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1.
The metabolic fate of [U-14C]sucrose in suspension culturesof Catharanthus roseus cells was monitored for 96 h after thecells were transferred to fresh complete (+Pi)or to phosphate-deficient Murashige and Skoog (Pi)medium. Sucrose was hydrolysed extracellularly to glucose andfructose. The rate of uptake of sugars by the cells was 1.53times higher in +Pi culture than in Piculture. Little difference in the rate of incorporation of radioactivityinto the ethanol-soluble fraction was found between the +Piand Pi cultures during the initial 24h of culture, but after 48 h the rate in +Picultures was higher than that in Pi cultures.Incorporation of radioactivity into ethanol-insoluble macromoleculeswas always significantly higher in the cells in +Picultures than in those in Pi cultures.The results suggest that Pi strongly affects the utilizationof sugars by cultured plant cells through the stimulation oftransport of sugars as well as through the activation of metabolism. Catharanthus roseus, Madagascar periwinkle, suspension culture, inorganic phosphate, sucrose, transport, metabolism 相似文献
2.
After removal of the embryo from developing seeds of Pisum sativum,the empty ovules (seed coats without enclosedembryo) were filled with a solution (pH 5.5) containing mannitol(usually 400 mM) to which various salts were added. A solutioncontaining two isotopes ((a) [2H]-sucrose/[14C]aminoisobutyricacid (AIB) or (b) [3H]valine/[14C]asparagine mixture) was administeredto the plant via the petiole subtending the fruiting node, and[2H]solute and [14C]solute unloading from the seed coat wasmeasured, in pulse-labelling experiments of about 5 h. The presenceof 25 or 50 mM K+ in the empty ovule enhancedthe release of sucrose from the seed coat particularly duringthe first hours of the experiment, but the stimulating effectof K+ on the release of labelled solutes derived from aminoacids was much smaller. The presence of 25 mM CaCl2 did notaffect the release of sucrose or amino acids from the seed coat.The effect of K+ on sucrose and amino acid release is explainedas an inhibition of sucrose and amino acid resorption from theseed coat apoplast into seed coat cells, after unloading fromthe seed coat unloading sites. It is suggested that amino acidrelease is much less affected by K+ than sucrose release, becausefar less resorption of amino acids by seed coat parenchyma cellstakes place during amino acid transport into the seed coat cavity. Pisum sativum, pea, assimilate transport, assimilate unloading, seed-coat exudate, seed development, sucrose resorption, surgical treatment 相似文献
3.
MARQUES I. A.; OBERHOLZER M. J.; ERISMANN K. H. 《Journal of experimental botany》1985,36(11):1685-1697
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: 16851697. 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
4.
《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
5.
The Sensitivity of Net Photosynthesis in Several Plant Species to Short-term Fumigation with Sulphur Dioxide 总被引:4,自引:0,他引:4
The effects of exposure of up to 2 h with sulphur dioxide ona range of plant species was observed by measuring changes inthe rate of net photosynthesis under closely controlled environmentalconditions. Ryegrass, Lolium perenne S23 was thespecies most sensitive to SO2; significant inhibition was detectedat 200 nl l1. Fumigations at 300 nl l1 also inhibitedphotosynthesis in field bean (Vicia faba cv. Three FoldWhite and Blaze) and in barley (Hordeumvulgare cv. Sonja). No effect was detected inwheat (Triticum aestivum cv. Virtue) at concentrationsup to 600 nl l1 SO2, or in oil-seed rape (Brassica napuscv. Rafal) except at 800 nl l1 SO2). Recoverycommenced immediately after the fumigation was terminated andwas complete within 2 h when inhibition had not exceeded 20%during the SO2 treatment. Key words: Sulphur dioxide, short-term fumigation, photosynthesis 相似文献
6.
