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1.
The marine diatoms Lauderia annulata and Synedra planctonicaharvested during exponential growth were exposed to differentdoses of u.v.-B (286, 439 and 710 J m2 d1) for2 days. Uptake of 15N-nitrate was estimated before, during andafter u.v.-B radiation over 2 days. Exposure to high levelsof u.v.-B (710 J m2 d1) caused irreversible damageat the second daily irradiance. Lauderia cells were less affectedby u.v.-B stress than Synedra cells. 15N-nitrate uptake wasreduced under u.v.-B irradiance but could be reactivated within1 day following exposure to a low dose (286 J m2 d1).Higher levels of u.v.-B radiation (710 J m2 d1)led to irreversible damage. The pattern of 15N-incorporationinto several amino acids of Lauderia varied after 2 days ofu.v.-B radiation. 15N enrichment of glutamine increased markedlyafter u.v.-B stress (717 J m2 d1) whereas I5Nexcess of aspartic acid was significantly reduced. Results arediscussed with reference to the u.v.-B damage of the nitratetransport system. 相似文献
2.
By manipulation of various growth regulators and physical conditions,plants have been regenerated from excised roots, stem segments,cotyledons, leaves, and callus cultures of red cabbage (Brassicaoleracea var. capitata) grown under in vitro conditions. Shootbuds were induced on isolated root segments (1 cm long) culturedon Murashige and Skoog's medium and the frequency of bud formationwas greatly enhanced by the addition of kinetin (0.5 part 106).Callus obtained from the seeds, cotyledons, and hypocotyl segmentscultured on a medium fortified with 2,4-D (1 part 106),kinetin (0.1 part 106), and coconut milk (10%, v/v) hasbeen repeatedly subcultured. The callus is slow growing, andon transference to a kinetin (2 parts 106) and IAA (2parts 106) medium underwent morphogenesis to give riseto plants. The significance of the propagation of red cabbageby in vitro culture is pointed out. 相似文献
3.
Toda Hideshige; Takahashi Masayuki; Ichimura Shun-ei 《Journal of plankton research》1984,6(4):647-662
The effect of temperature on post-embryonic growth of Neomysisintermedia was investigated under unlimited food conditionsin the laboratory. The effect of temperature on the size ofnewly released animals was negligibly small, but body size wasinversely related to temperature in adults. This was mainlycaused by the difference in the number of molts before maturation.The specific growth rate of N. intermedia increased exponentiallywith a temperature coefficient, Q10 of 4.6 from 0.018 d13C to 0.21 d1 at 20C in juveniles, and with a temperaturecoefficient of 2.7 from 0.006 d1 at 3C to 0.05 d1at 25C in adults. The rate in juveniles levelled off above20C, and dropped at 29C. Brood size and brood interval decreasedwith temperature increase, while the daily specific reproductionrate increased. The specific growth rate of gravid females,including production of egg matter, increased exponentiallywith a temperature coefficient of 3.3 from 0.015 d1 at10C to 0.093 d1 at 25C. The present laboratory experiments confirmed the temperaturecontrol on the growth of N. intermedia suggested in a hyper-eutrophiclake. 相似文献
4.
