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1.
Changes in respiratory metabolism accompanied by callus formationin cultured explants of carrot root were followed and the followingresults were obtained. 1) When the explant was cultured on amedium containing kinetin and 2,4-D, active cell division occurredand resulted in callus formation by the 9th12th days.2) Fresh weight remarkably increased after a lag-time of about5 days. Changes in protein content on fresh weight basis weresimilar to changes in fresh weight. 3) Respiration rate increasedduring the first few days, when growth could not be distinctlymeasured. Accompanying the rise in respiration, the C6/C1 ratioalso increased. As callus developed, the respiratory rate andC6/C1 ratio gradually decreased and RQ, became higher than unity.4) Alcohol dehydrogenase activity increased between the 4thand 9th days after culture. 5) When sub-cultured callus tissuewas fed with G-U-14C, some radioactivity was detected in thealcohol of the tissues. 6) These results suggest that duringthe first 46 days after culture the activity of the EMBDEN-MEYERHOF-PARNAS-TCApathway was remarkably increased and, as callus developed, therelative participation of the pentose phosphate pathway graduallyincreased and simultaneously alcohol fermentation occurred. (Received December 13, 1968; ) 相似文献
2.
Hypocotyl explants of S. melongena showed three types of regenerationthrough callus formation depending on the concentration of NAAin the medium. At 0.8 mg l1, only callus was produced.Lower concentrations resulted in callus, adventitious roots(optimum, 0.016 mg 11 NAA), and adventitious shoots (noNAA). Roots and shoots developed during the early stages ofculture. Higher concentrations of NAA depressed callus growthand stimulated embryoid formation (optimum 8.0 mg 11NAA), Embryoids were identifiable after about 6 weeks as greenspots on the surface of callus: Addition of 6-BA enhanced shootproduction but inhibited both root and embryoid production.Whole plants were obtained from embryogenic callus after transferto NAA free medium. Genotypic differences in response were observed. In general,the potential for embryogenesis was independent of or inverselyrelated to the potential for organogenesis. 相似文献
3.
Callus tissues were initiated from root, embryo and inflorescenceexplants of wheat. These callus cultures were used to studythe formation of roots and shoots in the absence and presenceof selected plant hormones. On a basal medium alone, only newly-initiatedembryo callus formed both roots and shoots while root callusonly formed roots. Inflorescence callus showed no signs of differentiation.The regenerative capacity of root and embryo callus tissueson medium lacking hormones decreased with increasing periodsof culture. Calluses which failed to differentiate in the absenceof hormones were selected for studies on hormone-mediated differentiation.NAA (1 mg 11) was effective in inducing roots from allcalluses irrespective of their origin or age. In contrast, shootformation was elicited by incubating newly-formed callus onbasal medium supplemented with kinetin (5 mg 11) andNAA (1 mg 11) but rapidly decreased with longer periodsof culture. The differences observed in differentiation of thecallus in the absence and presence of hormones is discussed. 相似文献
4.
5 x 105 M L-phenylalanine overcame the inhibitory effectof white light on cell division in artichoke callus culturesand increased extractable phenylalanine ammonia-lyase (PAL)activity compared to cultures grown in the presence of 5 x 104M phenylalanine The lower concentration of the amino acid alsoenhanced rates of uptake and incorporation of 14C labelled phenylalaninethroughout G1 and S. Differences between the two concentrationswere greatest during S with a 4-fold increase in uptake anda 3-fold increase in incorporation It is suggested thereforethat the capacity of 5 x105 M phenylalanine to offsetthe light effect is due to an indirect stimulatory effect onamino acid and protein metabolism Increased levels of extractablePAL activity would then be reflected by this general stimulationof protein synthesis. Helianthus tuberosus L, Jerusalem artichoke, callus culture, cell division, phenylalanine ammonia-lyase 相似文献
5.
