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1.
Both the initial and the terminal 1 hr portions of the subjectiveday fraction, namely the L1- arid L2-phases, of a 24 hr daymust be illuminated in order for the day to be perceived asa long day in the min-LD determination by the long-day plant,Lemna gibba G3 (9). The light requirement of the L1-phase wassatisfied by a 10 min red light pulse given at the beginningof the phase. The red light effect was erased by a subsequent10 min far-red light, indicating phytochrome-mediated processesoccurring in the L1-phase. The light requirement of the L2-phasewas satisfied by blue or far-red light given during the terminal10 min period of the phase; there was no indication of phytochromeinvolvement. The light action on the L1-phase was replaced by10–5 M of cyclic AMP or 10–7 M of DL-isoproterenol.The isoproterenol action was antagonized by 10–7 M ofDL-propranolol. Cyclic AMP (10–5 M) combined with salicylicacid (10–6 M), which can remove the light requirementof the L2-phase (10), rendered a completely dark day physiologicallyequivalent to a long day. Acetylcholine (10–5 M) exertednyctomimetic action on the L1-phase of the second light day.The action of acetylcholine was antagonized by cyclic AMP (10–5M). The L2-phase required no light in the presence of 10–7M of DL-propranolol, and this propranolol action was not affectedby isoproterenol. These findings suggest changes in membranepermeability caused by the light given during the L1- and L2-phases. (Received July 7, 1976; )  相似文献   

2.
Spectral dependence of the light sensitive L1- and L2-phasesof the critical photoperiod of Lemna gibba G3 was examined bythe min-LD method for wavelengths ranging from ca. 420 to 800nm. The L1-phase had a sharp peak of sensitivity at 650–680nm and a gentle slope of sensitivity ascending from 500 nm towardshorter wavelengths. The L2-phase showed remarkable sensitivityaround 750 nm and in the blue-violet regions (500 nm). Red/far-redphotoreversibility was confirmed for the LI-phase, but not forthe L2-phase. The properties of the light receptors involvedare discussed briefly. 1Present address: National Institute for Basic Biology, Myodaiji,Okazaki 444, Japan. (Received May 14, 1979; )  相似文献   

3.
For decades frequent mass mortalities of Lesser Flamingos (Phoeniconaiasminor Geoffroy) have been observed at alkaline-saline KenyanRift Valley lakes. To estimate the potential influence of toxiccyanobacteria on these mass deaths, the phytoplankton communitieswere investigated in Lakes Bogoria, Nakuru and Elmenteita. Cyanobacterialtoxins were analyzed both in the phytoplankton from the threelakes and in isolated monocyanobacterial strains of Arthrospirafusiformis, Anabaenopsis abijatae, Spirulina subsalsa and Phormidiumterebriformis. Lake Bogoria was dominated by the cyanobacteriumA. fusiformis. In L. Nakuru and L. Elmenteita the phytoplanktonmainly consisted of A. fusiformis, A. abijatae and Anabaenopsisarnoldii, and in L. Nakuru an unknown Anabaena sp. was alsofound. Furthermore, this is the first time A. abijatae and theunknown Anabaena sp. have been found in Kenyan lakes. Phytoplanktonwet weight biomass was found to be high, reaching 777 mg L–1in L. Bogoria, 104 mg L–1 in L. Nakuru and 202 mg L–1in L. Elmenteita. Using HPLC, the cyanobacterial hepatotoxinsmicrocystin-LR, -RR -YR, -LF and -LA and the neurotoxin anatoxin-awere detected in phytoplankton samples from L. Bogoria and L.Nakuru. Total microcystin concentrations amounted to 155 µgmicrocystin-LR equivalents g–1 DW in L. Bogoria, and 4593µg microcystin-LR equivalents g–1 DW in L. Nakuru,with anatoxin-a concentrations at 9 µg g–1 DW inL. Bogoria and 223 µg g–1 DW in L. Nakuru. In L.Elmenteita phytoplankton, no cyanobacterial toxins were found.A. fusiformis was identified as one source of the toxins. Theisolated strain of A. fusiformis from L. Bogoria was found toproduce both microcystin-YR (15.0 µg g–1 DW) andanatoxin-a (10.4 µg g–1 DW), whilst the A. fusiformisstrain from L. Nakuru was found to produce anatoxin-a (0.14µg g–1 DW). Since A. fusiformis mass developmentsare characteristic of alkaline-saline lakes, health risks towildlife, especially the Arthrospira-consuming Lesser Flamingo,may be expected.  相似文献   