Single clonal plants of white clover (Trifolium repens L) grownfrom explants in a Perlite rooting medium, and dependent fornitrogen on N2 fixation in root nodules, were grown for severalweeks in controlled environments which provided two regimesof CO2, and temperature 23/18 °C day/night temperaturesat 680 µmol mol1 CO2, (C680), and 20/15 °Cday/night temperatures at 340 µmol mol1 CO2 (C340)After 34 weeks of growth, when the plants were acclimatedto the environmental regimes, leaf and whole-plant photosynthesisand respiration were measured using conventional infra-red gasanalysis techniques Elevated CO2 and temperature increased ratesof photosynthesis of young, fully expanded leaves at the growthirradiance by 1729%, despite decreased stomatal conductancesand transpiration rates Water use efficiency (mol CO2 mol H2O1)was also significantly increased Plants acclimated to elevatedCO2, and temperature exhibited rates of leaf photosynthesisvery similar to those of C340 leaves instantaneouslyexposed to the C680 regime However, leaves developed in theC680 regime photosynthesised less rapidly than C340 leaves whenboth were exposed to a normal CO2, and temperature environmentIn measurements where irradiance was varied, the enhancementof photosynthesis in elevated CO2 at 23 °C increased graduallyfrom approx 10 % at 100 µmol m1 s1 to >27 % at 1170 µmol m2 s1 In parallel, wateruse efficiency increased by 2040 % at 315 µmolm2 s1 In parallel, water use efficiency increasedby 2040 % at 315 µmol m2 s1 In parallel,water use efficiency increased by 2040 % at 315 µmolm2 s1 In parallel, water use efficiency increasedby 2040 % at 315 µmol m2 s1 to approx100 % at the highest irradiance Elevated CO2, and temperatureincreased whole-plant photosynthesis by > 40 %, when expressedin terms of shoot surface area or shoot weight No effects ofelevated CO2 and temperature on rate of tissue respiration,either during growth or measurement, were established for singleleaves or for whole plants Dependence on N2, fixation in rootnodules appeared to have no detrimental effect on photosyntheticperformance in elevated CO2, and temperature Trifolium repens, white clover, photosynthesis, respiration, elevated CO2, elevated temperature, water use efficiency, N2 fixation 相似文献
5.
In situ light measurements were used to obtain information oninherent and apparent optical properties. The average verticalattenuation coefficient Kd(ave) varied from 1.1 to 4.6 In unitsm1 During three periods the variation in Kd(ave) correlatedwith changes in chlorophyll a concentration and specific attenuationcoefficients Ks, of 0.013, 0.014 and 0.022 m2 mg Chl a1were calculated. Chlorophyll-specific diffuse absorption coefficients(A,) for these periods were 0.012. 0.013 and 0.017 m2 mg Chla1 and only varied significantly from estimates of Ksin the period when scattering was intense. Absorption coefficientsa(zmid) and scattering coefficients b(zmid) calculated for themid-point of the euphotic zone ranged between 0.45 and 2.9 mand 3.552.0 m respectively. Chlorophyll-specific absorptioncoefficients Ka, of 0.005, 0.006 and 0.007 m2 mg Chl a1and scattering coefficients Kb of 0.05. 0.09 and 0.191 m2 mgChl a1 were measured during the three periods. The highKb value occurred when gas-vacuolate cyanobactena were dominant.Algal photosynthesis and light absorption were related throughthe maximum quantum yield m which varied between 0.019 and 0.11mol C Einstein1 while average quantum yields a, variedbetween 0.006 and 0.024 with a mean of 0.013 mol C Einstein1A comparison of changes in the mean irradiance of the mixedzone and chlorophyll concentration indicated that growth waslight limited below 0.040.05 Einsteins absorbed mg Chla1 day1. 相似文献
6.
A model of nitrogen uptake and distribution is presented whichdescribes these processes in relation to the amount of availablesoil nitrate and the rate of plant growth. Nitrogen uptake iseither sink or source limited. Sink limitation is based on maximumN-concentrations of plant compartments. The N-uptake model iscombined with a photosynthesis model based on the productivity-nitrogenrelationship at the single-leaf level. The model is parameterizedusing cauliflower as an example crop. Applied to an independentdata set, the combined model was able to predict leaf, stemand inflorescence nitrogen concentrations with correlation coefficientsbetween predicted and simulated values of 0.89, 0.66 and 0.86,respectively. The influence of nitrogen supply and light intensityon leaf nitrate-N could also be predicted with good accuracy(r2 = 0.87). Dry matter production based on the productivity-Nrelationship and the partitioning into leaf, stem and inflorescencewas also reproduced satisfactorily (r2 = 0.91, 0.93 and 0.92,respectively). Copyright 2000 Annals of Botany Company Brassica oleracea L. botrytis, cauliflower, nitrogen, nitrate, nitrogen supply, nitrogen uptake, nitrogen distribution, model 相似文献
7.