Explants of stem, leaves, roots, and cotyledons from etiolatedaxenically grown Vicia faba seedlings were cultured on a rangeof media. Shoot organogenesis was only obtained with nodal stemand cotyledonary node explants when cultured on MS medium with3% sucrose, 2.0 mg 11 BAP and 02 mg 11 NAA. Callusproliferation accompanied shoot organogenesis from nodal stemexplants. Successive subculture of nodal stem callus resultedin proliferation of regenerative callus which contained severalshoot bud initials. The capacity for shoot regeneration fromthis callus was maintained for 9 months. Histological studiesreveal de novo formation of meristematic centres in callus andtheir further development into bud primordia. High frequencyrooting of these adventitious shoots was obtained on half-strengthMS medium with 1.5% sucrose, 0.1 mg 11 NAA and 0.5 mg11 kinetin. Key words: Vicia faba, adventitious shoots, axillary shoots, de novomeristem formation, organogenesis, tissue culture 相似文献
6.
In vitro culture of Picea sitchensis (Bong.) Carr. needle explantson a number of basal culture media indicated that a complexmixture of organic additives was neither essential nor stimulatory.Adventitious bud production occurred at inorganic nitrogen levelsof 1560 x 103M and 7.530 x 103 Min the adventitious bud induction and elongation media, respectively,when a well-balanced ratio of NH4+:NO3 was maintained.However, necrosis was increased at the highest level of inorganicnitrogen. Organogenesis was more sensitive to changes in theratio of NH4+:NO3. Complete replacement of NH4+ withNO3 during the adventitious bud induction passage severelyinhibited organogenesis, indicating that a reduced form of nitrogenmay be essential for adventitious bud differentiation. Conversely,a high proportion of NH4+ in either the adventitious bud inductionor elongation medium increased tissue necrosis and inhibitedbud induction, reflecting the potential toxicity of this ion.Explants from different individual trees were found to varyconsiderably in their morphogenetic responses, but NH4+:NO3ratios of 1:5 or 1:2 were o ptimal for all individual treeswhich developed adventitious buds from needle cultures. Picea sitchensis, Sitka spruce, tissue culture, nitrogen 相似文献
7.
Aerenchyma and an Inducible Barrier to Radial Oxygen Loss Facilitate Root Aeration in Upland, Paddy and Deep-water Rice (Oryza sativa L.) 总被引:9,自引:0,他引:9
The present study evaluated waterlogging tolerance, root porosityand radial O2 loss (ROL) from the adventitious roots, of sevenupland, three paddy, and two deep-water genotypes of rice (Oryzasativa L.). Upland types, with the exception of one genotype,were as tolerant of 30 d soil waterlogging as the paddyand deep-water types. In all but one of the 12 genotypes, thenumber of adventitious roots per stem increased for plants grownin waterlogged, compared with drained, soil. When grown in stagnantdeoxygenated nutrient solution, genotypic variation was evidentfor root porosity and rates of ROL, but there was no overalldifference between plants from the three cultural types. Adventitiousroot porosity increased from 2026 % for plants grownin aerated solution to 2941 % for plants grown instagnant solution. Growth in stagnant solution also induceda tight barrier to ROL in the basal regions ofadventitious roots of five of the seven upland types, all threepaddy types, and the two deep-water types. The enhanced porosityprovided a low resistance pathway for O2 movement to the roottip, and the barrier to ROL in basal zones would have furtherenhanced longitudinal O2 diffusion towards the apex, by diminishinglosses to the rhizosphere. The plasticity in root physiology,as described above, presumably contributes to the ability ofrice to grow in diverse environments that differ markedly insoil waterlogging, such as drained upland soils as well as waterloggedpaddy fields. 相似文献
8.
