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DRAKEFORD DAVID R.; MUKHERJEE ILABANTA; REID DAVID M. 《Journal of experimental botany》1985,36(11):1705-1715
Drakeford, D. R., Mukherjee, I. and Reid, D. M. 1985. Some earlyresponses of Helianthus annuus L. to flooding. I. The effectsof flooding on the uptake and leakage of non-electrolytesby roots.J. exp. Bot. 36: 17051715. The object of this work was to examine some of the early effectsof flooding on roots. A hydroponic system was developed thatgave good control over watering, degree of oxygenation of thebathing medium and allowed measurement of short term changesin the composition of the bathing medium. Excised roots, floodedfor 24 h, were shown to take up less [3H) ß-alaninethan non-flooded roots and also leaked more [3H] ß-alanineinto a distilled water bathing medium. Further, flooded excisedroots lost more protein to the bathing medium, with young(57 d) roots showing greater losses than old(1114 d) roots. However, young roots had more proteinin the tissue even after greater loss. Young roots remainedhealthier and lost less fresh weight than old roots. Abscisicacid was shown to have a small role in protecting youngroots from the effects of flooding. Key words: ABA, abscisic acid, anaerobic, flooding, leakage, roots, uptake, waterlogging 相似文献
3.
The nature of metabolic products of 3indolylacetic acid(IAA) extracted from potato tuber disks treated with aeratedIAA solution has been investigated. Two major products, knownat first as V and P in these studieshave been isolated and V has been identified as3-indolylacetylaspartic acid (IacAsp). The rapid uptake of IAA is inhibitited by metabolic poisonssuch as 103 M. cyanide. The maximum mean internal concentrationexceeds the external concentration wellaerated cultures.The mean internal concentration, however only remains for aperiod and then falls off rapidly as a result of extrusion ofabsorbed IAA into the external solution. This extrusion is notinhibited by 10-3 cyanide; when the mean internal IAA concentrationis 150 µ mol/ml. and the localized IAA concentration musttherefore exceed this value. We conclude therefore that theIAA concentration in the sites where it has accumulated exceedsthe concentration of IAA outside. Uptake of IAA and also its further conversion are inhibitedby indolylacetonitrile and promoted by aspartate, but this promotionis not associated with any gain in amount of indolylacetylaspartate(IacAsp). The data suggest that IacAsp may be formed in tissue from boundIAA rather then free IAA. The accelerator found in potato and beans whichhas similar RF to IAcAsp has been shown definity to be someother substance or substances and not IAcAsp as was at firstthought possible. 相似文献
4.
Growth and Phosphate Transport in Barley and Tomato Plants During the Development of, and Recovery from, Phosphate-stress 总被引:12,自引:2,他引:10
Barley and tomato plants were cultured in nutrient solutionsincluding 0.15 mol m3 H2PO4. The phosphate supplywas discontinued and the subsequent effects on growth, internalphosphorus concentrations, phosphate absorption and translocationwere measured at frequent intervals. Growth rates were at firstunchanged and the internal phosphorus concentration decreased.During this phase the rate of phosphate transport by the rootssometimes increased significantly. Growth slowed more in shootsthan in roots during a second phase of stress development andvisual symptoms of deficiency appeared in tomato but not inbarley. During this phase, enhancement of phosphate uptake capacityreached a maximum in both species. The subsequent decline inuptake capacity was associated with visible symptoms of deficiencydeveloping in barley and intensifying in tomato. When stressedplants were returned to a solution containing 0.15 mol m3H2PO4 rapid absorption continued for several days afterthe internal phosphorus concentration had returned to the levelof the controls. Phosphate toxicity may have been the causeof leaf lesions and necrosis during the recoveryphase. Stomatal conductance in tomato was decreased at an early stageof stress development. Foliar-applied phosphate was absorbedmore rapidly by P-stressed barley leaves than by their controlsand much larger amounts were translocated from the leaves tothe roots. 相似文献
5.
