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1.
Interactions of C2H4, CO2, O2 and high temperature in stimulatinggermination of cocklebur (Xanthium pennsylvanicum Wallr.) seedswere studied and the phase sensitive to each factor during germinationwas determined. The combination of CO2 and enriched O2, andparticularly that of C2H4 and enriched O2, much more effectivelystimulated germination than CO2 and C2H4. At low temperature,however, the cooperation of CO2 and enriched O2 was lost andonly the effect of C2H4 in combination with CO2 or enrichedO2 remained. Carbon dioxide stimulated C2H4 production and induced germinationwhen it was applied in the first period of water imbibition,corresponding to the passive thrust forming phase. C2H4 becameeffective after the CO2-responsive phase. In contrast, bothO2 enrichment and high temperature became increasingly effectivewith the imbibition times. Anaerobiosis applied during the firstperiod of the germination process showed no inhibitory effect,whereas CO2 and C2H4 were stimulative even under such a condition. (Received August 26, 1974; )  相似文献   

2.
Growth of segments of embryonic axes and cotyledons excisedfrom dormant or nondormant cocklebur (Xanthium pennsylvanicumWallr.) seeds and CO2 and C2H4 production in these segmentswere examined in relation to the effects of temperature, CO2and C2H4. Both the nondormant axes and cotyledons grew evenat low temperatures below 23°C, but the dormant ones failedto grow. There was only little difference in the CO2 evolutionbetween the nondormant and dormant ones, but both the axis andcotyledon segments from the dormant seeds exhibited little orno C2H4 productivity, unlike the nondormant ones, at low temperatures.However, a high temperature of 33°C caused rapid extensiongrowth and C22H4 production even in dormant axes and cotyledons. The inability of dormant axes and cotyledons to grow disappearedcompletely in the presence of C2H4 at fairly low concentrations.Removal of endogenous CO2 and C2H4 reduced the growth in bothaxes and cotyledons, while exogenous CO2 mainly enhaced axialgrowth although exogenous C2H4 strongly stimulated the growthof both organs. Regardless of the dormant status, however, maximumgrowth of these organs occurred when C2H4 was given togetherwith CO2. We suggest that dormancy in cocklebur seeds is dueto the lack of growing ability in both organs, caused by thelack of C2H4 productivity in both dormant axes and cotyledons,particularly in the former. (Received December 2, 1974; )  相似文献   

3.
The axial growth of de-coated cocklebur (Xanthium pennsylvanicumWallr.) seeds, whose axes were divided into 4 zones, was examinedin relation to the temperature-dependent shift of the effectof C2H4 on germination. At 23?C, where both C2H4 and CO2 stimulatedgermination, CO2 promoted the axial growth at the radicle tipzone, whereas C2H4 promoted growth in the proximal portion ofthe axis. At 33?C, C2H4 inhibited germination, and stronglysuppressed the growth at the radicle tip, whereas the effectof CO2 did not change. The inhibition of growth at the radicletip zone was alleviated by O2 enrichment, which also reversedthe inhibition of germination. It is thus apparent that thetemperature-dependent shift of the action of C2H4 is associatedwith a temperature-dependent responsiveness of the radicle tipzone to C2H4. Growth of the radicle tip zone was sensitive toNaN3, whereas the proximal portion was sensitive to benzohydroxamicacid, an inhibitor of alternative respiration, suggesting thatthere may be an increase in the operation of the alternativerespiration path along a gradient of axial tissue from the tiptowards the cotyledonary side. The effects of CO2 and C2H4 arediscussed in relation to the different respiratory activitiesin each axial zone of cocklebur seeds. (Received May 9, 1986; Accepted November 6, 1986)  相似文献   