ADKINS STEPHEN W.; KUNANUVATCHAIDACH RATCHANEE; GRAY SIMONE J.; ADKINS ANDREA L. 《Journal of experimental botany》1993,44(12):1829-1835
Modifications to the gaseous envelope by callus during culturein Petri dishes were shown to reduce growth and promote necrosisof several rice (Oryza sativa L.) cultivars. Incubatingcallusunder a continuous flow of gas mixtures of known compositionsuggested that the inhibition of growth was caused by the accumulationof ethylene, the depletion of oxygen and, to a lesser extent,the accumulation of carbon dioxide. In order to evaluate theimportance of ethylene accumulation aminoethoxyvinylglycine(AVG), 1-aminocyclopropane-l-carboxylic acid (ACC and silvernitrate (AgNO3), were added to the nutrient medium and ethylenemeasurements performed during callus culture. Ethylene restrictedcallus growth particularly under high (35 °C) as comparedto moderate (25 °C) temperatures and under illuminated ascompared to darkened incubation. Under illuminated incubationat 25 °C AVG (5 mmol m3) and AgNO°(50 mmol m3)significantly improvedcallus growth (100 and 60% respectively)while ACC (200 mmol m3) significantly decreased growth(40%). AVG and AgNO3 were less effective under dark incubationat 25 °C where ethylene production was lower. Furthermore,callus growth was significantly better in large as comparedto small culture vessels since the ethylene concentration wasdiluted and more oxygen was available for respiration. Bettercontrol of ethylene and increased oxygen availability couldbe a way ofproducing healthy callus for the formation of embryogenictissues of otherwise recalcitrant cultivars of rice (e.g. IndicaIR42) and may be a way of improving manipulation of other cerealspecies. Key words: 1-Aminocyclopropane-1-carboxylic acid, aminoethoxyvinylglycine, callus, ethylene, Oryza sativa, silver nitrate 相似文献
9.
ITO OSAMU; OKANO KUNIO; KUROIWA MIYOKO; TOTSUKA TSUMUGU 《Journal of experimental botany》1985,36(4):652-662
Ten-day old kidney bean plants (Phaseolus vulgaris L. cv. Shin-edogawa)were exposed to 2.0 and 40 parts 106 NO2, and0.1, 0.2, and 0.4 parts 106 O3 alone or in combinationfor 2, 4, and 7 d. The effects of these air pollutants wereexamined with respect to the growth, partitioning of assimilates,nitrogen uptake, soluble sugar content, and root respiration. Decreased dry matter production was significant with all treatmentsexcept 2.0 parts 106 NO2 and 0.1 parts 106 O3.Exposure to mixtures of the gases produced more severe suppressionof growth than exposure to the single gases. Root/shoot ratiowas significantly lowered at 7 d by the gas treatments otherthan 2.0 parts 106 NO2 and 0.1 parts 106 O3. Thetotal nitrogen content of plants was increased by all treatments;the higher percent of nitrogen found with O3 exposure will resultfrom the growth retardation which increases the concentrationof nitrogen in the plants because the absorption of nitrogenby roots was unaffected. The combination of O3 with NO2 significantlydecreased the assimilation of NO2 by the plants. The concentration of soluble sugars in roots was decreased bythe gas treatments. There was a strong positive correlationbetween soluble sugar content and dry weight of the roots harvestedat 7 d. Root respiration was relatively unchanged until 5 dand then decreased significantly at 7 d by 2.0 parts 106NO2 and 02 parts 106 O3. Retarded growth of theroots and the decreased root respiration may be due to diminishedtranslocation of sugars from leaves to roots caused by exposureto air pollutants. The uptake of soil nitrogen was not closelyrelated with root respiration in the case of O3 exposure. Key words: NO2, O3, Phaseolus vulgaris, Growth, Sugars, Root respiration 相似文献
10.
Root growth in chickpea (Cicer arietinum) has been studied fromthe early vegetative phase to the reproductive stage in orderto elucidate its growth and maintenance respiration and to quantifythe translocation of assimilates from shoot to root. A carbonbalance has been drawn for this purpose using the growth andrespiration data. The increase in the sieve tube cross-sectionalarea was also followed simultaneously. Plants growing in a nutrient culture medium were studied todetermine the relative growth rate (RGR) 560 d aftergermination. RGR declined from 113 to 41 mg d1 g1during the measurement period. Simultaneous with the RGR analysis,respiration rate was also measured using an oxygen electrode.The respiration rate declined as the plants aged and a drasticreduction was recorded following anthesis. The relationshipbetween RGR and respiration rate was used to extrapolate themaintenance respiration (m) and growth respiration (1/YEG).The respiration quotient (r.q.) of the roots was 1.2 and theQ10 in the range 2025 °C was 2·2. A carbon balance for the roots was constructed by subtractingthe carbon lost during respiration from that gained during growth.The roots were found to respire no less than 80% of the carbontranslocated. The increase in the cross-sectional area composed of sieve tubeswas measured near the root-shoot junction as the plants grew.Chickpea has storied sieve plates which simplifies these measurements.Their cross-sectional area increased during growth mainly becauseof an increase in sieve tube number. The diameter of individualsieve tubes remained constant. Specific mass transfer (SMT) values for seive tubes into theroots have been computed during various stages of growth. SMTvalues were relatively constant before anthesis (approx. 6·5g h1 cm2), but decreased following anthesis. Wedid not evaluate possible retranslocation from roots: any suchretranslocation would have the effect of increasing our SMTvalues. Chickpea, Cicer arietinum, legume, root, respiration, phloem, translocation, carbon balance, specific mass transfer, sieve-tube dimensions 相似文献
11.