During the ripening stage of barley and rice, the sink activitywas defined as the dry matter increase per units sink size,leaf area and time, as follows: NAR = A.SinkW+NAR', where NAR is the net assimilation rate (g d.wt dm2d1);A is the sink activity [g d.wt g1d.wt (ear) dm2d1]; Sink W is ear wt per plant at heading (g d.wt);and NAR' is net assimilation rate excluding the assimilate ofsink organ (g d.wt dm2 d1). Plant material with 16 combinations of mutually different sink(ear) and source (leaf) size were produced at heading for eachcrop: parts of each leaf and ear were removed to produce fourgrades in barley, and also a part of each leaf was removed producingfour grades for four rice varieties showing different ear size.NAR and NAR' were determined during 26 and 21 d in barley andrice after heading, respectively. Sink activity (A), representedas the assimilation rate induced by the sink organ, was estimatedfrom the relationship between SinkW and NAR using the previousequation. The sink activity was significantly higher in ricewith a value of 00.028 g d.wt g1 d.wt (ear) dm2d1 vs. 00.0017 in barley, suggesting that therelative role of leaves for grain filling is considerably higherin rice than in barley. The sink activity obtained in the studymight be introduced into a model to predict the yields of barleyand rice. Hordeum vulgare L, barley, Oryza saliva L, rice, dry matter, NAR, sink, source, sink activity, model 相似文献
8.
Growth Analysis of Sweet Pepper (Capsicum annuum L.): 2. Interacting Effects of Irradiance, Temperature and Plant Age in Controlled Conditions 总被引:1,自引:0,他引:1
A growth analysis was carried out with sweet pepper plants grownin a phytotron. Irradiance conditions were: 0.84 or 3.25 MJm2 in 8 h, 1.67 MJ m2 in 16 h and 2.51 MJ m2in 24 h. Temperatures applied were 25 or 21 °C during thephotoperiod in combination with 25, 21 and 17 or 21, 17 and13 °C respectively during the nyctoperiod. Highest values for leaf area and total dry weight were foundwhen applying 1.67 MJ m2 in 16 h, followed by 3.25 MJm2 in 8 h, irrespective of the temperature regime. Continuousirradiance ultimately resulted in leaf drop. A reduction inthe day temperature decreased leaf area and total dry weight.At a day temperature of 25 °C the dry weight increased withdecreasing night temperature when applying 3.25 MJ m2in 8 h. At a day temperature of 21 °C leaf area and dryweight were reduced when 17 or 13 °C were applied duringa 16 h nyctoperiod. Values for relative growth rate, net assimilation rate, leafarea ratio and leaf weight ratio strongly decreased with advancingplant age. The effects of irradiance treatment on RGR and NARwere analogous to those on total dry weight while the reversepattern was observed for the LAR. A decrease in day temperaturedecreased the RGR. The effects of night temperature exhibitedstrong interactions with day temperature and photoperiod. Theinfluence of temperature on RGR was largely mediated throughchanges in the LAR. The latter parameter was highly correlatedwith the specific leaf weight. Capsicum annuum L., sweet pepper, growth analysis, irradiance, temperature, plant age 相似文献
9.
Growth and Nitrogen Fixation of Phaseolus vulgaris L. at Two Irradiances II. Nitrogen Fixation 总被引:1,自引:0,他引:1
Phaseolus vulgaris cv. Glamis plants grown at 7 and 28 W m228 W m2 in controlled environment cabinets showed copiousnodulation and high levels of acetylene reducing activity. Earlydifferences in nodulation were apparent before differences inphotosynthesis and were attributed to an effect of far-red lighton nodule development. Total plant nitrogen content was greater at 28 W m2 thanat 7 W 2 but nitrogen content as a percentage of d. wtwas greater at the lower irradiance level. Total acetylene reducing activity (nmol. min1 root1)was greater at 28 W m2 than at 7 W 2, but therewas no irradiance effect on specific activity (nmol. min1g d. wt of pink nodules1 or nmol. min1 pink nodule1). Transfer of 40-day-old plants from 7 W m2 to 28 W m2resulted in increased nodulesize(due toincreased size of infectedcells), accompanied by increased total, but not specific, acetylenereducing activity. Transfer of plants from 28 W m2 to 7 W m2 resultedin a fall of total acetylene reducing activity within 24 h,and senescence of large nodules. Specific acetylene reducingactivity was unaffected The results are interpreted as an effect of light on the productionof nitrogen fixing tissue, rather than on nitrogenase activity. 相似文献
10.