The metabolism of [2-14C]thymine, [2-14C]thymidine, [2-14C]uraciland [14C]uridine was investigated in protoplasts obtained fromsuspension cultures of Catharanthus roseus. Most of the exogenouslysupplied thymine, thymidine and uracil was degraded, and salvageof these pyrimidines accounted for 536 per cent of thetotal amount of 14C-labelled precursors which was metabolized.However, more than 80 per cent of the labelled uridine was utilizedfor the biosynthesis of nucleotides and nucleic acids, and therest was degraded. In contrast to the results from protoplastsof sugar cane cells in suspension culture, the data indicatethat protoplasts possess a pathway for the degradation of pyrimidines,and that the overall metabolism of these pyrimidines in protoplastsis very similar to the metabolism in the intact cells. Catharanthus roseus, madagascar periwinkle, protoplasts, pyrimidine metabolism 相似文献
7.
Collapse of Peroxide-Scavenging Systems in Apple Flower-Buds Associated with Freezing Injury 总被引:2,自引:0,他引:2
Changes in the metabolic activities of peroxide-producing systemsand peroxide-scavenging systems after freezing and thawing inflower buds of the apple, Malus pumila Mill., were studied withspecial reference to freezing injury. In flower buds of theMcIntosh apple that were frozen below lethal temperatures,the activity of NADH-Cyt c reductase (EC 1.6.99.3
[EC]
), one of theenzymes in the electron-transport chains that are related tothe peroxide-producing systems, decreased slightly, while thatof Cyt c oxidase (EC 1.9.3.1
[EC]
) hardly changed. By contrast, theactivities of glucose-6-phosphate dehydrogenase (EC 1.1.1.49
[EC]
),dehydroascorbate reductase (EC 1.8.5.1
[EC]
) and ascorbate peroxidase(EC 1.11.1.11
[EC]
), which are involved in the peroxide-scavengingsystems, decreased to very low levels. The activity of glyceraldehyde-3-phosphatedehydrogenase (EC 1.2.1.12
[EC]
) also decreased markedly. However,little change was observed in the activities of hexokinase (EC2.7.1.1
[EC]
), glucosephosphate isomerase (EC 5.3.1.9
[EC]
), glutathionereductase (EC 1.6.4.2
[EC]
) and glutathione peroxidase (EC 1.11.1.9
[EC]
).Examination of substrates involved in the peroxide-scavengingsystems revealed that the levels of glucose-6-phosphate andfructoses-phosphate decreased to approximately 104 to105 M and 105 M, respectively, and the levelsof GSH decreased to about 105 M or became barely detectable.A decrease in the levels of GSSG also occurred while levelsof ascorbate rose slightly. Similar results were observed withflower buds from Starking Delicious and Jonathanapple trees. These results suggest that the freezing injury to apple flower-budsis closely related to the collapse of the peroxide-scavengingsystems that are coupled with the pentose phosphate cycle. Theresults also suggest that the dysfunction of these peroxide-scavengingsystems is caused by H2O2, which may be produced during freezingand thawing. (Received March 14, 1992; Accepted June 5, 1992) 相似文献
8.
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
9.
A Cytochrome P450 Mediated Naringenin 3'-Hydroxylase from Sweet Orange Cell Cultures 总被引:1,自引:0,他引:1
Doostdar Hamed; Shapiro Jeffrey P.; Niedz Randall; Burke M.D.; McCollum T. Gregory; McDonald Roy E.; Mayer Richard T. 《Plant & cell physiology》1995,36(1):69-77
A microsomal flavonoid 3'-hydroxylase (F3'H) catalyzing themetabolism of naringenin to eriodictyol in Citrus sinensis (L.)Osbeck cv. Hamlin cell suspension cultures wasshown to be a cytochrome P450 enzyme. This reaction requiredO2 and NADPH and was inhibited by CO, with partial reversalof CO-inhibition by light at 450 nm. Cytochrome P450 contentranged from 1020 pmol (mg microsomal protein)1.The F3'H reaction was shown to be linear in regard to proteinconcentration between 2.5 and 25 µg of microsomal protein.The optimum pH for the reaction was 7.47.6 and the temperatureoptimum was between 30 and 37°C. The apparent Km and Vmaxfor naringenin were 24 µM±3.2 and 81.4±7.9pmol eriodictyol min1 (mg protein)1, respectively.The microsomal F3'H was also capable of forming dihydroquercetinfrom dihydrokaempferol (40 pmol min1 (mg protein)1)and of quercetin from kaempferol (3.25 pmol min1 (mgprotein1). Cytochrome c and ketoconazole were the bestinhibitors of WH activity followed by piperonyl butoxide anda-naphthoflavone. Light was shown to be an inducer of the F3'Halmost doubling the specific activity and increasing the microsomalcytochrome P450 content by 30% over that of dark grown cells.F3'H activity was also confirmed in microsomal preparationsof young (new flush) leaves from Hamlin treesand flavedo of Hamlin oranges, Marshgrapefruit, and Lisbon lemon. No activity wasobserved in older, hardened leaves and albedo of all the fruittested. Initiation of embryogenesis in the Hamlincell suspension cultures by switching from a sucrose mediumto a glycerol-based medium resulted in the down-regulation ofF3'H.