RYLE G. J. A.; ARNOTT R. A.; POWELL C. E.; GORDON A. J. 《Journal of experimental botany》1984,35(8):1156-1165
The respiratory effluxes of nodules and of roots of FiskebyV soyabean (Glycine max (L.) Merr.), grown in a controlled environment,were measured at intervals in air and 3% O2 from shortly afterthe onset of N2 fixation until plant senescence. The respiratoryburdens linked with nitrogenase plus ammonia metabolism, andnodule growth and maintenance, were calculated from gas exchangedata and related to the concurrent rates of N2 fixation. The specific respiration rates of nodules increased to a maximumof 21 mg CO2 g1 h1 at the time pods began development:the equivalent maximum for roots was c. 4.5 mg CO2 g1h1. Maximum nodule and root respiration rates per plantwere attained about 25 d later at the time N2 fixation peakedat 15 mg N d1 plant1. The relationship between nodule respiration and N2 fixationindicated an average respiratory cost of 13.2 mg CO2 mg1N until the last few days of plant development Separation ofnodule respiration into the two components: nitrogenase (+ NH3metabolism) respiration and nodule growth and maintenance respiration,indicated that the latter efflux accounted for c. 20% of nodulerespiration while N2 fixation was increasing and new noduletissue was being formed. When nodule growth ceased and N2 fixationdeclined, this component of respiration also declined. The respiratorycost of nitrogenase activity plus the associated metabolismof NH3 varied between 11 mg CO2 mg1 N during vegetativeand early reproductive growth, to 12.5 mg CO2 mg1 N duringthe later stages of pod development. Key words: N2 fixation, Respiration, Nodules, Nitrogenase 相似文献
12.
The specific respiration rates of nodulated root systems, ofnodules and of roots were determined during active nitrogenfixation in soya bean, navy bean, pea, lucerne, red clover andwhite clover, by measurements on whole plants before and afterthe removal of nodule populations. Similar measurements weremade on comparable populations of the six legumes, lacking nodulesbut receiving abundant nitrate-nitrogen, to determine the specificrespiration of their roots. All plants were grown in a controlled-environmentclimate which fostered rapid growth. The specific respiration rates of nodulated root systems ofthe three grain and three forage legumes during a 714-dayperiod of vegetative growth varied between 10 and 17 mg CO2g1 (dry weight) h1. This mean value consistedof two components: a specific root respiration rate of 69mg CO2 g1 h1 and a specific nodule respirationrate of 2246 mg CO2 g1 h1. Nodule respirationaccounted for 4270 per cent of nodulated root respiration;nodule weight accounted for 1240 per cent of nodulatedroot weight. The specific respiration rates of roots lackingnodules and utilizing nitrate nitrogen were generally 2030per cent greater than the equivalent rates of roots from nodulatedplants. The measured respiratory effluxes are discussed in thecontext of nitrogen nitrogen fixation, nitrate assimilation. Glycine max, Phaseolus vulgaris, Pisum sativum, Medicago sativa, Trifolium pratense, Trifolium repens, soya bean, navy bean, pea, lucerne, red clover, white clover, nodule respiration, root respiration, fixation, nitrate assimilation 相似文献
13.