Wheeler T.R.; Hong T.D.; Ellis R.H.; Batts G.R.; Morison J.I.L.; Hadley P. 《Journal of experimental botany》1996,47(5):623-630
Winter wheat (Triticum aestivum L. cv. Hereward) was grown inthe field inside polyethylene-covered tunnels at a range oftemperatures at either 380 or 684 µmol mol1 CO2.Serial harvests were taken from anthesis until harvest maturity.Grain yield was reduced by warmer temperatures, but increasedby CO2 enrichment at all temperatures. During grain-filling,individual grain dry weight was a linear function of time fromanthesis until mass maturity (attainment of maximum grain dryweight) within each plot. The rate of progress to mass maturity(the reciprocal of time to mass maturity) was a positive linearfunction of mean temperature, but was not affected by CO2 concentration.The rate of increase in grain dry weight per ear was 2.0 mgd1 greater per 1 C rise, and was 8.0 mg d1 greaterat 684 compared with 380 µmol mol1 CO2 at a giventemperature. The rate of increase in harvest index was 1.0%d1 in most plots at 380 µmol mol1 CO2 andin open field plots, compared with 1.18% d1 in all plotsat 684 µmol mol1 CO2. Thus, the increased rateof grain growth observed at an elevated CO2 concentration couldbe attributed partly to a change in the partitioning of assimilatesto the grain. In contrast, the primary effect of warmer temperatureswas to shorten the duration of grain-filling. The rate of graingrowth at a given temperature and the rate of increase in harvestindex were only independent of the number of grains per earabove a critical grain number of 2324 grains per ear({small tilde}20 000 grains m2). Key words: Winter wheat, grain growth, temperature, CO2, harvest index, critical grain number 相似文献
11.
The two parameters of the hyperbolic tangent equation, Pm and, were estimated from in situ vertical profiles of primary productionusing mesocosm data along a nutrient gradient. The parameters,derived from 4-h (around noon) 14C incubations, were used togetherwith the photosynthesis-light curve and hourly solar radiationdata to calculate daily primary production rates (Pd). Approximately40% of the daily production occurred in the 4 h around noon.Considering parameter uncertainty, there was no indication ofan increase in variation in production with increased nutrientloading, nor did biomass-specific P-I parameters increase. Annualproduction ranged from 82 to 901 g C m2 year1and was highest in the highest nutrient treatment tank. Dailyproductivity ranged from 0.02 to 9.1 g C m2 day1and was significantly correlated, in all treatments, with acomposite parameter BI0/k (where B is phytoplankton biomass;I0 is daily radiation and k is the extinction coefficient).Linear regressions of Pd against BI0/k indicated that much ofthe variability (86%) in productivity was explained by lightavailability and phytoplankton biomass. Two approaches for predictingproductivity were compared: (i) predicting production directlyfrom environmental variables (i.e. BI0/k) and (ii) predictingthe parameters of the P-I curve from environmental variablesand using these to calculate daily production. 相似文献
12.
The influence of mean temperature and total solar radiationon the daily increment of shoots of 12-year-old Picea sitchensisis described. Serial auto and cross-correlation analysis isused to show that variation in shoot increment is correlatedwith variations in weather occurring over several previous hours.The relationships between daily increments for the leading andtopmost five whorl shoots and the two controlling variablesof temperature and solar radiation are described for the firsthalf of the growing season by auto-regressive models fittedby time-series methods as described by Box and Jenkins. Thesedynamic system models showed that there was a delay of one dayand two days respectively in the influence of temperature andsolar radiation on shoot increment and that after these delaysthe response continued for more than a single day. The maximumfinal response (or steady state gain) of a typical topmost shootto temperature and solar radiation change was found to be 0.091mm d1(°C)1 and 0.027 mm d1 (MJ m2)1.For the normal range of these variables experienced this indicatesthat shoot extension was five times more sensitive to changesin temperature than to those in solar radiation. Picea sitchensis, Sitka spruce, shoot growth, weather influences, ARMA model, time-series analysis, Box-Jenkins method 相似文献
13.
Light, temperature and nitrogen as interacting factors affecting diel vertical migrations of dinoflagellates in culture 总被引:11,自引:0,他引:11
Diel vertical migrations of the marine dinoflagellates Gonyaulaxpolyedra Stein and Ceratium furca (Ehr.) Clap, et Lachm. werefollowed in a laboratory tube (2.02 m x 0.25 m) under a 12:12hlight:dark cycle. The effects of temperature stratification,two levels of surface irradiance and nitrogen depletion on patternsof vertical migrations were examined. At temperatures between2226°C with small temperature gradients, both speciesmigrated at a rate of 0.7 1.0 m h1. Steeper thermoclines(ca. 0.8°C 0.1 m1) with temperatures below ca. 20°Ccaused a marked decrease in swimming speed which resulted inaccumulations of cells in these thermocline regions. Under conditionsof nutrient sufficiency both algae migrated into the surfacelayers at irradiance values of over 1000 µE m2s1. Increasing nitrogen depletion caused the downwardmigration of both algae to commence progressively earlier inthe day and before the end of the light period. The earlierdownward migrations enabled a more complete descent throughthe thermocline. Nitrogen depleted cells of Gonyaulax continuedto undertake vertical migrations but avoided high irradiancesthus forming subsurface maxima at irradiance levels close to150 µE m2 s1. Ceratium cells which exhaustedboth inorganic nitrogen and phosphorus ceased to migrate accompaniedby a large change in cellular fluorescence. 相似文献
14.
Responses of CO2 assimilation to changes in irradiance: laboratory and field data and a model for beans (Phaseolus vulgaris L.) 总被引:1,自引:0,他引:1
The responses of net CO2 assimilation to sudden changes in irradiancewere studied in Phaseolus vulgaris L. in the laboratory andthe field. For irradiance changes between 50 µmol m2s1 to 350 µmol m2 s1 in the laboratory,assimilation rate increased with half-times of 2.7 and 4.1 minin well-watered and water-stressed plants, respectively. Ina field experiment with a change in irradiance from 400 to 1200µmol m2 s1 the response was faster (half-time=c.1.2 min). In all cases when irradiance was returned to a lowvalue, assimilation declined rapidly with a half-time of approximately1 min, which approached the time resolution of the gas-exchangesystem. The corresponding changes in stomatal conductance in responseto both increasing and decreasing irradiance were much slowerthan the assimilation responses, indicating that biochemicalprocesses, rather than CO2 supply, primarily determined theactual rate of assimilation in these experiments. The conceptof stomatal limitation to photosynthesis is discussed in relationto these results. A simple model for assimilation in a fluctuating light environmentis proposed that depends on a steadystate light response curve,an induction lag on increasing irradiance, andan induction-state memory. The likely importance of taking accountof such induction lags in natural canopy microclimates is considered. Key words: Models, Phaseolus vulgaris, photosynthetic induction, CO2 assimilation, stomatal limitation, sunflecks, water stress 相似文献
15.