1Mention of a trademark, warranty, proprietary product, or vendordoes not constitute a guarantee by the U.S. Department of Agricultureand does not imply its approval to the exclusion of other productsor vendors that may also be suitable. 相似文献
10.
Grande Karen D.; Bender Michael L.; Irwin Brian; Platt Trevor 《Journal of plankton research》1991,13(1):1-16
In vitrorates of gross and net oxygen production were measuredas a function of light intensity in some plankton communitiescollected from Bedford Basin, Nova Scotia, and in a monoclonalculture of Synechococcus. The rate of gross oxygen productionwas measured by a technique in which the stable oxygen isotope,18O, serves as a photosynthetic tracer Net oxygen productionwas measured by automated Winkler technique. The rate of communityrespiration in the light was then determined by the differencebetween gross and net rates of oxygen production. In the naturalpopulations examined, neither gross nor net oxygen productionrates were significantly inhibited at the highest light intensitymeasured (500800 µE m2 s1) In a samplein which the dark respiration rate was small relative to themaximal rate of production [Pmax;sensu Platt et al (1980) JMar. Res., 38, 687701] the rates of lightrespiration were 3 times greater. In two other communities,with high rates of dark respiration relative to Pmaxthe ratesof light respiration were closer to rates of darkrespiration. In the Synechococcus clone, both gross and netoxygen production rates were inhibited at high light intensities.Rates of light respiration were found to varyas a function of light intensity. The greatest rates of respirationwere measured in samples incubated at light intensities thatwere just saturating (100 µE m2 s1). Therates of 14C production were also measured as a function oflight intensity The photosynthetic quotients, based on 14C productionrates and gross oxygen production rates, average 1 9 相似文献
11.
The influences of Ca2+-free solutions and increasing K+ concentrationson the H14CO3 influx capacity of Chara corallina wereinvestigated. It was found that contact with Ca2freesolutions resulted in a gradual reduction in the H14CO3influx capacity of these cells. Recovery of this influx capacity,following the return of Ca2+ to the experimental solution, followeda mirror-image of the time course of decay. Potassium concentrations above a certain critical value (2 mM)induced a rapid reduction in H14CO3 influx capacity.Normal activity was recovered within 6090 min followingthe return to 0.2 mMK+ solutions. It was also shown that 10mM K+ can be used to determine the relative contribution of14C supplied by diffusion of 14CO2 and transport of H14CO3.The Ca2+ and K+ results are discussed in relation to the effectsof these treatments on the electrical properties of the plasmalemma. 相似文献
12.