4.
Esashi, Y., Hase, S. and Kojima, K. 1987. Light actions in thegermination of cocklebur seeds. V. Effects of ethylene, carbondioxide and oxygen on germination in relation to light.–J.exp. Bot. 38: 702–710. Effects of ethylene, CO2 and O2 on the germination of after-ripenedupper cocklebur (Xanthium pennsylvanicum Wallr.) seeds wereexamined in relation to pre-irradiation by red (R) or far-red(FR) light In order to remove the pre-existing Pfr, seeds weresoaked in the dark for various periods prior to light irradiationand gas treatments. Regardless of light, 0.3 Pa C2H4 promotedgermination at 23 ?C, but it strongly inhibited germinationwhen applied at 33 ?C, the optimal temperature for the germinationof this seed. However, delayed application of C2H4 during 33?C incubation stimulated germination independently of lightin a similar manner to that seen at 23 ?C. It is, therefore,suggested that the germination-regulating action of C2H4 iscompletely independent of phytochrome. In contrast, the germination-promoting effect of 3–0 kPaCO2 was pronounced only when the seeds were previously irradiatedby R, regardless of temperature, suggesting that CO2 actionto promote germination depends upon Pfr. A synergism betweenCO2 and C2H4 at 23 ?C was observed only in the germination ofseeds pre-irradiated by R, while at 33 ?C an antagonism occurredindependently of light. The stimulation of C2H4 production byCO2 was most striking in the cotyledonary tissue pre-irradiatedby R. However, the R-dependent enhancement of CO2-stimulatedC2H4 production was negated by the subsequent FR and it wasnot found in the presence of 1-aminocyclopropane-1-carboxylicacid (ACC). Moreover, the R dependency of the germination-promotingCO2 effect disappeared in the presence of C2H4. The R-dependentC2H4 production enhanced by CO2 may thus be involved, at leastpartially, in some step of conversion from methionine to ACC. The germination-promoting effect of C2H4, but not CO2, was enhancedby O2 enrichment regardless of light. However, the germination-promotingeffect of pure O2 itself appeared to depend upon pre-irradiationwith R Key words: Carbon dioxide, cocklebur seed, ethylene, far-red light, germination, oxygen, red light, Xanthium pennsyloanicum  相似文献   

5.
The responsiveness of non-dormant, upper cocklebur (Xanthiumpennsylvanicum Wallr.) seeds to various germination stimulants,such as CO2 C2H4 CS(NH2)2, BA and enriched O2, decreased withincreasing periods of water imbibition and was completely lostin the state of secondary dormancy. Unlike CO2 BA and CS(NH2)2however, C2H2 and enriched O2 effectively prevented the developmentof secondary dormancy, and their combination was the most effectivefor stimulating the germination of seeds which had undergoneimbibition for a long time. CS(NH2)2 and BA were effective,not by themselves but either under anaerobiosis or elevatedO2 tension. Growth of the axial and cotyledonary segments excisedfrom aged seeds remained responsive to these germination stimulantsand could be further stimulated by exogenous C2H2. With imbibitionat a lower temperature, the seeds maintained high germinationin response to various stimulants and a high rate of C2H2 andCO2 production during a long period of water imbibition. Theseresults are discussed in terms of the two possible causes forthe loss of responsiveness or induction of the secondary dormancy. (Received June 27, 1978; )  相似文献   

6.
Effects of C2H4 and CO2 on respiration of pre-soaked upper cocklebur(Xanthium pennsylvanicum Wallr.) seeds during a pre-germinationperiod were examined in relation to effects of the two gaseson germination. At 33?C, cocklebur seed germination was greatlystimulated. This high temperature-stimulated germination wasseverely inhibited by C2H4, but not by CO2, although both gasesstimulated germination at 23?C. C2H4 promoted seed respirationat 23?C, but its promotive effect decreases with increasingtemperature and disappeared at about 35?C, while CO2 stimulatedrespiration regardless of temperature. CO2 augmented the operationof the CN-sensitive, cytochrome path (CP) regardless of temperature,resulting in an increase in the ratio of the CP flux to a CN-resistant,alternative path (AP) flux. On the other hand, C2H4 augmentedthe operation of both paths, particularly of the AP, at 23?C,where it promoted germination. However, at 33?C where germinationis suppressed by C2H4, C2H4 preferentially stimulated respirationvia the AP, thus leading to an extremely high ratio of AP toCP. The inhibitory effect of C2H4 on germination at 33?C disappearedcompletely in enriched O2, under which conditions CP is knownto be augmented. At 23?C, CO2 and C2H4 acted independently incontrolling seed respiration, but they were antagonistic at33?C. The independent action appeared when the AP flux was verylow relative to the CP flux, while the antagonism appeared whenthe AP flux had risen. This differential action of the two gasesat different temperatures was also observed in the ATP level,adenylate pool size and energy charge of the axial tissues.These results suggest that the germination-controlling actionsof both CO2 and C2H4 are fundamentally manifested through themodification of respiratory systems. However, the germination-inhibitingeffect of C2H4 at 33 ?C was not removed by inhibitors of AP,and there was little difference in the adenylate compounds betweenthe C2H4-treated and non-treated seeds at 33?C. Therefore, thephysiological action of C2H4 can not be explained only in termsof regulation of the respiratory system. (Received January 24, 1986; Accepted November 17, 1986)  相似文献   