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
6.
The temperature dependence of the efflux kinetics of labelledwater in isolated maize roots has been studied. The purposeof these experiments was to obtain the energy of activation,E (kcal/mole), of the rate-limiting step in this radial exchangeprocess under various experimental conditions. Estimates ofE were obtained from linear relations between ln{D'w} and thereciprocal of the absolute temperature; values of the apparentdiffusion coefficient, D'w, of labelled water in the root werefound from an analytical treatment of the efflux data in termsof a cylindrical diffusion model. The energy of activation forlabelled-water exchange in normal roots was 14.9 kcal/mole.The corresponding value for dead (boiled) rootswas 3.9 kcal/mole. These values of E substantiate the view thatin normal roots the penetration of water across the membranesof the root cells constitutes the rate-determining step in theefflux whereas in dead roots extracellular diffusionof water is the source of rate-control. Similar temperature dependence studies were performed on theefflux kinetics from normal and dead roots treatedwith 105 M phenylmercuric acetate (PMA). The energiesof activation for labelled-water exchange in normal and deadroots under these conditions were respectively 15.5 and 5.3kcal/mole. Moreover, the results of the efflux experiments onPMA-treated roots were considered to indicate that this inhibitorproduces an alteration in some structural aspect of the rate-controllingmembranes. 相似文献
7.
KANAMORI-FUKUDA IKUKO; ASHIHARA HIROSHI; KOMAMINE ATSUSHI 《Journal of experimental botany》1981,32(1):69-78
Marked changes in the activity of the de novoand salvage pathways of pyrimidine biosynthesisduring growth of Vinca rosea cells in a batch suspension culturewere observed. The activity of these pathways was investigated by determiningthe contribution of 14C of [2-14Cluracil, 12-14Cluridine. and[6-14Clorotate to the cell constituents and by measuring theactivity of the several enzymes of these pathways. During the lag phase of the culture, uracil- anduridine-salvage pathways made the predominantcontribution to nucleotide biosynthesis, but, following theinitiation of cell division, the de novo pathwayfor nucleotide biosynthesis operated appreciably. These results suggest that nucleotide synthesis during cellgrowth in a suspension culture can be divided into two stages:a turnover stage, during the lag phase of cellgrowth, and a true biosynthetic stage, which isinitiated in the cell division phase. 相似文献
8.
A simple expression has been derived to predict the rate ofnet K uptake into exponentially growing plants of Lemna minor.Net uptake predictions are in good quantitative agreement withmeasurements of steady-state K influx, indicatingthat, in the steady state, K movements in theplant are essentially undirectional and that efflux is small.This close matching of inward K movement to the demands of theexpanding tissue is temporarily disturbed if plants are transferredto media of different K status. Uptake rates in the step-upare initially enhanced and then fall gradually towards a newsteady-state rate. In contrast, the step-downcauses an initial depression of uptake and then rates increasegradually towards the new steady-state rate. Itis argued that these changes in uptake rates are associatedwith alterations in the cytoplasmic K content. 相似文献
9.
《Journal of experimental botany》1977,28(6):1247
Effects of coupled solute and water flow in plant roots withspecial reference to Brouwer's experiment. Edwin L. Fiscus. p. 71 Abstract: Line 3 delete interval insertinternal. p. 73 Materials and Methods: line 6: delete diversion insert division line 9 equation should read Jv=Lp PRT(C0C1). 74 Last line of figure legend: 101 should read 1011. 75 Line 11: delete seems insert seem. le 1 column heading106 should read 1011. 77 delete ...membrane in series of... insert membranein series or... Delete final paragraph. 相似文献
10.
