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1.
White pine seedlings (Pinus strobus L.) were grown under highor low soil-moisture levels. The increase in the length andin the fresh weight of seedlings, respiration, photosynthesis,transpiration, translocation of photosynthate from shoots toroots, and bio-electric potentials between the tip and the baseof a stem were measured throughout the growing season from Aprilto October 1964. At both moisture levels the lowest translocation of recent photosynthatefrom shoots to roots occurred during early summer, or at thetime when the rate of root growth was the lowest and that ofthe shoot the highest. The specific activity of 14CO2, respiredby the shoots of such plants remained high throughout the 8h of the experiment, indicating a continuous utilization ofrecent photosynthate as a respiratory substrate. On the otherhand, early and late in the growing season, when translocationof recent photosynthate from shoots to roots and the rate ofroot growth were high, the specific activity of 14CO2, respiredby the shoots rapidly decreased during the 8 h of the experiment,indicating a drop in the utilization of recent photosynthateas respiratory substrate. The highest positive values for thepotential difference between the top and the base of the mainshoot also occurred in early summer or during the period ofhigh rates of transpiration per needle stomatal surface area.  相似文献   

2.
Populus plants were grown in a medium lacking calcium and exposedto 14CO2. In contrast to plants in the complete nutrient medium,the percentage amount of 14C-assimilates increased in the leavesof calcium-deficient plants and decreased in the stem and theroots. When plants were grown without potassium or magnesiumno differences in the amount of 14C-label occurred in comparisonwith plants in the complete nutrient medium. Translocation wasrecorded by microautoradiography. It was observed that considerableamounts of labelled photoassimilates were unloaded from thephloem in the middle part of the stem in plants of the completenutrient medium. In contrast, during calcium starvation 14C-labelwas restricted to the phloem of the stem. In addition, the concentrationsof magnesium and phosphorus showed a remarkable increase instem sieve tubes of calcium-deficient plants. When sieve tubesof source leaves from Populus, barley and maize were comparedwith those of sink leaves, the latter showed higher calciumconcentrations. The results suggest that calcium is a necessaryfactor in the regulation of phloem translocation. Key words: Calcium deficiency, phloem translocation, sieve element loading and unloading, X-ray microanalysis  相似文献   

3.
Gould, R. P. and Mansfield, T. A. 1988. Effects of sulphur dioxideand nitrogen dioxide on growth and translocation in winter wheat.—J. exp. Bot 39: 389–99 Winter wheat (Triticum aestivum L. cv. Avalon) was grown undersimulated autumn conditions for 4 weeks and exposed to a mixtureof SO2 and NO2. Biomass was measured after 2, 3 and 4 weeksand the flag leaves of sample plants were labelled with 14CO2.Biomass yields revealed an increase in shoot-to-root ratiosunder polluted conditions. The labelling experiments showedthat less assimilate was transported to the roots, whilst morewas allocated to the younger components of the plant. It appearedthat NO2 and SO2 also caused labelled photosynthate to be retainedin the labelled leaf. Reducing the photon flux exacerbated theeffects of SO2 and NO2 as indicated by changes in biomass andby the distribution of 14C. Key words: Wheat, SO2, NO2, growth, translocation  相似文献   

4.
Three-year-old Pinus strobus plants, grown under conditionsof either high or low light intensities, were brought from thenursery to the laboratory every three to four weeks from themiddle of April 1961 until January 1962. Translocation, measuredas the amount of 14C recovered from the roots at the end ofseven hours of illumination following exposure of the shootto 14CO2, was found to be high in the spring, dropping to negligibleamounts during June and July, increasing again in the autumnand declining after October. Seasonal variation in root respirationwas found to parallel that of translocation. Rates of apparentphotosynthesis were low during the spring, rising to a maximumduring September, and then declining over the winter. The respiration,photosynthesis, and translocation of the low-light grown plantsfollowed a similar pattern to those grown in high-light, exceptthat in general rates were of a lower order. In the high-light grown plants more than 90 per cent of theabsorbed carbon was present in the ethanol-soluble form, ofwhich sugars formed at least 90 per cent. This was even morepronounced in the case of low-light grown plants. The main sugarwas always sucrose. The raffinose content was found to decreaseduring the warmer months. The new needles, during their period of maximum growth, fixedcarbon dioxide photosynthetically at a rate comparable to thatof the old needles. The new stems also possessed a relativelyhigh carbon dioxide fixing ability. Shoot growth, as measured by the increase in length of the newleader stem and new needles, showed the typical patterns forpine species.  相似文献   