7.
Ethylene Production in Pea and Cocklebur Seeds of Differing Vigour   总被引:1,自引:0,他引:1  
Relationships between seed vigour and ethylene (C2H4) productionwere studied using C2H4-responsive fatty cocklebur seeds (Xanthiumpennsyhanicum Wallr.) and C2H4-insensitive starchy pea seeds(Pisum sativum L. cv. Alaska), which had been harvested in differentyears and subjected to different storage conditions. In bothspecies, the seeds with the highest vigour evolved the largestamounts of C2H4 during a period of water imbibition. The reductionof C2H4 production in cocklebur seeds occurred concomitantlywith the reduction in the growth potentials of both axial andcotyledonary tissues. Similarly, the activity of ACC-C2H4 conversionincreased with soaking, and was greater in seeds of high vigourcompared with those of low vigour. However, the change in ACCcontent in pea seeds differed from that in cocklebur seeds.That is, pea seeds with high vigour accumulated less ACC duringan imbibition period than those with low vigour. From theseresults it was suggested that the inferior C2H4 production bylow vigour pea seeds is mainly attributable to low ACC-C2H4conversion, whereas that by low vigour cocklebur seeds is dueto the shortage of ACC supply in addition to the reduced ACC-C2H4conversion. However, germination of deteriorated cocklebur seedswas not restored by exposure to ACC or C2H4, suggesting thatthe loss of seed vigour reduces the responsiveness of seedsto C2H4 as well as C2H4 production. Key words: Pea, cocklebur, seed vigour, ethylene production, 1-aminocyclopropane-1-carboxylic acid  相似文献   

8.
Seedlings of perennial ryegrass (Lolium perenne L. cv. Parcour)and white clover (Trifolium repens L. cv. Karina) grown at fivedifferent plant densities were exposed to ambient (390 ppm)and elevated (690 ppm) CO2 concentrations. After 43 d the effectsof CO2 enrichment and plant density on growth of shoot and root,nitrogen concentration of tissue, and microbial biomass carbon(Cmic) in soil were determined. CO2 enrichment of Lolium perenneincreased shoot growth on average by 17% independent of plantdensity, while effects on root biomass ranged between -4% and+ 107% due to an interaction with plant density. Since tilernumber per plant was unaffected by elevated CO2, the small responseof shoot growth to CO2 enrichment was atributed to low sinkstrength. A significant correlation between nitrogen concentrationof total plant biomass and root fraction of total plant drymatter, which was not changed by CO2 enrichment, indicates thatnitrogen status of the plant controls biomass partitioning andthe effect of CO2 enrichment on root growth. Effects of elevatedCO2 and plant density on shoot and root growth of Trifoliumrepens were not significantly interacting and mean CO2-relatedincrease amounted to 29% and 66%, respectively. However, growthenhancement due to elevated CO2 was strongest when leaf areaindex was lowest. Total amounts of nitrogen in shoots and rootswere bigger at 690 ppm than at 390 ppm CO2. There was a significantincrease in Cmic in experiments with both species whereas plantdensity had no substantial effect. Key words: CO2 enrichment, intraspecific competition, biomass partitioning, Lolium perenne, Trifolium repens, grassland  相似文献   