4.
The photosynthetic responses of eight tree and shrub speciesto simulated sunflecks was measured in the field. The net carbonexchange (NCE) of Corylus avellana and Ulmus glabra increasedwith irradiance up to the maximum irradiance of 230 µmolm–2 s–1. The NCE of Fraxinux excelsior, Hedera helixand the sun and shade forms of Rhododendron ponticum saturatedat about 120 µmol m–2 s–1 whereas the NCEof Ilex aquifolium, Daphne laureola and Fagus sylvatica hadeffectively saturated at 27 µmol m–2 s–1. In all cases the quantum efficiency of NCE could be predictedfrom measurements of chlorophyll fluorescence and the maximumvalue for NCE from measurements of stomatal conductance. Therelationships were combined into a model for predicting NCE/irradiancecharacteristics. Corylus avellana L., Daphne laureola L., Fagus sylvatica L., Fraxinus excelsior L., Hedera helix L., Ilex aquifolium L., Prunus laurocerasus L., Rhododendron ponticum L., Ulmus glabra Huds., gas exchange, stomatal resistance, water use efficiency, chlorophyll fluorescence, quantum efficiency  相似文献   

5.
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 (10–5–2 and 10–5 7 mol m–2 d–1,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 d–1 to 1 h d–1), Camelina saliva (1 min d–1to 8 h d–1), Eruca saliva (1 min d–1 to 24 h d–1),Lepidium sativum (I min d–1 to 8 h d–1) and Rorippapalustris (1 min d–1 to 8 h d–1), 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 lO–0–3 mol m–2 d–1.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 10–4 M GA2, co-applied (Brassica chinensis, Camelinasaliva, and Lepidium sativum) and with 2 x 10–2 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   

6.
The effect of photosynthetic photon flux density (PPFD) on carboxylationefficiency, estimated as the initial slope (IS) of net CO2 assimilationrate versus intercellular CO2 partial pressure response curve,as well as on ribulose-1, 5-bisphosphate carboxylase (Rubisco)activation was measured in Trifolium subterraneum L. leavesunder field conditions. The relationship between IS and PPFDfits a logarithmic curve. Rubisco activation accounts for theIS increase only up to a PPFD of 550 µmol photons m-2s-1. Further IS increase, between 550 and 1000 µmol photonsm-2 s-1, could be related to a higher ribulose fcwphosphate(RuBP) availability. The slow, but sustained IS increase above1000 µmol photons m-2 s-1 could be explained by the mesophyllCO2 diffusion barriers associated with the high chlorophylland protein content in field developed leaves. Key words: Photosynthesis, initial slope, ribulose-1, 5-bissphosphate carboxylase activation, light response, Trifolium subterraneum L  相似文献   

7.
5-Keto-D-[1-14C]gluconic acid, the most effective precursorof L(+)tartaric acid among all labeled compounds which haveever been tested in grapes, was found to be a good precursorof L(+)tartaric acid in a species of Pelargonium. The synthesisof labeled L(+)tartaric acid from D-[1-14C]glucose in Pelargoniumwas remarkably depressed when a 0.5% solution of D-gluconateor 5-keto-D-gluconate was administered continuously to leavestogether with D-[1-14C]glucose. Our results provide strong evidence that D-[1-14C]glucose ismetabolized in Pelargonium to give labeled L(+)tartaric acidvia (probably D-gluconic acid and) 5-keto-D-gluconic acid withoutpassing through L-ascorbic acid. Labeled L-idonic acid was found in young leaves of Pelargoniumwhich had been labeled with L-[U-14C]ascorbic acid. The synthesisof the labeled L-idonic acid increased when a 0.1% solutionof L-threonate was administered continuously to leaves togetherwith L-[U-14C]ascorbic acid. Specifically labeled compounds, recognized as the members ofthe synthetic pathway for L(+)tartaric acid from L-ascorbicacid via L-idonic acid in grapes, were administered to youngleaves of Pelargonium. Each compound (2-keto-L-[U-14C]idonicacid, L-[U-14C]idonic acid, 5-keto-D-[1-14C]gluconic acid and5-keto-D-[6-14C]gluconic acid) was partly metabolized, as ingrapes. The metabolic pathway starting from L-ascorbic acidto L(+)tartaric acid via L-idonic acid, however, did not actuallycontribute to the synthesis of L(+)tartaric acid in Pelargoniumprobably because the activity of each metabolic step was muchlower than that observed in grapes. (Received May 28, 1984; Accepted July 30, 1984)  相似文献   