5.
Cucumber (Cucumis sativus L.) seedlings were grafted onto cucumber-(CG) or figleaf gourd- (FG, Cucurbita ficifolia Bouché)seedlings in order to determine the effect of solution temperature(12, 22, and 32°C) on the mineral composition of xylem sapand the plasma membrane K+-Mg++-ATPase activities of the roots.Low solution temperature (12°C) lowered the concentrationof NO3 and H2PO4 in xylem sap of CG plants butnot of FG plants. Concentrations of K+, Ca++ and Mg++ in xylemsap were less affected than anions by solution temperature.The plasma membrane of FG plants grown in 12°C solutiontemperature showed the highest K+- Mg++-ATPase activity at allATP concentrations up to 3 mM and at low reaction temperatureup to 12°C, indicating resistance of figleaf gourd to lowroot temperature. (Received December 27, 1994; Accepted March 10, 1995)  相似文献   

6.
Scots pine (Pinus sylvestris L.) seedlings were grown for 3years in the ground in open top chambers and exposed to twoconcentrations of atmospheric CO2(ambient or ambient + 400 µmol mol-1) without addition of nutrients and water. Biomassproduction (above-ground and below-ground) and allocation, aswell as canopy structure and tissue nitrogen concentrationsand contents, were examined by destructive harvest after 3 years.Elevated CO2increased total biomass production by 55%, reducedneedle area and needle mass as indicated, respectively, by lowerleaf area ratio and leaf mass ratio. A relatively smaller totalneedle area was produced in relation to fine roots under elevatedCO2. The proportion of dry matter in roots was increased byelevated CO2, as indicated by increased root-to-shoot ratioand root mass ratio. Within the root system, there was a significantshift in the allocation towards fine roots. Root litter constituteda much higher fraction of fine roots in trees grown in the elevatedCO2than in those grown in ambient CO2. Growth at elevated CO2causeda significant decline in nitrogen concentration only in theneedles, while nitrogen content significantly increased in branchesand fine roots (with diameter less than 1 mm). There were nochanges in crown structure (branch number and needle area distribution).Based upon measurements of growth made throughout the 3 years,the greatest increase in biomass under elevated CO2took placemainly at the beginning of the experiment, when trees grownin elevated CO2had higher relative growth rates than those grownunder ambient CO2; these differences disappeared with time.Symptoms of acclimation of trees to growth in the elevated CO2treatmentwere observed and are discussed. Copyright 2000 Annals of BotanyCompany Elevated CO2, Pinus sylvestris, biomass production, allocation, fine roots, root litter, crown structure, nitrogen, C/N ratio  相似文献   

7.
Maize (Zea mays L., hybrid Cargill 147) seedlings, grown inaseptic conditions, were inoculated with three strains of Azospirillumlipoferum (Al op 33, Al iaa 320, and ATCC 29708) or culturedin different concentrations of indol-3-acetic acid (IAA) orgibberellin A3 (GA3). After 48 h, root length, root surfacearea, root dry weight, and shoot dry weight were measured inall treatments. Gibberellin content was evaluated in selectedroots of control and Azospirillum inoculated seedlings by gaschromatography-mass spectrometry-selected ion monitoring withthe use of deuterated gibberellins as internal standards. Thethree strains of A. lipoferum, IAA (2 ng ml–1), and GA3(40 to 400 pg ml–1) significantly enhanced root growth.Improvement of root hair growth and density was obtained mainlywith A. lipoferum strain Al op 33 and GA3 40 pg ml–1.GA3 was identified by gas chromatography-mass spectrometry (byboth, full scan and selected ion monitoring) in a free acidfraction from roots of the seedlings inoculated with A. lipoferum.In the roots of the non inoculated seedlings GA3 was found afterhydrolysis of a fraction expected to contain glucosyl conjugates. (Received April 26, 1993; Accepted September 27, 1993)  相似文献   

8.
The effect of salinity on glucose absorption and incorporation by pea roots   总被引:1,自引:0,他引:1  
Osmotic adaptation was observed in pea plants grown in Na2SO4salinized media but no complete adaptation was observed in plantsgrown in NaCl salinized media. The absorption of externally supplied glucose was depressedin pea root tips from plants grown in media salinized with eitherNaCl or Na2SO4. Under NaCl salinity this depression increasedwith increasing salinity. Under Na2SO4 salinity, no significantinhibition of absorption was observed in roots exposed to waterpotentials higher than –5 atmosphere. The amount of 14Creleased as CO2, expressed as the percent of absorbed 14C, increasedwith increasing salinity of both types. In roots grown underNaCl salinity, the incorporation of 14C into ethanol non-soluble,acid hydrolyzable substances was markedly inhibited. This inhibitionwas increased by increasing the external salinity. The effectof Na2SO4 salinity was similar but not so pronounced. The incorporation of 14C from externally supplied glucose intothe alkali-soluble fraction was practically uneffected by salinity.Non-extractable 14C was decreased in roots exposed to NaCl butwas not, apparently, effected by Na2SO4). Because of the smallnessof this fraction no clear cut conclusion can be made. Possiblemechanisms for the events are discussed. (Received October 26, 1972; )  相似文献   

9.
Changes in growth and yield parameters, and 14CO2 and (U-14C)sucrose incorporation into the primary metabolic pool, and essentialoil have been investigated under Mn-deficiency and subsequentrecovery in Mentha piperita, grown in solution culture. UnderMn-deficiency, CO2 exchange rate, total chlorophyll, total assimilatoryarea, plant dry weight, and essential oil yield were significantlyreduced, whereas chlorophyll a/b ratio, leaf area ratio andleaf stem ratio significantly increased. In leaves of Mn-deficientplants, 14CO2 incorporation into the primary metabolic pool(ethanol-soluble and -insoluble) and essential oil were significantlylower, whereas (U-14C) sucrose incorporation into these componentswas significantly higher as compared to the control. Among theprimary metabolites, the label was maximum in sugars, followedby organic acids and amino acids. A higher label in these metaboliteswas, in general, observed in stems of Mn-deficient plants ascompared to the control. Mn-deficient plants supplied with completenutrient medium for 3 weeks exhibited partial recovery in growthand yield parameters, and essential oil biogenesis. Thus, underMn-deficiency and subsequent recovery, the levels of primaryphotosynthetic metabolites and their partitioning between leafand stem significantly influence essential oil biogenesis. Key words: Mentha piperita, Mn-stress, 14CO2 and [U-14C] sucrose incorporation, oil accumulation, primary photosynthetic metabolites  相似文献   