9.
The quantum yields of photosynthetic O2 evolution were measuredin 15 species of C4 plants belonging to three different decarboxylationtypes (NADP-ME type, NAD-ME type and PEP-CK type) and 5 speciesof C3 plants and evaluated relative to the maximum theoreticalvalue of 0.125 mol oxygen quanta-1. At 25°C and 1% CO2,the quantum yield in C4 plants averaged 0.079 (differences betweensubgroups not significant) which was significantly lower thanthe quantum yield in C3 plants (average of 0.105 for 5 species).This lower quantum yield in C4 plants is thought to reflectthe requirement of energy in the C4 cycle. For the C4 NADP-MEtype plant Z. mays and NAD-ME type plant P. miliaceum, quantumyields were also measured over a range of CO2 levels between1 and 20%. In both species maximum quantum yields were obtainedunder 10% CO2 (0.105 O2 quanta-1 in Z. mays and 0.097 O2 quanta-1in P. miliaceum) indicating that at this CO2 concentration thequantum yields are similar to those obtained in C3 plants underCO2 saturation. The high quantum yield values in C4 plants undervery high CO2 may be accomplished by direct diffusion of atmosphericCO2 to bundle sheath cells, its fixation in the C3 pathway,and feedback inhibition of the C4 cycle by inorganic carbon. (Received June 6, 1995; Accepted August 15, 1995)  相似文献   

10.
Non-dormant small cocklebur seeds (Xanthium pennsylvanicum Wallr.)are potentiated to germinate, if they are subjected to anaerobiccondition for certain time periods after being sufficientlypre-soaked under aerobic conditions. This is termed "anaerobicinduction" of seed germination. Such induction was slightlyinhibited by CO2 applied during anaerobiosis, but markedly promotedby C2H4 Thus, C2H4 can exert its action even in anaerobiosis,but does not enhance the fermentative CO2 evolution. No actualanaerobic induction occurred when over 1? O2 was present, evenif C2H4 had been applied. Therefore, anaerobic induction seemsto be due to a concerted action of some anaerobically proceedingevents and the anaerobically produced C2H4. (Received May 31, 1976; )  相似文献   

11.
Etiolated Avena sativa L. coleoptile sections were used to determinethe influence of C2H4 on in vivo and in vitro rates of CO2 fixation,and to measure the influence of various permutations of C2H4,CO2, and malate on growth. Whereas 1 mM malate or 320 µI-1 CO2 stimulated growth by approximately 100 per cent, inhibitionof growth by 10-8 µ I-1 C2H4 was substantial only in thepresence of malate or CO2 The increase in growth rate in responseto these two agents was eliminated by the simultaneous applicationof C2H4. The in vivo rate of dark [14C]bicarbonate fixationand in vitro enzymic assays of fixation were not measurablyinhibited by C2H4. These results are discussed in the lightof evidence which indicates that CO2-stimulated growth is mediatedby dark fixation. The data do not support the view that C2H4inhibition of growth results from an inhibition of fixation,but suggests that C2H4 may inhibit some step in the processby which malate stimulates growth.  相似文献   

12.
This study investigated how CO2and temperature affect dry weight(d.wt) accumulation, total nonstructural carbohydrate (TNC)concentration, and partitioning of C and N among organs of twoimportant grasses of the shortgrass steppe,Pascopyrum smithiiRydb. (C3) andBouteloua gracilis(H.B.K.) Lag. ex Steud. (C4).Treatment combinations comprised two temperatures (20 and 35°C)at two concentrations of CO2(380 and 750 µmol mol-1),and two additional temperatures of 25 and 30°C at 750 µmolmol-1CO2. Plants were maintained under favourable nutrient andsoil moisture and harvested following 21, 35, and 49d of treatment.CO2-induced growth enhancements were greatest at temperaturesconsidered favourable for growth of these grasses. Comparedto growth at 380 µmol mol-1CO2, final d.wt of CO2-enrichedP.smithiiincreased 84% at 20°C, but only 4% at 35°C. Finald.wt ofB. graciliswas unaffected by CO2at 20°C, but wasenhanced by 28% at 35°C. Root:shoot ratios remained relativelyconstant across CO2levels, but increased inP. smithiiwith reductionin temperature. These partitioning results were adequately explainedby the theory of balanced root and shoot activity. Favourablegrowth temperatures led to CO2-induced accumulations of TNCin leaves of both species, and in stems ofP. smithii, whichgenerally reflected responses of above-ground d.wt partitioningto CO2. However, CO2-induced decreases in plant tissue N concentrationswere more evident forP. smithii. Roots of CO2-enrichedP. smithiihadgreater total N content at 20°C, an allocation of N below-groundthat may be an especially important adaptation for C3plants.Tissue N contents ofB. graciliswere unaffected by CO2. Resultssuggest CO2enrichment may lead to reduced N requirements forgrowth in C3plants and lower shoot N concentration, especiallyat favourable growth temperatures. Acclimation to CO2; blue grama; Bouteloua gracilis ; carbohydrate; climate change; global change; grass; growth; growth temperature optima; nitrogen; N uptake; Pascopyrum smithii; western wheatgrass  相似文献   

