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1.
The response of the germination of seeds of Barbarea vema (Mill.)Aschers, Brassica chinensis L., Brassica juncea (L.) Czern.& Coss., Brassica oleracea L. var. gongylodes L., Camelinasaliva (L.) Crantz, Eruca saliva Mill., Lepidium sativum L.,Nasturtium officinale R. Br., and Rorippa palustris (L.) Besserto white fluorescent light of different photon flux densitiesapplied for different daily durations in a diurnal alternatingtemperature regime of 20 °C/30 °C (16 h/8 h) was quantifiedby linear relations between probit percentage germination andthe logarithm of photon dose, the product of photon flux densityand duration. The low energy reaction, in which increasing dosepromotes germination, was detected in all the seed populationsbut in Barbarea vema and Brassica Juncea the lowest photon doseapplied (1052 and 105 7 mol m2 d1,respectively) was sufficient to saturate the response. Comparisons,where possible, between photoperiods demonstrated reciprocity,i.e. germination was proportional to photon dose irrespectiveof photoperiod, for the low energy reaction in Brassica oleracea(1 min d1 to 1 h d1), Camelina saliva (1 min d1to 8 h d1), Eruca saliva (1 min d1 to 24 h d1),Lepidium sativum (I min d1 to 8 h d1) and Rorippapalustris (1 min d1 to 8 h d1), but not in Brassicachinensis and Nasturtium officinale. The high irradiance reaction,in which increasing dose inhibits germination, was detectedin Barbarea vema, Brassica chinensis, Brassica juncea, Brassicaoleracea, and Camelina saliva. The minimum dose at which inhibitionwas detected was lO03 mol m2 d1.These results are discussed in the context of devising optimallight regimes for laboratory tests intended to maximize germination The response of germination to photon dose was also quantifiedwith 3 x 104 M GA2, co-applied (Brassica chinensis, Camelinasaliva, and Lepidium sativum) and with 2 x 102 M potassiumnitrate co-applied (Brassica chinensis). In the latter casepotassium nitrate had no effect in the dark and inhibited germinationin the light, but GA2, promoted germination substantially inall three species. Variation amongst seeds in the minimum photondose required to stimulate germination was not affected by co-applicationof GA2, in Brassica chinensis and Camelina saliva, whereas seedsof Lepidium salivum showed a narrower distribution of sensitivitiesto the low energy reaction in the presence of GA2 Barbarea vema (Mill.) Aschers, Brassica chinensis L., Brassica juncea (L.) Czern. & Coss., Brassica oleracea L. var. gongylodes L., Camelina saliva (L.) Crantz, Eruca saliva Mill., Lepidium satiaum L., Nasturtium officinale R. Br., Rorippa palustris (L.) Besser, Cruciferae, light, gibberellic acid, seed germination, seed dormancy 相似文献
2.
Plants of Lolium perenne L. cv. S23 were grown in sand culturesupplied with either ammonium (NH4+) or nitrate (NO3)in an otherwise complete nutrient solution at 12°C or 20°C.Three weeks after germination, plants were clipped weekly tosimulate grazing. After 10 weeks growth all nitrogen (N) wassupplied enriched with 15N to quantify the effects of form ofN supply and temperature on the relative ability of currentroot uptake and remobilization to supply N for laminae regrowth. The form of N supply had no effect on the dry matter partitioning,while at 20°C more dry weight was allocated to laminae regrowthand less to the remaining plant material. The current root uptakeof N, which subsequently appeared in the laminae regrowth, wassimilar for plants supplied with NH4+ or NO3, and bothwere equally reduced at the lower temperature of growth. Remobilizationof N to laminae regrowth was greater for plants receiving NH4+than NO3; remobilization with either form of N supplywas reduced at the lower temperature of growth. Remobilizationwas reduced to a lesser extent at 12°C than current rootuptake. It was concluded that remobilization became relativelymore important in supplying N for regrowth of laminae at lowertemperatures. Key words: Lolium perenne, ammonium, nitrate, temperature, remobilization 相似文献
3.
The phytochrome-dependent germination of spores was studiedin the fern Pteris vittata. Brief irradiations with red lightgiven at 0 and 25?C resulted in very similar germination rates.Irradiation with far-red light cancelled this promotive effect,irrespective of the temperature at which tested. The maximumrate of germination was induced by red light of ca. 70Jm2and half of the rate was induced by ca. 15Jm2 When sporesimbibed in the dark were kept for 1 h at 0 or 25?C under irradiationswith monochromatic lights from 660 to 730 nm at 10 nm intervals,spore germination was induced depending upon the establishedphotostationary states of phytochrome at both temperatures tested.The percent of PFR estimated in spores that had been irradiatedbriefly with red light was consistent with that resulted fromphotostationary states under different monochromatic lightsin terms of the percent of germination of a spore population.The threshold of the % PFR required for the germination of eachspore ranged widely from a few percent to 80% of the PFR. Thisdiversity may vary the timing of germination in nature.
1 Partial preliminary results of this research were introducedin a review by M.F. (1978).
3 Present address: Department of Biology, Faculty of Science,Tokyo Metropolitan University, Setagaya, Tokyo 158, Japan. (Received May 15, 1982; Accepted August 5, 1982) 相似文献
4.
Tobacco shoots were grown in vitro for 35 d, in MS culture mediummodified to include various sources (nitrate-N, ammonium-N ora mixture) and levels (0120 mM) of N, and in the presenceof 0180 mM NaCI or iso-osmotic concentrations of mannitol.Growth of control plantlets was significantly inhibited whenNH4+-N was the sole N source, and at high (120 mM) NO3-N supply. Under conditions of salt stress (90 and 180 mM NaCI)growth was repressed, with roots being more severely affectedthan shoots. Salinity also inhibited root emergence in vitro.The only alleviation of the salt stress by nitrate nutritionobserved in this study was on shoot growth parameters of plantletsgrown on 60 mM NO3-N and 90 mM NaCI. Although both weresignificantly inhibited by NaCI, nitrate reduc-tase activitywas more severely affected than nitrate uptake. When mannitolreplaced NaCI in the culture medium, similar Inhibition of growth,nutrient uptake and enzyme activity were recorded. These observations,together with the relatively low recorded values for Na+ andCI uptake, indicate that under in vitro salt stress conditionsthe negative effects of NaCI are primarily osmotic. Key words: Growth, nitrogen metabolism, osmotic stress, salinity 相似文献
5.
Ethylene, Nitrate and Nitrite Interactions in the Promotion of Dark Germination of Common Purslane Seeds 总被引:1,自引:0,他引:1
Ethylene (10 µ11) caused about one-third of highlydark-dormant seeds of common purslane (Portulaca oleracea L.)to germinate in the dark. Attempts were made to increase germinationin the dark with nitrate and ethylene combinations. When applieddirectly to the seeds, KNO3 did not stimulate germination andKNO3 plus ethylene did not increase germination above that ofethylene alone. Pre-incubation of seeds in KNO3 for 4 to 7 dbefore the ethylene applications significantly increased germination.The effects of the KNO3 pre-incubation were additive at eachof four ethylene concentrations (0.1100 µ111).Potassium nitrate was effective only when ethylene followedthe KNO3 pre-incubation period. Potassium nitrite stimulatedabout 25 per cent of the seeds to germinate without a pre-incubationperiod and without ethylene. Also, ethylene plus KNO2 enhancedgermination above that achieved by either stimulus alone. Silvernitrate did not block the ethylene promotion of germination,but reversed the typical ethylene inhibition of seedling growthfollowing germination. The results support the views that nitrateexerted its effect via conversion to nitrite within the seedand that the rate of nitrate conversion may be a limiting factorin the dark germination of common purslane seeds. Ethylene mayfacilitate nitrite activity by increasing seed sensitivity tothe stimulus. Common purslane, Portulaca oleracea L., ethylene, nitrate, nitrite, germination, dormancy 相似文献
6.
Acclimation of NO3 transport fluxes (influx, efflux)in roots of oilseed rape (Brassica napus L. cv. Bien venu) andtheir sensitivity to growth at low root temperature was studiedin relation to external NO3 supply, defined by constantconcentrations ranging from sub- to supra-optimal with respectto plant growth rate. Plants were grown from seed in flowingnutrient solutions containing 250 mmol m3 NO3at 17°C for 20d, and solution temperature in half the cultureunits was then lowered decrementally over 3 d to 7°C. Threedays later plants were supplied with NO3 at 1, 10, 100or 1000 mmol m3 maintained for 18 d. Dry matter productionwas decreased more by low root zone temperature than low [NO3]e. Root specific growth rates were inversely related to [NO3]eand shoot:root ratios increased with time at [NO3]e between101000 mmol m3. Net uptake of NO3 at 17°Cwas twice that at 7°C, and at both temperatures it doubledwith increasing [NO3]e between 110 mmol m3with further small increases at higher [NO3]e. Mean unitabsorption rates of NO3 between 06 d and 614d were linearly related (r2 of 0.790.99) to log10[NO].Steady-state Q10 (717°C) for uptake between 06d were 0.91, 1.62, 1.27, and 1.10, respectively, at [NO3]eof 1, 10, 100, and 1000 mmol m3, compared with correspondingvalues of 0.98, 1.38, 1.68, and 1.89 between 614 d. Thedata indicated that net uptake rates at 7 and 17°C divergedover time at high [NO3]e. Short-term uptake rates from1 mol m3 NO3 measured at 17°C were higherin plants grown with roots at 7°C than at 17°C; for7°C plants there was a strong inverse linear relationship(r2=0.94) between uptake rate and treatment log10 [NO3]ewhilst rates in 17°C plants were independent of prior [NO3]e. Rates of NO3 influx and efflux under different steady-stateconditions of NO3 supply and root temperature were calculatedfrom dilution of 15N added to culture solutions. Efflux wassubstantial relative to net uptake in all treatments, and wasinversely related to [NO3]e at 17°C but not at 7°C.Ratios of influx: efflux ranged from 1.62.9 at 17°Cand 1.31.8 at 7°C, indicating the proportionatelygreater impact of efflux at low root temperature. Ratios ofefflux: net uptake were 0.531.56 at 17°C and 1.213.58at 7°C. The apparent sensitivities of influx and effluxto steady-state root temperature varied with [NO3]e.Both fluxes were higher at 17°C than 7°C in the presenceof 1001000 mmol m3 NO3 but the trend wasreversed at 110 mmol m3 NO. Concentrations oftotal N measured in xylem exudate were at least 2-fold higherat 7°C compared with 17°C, attributable mainly to higherconcentrations of NO3 glutamine and proline. The resultsare discussed in terms of acclimatory and other responses shownby the NO3 transport system under conditions of limitingNO3 supply and low root temperature. Key words: Brassica napus, nitrate supply, efflux, influx, root temperature, xylem exudate 相似文献
7.
A Mathematical Model to Utilize the Logistic Function in Germination and Seedling Growth 总被引:5,自引:1,他引:4
Several models have been proposed to describe germination rates,but most are limited in statistical analysis and biologicalmeaning of indices. Therefore, a mathematical model is proposedto utilize the logistic function. The function was defined asan overall response including time, temperature, and the interactionbetween time and temperature. Cumulative germination percentagesover time were used to develop the model. Germination tests were conducted on indiangrass (Sorghastrumnutans (L.) Nash) strain IG-2C-F1, at constanttemperatures of 9, 12, 15, 20, 25, and 30 °C. The functionfitted the observed data over six temperatures at r2 = 0.99.Time to reach 10% of final germination (Gt10) increased from2.5 d at 30 °C to 44.0 d at 9 °C, and Gt50 (time toreach 50% of final germination) increased from 3.6 d at 30 °Cto 53.8 d at 9 °C. True germination rate (% d1) foreach temperature was maximum at Gt50. A linear model of 1/Gt50versus temperature was used to estimate the base temperatureof 8.3 °C for germination. An Arrhenius plot indicated achange occurred between 20 °C and 25 °C for temperatureresponse of germination. Published data on hypocotyl growthof Cucumis melo L. were recalculated using the model. Absolutegrowth rates showed a temperature response similar to the publishedweighted-mean elongation rates. Base temperature for hypocotylgrowth of C. melo was estimated as 8.8 °C. The proposedmodel proved to be useful in calculating and interpreting germinationand growth kinetics. Key words: Indiangrass, Sorghastrum nutans (L.) Nash, Germination rate, Threshold temperature, Arrhenius plot, Growth rate, Cucumis melo L 相似文献
8.