The development of taurine uptake into the unicellular greenalga Chlorella fusca 211-8b was characterized as a specificresponse to either nitrate or sulphate limitation. Taurine transportunder nitrogen starvation was stimulated by low pH and showeda biphasic kinetics with Km-values of 1.1 x 103 mol dm3and 1.0 x 102 mol dm3. Uptake was substantiallyinhibited by all - and ß-amino acids tested, whereassulphonate analogues failed to diminish taurine accumulation.Thus, uptake seemed to be mediated by a general aminoacid permease, unable to discriminate between carboxyland sulphonyl groups. However, Chlorella fusca could not catabolizethis unusual ß-amino acid and mobilize the amino-boundnitrogen for growth. Only a small group of -amino acids supportedthe growth of Chlorella fusca as an efficient nitrogen source. Key words: Taurine uptake, nitrogen starvation, amino acid uptake, Chlorella fusca. 相似文献
11.
Nitrogen Utilization in N-limited Barley During Vegetative and Generative Growth: IV. TRANSLOCATION AND REMOBILIZATION OF NITROGEN 总被引:1,自引:0,他引:1
Barley (Hordeum vulgare L., cvs Golf and Laevigatum) was grownunder nitrogen limitation in solution culture until near maturity.Three different nitrogen addition regimes were used: in theHN culture, the relative rate of nitrate-N additionwas 0·08 d1 until day 48 and then stepwise decreasedto, finally, 0·005 d1 during late grain-filling;the LN culture received 45% of the nitrogen addedin HN; the CN culture was maintained at RA 0·0375d1 throughout growth. At four different growth stages(vegetative,anthesis, and twice during grain-filling), 15N-nitrate was fedto the plants. In some cases (split root cultures),label was fed only to one-half of the root system. These wereharvested directly after labelling, whereas standardcultured plants were harvested at termination of theexperiment (day 148). Absorption of added nitrate was nearlycomplete in the HN and LN cultures, and translocation of nitrogenwithin the plants could thus be studied independently of differencesin nitrate absorption. Cycling of nitrogen absorbed by vegetativeplants accounted for up to 50% of the nitrogen recovered inthe roots. The sink strength of the roots for cycling nitrogen,however, declined during post-anthesis growth, and net lossof nitrogen from both roots and vegetative shoot tissue occurredconcomitantly with incorporation of labelled 15N-nitrogen. Thenitrogen of the vegetative shoot tissue was substantially lesslabelled than the nitrogen entering the ears, indicating thattranslocation of recently absorbed nitrogen to ears occurs withminor prior exchange with the bulk nitrogen of shoots. In caseswhere the sink strength of the ears was weak, as in LN-culturedLaevigatum (due to high frequency of sterile flowers) and inCN-cultured Golf, nitrogen translocated from roots appearedto be incorporated into the vegetative shoot tissue. There werealso indications that a fraction of the remobilized nitrogenwas actually lost from the plants in these cases. It is concludedthat the root remains efficient in translocation of nitrogento the aerial parts throughout ontogeny and that nitrogen takenup during grainfilling is preferentially directly translocatedto the developing grains. The further translocation of nitrogenreceived by vegetative shoot parts to ears appears mainly relatedto the potential of the ear to accumulate nitrogen. Nitrogenabsorbed/remobilized in excess of the sink strength of the earsis either invested in continued shoot growth, or is irreversiblylost from the plants. Key words: Barley, 15N-labelling, post-anthesis, remobilization, translocation 相似文献
12.
Particle-bound phytochrome: Differential pigment release by surfactants, ribonuclease and phospholipase C 总被引:1,自引:0,他引:1
Surfactants and hydrolytic enzymes were used to probe the natureof the constituents) to which phytochrome binds in paniculatefractions from red-irradiated Cucurbita. [14C]-choline and [3H]-uridinepre-labelled tissue was used to monitor the release of phospholipidsand RNA by these agents. Ribonuclease (RNase) digestion of 20,000xgpellets eliminates both the phytochrome and ribonucleoprotein(RNP) which cosediment at 31S. Little [14C]-choline occurs inthe 31S fraction and the amount is not changed by RNase digestion.This is further evidence that phytochrome binds directly tothe RNP in the 31S fraction rather than to any membranous materialpresent. The distribution profile of the RNA in a second ( =heavy)phytochrome fraction does not correlate with that of the pigment.This suggests that the phytochrome in this fraction is not boundto RNP. The RNA is of ribosomal origin but much less degradedthan that of the 31S RNP and is resistant to RNase digestion.Phospholipase C releases>80% of the [14C]-choline from theheavy fraction without freeing phytochrome. Thisindicates that the pigment does not bind to the polar head groupsof the membrane phospholipids present. Low concentrations ofdeoxycholate dissociate phytochrome from this fraction withoutreleasing substantial quantities of integral membrane proteinsor phospholipids. Some RNP is dislodged by the surfactant butthe phytochrome and RNP are not released as a complex. The datasuggest that the pigment in the heavy fractionmay be loosely bound to a protein constituent rather than toRNP or polar phospholipids.
1This work was done while on sabbatical leave from the WeizmannInstitute of Science, Rehovot, Israel. (Received April 1, 1976; ) 相似文献
13.
Young plants of Banksia hookeriana were grown in acid-washedsand with adequate phosphate and water supply, and a proportionwere inoculated with Phytophthora cinnamomi. There were no majordifferences in growth between uninoculated and infected plants,but there was a large increase in uptake of 32P with increasingroot disease. In healthy plants 32P uptake was greatest in youngleaf tissue, but in diseased plants labelled phosphate was directedmore towards older leaves where the activity was almost twicethat of young leaves. Enhanced uptake with disease was ascribed to possible blockageof the message or signal of phosphatetranslocation from shoot to root, such that the diseased rootincorrectly treated the shoot as P deficient and increased Puptake. Key words: Banksia hookeriana, Proteaceae, 32P uptake, Phytophthora cinnamomi 相似文献
14.
SINGH N; SINGH S N; SRIVASTAVA K; YUNUS M; AHMAD K. J; SHARMA S C.; SHARGA A N 《Annals of botany》1990,65(1):41-44
Five Gladiolus cultivars, namely Aldebaran, BrightEye, Illusion, Manisha andManmohan, were exposed to 1 and 2 µg l1sulphur dioxide to test their relative-sensitivity toleranceto the pollutant Plants were fumigated experimentally for 2h daily Foliar injury symptoms were observed first in Manishafollowed by Aldebaran and Illusionat the higher dose Photosynthetic pigments and leaf extractpH were significantly decreased, particularly in Manishaand Illusion Overall disturbances in the plantmetabolism due to SO2 treatment led to retarded growth of plants,as evident from decreased shoot length and phytomass valuesThe order of sensitivity of the five Gladiolus cultivars toSO2 was as follows, with the greatest first Manisha, Illusion,Aldebaran, Bright Eye, Manmohan Cultivars, Gladiolus, sensitivity, sulphur dioxide, tolerance 相似文献
15.
Algal 14C and total carbon metabolisms. 1. Models to account for the physiological processes of respiration and recycling 总被引:1,自引:0,他引:1
A consistent set of equations has been written to describe thenet rate of algal 14CO2 uptake (and where appropriate respirationand photosynthesis) which take into account separately complicationsdue to respiration of the labelled photosynthetic products andthe recycling of respiratory CO2. Written specifically intothe equations is the concept of new and oldcarbon, the coefficient q is used in the respiration model toallow for the differential respiration of organic material fromthe new and old carbon pools. Analyticalintegrals have been found for respiration and recycling models,and the behaviour of the models studied over periods of 12 h(i.e. up to 70% of the intrinsic generation time). The rateconstant for respiration has a greater effect on the behaviourof the recycling than the respiration model. Over short timecourses (up to 30% of the intrinsic generation time), the effectsof respiration and recycling on net 14CO2 uptake are quite distinct,especially at high P/R ratios, and not complicated by assumptionsover the value of q. Although the value of q will have a time-dependentsecondary effect on the modelled total carbon-specific respirationrate, this was found not to give rise to major problems of interpretation.Beyond 50% of the intrinsic generation time, the separate treatmentof respiration and recycling in the models becomes less satisfactory.It was concluded that the present equations, which are not constrainedby mass balance considerations, would not be appropriate fora model that combines the two processes. The pattern of recyclingat low P/R values is identified as one of the major uncertaintiesin producing models of 14C uptake. The effect of the releaseof dissolved organic material can be anticipated in a generalway. The models have been used to define an experimental strategyto establish the separate effects of respiration and recyclingon the time course of net 14C uptake. The initial rates givethe clearest resolution of the two processes and it would appearthat with photosynthetic rates in the region of 1 day1,incubation periods up to 36 h would be suitable to determinethe importance of recycling in controlling net 14C uptake. Withthe present models, only in the absence of recycling could theeffect of respiration be studied and the value of q established. 相似文献
16.