The relationship between the induction of tracheary elementdifferentiation and exogenous L-methionine was examined in agar-growncultures of soya bean callus initiated from Glycine max L. Wayneand Clark 63. Although Wayne is a normal cultivarsoya bean, seedlings of Clark 63 exhibit abnormal growth at25 °C due to exessive ethylene biosynthesis at this temperature.Wayne callus showed increased xylogenesis in the presence ofexogenous L-methionine (3.7 µg 11) in comparisonto IAAKN controls at both 20 and 25 °C. Clark 63callus produced greater numbers of tracheary elements in responseto exogenous L-methionine only at 25 °C. The induction ofxylem differentiation was independent of the maintenance temperatureof the stock cultures of both cultivars. Xylogenesis initiatedbyan IAAKN medium was inhibited by the addition of AgNO3(20 mg 11) to the extent of 76.5 per cent in cv. Wayneand 6 per cent in cv. Clark 63. The inhibitory effect was partiallyreversed by the addition of L-methionine (3.7 µg 11)to the IAAKNAgNO2 medium. These data support thehypothesis that xylogenesis in vitro involves auxin, cytokininand ethylene. differentiation, xylogenesis, L-methionine, ethylene, Glycine max L., soya bean, callus culture, auxin, kinetin 相似文献
13.
The Metabolism of Abscisic Acid 总被引:7,自引:2,他引:5
The light-catalysed isomerization of (+)-abscisic acid (ABA)to its trans isomer during isolation from leaves was monitoredby the addition of (±)-[2-14C]ABA to the extraction medium.(+)Trans-abscisic acid (t-ABA) was found to occur naturallyin rose (Rosa arvensis) leaves at 20µg/kg fresh weight;(+)-ABA was present at 594µg/kg. (±)-[2-14D]Trans-abscisicacid was not isomerized enzymically to ABA in tomato shoots. (±)-Abscisic acid was converted by tomato shoots to awater-soluble neutral product, Metabolite B, whichwas identified as abscisyl-ß-D-glucopyranoside. When(±)-[2-14C]trans-abscisic acid in an equimolar mixturewith (±)-[2-14C}ABA was fed to tomato shoots it was convertedto its glucose ester 10 times faster than was ABA. Trans-abscisyl-ß-D-glucopyrano8ide only was formedfrom (±)-[2-14C]t-ABA in experiments lasting up to 30h. Glucosyl abscisate was formed slowly from ABA and the freeacid fraction contained an excess of the unnatural ().ABAas did the ABA released from abscisyl-ß-D-glucopyranosideby alkaline hydrolysis. The (+).ABA appeared to be the solesource of the acidic Metabolite C" previously noted. The concentrations of endogenous (+)-, (+)-[2-14C]-, and ()-[2-14C]ABAremaining as free acid, and also in the hydrolysate of abscisyl-ß-D-glucopyranoside,were measured by the ORD, UV absorption, and scintillation spectrometryof highly purified extracts of ABA from tomato shoots whichhad been supplied with racemic [2-l4C]ABA. 相似文献
14.
Fully light-intercepting simulated swards of S24 perennial ryegrasswere exposed to contrasting environmental conditions in a growthroom for 4 days. Half experienced 20 h days of 120 Wm2(400700. nm) and 5 °C, and came to have a WSC (watersoluble carbohydrate) content of 235 mg g1 and half 4h days of 20 Wm2 and 25 °C leading to a WSC of 25mg g1. Their rates of CO2 efflux were monitored at anumber of temperatures during an 8 h dark period; half experiencedincreasing (530 °C) and half decreasing (305°C) temperatures. The high WSC swards hadrespiration rates of 3.7 mg CO2 g1 (d. wt) h1at 15 °C, and the low swards 0.8 mg CO2 g1h1. The order in which the temperatures were experiencedwas immaterial. Even the low WSC swards showedno evidence of a respiratory decline during the dark periodthat could be attributed to substrate shortage. The relationshipbetween temperature and CO2 efflux was best represented by logisticcurves. Even so, a Q10 of 2 fitted the data reasonably well,at least up to 20 °C, and has practical advantages wheninterpolating estimated between measured values of respirationin the construction of a carbon balance sheet. Lohum perenne L., ryegrass, respiration, temperature, Q10, soluble carbohydrate content, simulated sward 相似文献
15.