Diurnal temperature fluctuations induced change in soya bean-pod[Glycine max (L.) Merr.] carbon exchange rate (CER, where positiveCER represents CO2 evolution). CER appeared to depend linearlyon temperature. Linear regressions of CER on temperature interceptedthe temperature axis at 5°C (i.e. zero CER at 5°C).Slopes of these regressions (i.e. temperature sensitivity) changedover the season. The CER-temperature sensitivity coefficient,K, (calculated from observed values of CER. pod temperatureand temperature intercept) rose from less than 0·02 mgCO2 h1 pod1 °C1 during early pod-flll,peaked at over 0·04 mg CO2 h1 pod1 °C1at mid pod-fill, and then declined during late pod-fill andmaturation. Glycine max (L.) Merr., Soya bean, carbon exchange rate, temperature 相似文献
9.
The growth of four heathland species, two grasses (D. flexuosa,M. caerulea) and two dwarf shrubs (C. vulgaris, E. tetralix),was tested in solution culture at pH 4.0 with 2 mol m3N, varying the N03/NH4+ ratio up to 40% nitrate. In addition,measurements of NRA, plant chemical composition, and biomassallocation were carried out on a complete N03/NH4+ replacementseries up to 100% nitrate. With the exception of M. caerulea, the partial replacement ofNH4+ by NO3 tended to enhance the plant's growth ratewhen compared to NH4+ only. In contrast to the other species,D. flexuosa showed a very flexible response in biomass allocation:a gradual increase in the root weight ratio (RWR) with NO3increasing from 0 to 100%. In the presence of NH4+, grassesreduced nitrate in the shoot only; roots did not become involvedin the reduction of nitrate until zero ambient NH4+. The dwarfshrubs, being species that assimilate N exclusively in theirroots, displayed an enhanced root NRA in the presence of nitrate;in contrast to the steady increase with increasing NO3in Calluna roots, enzyme activity in Erica roots followed arather irregular pattern. Free nitrate accumulated in the tissuesof grasses only, and particularly in D. flexuosa. The relative uptake ratio for NO3 [(proportion of nitratein N uptake)/(proportion of nitrate in N supply)] was lowestin M. caerulea and highest in D. flexuosa. Whereas M. caeruleaand the dwarf shrubs always absorbed ammonium highly preferentially(relative uptake ratio for NO3 <0.20), D. flexuosashowed a strong preference for NO3 at low external nitrate(the relative uptake ratio for N03 reaching a value of2.0 at 10% NO3). The ecological significance of thisprominent high preference for NO3 at low NO3/NH4+ratio by D. flexuosa and its consequences for soil acidificationare briefly discussed. Key words: Ammonium, heathland lants, N03/NH4+ ratio, nitrate, nitrate reductase activity, soil acidification, specific absorption rate 相似文献
10.
The intact dormant seeds of Dioscorea tokoro germinate slowlyif at all between 11-23°C; for full and rapid germinationthey require prior chilling treatment [Okagami and Kawai (1982)Bot. Mag. Tokyo 95: 155]. The germination abilities of zygoticembryos detached from dormant seeds of this species were studiedunder various nutritional and temperature regimes. For germinationof embryos, the minimum nutritional components in Murashigeand Skoog's (1962) medium that were required were sucrose andNO3 or SO24. As the source of carbohydrate forgermination of detached embryos, sucrose, mannose and maltosewere effective; glucose and fructose were less effective; andrhamnose was entirely unable to support germination. Embryos detached from dormant seeds, incubated with the sucroseplus KNO3, germinated more rapidly with increasing temperatureup to 35°C. However, application of sucrose and KNO3 didnot induce germination of intact seeds above 26°C. Therefore,it is very possible that the endosperm exerts an inhibitoryfunction on germination at such high temperatures. When seeds were incubated after a cut was made over a smallpart of the edge of the endosperm in which the radicle of theembryo is encased, germination occurred rapidly but the increasein germination percentage was slight. This result suggests thatthe endosperm suppots part of the germination inhibition bymeans of a mechanical barrier or its impermeability to wateror gases. Physiological features of the endosperm alone or interactionsbetween the embryo and endosperm may contribute significantlyto the characteristics of dormancy of intact seeds of this species. (Received May 30, 1988; Accepted January 11, 1989) 相似文献
11.
The relationship between germination and PFR level in sporesof the fern Lygodium japonicum was investigated. Percent PFRestimated from direct spectrophotometric measurement of sporesincreased with the logarithm of total fluence of 660 nm-light.The transformation from PR to PFR was saturated by giving ca.200 Jm2 of 660 nm-light and half-saturated by ca. 55J2 of 660 nm-light. Clear positive correlation was observedbetween % PFR levels and germination rates in spores irradiatedwith 660 nm and/or 730 nm-light, or with 686 or 700 nm-light.The PFR percentage in spores was raised to 1634% by blue(415 nm) light irradiation. This PFR level was enough to causesome germination when produced by monochromatic light of redto far-red region, but blue light did not cause any germination. After 660 nm-light irradiation, the PFR level decreased graduallyin darkness (25±1°C) and PFR completely disappearedin 8 h, but 730 nm-light given even 16 h after 660 nm-lightirradiation inhibited germination.
4Present address: Tropical Botanic Garden and Research Institute,Navaranga Road, Trivandrum 695 011, India. (Received March 15, 1983; Accepted June 4, 1983) 相似文献
12.
Effects of chilling (5 °C) period, light and applied nitrogen(N) on germination (%), rate of germination (d to 50% of totalgermination; T50%) and seed imbibition were examined inClematisvitalba L. In the absence of chilling, light and N, germinationwas minimal (3%). When applied alone, both chilling and N increasedgermination. Chilling for 12 weeks increased germination to64%, and 2.5 mM NO-3or NH+4increased germination to 1012%.Light did not increase germination when applied alone, but didwhen applied in combination with chilling and/or N. Half theseed germinated when light was combined with 2.5 mM NO-3or NH+4.The influence of chilling, light and/or N on germination wasgreater when combined, than when either factor was applied alone.Both oxidized (NO-3) and reduced (NH+4) forms of N increasedgermination, but non-N-containing compounds did not, suggestingthe response was due to N and not ionic or osmotic effects. Without additional N, T50%decreased from 1620 d at zerochilling, to around 5 d at 8 and 12 weeks chilling. AlthoughT50%was not influenced by an increase in NO-3or NH+4from 0.5to 5.0 mM , it did increase with additional applied N thereafter.However, the magnitude of the N effect was small compared tothat of chilling. Like germination, seed imbibition increasedwith a longer chilling period, but in contrast imbibition decreasedslightly with increased applied NO-3or NH+4. It is argued thatincreased imbibition is not directly related to an increasein total germination, but that it may be related to the rateof germination. Possible mechanisms involved in the reductionin dormancy ofC. vitalba seed are discussed. Clematis vitalba L.; germination; dormancy; imbibition; rate of germination; chilling; light; nitrate; ammonium; nitrogen; phytochrome 相似文献
13.
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
14.
Nodulated white clover plants (Trifolium repens L. cv. Huia)were grown for 71 d in flowing nutrient solutions containingN as 10 mmol m3 NH4NO3, under artificial illumination,with shoots at 20/15°C day/night temperatures and root temperaturereduced decrementally from 20 to 5°C. Root temperatureswere then changed to 3, 7, 9, 11, 13, 17 or 25°C, and theacquisition of N by N2 fixation, NH4+ and NO3 uptakewas measured over 14 d. Shoot specific growth rates (d. wt)doubled with increasing temperature between 7 and 17°C,whilst root specific growth rates showed little response; shoot:root ratios increased with root temperature, and over time at11°C. Net uptake of total N per plant (N2 fixation + NH4++ NO3) over 14 d increased three-fold between 3 and 17°C.The proportion contributed by N2 fixation decreased with increasingtemperature from 51% at 5°C to 18% at 25°C. Uptake ofNH4+ as a proportion of NH4+ + NO3 uptake over 14 d variedlittle (5562%) with root temperature between 3 and 25°C,although it increased with time at most temperatures. Mean ratesof total N uptake per unit shoot f. wt over 14 d changed littlebetween 9 and 25°C, but decreased progressively with temperaturebelow 9°C, due to the decline in the rates of NH4+ and NO3uptake, even though N2 fixation increased. The results suggestthat N2 fixation in the presence of sustained low concentrationsof NH4+ and NO4 is less sensitive to low root temperaturethan are either NH4+ or NO3 uptake systems. White clover, Trifolium repens L. cv. Huia, root temperature, nitrogen fixation, ammonium, nitrate 相似文献
15.
MATTSSON M.; LUNDBORG T.; LARSSON M.; LARSSON C.-M. 《Journal of experimental botany》1992,43(1):25-30
Barley (Hordeum vulgare L., cvs Golf, Mette, and Laevigatum)was grown under nitrogen limitation in solution culture untilnear maturity. Three different nitrogen addition regimes wereused: in the HN culture the relative rate of nitrate-Naddition (RA) was 0·08 d1 until day 48 and thendecreased stepwise to, finally, 0·005 d1 duringgrain-filling; the LN culture received 45% ofthe nitrogen added in HN; the CN culture was maintainedat RA 0·0375 d1 throughout. Kinetics of net nitrateuptake were measured during ontogeny at 30 to 150 mmol m3external nitrate. Vmax (which is argued to reflect the maximuminflux rate in these plants) declined with age in both HN andLN cultures. A pronounced transient drop was observed just beforeanthesis, which correlated in time with a peak in root nitrateconcentration. Similar, but less pronounced, trends were observedin CN. The relative Vmax (unit nitrogen taken up per unit nitrogenin plants and day) in all three cultures declined from 1·32·3d1 during vegetative growth to 0·10·7d1 during generative growth. These values are in HN andLN cultures 15- to more than 100-fold in excess of the demandset by growth rates throughout ontogeny. Predicted balancingnitrate concentrations (defined as the nitrate concentrationrequired to support the observed rate of growth) were below6·0 mmol m3 in HN and LN cultures before anthesisand then decreased during ontogeny. In CN cultures the balancingnitrate concentration increased during grain-filling. Apartfrom the transient decline during anthesis, most of the effectof ageing on relative Vmax can be explained in terms of reducedcontribution of roots to total biomass (R:T). The loss in uptakeper unit root weight is largely compensated for by the declinewith time in average tissue nitrogen concentrations. The quantitativerelationships between relative Vmax and R:T in ageing plantsare similar to those observed for vegetative plants culturedat different RAs. The data support the contention that the capacity for nitrateacquisition in N-limited plants is under general growth control,rather than controlled by specific regulation of the biochemicalpathway of nitrate assimilation. Key words: Barley, nitrogen concentration, root: total plant biomass ratio, Vmax 相似文献
16.
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
17.
Seasonal changes in the photosynthesis and primary productionof Microcystis aeruginosa Kütz. were investigated in LakeKasumigaura during 19811982. Microcystis always showeda light-saturated photosynthesis-light curve. Both Pmax andthe initial slope of the photosynthesis-light curve of Microcystisin early summer were very high, so it was concluded that Microcystisutilized both low and high light intensities efficiently. ThePmax of Microcystis was found to be a function of the watertemperature except in August and September. The linear regressionon the temperature-Pmax relationship discontinued at 11°C,where the Pmax value dropped; Microcystis did not photosynthesizebelow 4°C. The initial slope of the curve was also descendingbelow 11°C. It is suggested that Microcystis changes itsphysiological properties below 11°C. The highest value ofgross production calculated for M. aeruginosa was 5.4 gC m2d1 in July; the annual gross production was estimatedto be 300 gC m2year1 (i.e., 40% of the total primaryproduction in this lake). 相似文献
18.
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
19.
Simulated mixed swards of Perennial Ryegrass (Lolium perenneL.) cv. S23 and White clover (Trifolium repens L.) cv. S100were grown from seed under a constant 20 °C day/15 °Cnight temperature regime and harvested at intervals over and88 d growht period. The swards received a nutrient solutiondaily, which was either High (220 mg l1) or Low (10 mgl1) in nitrate N. The nitrate was labelled with the 15Nisotope. An acetylene reduction assay was carried out on eachsward just prior to harvest. Rates of acetylene reduction agreed qualitatively with the l5Nanalyses but absolute values did not match (assuming a 4:1 C2H4:N2ratio) and errors in the acetylene assay are discussed. In theLow-N swards clover relied almost entirely on symbioticallyfixed N2, fixing more than ten times as much as the High-N cloverplants. In the Low-N treatment the grass was N-deficient despiteobtaining much more nitrate per unit root dry weight than clover.In the High-N swards, however, clover took up more nitrate perunit root weight than grass. The High-N clover plants also fixedsome N2 and maintained a higher total-N content than grass throughoutthe period. There was no evidence of transfer of symbioticallyfixed N from the clover to the grass in either treatment. Trifolium repens, Lolium perenne, nitrate, nitrogen fixation, 15N, acetylene reduction 相似文献
20.
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