carboxylic acid (ACC) oxidation, and ACC and l‐(malonylamino)cyclopropane‐l‐carboxylic acid (MACC) content after a 2‐min 40°C heat pulse. The short‐term heat pulse transiently inhibited ethylene production and ACC oxidation accompanied by a slight ACC accumulation within a 30‐min time period. Conjugation to MACC did not appear to play an integral role in heat‐regulated ethylene production. It was concluded that the major factor affecting ethylene production after heat treatment is the temporary inactivation of ACC oxidation. The possible roles of ACC synthase, ACC oxidase and lipoxygenase in regulating ethylene production after

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb08797.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY