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1.
Uptake and Transport of Calcium and the Possible Causes of Blossom-end Rot in Tomato 总被引:7,自引:1,他引:6
HO L. C.; BELDA R.; BROWN M.; ANDREWS J.; ADAMS P 《Journal of experimental botany》1993,44(2):509-518
The possible causes of blossom-end rot (BER) in tomato fruitwere investigated by comparing the uptake of calcium by theroots, the distribution of 45Ca within the fruit and the vascularbundle network in the fruit of susceptible cultivars (Calypsoand Spectra) with those of a less susceptible cultivar (Counter)grown in a range of salinities (electrical conductivity of 5,10 and 15 mS cm1). The daily calcium uptake rates at5 mS cm1 as estimated from the xylem exudation of thedecapitated stem stump in young plants of Calypso and old plantsof Spectra, were lower than that of Counter. The uptake of 45Caby, and the transport to, the distal part of the detached fruitof susceptible cultivars, especially Calypso, were less thanin Counter at 10 mS cm1. The number of vascular bundlesin both proximal and distal fruit tissues was similar in allcultivars and was only slightly reduced by salinity. However,the number of bundles containing lignified xylem vessels, asdetected by safranin staining, was reduced substantially bysalinity, particularly in Calypso. The estimated area of thefruit tissue served by individual xylem bundles in the BER susceptiblefruit grown at high salinity was greater than in Counter. Theincidence of BER in all trusses was linearly related to theproduct of average daily irradiance and daily temperature throughoutthe year. Temperature appears to be the major environmentalfactor which induces BER, regardless of cultivars and salinitytreatment. The most likely causes of BER in susceptible cultivarsare the interactions of (a) light and temperature on fruit enlargement,(b) inadequate xylem tissue development in the fruit and (c)competition between leaves and fruit for the available Ca. Key words: Lycopersicon esculentum, calcium transport, susceptibility to blossom-end rot, root exudation, xylem 相似文献
2.
Translocation of Calcium in Relation to Tomato Fruit Growth 总被引:5,自引:1,他引:4
Regulation of the uptake and distribution of calcium in thetomato plant was investigated in plants grown in recirculatingnutrient solutions at electrical conductivities of 2,7,12 and17 millisiemens (mS). Despite an increased calcium content inthe nutrient solution at high conductivity (717 mS),the accumulation of calcium by fruit was progressively reducedby increasing salinity, particularly in the distal half. Theincidence of blossom-end rot in fruit (BER) also increased withsalinity. The uptake of water and 45Ca by plants was substantially reducedin the high salinity treatment (17 mS) and, to a lesser extent,by high relative humidity (90 per cent r.h. at 20 °C). Further,the translocation of 45Ca from roots to shoots was reduced byhigh salinity, while the percentage distribution of 45Ca tothe apex was reduced by high humidity. Only approx. 2 per centof the 45Ca taken up by a plant was imported by the truss. The uptake of 45Ca and its distribution among pedicel, calyxand berry by detached fruit in 24 h showed that fruit from highsalinity plants had a reduced uptake and a lower accumulationof 45 Ca in the berry than in the calyx. In addition, plants grown at high conductivity had a lower rateof xylem sap exudation from decapitated plants. The fruit ofthese plants had a smaller xylem cross-sectional area in thefruit pedicel and a smaller calyx than those of the low conductivitytreatment. Calcium, translocation, tomato, fruit, blossom-end rot 相似文献
3.
Environmental Effects on the Diurnal Accumulation of 45Ca by Young Fruit and Leaves of Tomato Plants 总被引:1,自引:0,他引:1
Diurnal uptake and distribution of 45Ca in young fruiting tomatoplants were assessed 12 or 24 h after 45Ca was applied to thenutrient solution at the beginning of either the light (12 h)or the dark (12 h) period. During the experiment, the salinityof the nutrient solution (measured as electrical conductivity,EC) was either 2·5 or 17 mS cm1 and the relativehumidity (measured as vapour pressure deficit, VPD) was either0·2 or 0·6 kPa The uptake of 45Ca by a tomato plant over 12 h was higher inthe light than in the dark but the difference was less at lowhumidity. More 45Ca was transported from the roots to the shootin the light than in the dark. More than half of the 45Ca inthe shoot was accumulated by the stem; the proportion of 45Cain the stem was greater in the dark and was further enhancedby high humidity to more than 80% of the 45Ca in the shoot.The accumulation of 45Ca by the fruit truss in the dark wasgreater than in the light in all experimental conditions. Underlow humidity the accumulation of 45Ca by young leaves was similarin both light and dark. In high humidity there was considerablyless accumulation of 45Ca by the young leaves in the dark The uptake of 45Ca continued over 24 h but the transport of45Ca to individual organs in the second 12 h period was affectedby both light and humidity. Some of the 45Ca accumulated byyoung leaves and fruit in the second period appears to havebeen derived from 45Ca released from the xylem wall along thetransport pathway in the stem The roles of root pressure and transpiration in the diurnalaccumulation of calcium in young fruit and leaves are discussed Calcium, diurnal translocation, tomato, young fruit and leaves 相似文献
4.
Regulation of the Partitioning of Dry Matter and Calcium in Cucumber in Relation to Fruit Growth and Salinity 总被引:1,自引:0,他引:1
The regulation of the partitioning of dry matter and calciumin relation to fruit growth was investigated in cucumber plantsgrown in the salinity range of 3-8 mS cm-1 in NFT (NutrientFilm Culture), with or without a fruit pruning treatment. Thedry weight gain of the plants was proportional to the outdoorintegral irradiance, with a common daily rate of 1 g MJ-1 m-2in two crops grown under summer (18 MJ m-2 d-1) and autumn (7MJ m-2 d-1) conditions. Within the salinity range studied, thereduction of plant dry weight was 9% mS-1 cm-1. However, fruitdry weight was only reduced at salinities above 5·5 mScm-1, although the daily dry matter accumulation by fruit, asa percentage of total dry matter accumulation, was increased.Salinity reduced the dry matter accumulation in the young shootproportionally more than in the fruit. Although the total plantCa content was reduced by 13% mS-1 cm-1, the Ca content of theyoung shoot was reduced by 16·6%, compared to 11% inthe fruit. Pruning fruit reduced neither plant dry weight norCa uptake. The growth of the remaining fruit, and to a lesserdegree of the young shoot, accounted for all surplus assimilates.Thus, fruit were the dominant sinks for assimilates whilst themature leaves were the strongest sinks for Ca. Nevertheless,the fruit sustained the capacity to import Ca better than theyoung shoot, when supplies of both assimilates and Ca were reducedby high salinity.Copyright 1994, 1999 Academic Press Cucumber, Cucumis sativus L., salinity, fruit pruning, dry matter and calcium 相似文献
5.
Simultaneous measurement of export from leaves and import tofruits were made on tomato plants reduced to one fully expandedleaf and one fruit. Experimental leaves were exposed to sixlight flux densities (0.5100 W m2) for 24 h whilerapidly growing fruits were kept in the dark at 22 °C. The rates of export of assimilate from these leaves varied from70 to 120 mg C leaf1 day1 corresponding with ratesof carbon fixation from 3 to 290 mg C leaf1 day1.Export from leaves with the lowest carbon fixation rates weremaintained by a loss of up to one-sixth of their initial carbon.In contrast, leaves with the highest carbon fixation rates exportedonly half the newly fixed carbon. The rates of import of assimilate to similar-sized fruits (c.16 cm3) were between 80 and 110 mg C fr1 day1but differed from the export rates of the source leaves. Thespecific growth rates and the specific respiration rates ofthe fruits were related to their initial carbon content at thebeginning of the experiment. Thus, over 24 h, the rate of importwas predetermined by the developmental stage of the fruit unalteredby the rate of current carbon fixation in the source leaf. Translocationof assimilate was regulated by sink demand under both source-and sink-limiting conditions in this short-term situation. The dynamic relationship between assimilate production in leavesand its utilization in fruits is discussed together with therole of sucrose concentration in these organs in regulatingtransport. Lycopersicon esculentumL, tomato assimilate translocation, source-sink relationships 相似文献
6.
Photosynthetic 14C fixation by Characean cells in solutionsof high pH containing NaH14CO3 gave a measure of the abilityof these cells to take up bicarbonate (H14CO3). Whereascells of Nitella translucens from plants collected and thenstored in the laboratory absorbed bicarbonate at 11.5µµmoles cm2 sec1, rates of 38µµmoles cm2 sec1 were obtained withN. translucens cells from plants grown in the laboratory. Influxesof 56 µµmoles cm2 sec1 wereobtained with Chara australis, 38 µµmolescm2 sec1 with Nitellopsis obtusa, and 15µµmoles cm2 sec1 with Tolypella intricata.It is considered that these influxes represent the activityof a bicarbonate pump, which may be an electrogenic process. In solutions of lower pH, H14CO3 uptake would be maskedby rapid diffusion of 14CO2 into the cells: the four Characeanspecies fixed 14CO2 at maximum rates of 3040 µµmolescm2 sec1 (at 21° C). 相似文献
7.
Influence of the Form of Nitrogen Supply on Root Uptake and Translocation of Cations in the Xylem Exudate of Maize (Zea mays L) 总被引:1,自引:0,他引:1
Concentrations of inorganic cations are often lower in plantssupplied with NH4+ as compared with NO3. To examine whetherthis is attributable to impaired root uptake of cations or lowerinternal demand, the rates of uptake and translocation of K,Mg, and Ca were compared in maize plants (Zea mays L.) withdifferent growth-related nutrient demands. Plants were grownin nutrient solution with either 1·0 mol m3 NO3or NH4+ and the shoot growth rate per unit weight of roots wasmodified by varying the temperature of the shoot base (SBT)including the apical shoot meristem. The shoot growth rate per unit weight of roots, which was takenas the parameter for the nutrient demand imposed on the rootsystem, was markedly lower at 12°C than at 24°C SBT.As a consequence of the lower nutrient demand at 12°C SBT,uptake rates of NO3 and NH4+ declined by more than 50%Compared with NO3 supply, NH4+ nutrition depressed theconcentrations of K and particularly of Ca in the shoot, bothin plants with high and with low nutrient demand. This indicatesa control of cation concentration by internal demand ratherthan by uptake capacity of the roots. Translocation rates of K, Mg and Ca in the xylem exudate werelower in NH4+- than in NO3-fed plants. Net accumulationrates of Ca in the shoot were also decreased, whereas net accumulationrates of K in the shoot were even higher in NH4+-fed plants.It is concluded that reduced cation concentrations in the xylemsap of plants supplied with NH4+ are due to the lower demandof cations for charge balance. The lower K translocation tothe shoot is compensated by reduced retranslocation to the roots.For Ca, in contrast, decreased translocation rates in NH4+-fedplants result in lower shoot concentration. Key words: Nitrogen form, cation nutrition, charge balance, xylem exudate, recirculation 相似文献
8.
The water-mould fungus Phytophthora cinnamomi Rands causes drought-likesymptoms on many hosts, and yet the mechanisms by which infectionleads to wilting are not fully understood. This is the firststudy to describe in detail changes in soil water around theroot with infection. Computer-assisted tomography (CAT) wasused with Lupinus angustifolius L. cv. Yandee to examine drawdowns(removal of soil water) around a central root infected by P.cinnamomi in a white sand. No growth differences in roots or shoots were found betweenhealthy and diseased plants during the 8 d of the experiment.However,drawdowns failed at high levels of inoculum (816 /Pc-infectedmillet seeds/plant) by 8 d. Water contents in pots with uninfectedplants were in the range 0·090·12 cm3 watercm3 soil in the centre of the pot, while water contentsin pots with infected plants at 16 millet seeds applied werein the range of 0·160·19 cm3 water cm3soil in the centre of the pot. A higher transpirational demand produced lower soil water contentsnear the root but this effect was confounded with infection:disease was more pronounced with higher transpirational demand,and disease led to an increase in water content. Key words: Root disease, Phytophthora cinnamomi, water uptake, soil-root interface, computer-assisted tomography 相似文献
9.
Diurnal regulation of NO-3 uptake in soybean plants IV. Dependence on current photosynthesis and sugar availability to the roots 总被引:1,自引:0,他引:1
Delhon Patricia; Gojon Alain; Tillard Pascal; Passama Lucien 《Journal of experimental botany》1996,47(7):893-900
The short-term dependence of NO3 uptake upon photosynthesisand sugar supply to the roots of soybean plants was investigatedin a series of experiments where CO2 availability, light intensityor conduction of phloem sap to the roots were severely limited.Removal of CO2 from the atmosphere or girdling of the stem equallyprevented the stimulation of NO3 uptake when plants weretransferred from darkness to the light. The effect of thesetwo treatments can be reversed by CO2 re-supply or by additionof 10 mM glucose in the nutrient solution, respectively. Glucosewas also more effective in stimulating NO3 uptake byintact plants in darkness than in light. Collectively, theseobservations are interpreted as evidence that the diurnal changesin NO3 uptake are due to decreased phloem transport ofphotosynthates in darkness. Accordingly, the magnitude of thesechanges was much dependent on starch accumulation in the leavesat the end of the photo-period. Shading the plants lowered thisaccumulation, and resulted in an amplification of the diurnalchanges in NO3 uptake. These results are discussed inconnection with the hypothesis that the carbon-dependent plasticityof the night/day ratio of NO3 uptake is an importantfeature of the co-ordination of the acquisition of N and C bythe plant. Key words: Glycine max, light/dark cycle, NO3 uptake, C and N acquisition 相似文献
10.
A semi-closed system to label with 14C and trace photoassimilatesunder steady state conditions is described. It was used to elucidatethe effects of night temperature on the carbon budget of tomato The third leaf kept at 25 °C in 8 h light of 36 W m1(PAR) assimilated 13·77 mg C . d1. By the endof the photoperiod, 46% of the carbon assimilate was exportedto the sinks, out of which 27% was respired and 19% was accumulatedin the sinks, respectively The plants were then kept in the dark for 16 h at 15, 20, 25and 30%C. The export in the night-time increased with nighttemperature, reaching 1827% of the carbon assimilated.Thus, the total export in a whole day amounted to 6372%of the carbon assimilated, out of which 35 and 42% were lostby respiration and 29 and 31% was accumulated in the sinks at15 and 30 °C, respectively. Thus, accumulation in the sinksdiffered little with night temperature, while that in the sourceleaf, and hence the total accumulation, decreased with increasingnight temperature The export started early in the morning and was much greaterin the light than in the dark. In addition, the day/night ratioof export was lower at higher night temperatures The percentage distribution of 14C-assimilates to the lowerparts decreased, while that to the upper parts increased withincreasing night temperature. The calculated respiratory lossin individual sinks seemed to correspond to the distributionpattern of 14C-assimilates Carbon budget, 14C, 14C steady state feeding, translocation, respiration, assimilate distribution, temperature, tomato 相似文献
11.
An analysis of the accumulation of water and dry matter in tomato fruit 总被引:24,自引:6,他引:18
Abstract Previously published data from tomato plants grown in nutrient solutions having one of three electrical conductivities (2, 12 and 17 mS cm?1) were analysed. The rate of water import into the fruit, and the proportion of this conducted by the xylem stream were calculated from the daily rates of transpiration and the net accumulation of water and calcium. The rate of water import decreased as the conductivity of the nutrient solution rose, the maximum daily import rates in the third week after pollination being 3.2, 3.0 and 1.8 g fruit?1 d?1 for fruit grown at 2, 12 and 17 mS cm?1, respectively. During fruit development, the proportion of water imported via the xylem fell from 8–15% to 1–2% at maturity. The principal source of water for tomato fruit growth was phloem sap. Based on the daily rates of net dry matter accumulation, respiration and phloem water import, the calculated dry matter concentration of the phloem sap declined from 7 to 3%, or from 12.5 to 7.8% during fruit development in low or high salinity, respectively. The similar dry matter accumulation of fruit grown at different salinities was due to changes in both volume and concentration of phloem sap. Potassium salts in tomato fruit were calculated lo have contributed –0.29, –0.48 and –0.58 MPa to total fruit osmotic potential in the 2, 12 and 17 mS cm?1 treatments, respectively, which accounted for 38% or 49% of the measured total osmotic potential of the 2 mS cm?1 or 17 mS cm?1 treatments. The contribution of hexoses to total fruit osmotic potential in the young fruit was from about –0.1 to –0.2 MPa at all salinities. The osmotic potential of tomato fruit is regulated more by potassium salts than by hexoses. 相似文献
12.