10.
Marques, I. A., Oberholzer, M. J. and Erismann, K. H. 1985.Metabolism of glycollate by Lemna minor L. grown on nitrateor ammonium as nitrogen source.—J. exp. Bot. 36: 1685–1697. Duckweed, Lemna minor L., grown on inorganic nutrient solutionscontaining either NH4+ or NO3 as nitrogen source wasallowed to assimilate [1-14C]- or [2-14C]glycollate during a20 min period in darkness or in light. The incorporation ofradioactivity into water-soluble metabolites, the insolublefraction, and into the CO2 released was measured. In additionthe extractable activity of phosphoenolpyruvate carboxylasewas determined. During the metabolism of [2-14C]glycollate in darkness, as wellas in the light, NH4+ grown plants evolved more 14CO2 than NO3grown plants. Formate was labelled only from [2-14C]glycollateand in NH4+ grown plants it was significantly less labelledin light than in darkness. In NO3 grown plants formateshowed similar radioactivity after dark and light labelling.The radioactivity in glycine was little influenced by the nitrogensource. Amounts of radioactivity in serine implied that thefurther metabolism of serine was reduced in darkness comparedwith its metabolism in the light under both nitrogen regimes.In illuminated NH4+ plants, serine was labelled through a pathwaystarting from phosphoglycerate. After [1-14C]glycollate feedingNH4+ grown plants contained markedly more radioactive aspartateand malate than NO3 plants indicating a stimulated phosphoenolpyruvatecarboxylation in plants grown on NH4+. Key words: Photorespiration, glycollate, nitrogen, Lemna  相似文献   

11.
HARRIS  D.; DAVY  A. J. 《Annals of botany》1988,61(2):147-157
We report physiological aspects of the response of seedlingsof the strandline grass Elymus farctus to short-term burialwith sand. Seedlings were buried at the two-leaf stage for oneweek and compared with non-buried controls - before, duringand after burial. Photosynthetic CO2 uptake was measured byinfrared gas analysis and carbon translocation from the youngestexpanded leaf was monitored after exposure to 14CO2. The concentrationsof water-soluble carbohydrate, and total nitrogen, phosphorusand potassium in component organs were determined. Net photosynthetic capacity was almost completely inhibitedby 5 d of burial. However, plants uncovered after 7 d of burialrecovered full photosynthetic competence within 24 h. Therewas a sharp, sustained depression in the water-soluble carbohydrateconcentration of the roots and stems after burial, whereas leaves1–3 had much higher concentrations than non-buried plantsfor up to 20 d after uncovering. Burial virtually suppressedthe translocation of 14C to stem, roots and expanding leaves,and this effect persisted even after full recovery of net photosynthesis.The proportional allocation of total N, P and K to leaves wasincreased after burial, mainly at the expense of the roots.Changes both in nutrient concentration and in the relative massesof organs contributed to this effect. The apparent reversal of the normal source-sink relationshipsfor carbohydrate between photosynthetic and non-photosyntheticorgans, and the differential allocation of inorganic nutrients,may contribute to the maintenance of photosynthetic capacityduring burial. The rapid recovery of net photosynthesis afterre-exposure suggests that these responses may be advantageousfor survival of E. farctus seedlings in the early stages ofgrowth in a physically unstable and unpredictable environment. Sand burial, photosynthesis, translocation, nutrient allocation, Elymus farctus, sand couch grass  相似文献   

12.
The loss of organic material from the roots of forage rape (Brassicanapus L.,) was studied by pulse-labelling 25-d-old non-sterilesand-grown plants with 14CO2. The distribution of 14C withinthe plant was measured at 0, 6 and 13 d after labelling whilst14 C accumulating in the root-zone was measured at more frequentintervals. The rates of 14C release into the rhizosphere, andloss of 14CO2 from the rhizosphere were also determined. Thesedata were used to estimate the accumulative loss of 14C fromroots and loss respiratory 14CO2 from both roots and associatedmicro-organisms. Approximately 17-19% of fixed 14CO2 was translocatedto the roots over 2 weeks, of which 30-34% was released intothe rhizosphere, and 23-24% was respired by the roots as 14CO2. Of the 14C released into the rhizosphere, between 35-51%was assimilated and respired by rhizosphere micro-organisms.Copyright1993, 1999 Academic Press Brassica napus L., carbon loss, carbon partitioning, microbial nutrition, microbial respiration, forage rape, pulse-labelling, rhizodeposition, root respiration, sand culture  相似文献   