8.
Nitrate reductase activity (NRA, in vivo assay) and nitrate(NO-3) content of root and shoot and NO-3 and reduced nitrogencontent of xylem sap were measured in five temperate cerealssupplied with a range of NO-3 concentrations (0·1–20mol m–3) and three temperate pasture grasses suppliedwith 0·5 or 5 0 mol m–3 NO-3 For one cereal (Hordeumvulgare L ), in vitro NRA was also determined The effect ofexternal NO-3 concentration on the partitioning of NO-3 assimilationbetween root and shoot was assessed All measurements indicatedthat the root was the major site of NO3 assimilation in Avenasatwa L, Hordeum vulgare L, Secale cereale L, Tnticum aestivumL and x Triticosecale Wittm supplied with 0·1 to 1·0mol m–3 NO-3 and that for all cereals, shoot assimilationincreased in importance as applied NO-3 concentration increasedfrom 1.0 to 20 mol m–3 At 5.0–20 mol m–3 NO3,the data indicated that the shoot played an important if notmajor role in NO-3 assimilation in all cereals studied Measurementson Lolium multiflorum Lam and L perenne L indicated that theroot was the main site of NO-3 assimilation at 0.5 mol m–3NO-3 but shoot assimilation was predominant at 5.0 mol m–3NO-3 Both NRA distribution data and xylem sap analysis indicatedthat shoot assimilation was predominant in Dactylis glomerataL supplied with 0.5 or 5.0 mol m–3 NO-3 Avena sativa L., oats, Hordeum vulgare L., barley, Secale cereale L., rye, x Triticosecale Wittm., triticale, Triticum aestivum L., wheat, Dactylis glomerata L., cocksfoot, Lolium multiflorum Lam., Italian ryegrass, Lolium perenne L., perennial ryegrass, nitrate, nitrate assimilation, nitrate reductase activity, xylem sap  相似文献   

9.
The life cycles, biomass and secondary production of three sympatricfreshwater basommatophoran snails, Lymnaea palustris (MÜller),Physa fontinalis Linnaeus and Anisus rotundatus (Poiret) werestudied during two years in a freshwater ditch. L. palustrisexhibited an iteroparous life-cycle whereas the two other speciespresented a semelparous life-cycle, adults died just after oviposition.L. palustris secondary production (dry weight) value was higher(P = 11 298.4 mg 0.1 m–1 yr–1) than those of P.fontinalis (P = 846.3 mg 0.1 m–2 yr–1) and A. rotundatus(P = 1192 mg 0.1 m–2 yr–1). (Received 16 March 1992; accepted 30 June 1992)  相似文献   

10.
A new model is proposed which relates the weight of plants totheir spatial arrangement. The weight of each plant is calculatedas the integral of the function f(r) = L(cr2 + 1)–2 overan area allocated to it, r being distance from the plant, withL and c parameters to be specified. The model is thus concise,general, in that it can be used to describe the effects of anyspatial arrangement on plant weight, and the parameters L andc have a biological interpretation. It is also consistent withthe commonly-used relationship between plant weight (w) anddensity (p), w–1 = a+bp. We show for carrots (Daucus carota L.) and red beet (Beta vulgarisL.), that the mean weights fitted by the model agree as wellwith the experimentally observed mean plot weight as those fittedby more complex models with more parameters, some of which arenot as general. We show also that the parameter c can be predictedfrom the time from sowing to harvest, with good results whentested on sets of data independent of those to which the modelhad been fitted. The assumptions on which the model is based,its application, and extensions to it are discussed. Crop yield, plant density, plant arrangement, carrot, Daucus carota L., red beet, Beta vulgaris L., soya bean, Glycine max L., mathematical model  相似文献   

11.
Four species,Sinapis albaL.,Medicago sativaL.,Gypsophila paniculataL.andPicea abies(L.) Karsten, were grown in three light regimes:darkness, low light (25 µmol m-2s-1for 10 min d-1) andhigh light (120 µmol m-2s-1for 12 h  d-1) and fourlevels of carbon dioxide: 0, 350, 700 and 1400±50 µll-1. Germination was not affected by any of the treatments.The effects of carbon dioxide on stem elongation were identicalin low and high light: stem length increased at a decreasingrate with level of carbon dioxide in all species. Level of carbondioxide also affected stem elongation in complete darkness,but the pattern was more complex and varied among species. Totalweight did not vary with level of carbon dioxide to any significantextent in either darkness or low light, but increased with levelof carbon dioxide at high light in all four species. Due tothe absence of any effect of carbon dioxide on growth in darknessand low light, we suggest the effects of carbon dioxide on stemelongation are independent of effects on growth and may be dueto a direct interaction with developmental processes. In contrast,level of carbon dioxide had little effect on allocation patternsin the dark and low light experiments, but had marked effectsin high light. Therefore, the effect of carbon dioxide on allocationwas probably due to the effects of carbon dioxide on growthrather than to any direct interaction between carbon dioxideand development. An understanding of the mechanisms by whichcarbon dioxide affects development may help us understand theoften variable effects of carbon dioxide upon plants.Copyright1998 Annals of Botany Company Sinapis albaL.;Medicago sativaL.;Gypsophila paniculataL. andPicea abies(L.) Karsten; elevated carbon dioxide; stem elongation; germination; allocation; phytochrome.  相似文献   

12.
Light-enhanced active pyruvate uptake into mesophyll chloroplastsof C4 plants was reported to be mimicked by either of the twotypes of cation jump: H+-jump in maize and phylogenically relatedspecies (H+-type) and Na+-jump in all the other C4 species tested(Na+-type) [Aoki, N., Ohnishi, J. and Kanai, R. (1992) PlantCell Physiol. 33: 805]. In this study, medium and stromal pH was monitored in the suspensionof C4 mesophyll chloroplasts. Medium alkalization lasting for5 to 10 seconds after pyruvate addition was detected by a pHelectrode and observed only in the light and only in mesophyllchloroplasts from H+-type species, Zea mays L. and Coix lacryma-jobiL., but not in those from Na+-type species Panicum miliaceumL., Setaria italica (L.) Beauv. and Panicum maximum Jacq. Theinitial rate of H+ consumption showed good correlation with[14C]pyruvate uptake measured by silicone oil filtering centrifugation,both being inhibited by N-ethylmaleimide and 7-chloro-4-nitrobenzo-2-oxa-l,3-diazole to the same degree. The ratio of the rate of H+ uptaketo that of pyruvate uptake was always about 1. Pyruvate-inducedacidification of the stroma was observed in maize mesophyllchloroplasts. These results show one to one cotransport of H+and pyruvate anion into mesophyll chloroplasts of H+-type C4species in the light. (Received January 5, 1994; Accepted May 6, 1994)  相似文献   

13.
By direct somatic embryogenesis in vitro a clone of asepticplantlets can be raised from a single immature embryo of Trifoliumrepens (white clover) within about 6 weeks of pollination. Embryoidsare induced directly from intact zygotic embryonic tissue ona culture medium containing 0·025 or 0·05 mg 1–1BAP and 1·0 g 1–1 yeast extract. Similar directsomatic embryogenesis has also been achieved for Trifolium pratense(red clover) and Medicago sativa (lucerne). Applications ofembryo propagation by direct somatic embryogenesis are discussed,particularly in relation to multiple screening of host genotypesfor analysis of host/pathogen and legume/Rhizobium interactions. Trifolium repens L., Trifolium pratense L., Medicago sativa L., clover, lucerne, tissue culture, embryoid, somatic embryogenesis, legumes  相似文献   

14.
The rate of net photosynthesis (P) of whole plant stands oftomato (Lycopersicon esculentum Mill.), cucumber (Cucumis sativusL.) and sweet pepper (Capsicum annuum L.) was measured in sixlong-term experiments in large greenhouses under normal operatingconditions and CO2-concentrations between 200 and 1200 µmolmol-1. The objective was to quantify the responses to lightand carbon dioxide and to obtain data sets for testing simulationmodels. The method of measuring canopy photosynthesis involvedan accurate estimation of the greenhouse CO2 balance, usingnitrous oxide (N2O) as tracer gas to determine, on-line, theexchange rate between greenhouse and outside air. The estimatedrelative error in the observed P was about ± 10%, exceptthat higher relative errors could occur under particular conditions. A regression equation relating P to the photosynthetically activeradiation, the CO2 concentration and the leaf area index explained83-91% of the variance. The main canopy photosynthesis characteristicscalculated with the fitted regression equations were: canopyPmax 5-9 g m-2 h-1 CO2 uptake; ratio Pmax/LAI 1·5-3 gm-2 h-1; light compensation point 32-86 µmol s-1 m-2;light use efficiency (quantum yield) at low light 0·06-0·10µmol µmol-1 and CO2 compensation point 18-54 µmolmol-1. The results were related to the prevailing conditions.Copyright1994, 1999 Academic Press Canopy photosynthesis, Capsicum annuum L., carbon dioxide, CO2, CO2 balance, CO2 use efficiency, cucumber, Cucumis sativus L., glasshouse, greenhouse, light use efficiency, Lycopersicon esculentum Mill., sweet pepper, tomato, tracer gas  相似文献   

