摘要:

Cell cultures ofAsparagus officinalisL. ev. “Argenteuil” were used to study the effect of glucose on the synthesis of glutamate dehydrogenase and acid phosphatase. Both the enzymes are progressively repressed by increasing the glucose concentration in the culture medium. Furthermore, synthesis of glutamatc dehydrogenase and acid phosphatase in cells grown in the presence of high glucose concentrations is derepressed by the addition of the cyclic adenosine 3′:5′‐monophosphate to the culture medium. These data support the hypothesis that also in cells from higher plants a regulatory mechanism exists with some similarities to the “catabolite repression” mechanism operating in several prokaryotes and low

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04250.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Seedlings of spring wheat (Triticum aestivumL. cv. Svenno) were cultivated at 20°C in continuous light or darkness with the roots in nutrient solutions for six days. The plants were starved for K+during different periods of time to produce plants with various K+status. In one cultivation light‐grown plants were pretreated in darkness, and vice versa, before the uptake experiment. In all experiments, roots were put in a complete nutrient medium containing 2.0 mMK+radiolabelled with86Rb. The uptake time was varied (5, 60 or 120 min).The K+concentration in the roots, [K+]root, increased during the course of the uptake experiments, especially in light and at initially low [K+]root, At the same time K+(86Rb) influx in the roots decreased. The simoidal relationship obtained between K+(86Rb) influx and [K+]rootwas affected by these changes, and Hill plots gave various Hill coefficients, nH, depending on the duration of the uptake experiments. nHfrom three apparently straight line segments of the same plot, in different [K+]root‐ intervals, indicated a falling degree of interaction between the binding sites as [K+]rootincreased. For the dark‐grown plants negative cooperativity could not be demons

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04251.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The presence of Ni2+in the incubation medium of maize root segments (Zen maysL. cv. Dekalb XL 640) induces an early and significant enhancement of the rate of proton extrusion both in the absence and presence of fusicoccin; with time, an inhibition of proton extrusion and a leakage of K+appear. The inhibition of proton extrusion is accompanied by a decrease in the dark CO2fixation and by a decrease in the level of malate in the cells. Ni2+inhibits in vitro phosphoenolpyruvale carboxylase activity of maize roots. The data indicate a correlation between the operativity of the proton pump and that of the malate‐pH stat mechanism for the homeostasis of cytoplasmic p

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04252.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Spikes of barley (Hordeum vulgareL.) cultivar Bomi and high‐lysine mutants Riso 1508 and Riso 56 were cultured on liquid media at varying N and sucrose levels. Bomi accumulated N in response to increasing N levels in the medium and a higher level was reached than in spikes of intact plants. The distribution of N in salt‐soluble, hordein, and non‐protein N fractions appeared to be normal. Endosperm dry weight and starch were lower than in intact plants and declined at higher N levels. A linear relationship was observed between starch content and the concentration of sucrose in the endosperm water. Uptake of culture medium by the spikes was affected by both N and sucrose concentration. The mutants had lower dry weights and starch contents, and higher sucrose contents than Bomi. At high N levels, the mutants accumulated less hordein, and more non‐protein N th

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04253.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Potassium uptake and release in roots and translocation to the shoots were studied in 14‐day‐old winter wheat (Tritictum aestivum L. cv. Martonvásári8) of different K status. Transport processes were measured in the growth solutions for 5 h ensuring near‐equilibrium conditions. The uptake showed three phases: (1) at low external K+concentrations it increased with increasing concentrations and culminated at 0.1 mM: (2) between 0.1 and 1 mMit decreased, and (3) it increased again above 1 mM: The release of K+showed a constant low level below 1 mMwhile paralleling the uptake above that. The uncoupler 2,4‐dinitrophenol inhibited uptake phases (1) and (2), whereas it did not affect either phase (3) or K+release. Translocation showed similar patterns. It is concluded that phases (1) and (2) depend on metabolic energy while phase (3) is mostly passive. It is emphasized that different types of regulation seem to operate in the transport mechanism: i.e. limitation by transport sites, control by negative feedback and by K+/K+exchange, res