13.
Panicum hians and Panicum milioides were found to have characteristicsintermediate to those of C3 and C4 species with respect to CO2compensation point, percentage inhibition of photosynthesisby O2 at various O2/CO2 solubility ratios, and water use efficiency.C4 species have a higher carboxylation efficiency than eitherthe intermediate or C3 species. During photosynthesis, evenunder 2.5% O2, C4 species have a higher affinity for intercellularCO2 (Km 1.6 µM) apparently due to the initial carboxylationthrough PEP carboxylase. Under low O2 the intermediate and C3species had a similar affinity for intercellular CO2 duringphotosynthesis (Km 5–7 µM) consistent with carboxylationof atmospheric CO2 through RuDP carboxylase. There were considerablevariation in photosynthesis/unit leaf area at saturating CO2levels in the species examined which in part is due to differencesin RuDP carboxylase /unit leaf area. The highest rates of photosynthesis/unitleaf area under CO2-saturating conditions were with the C3 specieswhich had a correspondingly high level of RuDP carboxylase/unitleaf area. Possibilities for the greater efficiency of P. hiansand P. milioides in comparison to C3 species in utilizing lowlevels of CO2 in the presence of atmospheric O2 are discussed. 1 This research was supported by the College of Agriculturaland Life Sciences, University of Wisconsin, Madison; and theUniversity of Wisconsin Research Committee with funds from theWisconsin Alumni Research Foundation. (Received June 25, 1977; )  相似文献   

14.
Open-flow assays of acetylene reduction activity {ARA)and CO2production in nodulated roots were performed in situ with soybean{Glycine max (L.) Merr.) cv. Kingsoy grown hydroponically withorthophosphate (Pi) nutrition either limiting (low-P) or non-limiting(control) for plant growth. Nodule growth was more limited thanshoot growth by P deficiency. During ARA assays, nitrogenaseactivity declined a few minutes after exposure of the nodulatedroots to C2H2, and this acetyleneinduced decline (C2H2-ID) wastwice as intense at low-P. Moreover, the minimum ARA after theC2H2-ID was reached about 10 min earlier at low-P. The intensityof the C2H2-ID was correlated negatively with nodule mass perplant and positively with the ratio of shoot/nodule mass. Afterinitial exposure to C2H2, the nodulated-root CO2 productionwas transiently stimulated and, moreover, this increase was2-fold higher at low-P. Then, the nodulated-root CO2 productiondecreased with nodule C2H4 production. During the C2H2-ID, thenodule nitrogenase-linked respiration, which was computed asthe variable component of the linear regression between CO2and C2H4 production, was 2-fold higher at low-P. Furthermore,the microscopic observation of nodule sections revealed thatstarch deposits were decreased at low-P. However, nitrogenaseactivity, i.e. ARA before the C2H2-ID, was not affected by Pdeficiency. It is argued that P deficiency increased the C2H2-IDbecause it increased nodule permeability to O2 diffusion. Key words: Acetylene reduction, nitrogen fixation, phosphorus, respiration, soybean, Glycine max (L.) Merr  相似文献   

15.
Experiments were carried out to investigate the long-term influenceof humidity on the short-term responses of stomata and CO2 assimilationto vapor pressure difference in Oryza sativa (rice, C3 species)and Panicum maximum (green panic, C4 species). Plants were grownfor four weeks in growth chambers set at 35% and 85% relativehumidity at 25C air temperature, 38+2 Pa CO2 partial pressureand 1,700µmol m-2s-1 photon flux density. Soil was saturatedwith water in both humidity treatments. Low humidity pretreatmentscaused low leaf conductance and low rates of transpiration andCO2 assimilation in O. sativa, but small changes in stomatalresponses to humidity and in CO2 assimilation were found inP. maximum. From the short-term gas exchange experiments, itwas noted that the responsiveness of leaf conductance to vaporpressure difference were affected by humidity pretreatmentsin O. sativa, whereas unaffected in P. maximum. In O. sativameasurements of CO2 assimilation as a function of internal CO2partial pressure (A-Ci curve) indicated that low humidity pretreatmentsreduced the CO2 assimilation at high internal CO2 partial pressure,but the initial slope of the A-Ci curve was unaffected. Furthermore,plant characteristics such as total dry weight and leaf areaof plants subjected to low umidity were lower than plants subjectedto high humidity. The reductions in O. sativa, however, werelarger than in P. maximum. Stomatal frequency from low humiditygrown plant was higher than that from high humidity grown plantsin both species although there is no significant difference.The data indicated that if the short term inhibition of netCO2 assimilation at a high vapor pressure difference was imposedduring vegetative growth, the photosynthetic biochemistry andthe resultant plant growth were largely depressed in O. sativa,a C3 species. (Received May 26, 1992; Accepted November 2, 1992)  相似文献   