Effect of Abscisic Acid on Sorbitol Uptake in Growing Apple Fruits 总被引:11,自引:1,他引:10
Levels of abscisic acid (ABA) in the fruit flesh of developingapples (cv. Golden Delicious) were measured by electron capturegas chromatography. ABA content of the tissue, calculated ona fresh weight basis, decreased at a constant rate from 200µg g1 in young fruit to 10 µg g1 inolder fruit and then increased when the ripening process commenced.On a whole fruit basis, the ABA level increased during the initialphase of fruit growth, remained constant during the linear growthphase and increased again when fruits started to ripen. During fruit development the ABA content correlated with therate of sorbitol uptake, when measured after discs of fruittissue were incubated in [14C]sorbitol. Sorbitol uptake washigh during the initial growth phase and declined at a constantrate during fruit development. ABA present in the incubation medium stimulated sorbitol uptakeinto fruit tissue at concentrations higher than 108 M,whereas indolyl-3-acetic acid had no effect on uptake. When comparing sorbitol uptake in different zones of young fruit,it was found that uptake was higher in discs of outer fruitlayers than in discs from inner fruit zones. Key words: Pyrus malus, Apple, Abscisic acid, Sorbitol 相似文献
13.
Delhon Patricia; Gojon Alain; Tillard Pascal; Passama Lucien 《Journal of experimental botany》1995,46(10):1595-1602
Experiments were performed with soybean plants to test the hypothesisthat the inhibition of NO3 uptake in darkness is dueto feedback control by NO3 and/or Asn accumulating inthe roots. Xylem export of N compounds was shown to depend onwater flux in both excised root systems and 15N-labelled intactplants, suggesting that the shortage of transpiration in darknessmay be responsible for the retention of NO3 and Asn inthe roots. This was verified in experiments where the light/darkpattern of transpiration was modulated in intact plants by changingthe relative humidity of the atmosphere. Any decrease of transpirationat night was associated with a concurrent stimulation of NO3and Asn accumulations in the roots. However, the light/darkrhythmicity of NO3 uptake was only marginally affectedby these treatments, and thusappeared quite independent fromtranspiration and root NO3 or Asn levels. Typically,the maintainance of a constant transpiration during the day/nightcycle did not suppress the inhibition of NO3 uptake indarkness, whereas it almost prevented the dark increase in rootNO3 and Asn contents. These data strongly support theconclusion that the effect of light on NO3 uptake isnot mediated by changes in translocation and accumulation ofN compounds. Key words: Glycine max, light/dark, cycles, nitrate uptake, transpiration, transport of N compounds, accumulation of N compounds 相似文献
14.
The Regulation of Citric Acid Accumulation and Carbon Recycling During CAM in Ananas comosus 总被引:4,自引:0,他引:4
The carbon balance of shade-grown Ananas comosus was investigatedwith regard to nitrogen supply and responses to high PAR. Netdark CO2 uptake was reduced from 61.2 to 38.5 mmol CO2 m2in N limited (N) plants grown under low PAR (60 µmolm2 s1) and apparent photon yield declined from0.066 to 0.034 (mol 02.mol1 photon), although photosyntheticcapacities (measured under 5% CO2) were similar. Following transferfor 7 d to high PAR (600. µmol m2 s1), netCO2 uptake at night increased by 14% in +N plants, and daytimephotosynthetic capacity was higher, with a maximum value of7.8 µmol m2 s1. The magnitude of dark CO2 fixation during CAM was measured asdawndusk variations in leaf-sap titratable acidity (H+)and as the proportion of malic and citric acids. The contributionfrom re-fixation of respiratory CO2 recycling (measured as thedifference between net CO2 uptake and malic acid accumulation)varied with growth conditions, although it was generally lower(30%) than reported for other bromeliads. Assuming a stoichiometryof 2H+: malate and 3H+: citrate, there was a good agreementbetween titratable protons and enzymatically determined organicacids. The accumulation of citric acid was related to nitrogensupply and PAR regime, increasing from 7.0 mol m3 (+Nplants) to 18 mol m3 (N plants) when plants weretransferred to high PAR; malate: citrate ratios decreased from13.1 to 2.5 under these conditions. Under the low PAR regime, leaf-sap osmotic pressure increasedat night in proportion to malic acid accumulation. However,following the transfer to high PAR for 7 d, there was a muchgreater depletion of soluble sugars at night which correspondedto a decrease in leaf-sap osmotic pressure. Although a rolefor citric acid in CAM has not been properly defined, it appearsthat the accepted stoichiometry for CAM in terms of gas exchange,titratable acidity, malic acid and osmotic pressure may nothold for plants which accumulate citric acid. Key words: Ananas comosus, CAM, citric acid accumulation, carbon recycling 相似文献
15.