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04254.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The sequence of inhibition of cation uptake caused by a series of cationic inhibitors may shift dramatically on varying the experimental conditions. This sequence depends upon the concentration of the inhibitory cation, the concentration of the substrate cation, the charge density of the cell membrane, the ionic strength of the medium and the affinity of the substrate cation for the negative groups located on the cell membrane. A shift in sequence between inhibitory cations can only occur if one of the inhibitory cations shows a greater affinity for the translocation site than the other, while the affinity for the negative groups on the cell membrane is lower.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04255.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Changes in activity of endogenous cytokinin‐like substances were examined in intact plants and excised leaves of Begonia x chemantha Everett cv. Prinsesse Astrid (Christimas Begonia) by means of the tobacco callus bioassay. Cytokinin activity in the leaves of intact plants was higher in plants grown at 18°C than in those grown at 21° or 24°C. In excised leaves, an increase in cytokinin activity was observed during the first 4 days following leaf detachment. However, after the seventh day cylokinin activity decreased again. This decrease was more profound in leaves exposed to 24°C than in those exposed to 18°C.Treatment of detached leaves with gibberellic acid (2.8 mM) caused an increase in measurable cytokinin activity. This increase was more profound in the zones of activity which correspond with zeatin glucosides on paper and Sephadex LH‐20 chromatography. Additional zones of activity appeared after Sephadex chromatography. These were of a more slow moving nature with elution volumes corresponding to Nb‐(Δ2‐isopentenyl)adenine and its derivaties. Water‐treated control leaves had higher activity in the regions corresponding to zeatin and

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04256.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The influences of various day/night air temperatures on net CO2uptake and nocturnal acid accumulation were determined forOpuntia ficus‐indica, complementing previous studies on the water relations and responses to photosynthetically active radiation (PAR) for this widely cultivated cactus. As for other Crassulacean acid metabolism (CAM) plants, net nocturnal CO2uptake had a relatively low optimal temperature, ranging from 11°C for plants grown at day/night air temperatures of 10°C/0°C to 23°C at 45°C/35°C. Stomatal opening, which occurred essentially only at night and was measured by changes in water vapor conductance, progressively decreased as the measurement temperature was raised. The CO2residual conductance, which describes chlorenchyma properties, had a temperature optimum a few degrees higher than the optimum for net CO2uptake at all growth temperatures. Nocturnal CO2uptake and acid accumulation summed over the whole night were maximal for growth temperatures near 25°C/15°C, CO2uptake decreasing more rapidly than acid accumulation as the growth temperature was raised. At day/night air temperatures that led to substantial nocturnal acid accumulation (25°C/15°C.). 90% saturation of acid accumulation required a higher total daily PAR than at non‐optimal growth temperatures (10°C/0°C and 35°C/25°C). Also, the optimal temperature of net CO2uptake shifted downward when the plants were under drought conditions at all three growth temperatures tested, possibly reflecting an increased fractional importance of respiration at the higher temperatures during drought. Thus, water status, ambient PAR, and growth temperatures must all be considered when predicting the temperature response of gas exchange forO. ficus‐indicaand presumably f

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04257.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Recent evidence has supported the folllowing views:1. Polyphenol oxidase (PPO) is a plastidic enzyme that is unclear‐coded, but is inactive until incorporated into the plastid.2. In healthy green tissues PPO exists in a latent form on the thylakoid membrane and is not involved in synthesis of phenolic compounds. In leucoplasts, proplastids, or amyloplasts PPO is often present in a latent form in rudimentary thylakoids.3. PPO normally functions as a phenol oxidase in vivo only in sencent or damaged cells.4. In the functional chloroplast, PPO may be involved in some aspect of oxygen chemistry – pherhaps mediation of pseudocyclic photophosphorylat

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb04258.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY