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1.
Nitrate provision has been found to regulate the capacity forChara corallina cells to take up nitrate. When nitrate was suppliedto N sufficient cells maximum nitrate uptake was reached after8 h. Prolonged treatment of the cells in the absence of N alsoresulted in the apparent ability of these cells to take up nitrate.Chlorate was found to substitute partially for nitrate in theinduction step. The effects on nitrate reductionwere separated from those on nitrate uptake by experiments usingtungstate. Tungstate pretreatment had no effect on NO3uptake induced by N starvation, but inhibitedNO3 uptake associated with NO3 pretreatment. Chloridepretreatment similarly had no effect on NO3 uptake inducedby N deprivation, but inhibited NO3 uptake followingNO3 pretreatment. The data suggest that there are atleast two mechanisms responsible for the inductionof nitrate uptake by Chara cells, one associated with NO3reduction and induced by CIO3 or NO3and one associated with N deprivation. Key words: Nitrate, Chlorate, Chara corallina, Induction 相似文献
2.
C.E. DEANE-DRUMMOND 《Plant, cell & environment》1985,8(2):105-110
Abstract. Net NO3 uptake by NO− 3 deficient Chara cells was used to calculate [NO− 3 ]c assuming that the cytoplasm occupies 10% total volume and that nitrate reduction and storage are negligible (i.e. maximum [NO− 3 ]c was calculated). A linear relationship was found between NO− 3 efflux and [NO− 3 ]c . There was an initial burst of NO− 3 efflux when NH+ 4 was added, followed by a slower efflux rate which matched influx rate such that net NO− 3 uptake was zero. Over 50% of NO− 3 that had been taken up in 2 h was lost within the first 5 min of NH+ 4 addition. The Nernst equation was used to predict the direction of the electrochemical driving force for NO− 3 entry. Under the experimental conditions used NO− 3 efflux is actively transported. The differential involvement of both NO− 3 influx and NO− 3 efflux in the regulation of NO− 3 uptake is discussed and a model is proposed to account for these results which envisages discrete NO− 3 influx and NO− 3 efflux carriers. 相似文献
3.
Nitrate Transport Characteristics in Hordeum vulgare L. Seedlings using Three Different Tracer Techniques 总被引:2,自引:0,他引:2
Deane-Drummond, C. E. and Thayer, J.R. 1986. Nitrate transportcharacteristics in Hordeum vulgare L. seedlings using threedifferent tracer techniques.J. exp. Bot. 37: 429439. and have been used to investigate various properties of nitrate uptake and translocation intoHordeum vulgare L seedlings. Short term / influx into seed lings grown in CaSO4 was stimulated by after a lag of 2 h. The apparent kinetics of shortterm / influx over the concentration range 0?00?7mol m fitted Michaelis-Menten equations The apparent Vmax didnot change when seedlings were used that had been pretreatedin 10 or 100 mmol m3 and Vmax=3.77 and 3?56µmol g1 fr. wt. h1respectively. The apparent Michaelis constants were also similarand Km=0?47 and 0?45 mol m3 respectively. Longer term pulse chase experiments with the heavy isotope 15Nhave shown that feeding roots with resulted in the preferential appearance of 15N labelled aminoacids in the xylem sap. Pulse chase experiments with the radioisotope13N have shown that feeding shoots with resulted in a radial pattern of distnbution of labelin the leaf veins, which can be detected using autoradiography. The limitations and advantages of all three techniques are comparedby reference to other known experimental data. Key words: 36Chlorate, 13nitrate, 15nitrate, Hordeum vulgare 相似文献
4.
Absence of nitrate reductase activity in San 9789 bleached leaves of barley seedlings (Hordeum vulgare cv. Midas) 总被引:1,自引:1,他引:0
Abstract San 9789 (norflurazone) blocks carotenoid synthesis which allows chlorophyll bleaching in the light, and has been used recently as a tool to study phytochrome responses without interference from photosynthetic pigments. By using this herbicide, we have found that nitrate reductase activity and light dependent nitrite reduction were lost simultaneously from achlorophyllous areas of barley leaves, with the green areas of the leaf tip still showing high activities. By contrast nitrate reductase is still present in the roots of herbicide treated plants. We suggest that intact chloroplasts are required for the presence of nitrate reductase in barley leaves. 相似文献
5.
CELIA E. DEANE-DRUMMOND 《Plant, cell & environment》1984,7(5):317-323
Abstract. Nitrate uptake into Chara corallina cells at different external pH (pHo) after different NO3− pretreatment conditions has been investigated. Following NO3− pretreatment (0.2 mol m−3 NO3−) there was little effect of pHo on subsequent net NO3− uptake into Chara cells. After N deprivation (2 mmol m−3 NO3−) there was a pronounced effect of pHo on nitrate uptake, the maximum rate occurring at pHo 4.7. There was no consistent relationship between OH− efflux and NO3− uptake in short term experiments (< 1 h). NO3− efflux was also sensitive to pHo, the maximum rate occurring at ∼ pHo 5.0. An inhibitor of the proton pump, DES, immediately stimulated NO3− uptake into cells pretreated with NO3− and prevented the time-dependent decrease in NO3−, uptake into Chara cells that had been previously treated with low N (2 mmol m−3 NO3−). NO3− efflux was found to be very sensitive to DES with Ki= 0.7 mmol m−3. At the optimum pHo for NO3− uptake the effect of DES on membrane potential (ψm) were slight, and only apparent after 30 min. The results are interpreted in context of current models relating NO3− uptake and H+ pump activity. A new model for NO3− uptake is proposed which involves NO3−/NO3− exchange at steady state. 相似文献
6.