15.
As rice can use both nitrate (NO3-) and ammonium (NH4+), we have tested the hypothesis that the shift in the pattern of cultivars grown in Jiangsu Province reflects the ability of the plants to exploit NO3- as a nitrogen (N) source. Four rice cultivars were grown in solution culture for comparison of their growth on NO3- and NH4+ nitrogen sources. All four types of rice, Xian You 63 (XY63), Yang Dao 6 (YD), Nong Keng 57 (NK) and Si You 917 (SY917), grew well and produced similar amounts of shoot biomass with 1 mmol/L NH4+ as the only N source. However, the roots of NK were significantly smaller in comparison with the other cultivars. When supplied with 1 mmol/L NO3-, YD produced the greatest biomass; while NK achieved the lowest growth among the four cultivars. Electrophysiological measurements on root rhizodermal cells showed that the NO3--elicited changes in membrane potential (ΔEm) of these four rice cultivars were significantly different when exposed to low external NO3- (<1 mmol/L); while they were very similar at high external NO3- (10 mmol/L). The root cell membrane potentials of YD and XY63 were more responsive to low external NO3- than those of NK and SY917. The ΔEm values for YD and XY63 rhizodermal cells were almost the same at both 0.1 mmol/L and 1 mmol/L NO3-; while for the NK and SY917 the values became larger as the external NO3- increased. For YD cultivar, ΔEm was measured over a range of NO3- concentrations and a Michaelis-Menten fit to the data gave a Km value of 0.17 mmol/L. Net NO3- uptake depletion kinetics were also compared and for some cultivars (YD and XY63) a single-phase uptake system with first order kinetics best fitted the data; while other cultivars (ND and SY917) showed a better fit to two uptake systems. These uptake systems had two affinity ranges: one had a similar Km in all the cultivars (0.2 mmol/L); the other much higher affinity system (0.03 mmol/L) was only present in NK and SY917. The expression pattern of twelve different NO3- transporter genes was tested using specific primers, but only OsNRT1.1 and OsNRT2.1 expression could be detected showing significant differences between the four rice cultivars. The results from both the physiological and molecular experiments do provide some support for the hypothesis that the more popular rice cultivars grown in Jiangsu Province may be better at using NO3- as an N source.  相似文献   

16.
The effects of different applied NO3 concentrations onextension growth and final length and area of leaves 1–4of five cereals and six pasture grasses of temperate originwere examined. Increased applied NO3 in the range 0.1–0.5.0mol m–3 caused decreased duration of growth but increasedgrowth rate and final length of leaves 2–4 of the cerealsAvena saliva, Hordeum vulgare, Secale cereale, x Triticosecaleand Triticum aestivum. For all cereals, increased NO3resulted in increased area of leaves 1–4. Pasture grasseswere supplied either 0.5 or 50 mol m–3 NO3. Increasedapplied NO3 (0.5–5.0 mol m–3) resulted indecreased duration of growth and increased growth rate and finalarea of leaves 1–4 of Bromus wiltdenowii, leaves 2–4ofFestuca arundinaceae and leaves 3 and 4 of Lolium muitiflorum.In addition, length of leaves 3 and 4 of B. witidenowii increasedwith increased NO3. Increased NO3 resulted inincreased area of leaves 2–4 of Dactylis gtomerata andLolium perenne and leaves 3 and 4 of Phalaris aquaiica but hadno effect on extension growth of all three species. Avena sativa L, oat, Hordeum vulgare L, barley, Secale cereale L, rye, x Triticosecale Wittm, triticale, Triticum aestivum L, wheat, Bromus willdenowii Kunth, prairie grass, Dactylis gtomerata L, cocksfoot, Festuca arundinaceae Shreb, tall fescue, Lolium multijlorum Lam, Italian ryegrass, Lolium perenne L, perennial ryegrass, Phalaris aquatica L, nitrate, leaf extension, leaf expansion  相似文献   