13.
Amino acid composition of the free amino acid pool and the TCA-insolubleprotein fraction were investigated in root tips of pea and Tamarixtetragyna plants grown at various levels of NaCl salinity. Salinitystress induced an increase of proline content, mainly in thefree amino acid pool in both plants, and of proline or hydroxyprolinecontent in the protein. Externally-supplied proline was absorbedand incorporated into protein, by pea roots, more effectivelythan by Tamarix roots. Salinity stress, apparently, stimulatedthe metabolism of externally-supplied labelled proline. Pearoots have a very large pool of free glutamic acid; however,70 per cent of the 14C from externally-supplied 14C-U-glutamicacid was released as CO2. Very small amounts of it were incorporatedinto protein. No measurable amount of radioactivity could bedetected in any one of the individual amino acids, either ofprotein hydrolysate or the free amino acid pool. Proline very effectively counteracted the inhibitory effectof NaCl on pea seed germination and root growth. A similar effectbut to a lesser degree was achieved with phenylalanine and asparticacid. The feasibility of proline being a cytoplasmic osmoticumis discussed.  相似文献   

14.
The effects of plant phosphorus (P) status and the mycorrhizal(M) fungus, Glomus intraradices Schenck & Smith, on thecarbon (C) economy of sour orange (Citrus aurantium L.) weredetermined during and following active M colonization. Therewere four treatments: M seedlings grown at standard-strength(1 mM) P (M1) and nonmycorrhizal (NM) plants grown at one, twoand five times standard-strength P (NM1, NM2 and NM5). Mycorrhizalcolonization, tissue dry mass, P content, root length and leafarea were determined in five harvests from 6 to 15 weeks ofage. Rate of C assimilation (A) was determined at 7, 8 and 12weeks by gas exchange. Partitioning of 14 C was determined from7 to 15 weeks using a 10-min pulse followed by a 24-h chaseperiod. For a given attribute, M1 plants were compared to thecurve defining the NM response as a function of tissue P concentration.In contrast to the large effects of P nutrition on C economyof sour orange, M effects were generally subtle. Mycorrhizaeincreased the root biomass fraction, the root length/leaf arearatio and the percentage of 14C recovered from below-groundcomponents. A higher percentage of below-ground 14 C was inthe respiration and soil fractions in M than NM plants of equivalentP status. Mycorrhizal plants tended to enhance A only for abrief period. Mycorrhizal plants had lower relative growth ratesthan NM plants of equivalent P status, suggesting that the temporarilyenhance A of M plants did not fully compensate for their greaterbelow-ground carbon expenditure. Problems of interpreting thedynamic effects of mycorrhizae on C economy that are independentof P nutrition are discussed.Copyright 1993, 1999 Academic Press Citrus aurantium L., sour orange, carbon economy, 14carbon, CO2 assimilation, vesicular-arbuscular mycorrhizae, phosphorus fertilization, phosphorus nutrition  相似文献   

15.
Carob seedlings were grown hydroponically for 9 weeks under360 and 800 µl l-1CO2. One of two nitrogen sources, nitrateor ammonium, was added to the nutrient medium at concentrationsof 3 mol m-3. Root systems of the developing plants suppliedwith nitrate compared to those supplied with ammonium were characterizedby:(a)more biomass on the lower part of the root;(b)fewer lateralroots of first and second order;(c)longer roots;(d)higher specificroot length;(e)a smaller root diameter. The morphology of theroot systems of nitrate-fed plants changed in the presence ofelevated carbon dioxide concentrations, resembling, more closely,that of ammonium-fed plants. Total leaf area was higher in ammonium-than in nitrate-fed plants. Nitrate-fed plants had greater totalleaf area in the presence of high carbon dioxide than in normalCO2, due to an increase in epidermal cell size that led to developmentof larger leaflets with lower stomatal frequency. The observedchanges in the morphology of roots and shoots agreed with theresults observed for total biomass production. Nitrate-fed plantsincreased their biomass production by 100% in the presence ofelevated CO2compared to 15% in ammonium-fed plants, indicatingthat the response of carob to high CO2concentrations is verydependent on the nitrogen source. Under elevated CO2, nitrate-grownplants had a larger content of sucrose in both roots and shoots,while no significant difference was observed in the contentof sucrose in ammonium-grown plants, whether in ambient or enrichedcarbon dioxide. Hence, the differences in soluble carbohydratecontents can, at least partly, account for differences in rootand shoot morphology.Copyright 1997 Annals of Botany Company Ceratonia siliquaL.; carob; ammonium; carbohydrate; carbon dioxide; nitrate; morphology; sucrose  相似文献   