KUMAR V.; LAOUAR L.; DAVEY M. R.; MULLIGAN B. J.; LOWE K. C. 《Journal of experimental botany》1992,43(4):487-493
The effects have been studied of the non-ionic surfactant, PluronicF-68, on the growth of transformed roots, callus and protoplastsof Solanum dulcamara L. Root growth was stimulated by additionof 0001005% (w/v) of freshly-prepared, commercial gradePluronic to culture medium, with maximum increases in root freshand dry weights at 001%. Higher concentrations (0510%w/v) of freshly-prepared Pluronic inhibited growth. A Pluronicfraction, prepared by passage through silica-Amberlite resin,retarded root growth even at concentrations that were stimulatorywith the commercial preparation. Similarly, commercial gradePluronic solutions stored at 4C or 22C for 5 d (aged)also inhibited root growth. Roots grew faster on Pluronic F-68-treatedmembrane rafts compared with growth on commercially-availablerafts; such growth enhancement was comparable to that seen inmedium supplemented with 001% (w/v) freshly-prepared commercialPluronic. Callus growth was also stimulated by the addition of freshly-prepared,commercial grade Pluronic F-68 to medium, with maximum increasesat 01% (w/v); in contrast, 10% (w/v) Pluronic was inhibitoryto callus growth. The mean plating efficiency (15 d after plating)of protoplasts cultured at densities of 0120105 cm3was increased up to 26% by 01% (w/v) Pluronic, while 10% wasinhibitory. Both root and callus soluble carbohydrates and proteinswere increased by exposure to freshly-prepared, commercial Pluronic.Similarly, the specific activities of malate dehydrogenase andacid phosphatase were increased in Pluronic F-68-treated callusand roots. The biotechnological implications of these resultsare discussed in relation to the potential value of non-ionicsurfactants as growth-stimulating additives to plant culturemedia. Key words: Solanum dulcamara, Pluronic F-68, surfactant, transformed roots, callus, protoplasts, malate dehydrogenase, acid phosphatase 相似文献
14.
Ethylene accumulation in waterlogged Rumex plants promotes formation of adventitious roots 总被引:8,自引:0,他引:8
Visser Eric J.W.; Bgemann Gerard M.; Blom Cornelis W.P.M.; Voesenek Laurentius A.C.J. 《Journal of experimental botany》1996,47(3):403-410
Accumulation of the gaseous plant hormone ethylene is very importantfor the induction of several responses of plants to flooding.However, little is known about the role of this gas in the formationof flooding-induced adventitious roots. Formation of adventitiousroots in Rumex species is an adaptation of these plants to floodedsoil conditions. The large air-spaces in these roots enablesdiffusion of gases between shoot and roots. Application of ethylene to non-flooded Rumex plants resultedin the formation of adventitious roots. In R. palustris Sm.shoot elongation and epinasty were also observed. The numberof roots in R. thyrsiflorus Fingerh. was much lower than inR. palustris, which corresponds with the inherent differencein root forming capacity between these two species. Ethyleneconcentrations of 1.52µI I 1 induced a maximumnumber of roots in both species. Quantification of ethylene escaping from root systems of Rumexplants that were de-submerged after a 24 h submergence periodshowed that average ethylene concentrations in submerged rootsreached 1.8 and 9.1 µl I1 in R. palustris and R.thyrsiflorus, respectively. Inhibition of ethylene productionin R. palustris by L--(2-aminoethoxyvinyl)-glycine (AVG) or-aminobutyric acid (AIB) decreased the number of adventitiousroots induced by flooding, indicating that high ethylene concentrationsmay be a prerequisite for the flooding-induced formation ofadventitious roots in Rumex species. Key words: Adventitious roots, epinasty, ethylene, flooding, Rumex, shoot elongation 相似文献
15.
Induction of CN-insensitive respiration with low concentrationsof respiratory inhibitors was studied. If roots were treatedwith 103 M CN for 96 hr, the plants died, whilethose treated with 104 M CN showed healthy growth. O2 uptake in untreated rice and wheat roots showed a negativeresponse to 102 M CN to a considerable extent.On the other hand, pretreatment with 104 M CNfor more than 6 hr did not greatly affect respiratory rate,but made respiration insensitive to 102 M CN.A similar induction of CN-insensitivity was also broughtabout with 104 and 103 M H2S and 104 MNaN3. (Received July 6, 1971; ) 相似文献
16.