Feeding behavior of the brittle star Ophiura ophiura includesorienting posture, orienting movements, arm walking,changing the direction of walking arm coilingand ingestion. All sequential behavior patterns were releasedor enhanced by single low-molecular-weight compounds. Stimuliwhich released walking behavior at high concentrations(104 M) in all the test animals are listed in decreasingorder of sensitivity: sarcosine, glycine, urea, L-valine, L-leucine,L-methionine, L-homocysteine, L-norvaline, L-norleucine, L-threonine,L-serine, S-methyl-L-cysteine, L-proline. Threshold values forsingle amino acids were as much as 100 times different in differentindividuals and ranged from 3 x 109 to 3 x 107M for the most effective stimulus, sarcosine, and from 106to 104 M for proline. Above 105 M, only L-prolineregularly released a second behavior pattern, the arm coilingresponse, which temporarily inhibited the walkingbehavior. Behavioral thresholds for the walkingbehavior for L(+)-lactate and L-alanine were higher than thosefor the orienting movements. Thyoglycolic acid and ß-alaninereleased tube feet walking, which is not part of the feedingbehavior. Structureactivity comparisons were studied at estimated105 M concentrations. Gycline, sarcosine, L-valine, L-norvaline,L-leucine, L-isoleucine, DL-norleucine and DL-homocysteine releasedarm walking behavior in more than 75% of all thetests. With the exceptions of S-methyl-and S-ethyl-cysteine,and glycine methylester, derivatives of amino acids were noteffective behavioral stimuli in Ophiura ophiura. L-Isomers ofvaline and leucine regularly stimulated the walkingbehavior while their D-isomers were effective in some testsand ineffective in others. Acetylcholine iodide, acetyl-ß-methylcholine chloride and choline phosphate chloride regularly releasedwalking behavior at concentrations above 105M. 相似文献
17.
The Use of Agar Nutrient Solution to Simulate Lack of Convection in Waterlogged Soils 总被引:12,自引:2,他引:12
Agar at 0.1% in nutrient solution (stagnant solution)was used to prevent turbulence (convection), thus simulatingthe slow gas movements which occur in waterlogged soils. Wheat,aged between 6 and 16 d at the start of the treatment, was usedto test plant growth and development in this stagnant solutionfor 815 d. K-MES buffer at 5 mol m-3was used to retainthe pH of the rhizosphere in the stagnant solution at pH 6.5. The prevention of convection reduced dissolved oxygen concentrationsin the bulk solution from 0.275 to below 0.05 mol m-3after 1d, while ethylene accumulated over 10 d to 6.5x10-6m3m-3(ppm). Aerenchyma of nodal roots grown in stagnant solution comprised22% of the cross sectional area of the root 50 mm behind theroot tip; this was similar to values recorded earlier for nodalroots of wheat in waterlogged soil and contrasts with 7.6% forroots in non-flushed solution without agar (referred to in thispaper as semi-stagnant solution) and 2.4% in N2-flushedsolution. Increases in dry weight and numbers of nodal roots with timewere larger for stagnant and N2-flushed, than for semi-stagnantor aerated solution. In contrast, seminal roots did not growin stagnant solution, while seminal roots in N2-flushed solutiongrew much less than in semi-stagnant or aerated solution. In the stagnant solution, relatively high concentrations ofN, K and P were required to avoid limitations in mineral uptakeinto the roots, due to the long diffusion pathway from the bulksolution imposed by the lack of convection. Nevertheless, ourdata show that the slow growth imposed by the lack of convectionwas due to factors other than low mineral nutrition. The mostlikely cause was the change in the dissolved gas compositionof the root media, particularly of the rhizosphere. In conclusion, in terms of anatomy and morphology the rootsgrown in the stagnant solution more closely resembled thosefrom waterlogged soil than did those grown in either semi-stagnantor N2-flushed solution. Triticum aestivum; wheat; waterlogging; lack of convection; aerenchyma; root development; nutrient uptake 相似文献
18.