16.
Net photosynthetic rates per unit ground area for plant standsof Solanum melongena L. var. esculentum (aubergine) and Amaranthuscaudatus L. var. edulis (grain amaranth) were measured over10 min intervals in an airtight, glass, controlled-environmentcabinet for a range of light flux densities provided by thediurnal variation in daylight. Light response curves for photosynthesisof stands, grown at ambient CO2 concentration, were definedat 400, 800 and 1200 vpm CO2. Light compensation points for these stands were around 20-30J m-2 s-1 and decreased slightly at higher CO2 concentrations.For aubergine, a C3 species, the short-term effects of CO2 enrichmentwere to increase the initial slope as well as the asymptoteof the light response curve, reducing light saturation at moderateto high light flux densities; but for amaranthus, a C4 species,saturation was less apparent and CO2 enrichment scarcely increasedphotosynthesis except at light flux densities above 150 J m-2s-1. The canopies intercepted 93-98% of incident light. The efficiencyof utilization of intercepted light in photosynthesis (µgCO2 J-1) increased from zero at the light compensation pointto a maximum at an optimum light flux density of about 100 Jm-2 s-1 (the optimum rose a little with CO2 enrichment) anddecreased slightly with further increase in light. Maximum utilizationefficiencies at 400 vpm CO2 were 8-9 µg CO2 J-1. Enrichmentto 1200 vpm did not affect the peak utilization efficiency ofthe C4 amaranthus, but increased that aubergine to 12·2µg CO2 J-1 (equivalent to some 14% when using the heatof combustion of plant dry matter to convert to the dimensionlessform). This is among the highest recorded efficiencies of lightutilization for stands, and relates to the exceptionally favourableenvironment, with optimal control of CO2 concentration, humidity,temperature, water supply and mineral nutrition.Copyright 1993,1999 Academic Press Amaranthus caudatus L. var. edulis, Solanum melongena L. var. esculentum, canopy photosynthesis, CO2 enrichment, light interception, light utilization, photosynthetic efficiency  相似文献   

17.
The effects of CO2 on dormancy and germination were examinedusing seeds of cocklebur (Xanthium pennsylvanicum Wallr.) andgiant foxtail (Setaria faberi Herrm.). The rate of germinationof the giant foxtail seeds as well as cocklebur was promotedby exogenously applied CO2 at a concentration of 30 mmol mol-1regardless of the sowing conditions. However, seeds which failedto germinate in the presence of CO2, entered a secondary phaseof dormancy under unfavourable germination conditions. If CO2was applied to seeds under conditions such as water stress imposedwith a 200 mol m-3 mannitol solution, a hypoxic atmosphere of100 mmol mol-1 O2 or a treatment of 0·1 mol m-3 ABA,development of secondary dormancy was accelerated. These contrastedeffects of CO2 were observed in ecological studies. Under naturalfield conditions germination of buried giant foxtail seeds respondedpositively to CO2 during a period of release from primary dormancyfrom Feb. to May, but CO2 accelerated secondary dormancy commencingin early Jun. In other words, in the presence of CO2, both theenvironmental conditions and the germination states of the seedsclearly showed secondary dormancy-inducing effects. Thus, itseems that CO2 has contrasted effects on regulation of dormancyand germination of seeds depending on the germination conditions.Copyright1995, 1999 Academic Press Xanthium pennsylvanicum, cocklebur, Setaria faberi, giant foxtail, CO2, water stress, hypoxia, ABA, germination, secondary dormancy  相似文献   