Maintenance and Constructive Respiration, Photosynthesis, and Net Assimilation Rate in Seedlings of Pitch Pine (Pinus rigida Mill.) 总被引:1,自引:0,他引:1
Pitch pine seedlings were grown at constant temperature andphotoperiod. Net CO2-uptake h1 g1 leaves decreasedsteadily during ontogeny until leaf production ceased. Thereafter,there was no change or a slight increase. Though the ontogeneticpattern was the same in populations native to different geographicareas, there were differences among populations in the rateof CO2-uptake. Root respiration, calculated from the differencebetween CO2-uptake and net assimilation rate, accounted for6 to 69 per cent of diurnal assimilation. Growth of shoots and roots was episodic and out of phase. Spurtsof growth could be forecast by high rates of respiration 4 weeksearlier, probably because high-energy syntheses precede theprocesses of cell elongation and cell wall formation. Maintenanceand constructive respiration were substantially higher for theshoots (85 per cent leaf tissue) than for the roots. Constructiverespiration was proportional to photosynthesis. 相似文献
17.
Etienne H.; Lartaud M.; Carron M.P.; Michaux-Ferrire N. 《Journal of experimental botany》1997,48(1):129-137
In Hevea brasiliensis (Mll. Arg.), increasing the calcium contentof the friable callus maintenance medium from 3 to 9 mM stimulatedregeneration potential through somatic embryogenesis. This stimulationcould be attributed to the homogeneous cytological structureof calluses, which were formed of undifferentiated cells capableof somatic embryogenesis in optimal culture conditions. Thevery marked increase in the active cell population was sufficientto cause a decrease and a stabilization of water and osmoticpotentials of the calluses, whereas their water content increased.The regeneration capacity of calluses cultured on a medium withadditional CaCl2 was greater in terms of both quantity (numberof somatic embryos produced was increased 2-fold) and quality(germination efficiency trebled). High CaCl2 concentrations (9 mM CaCl2) in the embryogenesisinduction medium favoured somatic embryo development when calluseswere maintained 2 months on the same medium. In this case, additionof benzylaminopurine (BAP) and 3,4-dichlorophenoxy- acetic acid(3,4-D) increased the number of embryos produced (243 embryosg1 FW callus) and their germination capacity (27%). These culture conditions were used to determine the optimumembryogenesis induction period. The length of the period affectedboth the intensity of embryogenesis (maximum 5677 d)and somatic embryo quality (maximum 4970 d). The bestresults were obtained with a 70 d embryogenesis induction period,within which 355 embryos g1 FW callus were obtained,with 35% germination. Key words: Calcium, somatic embryogenesis, long-term culture, water status, histology 相似文献
18.
Effects of cytokinin on adventitious root formation in callus cultures ofVigna unguiculata (L.) walp
Woong-Young Soh Pil-Son Choi Duck-Yee Cho 《In vitro cellular & developmental biology. Plant》1998,34(3):189-195
Summary Yellowish compact callus, induced from cowpea hypocotyls on Murashige and Skoog(MS) medium (1962) containing 0.2 mg/l(0.93
μM) kinetin and 0.4 mg/l (1.81 μM) 2,4-dichlorophenoxyacetic acid (2,4-D), was subcultured on MS medium containing cytokinin alone, auxin alone, or auxins
plus cytokinins in order to determine the effect of cytokinins on root organogenesis in callus cultures. The callus actively
proliferated on the same medium but did not show any organogenic activity macroscopically as well as microscopically. On medium
with N6-benzyladenine (BA) and 1-naphthaleneacetic acid (NAA), the yellowish compact callus first changed to pale green compact callus
and then many green spots appeared on its surface under light culture. But the yellowsih compact callus remained yellowish
and white spots appeared on its surface in dark culture. These spots gradually became white nodular structures. Adventitious
root formation from the nodular structures occurred not only on the same medium, but also on medium with either auxin or cytokinin
but not both. Yellowish compact callus on medium with auxin alone was transformed to yellowish friable callus, which did not
develop adventitious roots. The yellowish friable callus could gain rhizogenic activity only after morphological modification
to pale green compact callus on medium with auxin plus cytokinin. The modified callus did not form adventitious roots on medium
with auxins but only with cytokinins. Therefore, it is suggested that cytokinins have stimulating effects on root formation
from callus that previously did not show rhizogenic activity on medium with auxins alone. In addition, the rhizogenic potential
of cowpea callus was discriminated from that of leaf explants, which formed adventitious roots directly on medium with auxin
alone. 相似文献
19.