The partition of 14C labelled current assimilates to root insimulated swards of Lolium perenne cv. S24 was measured duringthe transition from vegetative growth in autumn to reproductivegrowth in spring under close to natural conditions of lightand temperature. Assimilate partitioning was also measured inestablished swards cut three times during thegrowing season and in vegetative seedling swardsgrowing in autumn and in spring. All measurements were madewhen the swards had achieved more than 90 per cent light interception,and all swards were abundantly supplied with water and mineralnutrients. During autumn there was a gradual decrease in the proportionof assimilates partitioned to the roots in both the establishedand the seedling swards. In the established swards,partition to roots was low over winter, increased during earlyspring, but decreased dramatically, later in the spring, whenstem elongation began. In contrast, in the unvernalized vegatativeseedling swards in spring, partition to roots remained high. The seasonal pattern of assimilate partitioning is consideredin relation to changes in the natural environment and the rateat which the crop fixed carbon in photosynthesis. A decreasein the proportion of assimilates partitioned to roots duringlate spring was significant in increasing the production ofshoot at that time but seasonal differences in partition contributedvery little to the marked differences in shoot growth betweenthe spring and autumn crop. Lolium perenne L., perennial ryegrass, partition of assimilates, flowering 相似文献
19.
The effects of the foliar application of phytocidal concentrationsof 2-methyl-4-chlorophenoxyacetic acid (MCPA) on change in totaldry weight, and in available carbohydrate (starch,total and reducing sugars), totalnitrogen, phosphorus, potassium, calcium, and magnesium of topsand roots of tomato plants have been followed over a periodof 14 days following spraying. There were two main treatmentsnutrient(nutrient supply to roots continued after spraying) and water(distilled water only supplied to roots after spraying) andwater (distilled water only supplied to rootsafter spraying)the sub-treatments consisting of MCPAversus no-MCPA for each of the main treatments.Twelve different times of sampling were used. In analysing the present data, the quantity residualdry weight (total dry weight less available carbohydrate),which was originally introduced by Mason and Maskell as a basisof reference for analyses of plant organs in short-period experimentsnot involving appreciable growth, has been used as an estimateof the permanent structure of plant growth. This new use ofthe residual dry weight basis has brought outimportant features which were obscured when the data were leftin their primary form (as percentages of total dry weight oramounts per plant). Growth, as measured by increase in residual dry weight,was greatly inhibited by 2-methyl-4-chlorophenoxyacetic acidshortly after spraying, in both the presence and the absenceof nutrient. In the presence of 2-methyl-4-chlorophenoxyacetic acid, netassimilation rate (estimated as rate of increase in total dryweight per gram residual dry weight of the tops)was greatly diminished while uptake of total nitrogen and ofP2O5 (estimated as increase in total nitrogen or of P2O5 ofthe whole plant per day per 1 g. residual dry weightof the roots) appeared to undergo a similar but much smallerdiminution. It seemed probable, however, that in the presenceof MCPA a larger proportion of the carbohydrate actually formedwas utilized for synthesis of aminoacids and protein. In the plant as a whole there was no evidence of actual depletionof available carbohydrate as a result of MCPAtreatment, this fraction showing a steady increase in all treatmentsthroughout the experiment. The rate of increase was, however,much reduced by MCPA treatment. The tops presentedmuch the same picture as the whole plant, but for the rootsthe situation was