16.
FORD  ELSIE M. 《Annals of botany》1967,31(1):113-119
One-year rooted shoots of M.VII apple rootstock were grown fora single season by spraying their roots continuously with nutrientsolutions containing either < 3 ppmMg(Mg(0)) or 45 ppm(Mg(0))to give, respectively, potentially very deficient or healthyplants. The new shoots of half the plants in each of these treatmentswere dipped periodically in a 2 per cent solution of MgSO4.7H2O plus ‘wetter’. Mg(0) undipped plants developed severe symptoms of Mg deficiency,growth was poor, and the shoot/root dry-weight increment ratiowas high; none of these characteristics was found in Mg(0) dippedplants, whose growth was not appreciably less than that of Mg(2)undipped controls. There was little translocation of Mg from leaves to roots: theconcentration of Mg in roots of Mg(0) dipped plants was as lowas that of the undipped. The large accumulation of Mn and, toa less extent, of Fe in Mg(0) dipped roots was not apparentlydetrimental to growth. Growth of Mg(2) dipped plants was similar to that of the undipped. Dipping had little effect on the chemical composition of leaves,except to raise the concentration of Mg.  相似文献   

17.
Lehnherr, B. M?chler, F. and N?sberger, J. 1985. Effect of CO2concentration during growth on a CO2 concentrating mechanismin white clover as predicted from differential 14CO2/12CO2 uptake.-J. exp. Bot. 36: 1835-1841. White clover was grown at 20 and100 Pa p(CO2). The CO2 response of net photosynthesis and differentialuptake of 14CO2 and 12CO2 by leaves were measured at varioustemperatures and at various O2 and CO2 partial pressures andcompared with predictions from ribulose bisphosphate carboxylase/oxygenasekinetics. Discrepancies between the observed gas exchange characteristicsfor the leaves and those predicted from the enzyme kineticswere interpreted as being due to a CO2 concentrating mechanism.Plants grown at 20 Pa p(CO2) showed a higher affinity for CO2than plants grown at 100 Pa p(CO2) when measured at 10 ?C. Nodifference in affinity was found at 30 ?C. The postulated CO2concentrating effect was greater in plants grown at low CO2than in plants grown at high CO2 concentration and occurredonly at low temperature and low CO2 partial pressure. It issuggested that plants grown at the lower CO2 partial pressurehave a higher affinity for CO2 due to a more efficient CO2 concentratingsystem than plants grown at the higher CO2 partial pressure. Key words: Photosynthesis, CO2, concentration, RuBP carboxylase/oxygenase  相似文献   