The incorporation of radioactivity from precursors of methylester and galacturonosyl residues into pectin was investigatedusing tissue slices cut from ripening pear fruits. Incorporationfrom 14CH3 methionine into methyl ester of water soluble pectinincreased 10 fold in 4 d at 18 °C and declined in laterstages of ripening. Activity from [3H]inositol could not bedetected in gaJacturonic acid released enzymically from solublepolysaccharides. When l3H]glucose was used as a precursor, activitycould be detected in galacturonic acid released from both thesoluble and insoluble polysaccharide fractions. Methionine wasa more efficient precursor of methyl ester groups than S-adenosylmethionine or S-methyl methionine; incorporation from all threeprecursors was inhibited under nitrogen. Radioactively labelledmethyl ester did not decline during a 225 min chasefollowing a 15 min pulse of [14CH3]methionine;the total pectin content of slices increased by 20% during this4 h incubation. 相似文献
16.
Trimming and solubilization of xyloglucan after deposition in the walls of cultured rose cells 总被引:3,自引:1,他引:2
A pulse-chase technique involving the in vivo feeding of L-[1-3H]arabinoseto suspension-cultured rose (Rosa) cells at 4 d and 9 d aftersubculture (fast- and slow-growing, respectively) was used tocreate a population of [3H]xyloglucan molecules and to followtheir subsequent fate. The weight-average relative molecu larmass (Mw) of [3H]xyloglucan freshly deposited in the cell wallwas 160 000 and 240 000 in the fast- and slow-growing cells,respectively. The wall-bound [3H]xyloglucan of both culturesunderwent a decrease in Mw of 40 000 during the first 2 d afterthe pulse-labelling. At the same time, 2030% of the initially-deposited[3H]xyloglucan disappeared from the cell wall, and a similaramount appeared in solution in the culture medium. Its failureto remain bound to the cell wall and its low Mw (39 000) indicatedthat this soluble extracellular ( was derived from partial degradationof segments of wall-bound xyloglucan that were not directlyhydrogen-bonded to microfibrils (loose ends andtethers). The possible enzymic basis and biologicalroles of the degradation are discussed. Key words: Cell expansion, cell wall, hemicellulose, sloughing, xyloglucan 相似文献
17.
Developmental control of xylem hydraulic resistances and vulnerability to embolism in Fraxinus excelsior L.: impacts on water relations 总被引:3,自引:0,他引:3
Welbaum G.E.; Bian D.; Hill D.R.; Grayson R.L.; Gunatilaka M.K. 《Journal of experimental botany》1997,48(3):655-663
The freezing tolerance of many plants, such as pea (Pisum sativum),is increased by exposure to low temperature or abscisic acidtreatment, although the physiological basis of this phenomenonis poorly understood. The freezing tolerance of pea shoot tips,root tips, and epicotyl tissue was tested after cold acclimationat 2C, dehydration/rehydration, applications of 104M abscisic acid (ABA), and deacclimation at 25C. Tests wereconducted using the cultivar Alaska, an ABA-deficientmutant wil, and its wildtype. Freezinginjury was determined graphically as the temperature that caused50% injury (T50) from electrical conductivity. Endogenous ABAwas measured using an indirect enzyme-linked immunosorbant assay,and novel proteins were detected using 2-dimensional polyacrylamidegel electrophoresis. The maximum decrease in T50 for root tissuewas 1C for all genotypes, regardless of treatment. For Alaskashoot tips and epicotyl tissue, exogenous ABA increased thefreezing tolerance by 1.5 to 4.0C, while coldtreatment increased the freezing tolerance by 7.5 to14.8C. Cold treatment increased the freezing toleranceof shoot tips by 9 and 15C for wiland wild-type, respectively. Cold acclimationincreased endogenous ABA concentrations in Alaskashoot tips and epicotyls 3- to 4-fold. Immunogold labeling increasednoticeably in the nucleus and cytoplasm of the epicotyl after7 d at 2C and was greatest after 30 d at the time of maximumfreezing tolerance and soluble ABA concentration. Cold treatmentinduced the production of seven, three, and two proteins inshoot, epicotyl, and root tissue of Alaska, respectively.In Alaska shoot tissue, five out of seven novelproteins accumulated in response to both ABA and cold treatment.However, only a 24 kDa protein was produced in wiland wild-type shoot and epicotyl tissues aftercold treatment. Abscisic acid and cold treatment additivelyincreased the freezing tolerance of pea epicotyl and shoot tissuesthrough apparently independent mechanisms that both resultedin the production of a 24 kDa protein. Key words: Pisum sativum, cold acclimation, immuno-localization 相似文献
18.