Root growth of 7-d-old wheat (Triticum aestivum cv. Gamenya)seedlings was impaired at dissolved O2 concentrations of 0.01and 0.055 mol m3 O2, while growth at 0.115 mol m3O2 was the same as that in continuously aerated controls (0.26mol m3 O2). Oxygen uptake by apical (02 mm), expanding (24mm) and expanded (1012 mm) tissues of the roots decreasedbelow 0.16, 0.09 and 0.05 mol m3 O2, respectively. Thishierarchy is consistent with the metabolic rates of these tissues.There was a small (c. 9%) inhibition of O2 uptake and some netsynthesis of ethanol and alanine in root apices at 0.115 molm3 O2. Significant amounts of anaerobic end-productsaccumulated at 0.055 mol m3 O2 and even more so at 0.01mol m3 O2, indicating that oxidative phosphorylationwas strongly inhibited. Net alanine synthesis increased in fully expanded (1016mm) tissues exposed to <0.0030.01 mol m3 O2,and this increase was accompanied either by a proportionallysmaller increase in the concentration of other free amino acidsor by a net decrease in free amino acid levels excluding alanine.This suggests that alanine was synthesized as an end-productof anaerobic catabolism and did not accumulate simply becauseof decreased net protein synthesis. Comparing the carbon flow to CO2, ethanol, lactate and alaninein roots at 0.01 mol m3 O2 with carbon loss as CO2 inaerated roots suggests that carbon flow to products of metabolismwas not greatly enhanced due to O2 deficiency. This infers,but does not prove that, in wheat, generation of energy duringperiods of O2 deficiency is not enhanced due to a Pasteur effect. Key words: Anaerobic, fermentation, oxygen, wheat 相似文献
20.
Cultivated Agave mapisaga and A. salmiana can have an extremelyhigh above-ground dry-weight productivity of 40 Mg ha1yr1. To help understand the below-ground capabilitiesthat support the high above-ground productivity of these Crassulaceanacid metabolism plants, roots were studied in the laboratoryand in plantations near Mexico City. For approximately 15-year-oldplants, the lateral spread of roots from the plant base averaged1.3 m and the maximal root depth was 0.8 m, both considerablygreater than for desert succulents of the same age. Root andshoot growth occurred all year, although the increase in shootgrowth at the beginning of the wet season preceded the increasein growth of main roots. New lateral roots branching from themain roots were more common at the beginning of the wet season,which favoured water uptake with a minimal biomass investment,whereas growth of new main roots occurred later in the growingseason. The root: shoot dry weight ratio was extremely low,less than 0.07 for 6-year-old plants of both species, and decreasedwith plant age. The elongation rates of main roots and lateralroots were 10 to 17 mm d1, higher than for various desertsucculents but similar to elongation rates for roots of highlyproductive C3 and C4 agronomic species. The respiration rateof attached main roots was 32 µmol CO2 evolved kg1dry weight s1 at 4 weeks of age, that of lateral rootswas about 70% higher, and both rates decreased with root age.Such respiration rates are 4- to 5-fold higher than for Agavedeserti, but similar to rates for C3 and C4 agronomic species.The root hydraulic conductivity had a maximal value of 3 x 107ms1 MPa1 at 4 weeks of age, similar to A. deserti.The radial hydraulic conductivity from the root surface to thexylem decreased and the axial conductivity along the xylem increasedwith root age, again similar to A. deserti. Thus, although rootsof A. mapisaga and A. salmiana had hydraulic properties perunit length similar to those of a desert agave, their highergrowth rates, their higher respiration rates, and the greatersoil volume explored by their roots than for various desertsucculents apparently helped support their high above-groundbiomass productivity Key words: Crassulacean acid metabolism, productivity, root elongation rate, root system, water uptake 相似文献