The photosynthetic response to CO2 concentration, light intensityand temperature was investigated in water hyacinth plants (Eichhorniacrassipes (Mart.) Solms) grown in summer at ambient CO2 or at10000 µmol(CO2) mol1 and in winter at 6000 µmol(CO2)mol1 Plants grown and measured at ambient CO2 had highphotosynthetic rate (35 µmo1(CO2) m2 s1),high saturating photon flux density (15002000) µmolm2 s1 and low sensitivity to temperature in therange 2040 °C. Maximum photosynthetic rate (63 µmol(CO2)m2 s1) was reached at an internal CO2 concentrationof 800 µmol mol1. Plants grown at high CO2 in summerhad photosynthetic capacities at ambient CO2 which were 15%less than for plants grown at ambient CO2, but maximum photosyntheticrates were similar. Photosynthesis by plants grown at high CO2and high light intensity had typical response curves to internalCO2 concentration with saturation at high CO2, but for plantsgrown under high CO2 and low light and plants grown under lowCO2 and high light intensity photosynthetic rates decreasedsharply at internal CO2 concentrations above 1000 µmol1. Key words: Photosynthesis, CO2, enrichment, Eichhornia crassipes 相似文献
16.
The productive and optical status of the oligotrophic waters of the Southern Aegean Sea (Cretan Sea), Eastern Mediterranean 总被引:2,自引:0,他引:2
Primary production, pigment concentrations and spectral measurementsof downwelling irradiance were made at four stations in fourseasons (spring, summer, autumn, winter) during 1994 in thewaters of the South Aegean Sea (Cretan Sea), Eastern Mediterranean.Rates of production were determined using in Situ incubationtechniques and included measurements at the surface microlayer.Depth-integrated values averaged over season were 5.66 mg Cm2 h1 for primary production and the correspondingchlorophyll (Ch1) a and phaeophytin (Phaeo) a values had meansof 4.87 and 1.21 mg m3 respectively. The assimilationratio remained very low (mean over season: 1.19 mg C mg2Chl a h1 as did the Phaeo a/Chl a ratio (mean over season:0.24). The annual production for the area was estimated to yield24.79 g C m2 year1. Primary production and Chla estimates showed statistically significant seasonal, spatialand depth variations. The spectral values of the attenuationcoefficient Kd ( 相似文献
17.
Growth and dark respiration were measured in dense, miniatureswards of kikuyu grass grown at constant temperatures of 15,20, 25 and 30 °C. Total respiration over the first 12 hof darkness was very high and CO2 efflux per unit surface areavaried from 2.4 to 3.9 g CO2 m2 h1 at 15 and 30°C respectively. Such rates were consistent with the correspondinglyhigh net growth rates of 24 and 63 g d. wt m2 d1and the heavy yields of herbage. When plants were kept in thedark, CO2 efflux subsequently declined rapidly to a lower, constantrate which was taken to be the maintenance respiration rate.The half-life of the declining phase of respiration averaged10.9 and 6.0 h at 15 and 30 °C respectively, and was curvilinearlyrelated to the specific maintenance respiration rate (m). Therapid decline in respiration was consistent with the low concentrationsof total soluble carbohydrate and starch in the herbage. Valuesof m for lamina and top growth increased with temperature witha Q10 of 2.6 and 1.42 respectively, but m of stems alone wasnot affected by temperature. Using results from this study forkikuyu and from McCree (1974) for sorghum and white clover,it was noted that all three species have similar m when grownat temperatures which are near their respective optimums forgrowth. Kikuyu, Pennisetum clandestinum, growth, respiration, temperature 相似文献
18.
The stomatal response of seedlings grown in 360 or 720 µmolmol1 to irradiance and leaf-to-air vapour pressure deficit(VPD) at both 360 and 720 µmol mol1 to CO2 wasmeasured to determine how environmental factors interact withCO2 enrichment to affect stomatal conductance. Seedlings offour species with different conductances and life histories,Cercis canadensis (L.), Quercus rubra (L.), Populus deltoides(Bartr. ex Marsh.) P. nigra (L.), and Pinus taeda (L.), weremeasured in hopes of identifying general responses. Conductanceof seedlings grown at 360 and 720 µmol mol1 CO2were similar and responded in the same manner to measurementCO2 concentration, irradiance and VPD. Conductance was lowerfor all species when measured at 720 than when measured at 360µmol mol1 CO2 at both VPDs ({small tilde}1.5 and{small tilde}2.5 kPa) and all measured irradiances greater thanzero (100, 300, 600,>1600 µmol m2 S2)The average decrease in conductance due to measurement in elevatedCO2 concentration was 32% for Cercis, 29% for Quercus, 26% forPopulus, and 11% for Pinus. For alt species, the absolute decreasein conductance due to measurement in CO2 enrichment decreasedas irradiance decreased or VPD increased. The proportional decreasedue to measurement in CO2 enrichment decreased in three of eightcases: from 0.46 to 0.10 in Populus and from 0.18 to 0.07 inPinus as irradiance decreased from>1600 to 100 µmolm2 s1 and from 0.35 to 0.24 in Cercis as VPD increasedfrom 1.3 to 2.6 kPa. Key words: Stomatal conductance, CO2 enrichment, irradiance, vapour pressure deficit 相似文献
19.