Removal of the blade from the leaf subtending the first flowerbud on Cyclamen persicum Swan Lake plants causedthe petiole of that leaf to senesce, but had no effect on thegrowth of the flower peduncle in the debladed petiole's axil.A 10 mg NAA l1 application generally had no effect onpetiole senescence, peduncle elongation or flowering date whenapplied to the cut end of the petiole after blade removal. A25 mg GA3 l1 application or a combination of 25 mg GA3l1 application or a combination of 25 mg GA3 l1plus 10 mg NAA l1 delayed petiole senescence and enhancedpeduncle elongation and subsequent flowering. No treatment significantlyaltered peduncle length at the time of flowering. Cyclamen persicum Mill, Swan Lake, tissue receptivity, flowering, GA3, NAA 相似文献
19.
Zoea I larvae of the brown shrimp Crangon crangon (Decapoda)were exposed to varying levels of UV radiation in a sunshinesimulator. Short-term exposures (08 h)were used to determine the highest UV dose with no significanteffect (NOEC; defined by limit of detection) and the lethaldose of 10 and 50% mortality (LD10 and LD50). Crangon crangonshowed a relatively high sensitivity to UVB radiation (NOEC= 10 kJ m2, LD10 = 15 kJ m2, LD50 = 24 kJ m2)compared to other crust-acean species. LD values (19971998)showed no adaptation to seasonal light regimes. Long-termexposures (010 days) were carried out to assessthe range where the law of reciprocity is valid.The larvae were exposed to UV levels of 0.2, 0.4 and 0.7 J m2for appropriate time intervals, always cumulating in a sublethaldose of 5 kJ m2 day1. Results reflect a possiblethreshold (0.20.4 J m2 UVB) in the effect of thedifferent UVB doses used; thus, a proportional relationshipof intensity and exposure time can only be shown at UVB levelsabove this threshold intensity. 相似文献
20.
The effect of the leafless mutation (in whichtendrils replace leaflets and the stipules are reduced to avestigial form) upon foliage area, photosynthetic net CO2 uptakepotential, dry matter production and seed yield in Pisum sativumwas studied by comparing two near-isogenic lines of genotypeafafstst and ++++. The mutation is of potential agronomic valuein that it offers improved lodging resistance, crop drying andharvester throughput. In the conventional phenotype the total foliage area of themain axis attained a plateau (456 cm2) at day 56 from seedlingemergence, whereas corresponding values for the leaflessmutant showed a total area of 208 cm2 at day 68 with no indicationof a plateau. The agronomic consequence of this is discussed.During the vegetative phase of the plant the maximum CO2 uptakepotential in the fully expanded conventional leaf was 8·5mg CO2 leaf1 h1 and in the leaflessmutant this value was 7·0 mg CO2 leaf1 h1.For most leaves of the latter phenotype this valuewas between 30 and 60 per cent less than for their conventionalcounterpart. There was a consistently higher photosyntheticpotential per unit area in tendrils of the leaflessmutant than in leaflets of the conventional phenotype. The respectivemean specific values for the two phenotypes were 53 and 37 mgCO2 dm2 h1. The problem of obtaining a meaningfulsurface area value for tendrils is discussed and the cylindricalnature of tendrils is taken into account. The leafless mutant consistently accumulated 50per cent less dry matter than did conventional plants in theperiod from seedling emergence to anthesis and yield of maturedry seed per plant showed a reduction of 50 per cent both inseed number and total seed weight. The implications for future breeding and selection programmesaimed at haulm reduction are discussed in relation to evaluatingthe ability of the background genotype to produce adequate tendrilsin the presence of afafstst. Triticum aestivum, wheat, callus culture, organogenesis 相似文献