18.
In 4 cultivars of tomato (Lycopersicon esculentum Mill.), theearly detachment of fruits advanced ripening and considerablyreduced the threshold value of endogenous C2H4. This indicatesa supply from the vegetative parts of (a) labile ripening-inhibitingsubstance(s) antagonizing the action of C2H4. The endogenous level of CO2 increased shortly after the risein C2H4, and maximum levels of C2H4 and CO2 occurred almostsimultaneously. The activity of PE showed no connection with ripening, but PGactivity did not occur until the onset of ripening. However,this activity increased at considerably higher C2H4 concentrationsthan the rise in WSP, and was independent of the possible presenceof ripening inhibitor(s). Hence PG is considered not to be involvedin the primary events leading to fruit ripening. Exposure of fruits to different C2H4 concentrations in the ambientatmosphere also showed PG activity to increase only after therise in WSP had started. Other pectin degrading or synthesizingenzymes may be involved. In the non-ripening Rin mutant of cv. Rutgers, no rise occurredin C2H4, CO2, WSP, and PG activity. 1 Present address: Department of Agricultural Chemistry, Facultyof Agriculture, Kochi University, Otsu 200 Monobe, Nangoku City,Kochi Prefecture 783, Japan. (Received February 16, 1978; )  相似文献   

19.
Pascopyrum smithii (C3) andBouteloua gracilis (C4) are importantforage grasses native to the Colorado shortgrass steppe. Thisstudy investigated photosynthetic responses of these grassesto long-term CO2enrichment and temperature in relation to leafnonstructural carbohydrate (TNC) and [N]. Glasshouse-grown seedlingswere transferred to growth chambers and grown for 49 d at twoCO2concentrations (380 and 750 µmol mol-1) at 20 and 35°C, and two additional temperatures (25 and 30 °C) at750 µmol mol-1CO2. Leaf CO2exchange rate (CER) was measuredat a plant's respective growth temperature and at two CO2concentrationsof approx. 380 and 700 µmol mol-1. Long-term CO2enrichmentstimulated CER in both species, although the response was greaterin the C3,P. smithii . Doubling the [CO2] from 380 to 750 µmolmol-1stimulated CER ofP. smithii slightly more in plants grownand measured at 30 °C compared to plants grown at 20, 25or 35 °C. CO2-enriched plants sometimes exhibited lowerCER when compared to ambient-grown controls measured at thesame [CO2], indicating photosynthetic acclimation to CO2growthregime. InP. smithii , such reductions in CER were associatedwith increases in TNC and specific leaf mass, reductions inleaf [N] and, in one instance, a reduction in leaf conductancecompared to controls. InB. gracilis , photosynthetic acclimationwas observed more often, but significant changes in leaf metabolitelevels from growth at different [CO2] were generally less evident.Temperatures considered optimal for growth (C3: 20 °C; C4:35 °C) sometimes led to CO2-induced accumulations of TNCin both species, with starch accumulating in the leaves of bothspecies, and fructans accumulating only inP. smithii. Photosynthesisof both species is likely to be enhanced in future CO2-enrichedand warmer environments, although responses will sometimes beattenuated by acclimation. Acclimation; blue grama (Bouteloua gracilis (H.B.K.) Lag ex Steud.); leaf nitrogen concentration; nonstructural carbohydrates; photosynthesis; western wheatgrass (Pascopyrum smithii (Rydb.) Love)  相似文献   

20.
The rates of photosynthetic 14CO2 fixation by Chlorella vulgarisllh, grown under high CO2, were determined between 4 to 37°Cwith air containing from 300 to 13,000 ppm 14CO2. When the CO2level was increased, both the rate of photosynthesis and theoptimum temperature for maximum photosynthesis increased. Themaximum photosynthetic rate was reached at 12°C with 300ppm l4CO2. Among the photosynthetic products fromed at 300 ppm 14CO2, glycolatedecreased greatly when the temperature was raised from 20 to30°C. At 3,000 ppm 14CO2 an insignificant amount of glycolatewas formed at all temperatures, whereas 14C-incorporation intothe insoluble fraction, sucrose, and the lipid fraction wassignificantly higher than at 300 ppm 14CO2. The 14C in sucrosewas greatly increased and the radioactivity in the insolublefraction decreased when the temperature was raised from 28 to36°C. (Received April 8, 1980; )  相似文献   

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