The Diurnal Pattern of Nitrate Uptake and Reduction by Spinach (Spinacia oleracea L.) 总被引:2,自引:0,他引:2
Spinach plants were grown in bowls of aerated nutrient solutionin a controlled environment chamber for 24 h, and harvestedevery 3·5-5 h to record their growth, nitrate and wateruptake, and plant nitrate concentration. Twelve such experimentsare described, either with a 14/10 h dark/light regime, or continuouslight or darkness. The irradiance was either 110, 320, or 510µmol m-2 s-1 (PPFD). All these regimes began at the endof the light period of a 14/10 h dark/light regime (510 µmolm-2 s-1) lasting approximately 2 weeks. Nitrate uptake rate per g of dry weight of plant continued almostunabated at about 17 µmol h-1 through the initial 14-hdark period, and then fell away sharply if the light was notrestored, but increased slightly when it was. With continuouslight at 510 µmol m-2 s-1, uptake rate rose steadily forthe first 24 h of light, and then fell sharply for about 6 h.Shoot nitrate concentration increased about three-fold in thedark phase, and declined in the light at a rate which was positivelyrelated to the irradiance. Root nitrate concentration was severaltimes higher than that of the shoot: its diurnal change wassmaller (relative to the mean) than that of the shoot. Nitratereduction occurred to a small extent in the dark, and increasedrapidly as soon as the lights came on, to remain at a roughlyconstant rate (related to the irradiance) throughout the lightphase. Dry matter increase in the light was related to irradiance,but with little increase above 320 µmol m-2 s-1. Respiratoryweight loss in the dark was not detectable. Rate of fresh weightincrease was approximately constant throughout light and darkperiods. The results compare quite well with the predictions of a simplesimulation model, based on the pump/leak principle.Copyright1994, 1999 Academic Press Spinacia oleracea, nitrate, uptake, reduction, influx, efflux, diurnal, regulation, model, simulation 相似文献
20.
A linear relationship between constant temperatures in the sub-optimaltemperature range and germination rate is shown in both Quercusrobur L and Castanea sativa Mill germinated under nominal darkconditions. The mean base temperature was interpolated for Qrobur as 0 8 ? or 2-4 ?, depending on seed lot provenance, andfor C. sativa as 1 -4? The optimum temperature for germinationin Q. robur was about 20? compared with around 28 ? in C. sativaOver the sub-optimal temperature range the distribution of thermaltimes was log-normal for each population studied their spreadvarying both between Q robur seed lots and between species However,in C. sativa germinated close to the mean base temperature,the distribution in thermal times was reduced Thermal timesto germination were decreased in Q. robur and C sativa by approximately0 3 and 0-5 log-units, respectively, when the pericarp was removed,i.e in the seeds, but the sensitivity of the response remainedrelatively unaltered In both species the germination rate was the same when nominaldark or safe green light conditions were employed during thegermination test. However, at 21 ? Q robur exhibited the highirradiance reaction (HIR) at photon doses above 30mmol m2d1. HIR first affected the germination rate by an inhibitionof radicle extension The sensitivity of the response to thermaltime was reduced as photon dose increased. This photo-inhibitionwas exacerbated at supra-optimal temperatures. In contrast,C. sativa germination rate at 26 ? was little influenced bylight at a photon dose of 752 mmol m2 d1 Key words: Seed germination rate, temperature, thermal time, light, photon dose 相似文献