The effect of growth temperature on the short term influx of86Rb+/K+, 36Cl/Cl, , 45Ca2+/Ca2+and into barley plants (Hordeum vulgareL. cv. Betzes) has been examined. When barley plants were grownwith a differential root: shoot temperature (15 ?C/25 ?C) therewas a marked stimulation of influx of all ions except Ca2+.Q10 measurements were close to 2.0 for all ions except Ca2+,where Q10 1.0 was found. Kinetics of ion influx showed thatthere had been almost complete compensation for the lower growingtemperature over a range of concentrations. The regulation of uptake was affected by growth temperature. On exposure to 15?C efflux/influx fell initially but was restored after 5 d. Sensitivity of net uptake to was increased by growth at a lower temperature. The importance of these observations in relationto application to field experiments and the proposed mechanismfor uptake is discussed. Key words: Growth temperature, Nitrate, Ammonium 相似文献
7.
ANTHONY D. M. GLASS M. YAEESH SIDDIQI CELIA E. DEANE-DRUMMOND 《Plant, cell & environment》1983,6(3):247-253
Abstract. A microcomputer-based system for the measurement of changes of ion activity (H+ , NO3 − , K+ ) in the uptake solutions during ion absorption by roots of intact plants is described. Ion activities are measured by means of ion-specific electrodes in a multichannel programmable voltmeter (data acquisition/control unit) which is activated by means of a microcomputer. Incoming data are stored digitally on tape cassettes or floppy discs via the microcomputer. The speed of sampling and large numbers of samples which can be simultaneously measured and recorded make this an extremely versatile system which might be employed for measuring and recording any number of analogue voltage signals. 相似文献
8.
The effects of Cl and pretreatment on 36Clinflux and influx into Characorallina cells were examined. Both treatments reduced 36Clinflux into C. corallina cells in the acid pH range (4.57.0). pretreatment stimulated influx into C. corallina cells, but Cl pretreatment hadno effect. There was a direct inhibitory effect of CI on influx into C. corallina cells, but no apparenteffect on net NO uptake. The time course of 36Cl accumulation into cytoplasmic and vacuolarcompartments during incubation of the cells with showed that significant radioactivity appeared in the vacuolarsap after 30 min. There was a linear increase in the percentageof total 36CI which crossed the tonoplast (c-v). There was noeffect of Cl or pretreatment on accumulation of radioactivity in the vacuole. Thin layer chromatography ofthe vacuolar sap showed that after 2 h only one component waspresent which had an RF which was similar to 36CI. Therate of accumulation of 36C1 in the vacuole could beused to estimate rates of reduction. Key words: Chloride, Chlorate, Chara, Nitrate 相似文献
9.
36C1O3/NO3 influx into Chara cells was found to be sensitiveto pHo and a maximum was found at pHo = 4.5. By contrast 14Cmethylamine influx into Chara showed a maximum at pHo = 8.5,and at this pHo influx rates were about 150 times higher thanrates of 36C1O3/NO3 influx. However, at pHo = 4.5, 36C1O3/NO3influx rates were, in some cases, comparable with rates of 14Cmethylamine influx. 36C1O3/NO3 influx into Chara cells was stimulatedby Rb +, K+, Na +, and NH4+, but not by Cs+ or Li +. NO3 andCl reduced 14C methylamine influx into Chara by 30%. NH4+ causedvery considerable inhibition of 14C methylamine influx intoChara, but had no effect on 36C1O3/NO3 influx in the presenceof K +. Net NO3 uptake into Chara was completely prevented byNH4+ even at relatively low NH4+ concentrations (25 mmol m 3).This latter effect was reversed by diethylstilbestrol (DES).Evidence is presented for the stimulation of NO3 efflux by NH4+as the mechanism responsible for the immediate effects of NH4+on net NO3 uptake into Chara cells. Key words: Chara, 14C methylamine, 36ClO3, pH 相似文献
10.
The use of chlorate as an analogue for NO3 during nitrateuptake into Chara corallina cells has been investigated. NO3inhibits 36C1O3 influx into Chara over the concentrationrange 01000 mmol m3. Lineweaver-Burke plots ofthe data are characteristic of competitive inhibition by NO3in the low concentration range (0300 mmol m3 ClO3)and apparent KINO3 is 140 mmol m3 which is of a similarorder of magnitude as apparent KmCIO3- 180 mmol m3. Athigher substrate concentrations the inhibition by NO3was not characteristic of competitive or uncompetitive inhibition. 36C1O3/NO3 influx was dependent on K+ and Ca2+in the external medium and inhibited by FCCP. NO3 pretreatmentor N starvation increased subsequent 36C1O3/NO3influx into Chara. A comparison between rates of net NO3uptake and 36C1O3/NO3 influx supported the previoushypothesis that NO3 efflux is an important componentin the determination of overall uptake rates. Key words: Nitrate, Chara, 36CIO3 相似文献