18.
The single-gene mutation afila in pea (Pisum sativum L.) resultsin the replacement of proximal leaflets with branched tendrils,thereby reducing leaf area. This study investigated whethertheafila line could adjust biomass partitioning when exposedto varying nutrient regimes, to compensate for reduced leafarea, compared with wild-type plants. Wild-type and afila near-isogeniclines were grown in solution culture with nitrate-N added toinitially N-starved seedlings at relative addition rates (RN)of 0.06, 0.12, 0.15 and 0.50 d-1. The relative growth rate (RW)of the whole plants closely matched RNat 0.06 and 0.12 d-1,but higher RNresulted in a slightly higher growth rate. At agiven RN, the wild-type line had lower plant nitrogen statusthan the afila line. RWof the roots of the afila line was lessthan RWof the roots of the wild-type at the three higher ratesof N supply despite a greater accumulation of N in the rootsof the afila plants. Consequently, plant nitrogen productivity(growth rate per unit nitrogen) was lower for afila. Dry matterallocation was strongly influenced by nitrogen status, but nodifferences in shoot–root dry matter allocation were foundbetween wild-type and afila with the same plant N status. Theseresults imply that decreased leaf area as a result of the single-genemutation afila affects dry matter allocation, but only accordingto its effect on the nitrogen status. Copyright 2000 Annalsof Botany Company Pisum sativum, pea, nitrogen limitation, growth, shoot–root allocation, relative growth rate, nitrogen productivity, isolines  相似文献   

19.
The growth, morphology and carbon allocation patterns of F1progeny white clover (Trifolium repens L.) plants selected foreither low (‘LBF’) or high (‘HBF’) frequencyof stolon branching were compared in two controlled-environmentexperiments. Selections from within both a small-leaved (‘GrasslandsTahora’) and a large-leaved (‘Grasslands Kopu’)clover cultivar were compared, and plants were grown under arelatively lenient defoliation treatment (expt 1) or under threelevels of defoliation seventy (expt 2). Carbon allocation patternswere measured by 14CO2 pulse-chase labelling using fully unfoldedleaves on the main (parent) stolon. LBF and HBF displayed consistent differences in the selectedcharacter though, within cultivars, the difference between selectionswas most pronounced for Kopu. The selections developed fundamentallydifferent branching structures resulting from differences inbranching frequency, with total branch weight per plant averaging122 mg for LBF and 399 mg for HBF (mean of both experiments).More C moved from parent stolon leaves to branches in HBF thanin LBF (mean 22.6% vs. 15.1% respectively of the 14C exportedfrom source leaves). More C also moved to stolon tissue in HBF,but, counterbalancing this and the difference in allocationto branches, less moved to developing leaves and roots on theparent stolon itself compared to LBF. However, the total weightof developing leaves and roots per parent stolon was generallygreater in HBF than in LBF, probably reflecting greater C importby these sinks from the higher number of branches present perplant in the former selection. HBF plants were consistentlylarger at harvest than LBF plants. There were no defoliationtreatment x selection interactions in C allocation patternsin expt 2. The implications of the results for plant performancein grazed pastures are discussed. Branching, carbon translocation, defoliation, growth, morphology, Trifolium repens, white clover  相似文献   

20.
Seedlings of Cucumis sativus L. grew much less vigorously whencultured in potassium-deficient nutrient solution than in fullnutrients. The poorer growth was attributed to reduced CO2 fixationby the cotyledons, which form the bulk of the photosyntheticsurface at this stage, and to a much lower level of export ofphotosynthetic products from the cotyledons. The magnitude ofthese effects increased as the seedlings aged and they werea major factor in the poorer development of the plumule in potassium-deficientplants. Electron microscopic examination of the cotyledons shows thatthe lower 14CO2 fixation in potassiumstarved seedlings is associatedwith poorly-defined granal stacks and a proliferation of intergranalthylakoids. In plants grown in full nutrients the incorporationof radiocarbon into a cell wall fraction and into other insolublecomponents of the cell increased with cotyledon age whereasin potassium-deficient seedlings there was an increase in thepercentage of the total radiocarbon in the soluble fraction.This suggests either that the incorporation of photosyntheticproducts into cellular components was inhibited or that theability of the cotyledon to translocate photosynthetic productsto the rest of the seedling was reduced in plants grown in potassium-deficientconditions.  相似文献   

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