Investigations of Carbon Transport in Plants: II. THE EFFECTS OF LIGHT AND DARKNESS AND SINK ACTIVITY ON TRANSLOCATION 总被引:4,自引:0,他引:4
The use of 11C as a tracer has allowed repetitive measurementsof the speed of assimilate translocation to be made on singlemaize plants throughout prolonged periods of light and darkness.The speed appeared to double when the light was switched on.The time required to achieve a maximum speed, usually about3·5 cm min1, depended on the duration of the previousdark period. When the plant was transferred to darkness thespeed immediately decreased by about 20 per cent and continuedto decrease over the next 20 h to values of 0·5 to 0·9cm min1. The mean speed of translocation in tomato in the light, andother C3 plants, was usually about 1 cm min1. It wasreduced by 1530 per cent when the fruit was removed orcooled from 26 to 10°C. 相似文献
16.
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
17.
Lee, H. S. J. and Griffiths, H. 1987. Induction and repressionof CAM in Sedurn relephluni L. in response to photopcnod andwater stress.J. exp. Bot. 38: 834841. The introduction and repression of CAM in Sedurn telephiunmL, a temperate succulent, was investigated in watered, progressivelydrouglited and rewatered plants in growth chambers. Measurementswere made of water vapour and CO2 exchange, titratable acidity(TA) and xylem sap tension. Effects of photoperiod were alsostudied. CAM was induced by drought under long or short days,although when watered no CAM activity was expressed. C3-CAM intermediate plants were used for the investigation ofwater supply. Those which had received water and those drought-stressedboth displayed a similar nocturnal increase in TA, with a day-nightmaximum (H+) of 69 µmol g1 fr. wt. The wateredplants took up CO2 at a maximum rate of 2?2 µmol m2s1 only in the light period, while the droughted plantsshowed a maximum nocturnal CO2 uptake rate of 0?69 µmolm2 s1. Subsequently, as CAM was repressed, thewatered S. telephiwn displayed little variation in TA, withconstant levels at 42 µmol g1 fr. wt. (day 10).After 10 d of drought stress, the CAM characteristics of S.telephiurn were aLso affected, with reduced net CO2 uptake andH+. The transition between C3 and CAM in S. telephium can be describedas a progression in terms of the proportion of respiratory CO2which is recycled and refixed at night as malic acid, in comparisonwith net CO2 uptake. Recycling increased from 20% (day 1) to44% (day 10) as a result of the drought stress and was highin both the CAM-C3 stage (no net CO2 uptake at night) and alsoin the drought-stressed CAM stage (reduced net CO2 uptake atnight). The complete C3-CAM transition occurred in less than8 d, and the stages could be characterized by xylem sap tensionmeasurements: CAM = 0?50 MPa C3-CAM = 0?36 MPa C3 = 0?29 MPa. Key words: CAM, Sedum telephium L., recycling 相似文献
18.
Source--sink Relationships and Carbon Metabolism in Tomato Leaves 1. 14C Assimilate Compartmentation
Effects of the interaction between assimilate availability andsink demand on the metabolism of 14C assimilates in tomato leaveshave been examined in plants where the sourcesink relationshipof assimilates was simplified to one leaf and one fruit truss. During experimentation the source leaf was exposed to either80 or 20 W m2 (PAR), while the truss was either retainedor removed. Under these four source-sink conditions, a timecourse study was made on 14C assimilate distribution in thesource leaf over a period of 23 h after pulse feeding with 14CO2. While truss removal caused a temporary increase of 14C sucrosein leaves under both irradiances, the principal assimilatesaccumulated were starch and hexoses. Decreased 14C export followingtruss removal was observed within a day in well-illuminatedleaves but after 3 days in leaves under low light. The accumulationof 14C sucrose at the end of the light period was affected bytruss removal in high light leaves only 3 days later. These observations suggest that while the compartmentation ofnewly fixed assimilate was affected rapidly by the change ofsourcesink relationship, carbon export, as measured by14C loss, was affected only gradually. The possible effect of sucrose accumulation on photosynthesisis discussed. 相似文献
19.