quite different. While the roots of the no-MCPAplants and also of the MCPA-water plants showeda steady increase in available carbohydrate, those of the MCPA-nutrientplants rose only very slightly (from the initial value of 8mg. per plant to about 10 mg.) during the first 2 days, andthen in the next 2 days declined to a value (about 6 mg.) belowthe initial and remained at this low level for the rest of theexperiment. It is suggested that the phytocidal effect of 2-methyl-4-chlorophenoxyaceticacid in the presence of nutrient may be due to depletion ofthe available carbohydrate supplies in the roots,which is shown to be brought about, in part, by reduced transportfrom the tops, and partly by the relatively greater utilizationof the carbohydrate present. These results offer an explanationfor the facts that plants showing vigorous growth are more easilykilled by MCPA and that perennial plants, particularly thosewith storage tissues in their roots, are more resistant. Further,they suggest the useful practical application that MCPA treatmentshould be given when the carbohydrate reserves of the rootsare at a minimum. For perennial plants, conditions might beexpected to be optimal for the application of MCPA in late spring,at a time when the first flush of growth is slowingdown and before any appreciable new reserves of carbohydratehave been accumulated. It was also shown that 2-methyl-4-chlorophenoxyacetic acid preventedthe net synthesis of starch, but still permitted an appreciablenet formation of sucrose. 2-methyl-4-chlorophenoxyacetic acid appeared to have no effecton the uptake of potassium, calcium, or of magnesium. The lackof effect on potassium is contrasted with the previous observationby Rhodes, Templeman, and Thruston (1950) that sub-lethal concentrationsof MCPA, applied over a relatively long period to the rootsof tomato plants, specifically depressed the uptake of potassium. 相似文献
20.
Diurnal variation in the simultaneous uptake and 'sink' allocation of NH4+ and NO3- by Lolium perenne in flowing solution culture 总被引:2,自引:0,他引:2
Ourry Alain; Macduff James H.; Prudhomme Marie-Pascale; Boucaud Jean 《Journal of experimental botany》1996,47(12):1853-1863
Perennial ryegrass (Lolium perenne L.) was grown in flowingsolution culture under artificial illumination with a 10 h lightperiod. The diurnal fluctuations in the net uptake of and from a 20 mmol m3 NH4NO3 supply were measured (i) fromthe amounts of these ions supplied automatically to maintainconcentrations in solution, and (ii) by 15N pulse-labellingthroughout the diurnal cycle. Diurnal variation in leaf extension,translocation and allocation of assimilated C (14CO2 pulse-labelling)and N (15N pulse and steadystate labelling) were also followed.The apparent sinkstrength of different organsfor recently assimilated C and N was calculated from the concentrationof label recovered in the tissues. Ammonium and showed qualitatively similar diurnal patterns ofnet uptake, with minimum and maximum rates, respectively, atthe start and end of the photoperiod; but uptake showed a proportionately steeper declineduring the dark period. This trend was mirrored by the decreasein translocation of N from roots to shoots during the dark,concurrent with an increase in the relative allocation of -N to expanding leaves and young tillers,and in -N to older expanded leaves. Overall the apparent sink-strength ofexpanding leaves for N declined during the dark period. Pulse-chasesof 14CO2 fed to the youngest fully expanded leaf at the startand end of the photoperiod showed that translocation of 14Cto the roots continued throughout the dark period, but thatthe apparent rate was halved after 9 h of darkness. The resultswere interpreted as contrary to the carbohydrate supplylimitation hypothesis for the dark-related decline inN uptake, but compatible with regulation by sink-strengthfor N. Key words: Nitrate, ammonium, diurnal variation, perennial ryegrass, translocation 相似文献