Nodulated white clover plants (Trifolium repens L. cv. Huia)were grown as simulated swards for 71 d in flowing nutrientsolutions with roots at 11 C and shoots at 20/15 C, day/night,under natural illumination. Root temperatures were then changedto 3, 5, 7, 11, 13, 17 or 25 C and the total N2, fixation over21 d was measured in the absence of a supply mineral N. Alltreatments were subsequently supplied with 10 mmol m2NO2 in the flowing solutions for 14 d, and the relativeuptake of N by N2, fixation and NO3 uptake was compared.Net uptake of K+ was measured on a daily basis. Root temperature had little effect on root d. wt over the 35-dexperimental period, but shoot d. wt increased by a factor of3.5 between 3 and 25 C, with the sharpest increase occurringat 711 C. Shoot: root d. wt ratios increased from 25to 68 with increasing temperature at 725 C. N2-fixationper plant (in the absence of NO2 ) increased with roottemperature at 313C, but showed little change above13 C. The ratios of N2 fixation: NO2 uptake over 14d (mol N: mol N) were 0.470.77 at 37 C, 092154at 1117 C, and 046 at 25 C, reflecting the dominanceof NO3 uptake over N2 fixation at extremes of high andlow root temperature. The total uptake of N varied only slightlyat 1125 C (095110 mmol N plant1),the decline in N2 fixation as root temperature increased above11 C was compensated for by the increase in NO 3 uptake.The % N in shoot dry matter declined with decreasing root temperature,from 32% at 13 C to 15% at 3 C. In contrast, concentrationsof N expressed on a shoot water content basis showed a modestdecrease with increasing temperature, from 345 mol m3at 3 C to 290 mol m3 at 25 C. Trifolium repens L, white clover, root temperature, N2 fixation, potassium uptake, nitrate uptake, flowing solution culture 相似文献
20.
HAAG-KERWER ANGELA; FRANCO AUGUSTO C.; LUTTGE ULRICH 《Journal of experimental botany》1992,43(3):345-352
Gas exchange and organic acid accumulation of the C3-CAM intermediateClusia minor L. were investigated in response to various day/nighttemperatures and two light regimes (low and high PAR). For bothlight levels equal day/night temperatures between 20°C and30°C caused a typical C3 gas exchange pattern with all CO2uptake occurring during daylight hours. A day/ night temperatureof 15°C caused a negative CO2 balance over a 24 h periodfor low-PAR-grown plants while high-PAR-grown plants showeda CAM gas exchange pattern with most CO2 uptake taking placeduring the dark period. However, there was always a considerablenight-time accumulation of malic acid which increased when thenight-time temperature was lowered and had its maximum (54 mmolm2) at day/night temperature of 30/15°C. A significantamount of malic acid accumulation (23 mmol m2) in low-PAR-grownplants was observed only at 30/15°C. Recycling of respiratoryCO2 in terms of malic acid accumulation reached between 2·0and 21·5 mmol m2 for high-PAR-grown plants whilethere was no significant recycling for low-PAR-grown plants.Both low and high-PAR-grown plants showed considerable night-timeaccumulation of citric acid. Indeed under several temperatureregimes low-PAR-grown plants showed day/night changes in citricacid levels whereas malic acid levels remained approximatelyconstant or slightly decreased. It is hypothesized that lowand high-PAR-grown plants have different requirements for citrate.In high-PAR-grown plants, the breakdown of citrate preventsphotoinhibition by increasing internal CO2 levels, whereas inlow-PAR-grown plants the night-time accumulation of citric acidmay function as an energy and carbon saving mechanism. Key words: C. minor, C3, CAM, citric acid, light intensity 相似文献