17.
C-starts are high acceleration swimming movements critical forpredator avoidance by fishes. Since larval fishes are particularlyvulnerable to predation, C-start behavior is likely to be especiallyimportant during early life history stages. This paper examinesthe developmental changes in C-start performance with kinematicdata on immature chinook salmon (Oncorhynchus tshawytscha) (eleuthroembryostage, sensu Balon, 1975). The scaling of C-start kinematicsof immature fishes differs from that of adults. Adult C-startdurations increase with increasing body length while C-startdurations of immature fishes decrease (e.g., adult stage 1 duration[sec] = 0.0019.length [L] [cm] $ 0.026 [R2 = 0.77] [Webb, 1978];eleuthroembryos stage 1 duration [sec] = –0.026L [cm]$ 0.100 [R2 = 0.81]). Distance traveled during stage 2 alsodiffers between adult and immature fishes. Adult distance traveledscales directly with length (distance [cm] = 0.38L1.01 [cm],R2 = 0.96 [Webb, 1978]) while chinook eleuthroembryo distancetraveled is positively allometric with length (distance [cm]=0.37L131 [cm], R2 = 0.83). There are similarities in the developmentof C-starts and burst swimming. For example, mean velocity scalessimilarly between the two locomotor modes (For burst swimming:Umean [cm/sec] = 8.1 ± 1.1L [cm] $ 4.89 [R2 = 0.86] [Webband Corolla, 1981]. For C-start stage 2: Umean [cm/sec] = 10.96L[cm] - 14.09 [R2 = 0.70]). This study demonstrates that C-startescape performance improves during early post-hatching development.Comparisons of immature chinook salmon fast-starts with dataon larval burst swimming and on adult C-starts suggest thatchanges specific to developing fish affect the scaling of kinematicparameters.  相似文献   

18.
Surfacing and water-leaving behaviour (quitting) of aquaticpulmonate snails was investigated in the laboratory. Regressioncoefficients of surfacing rate per hour for 16 snails in 200cm3 of water were 1.28 for L. peregra, 1.35 for B. glabrata(albino form), 0.47 for B. glabrata (pigmented form) and 0.17for B. jousseaumei. Disturbance, snail size and conditioningof the water were relatively unimportant factors; water volumeadjusted by depth was also unimportant up to 50 mm depth. Importantfactors controlling surfacing appeared to be population density,time of year, temperature, water volume adjusted by perimeterand dissolved oxygen concentration. The response to the latterwas not clear and both B. glabrata and L. peregra orientatedalmost as well to a nitrogen/water interface as to an air/waterinterface. Water-quitting regressed on volume, which had beenadjusted by perimeter variation, revealed a curvilinear relationshipfor B. glabrata, with maximum quitting at 1 snail per 7cm3 (1snail per 14cm of climbable perimeter). L. peregra showed anegative exponential curve, with maximum quitting at 1 snailper 3 cm3 of water (1 snail per 8 cm of climbable perimeter).These data could be relevant to design and management of irrigationchannels where bilharzia might occur. (Received 28 November 1990; accepted 22 October 1991)  相似文献   

19.
The net efflux of H+ from lucerne (Medicago saliva L.), redclover (Trifolium pratense L.) and white clover (Trifolium repensL.) growing in flowing solution culture and dependent upon symbioticfixation of atmospheric N, was measured over a 75 d experimentalperiod. Considerable and rapid increases in acidity of the nutrientsolution of up to 1.45 pH units were recorded when the pH wasriot held constant over a 30 h period. There was little differencein H+ efflux when solution pH was held constant at 4.75, 5.75or 6.75, but there was an immediate cessation when it was adjustedto 3.75. Differences in the daily net efflux of H+ closely followedthe pattern of daily differences in incoming radiation, andthere was also evidence of a diurnal pattern of H+ efflux. Althoughthere were initially distinct differences between the speciesin the calculated rate of net H+ efflux (µg H+ g–1dry shoot d), by day 75 these had diminished. In allspecies, however, the maximum rate of efflux per unit of shootsoccurred during the earlier rapid phases of growth. The measuredefflux of H+ was well equated with the plant content of excesscations (as measured by ash alkalinity) and, on average, theratio of acidity produced to N assimilated (expressed as anequivalent) was 0-24. Medicago sativa L., Trifolium pratense L., Trifolium repens L., lucerne, red clover, white clover, acidification, cation/anion balance, flowing solution culture, H+ efflux, nitrogen fixation  相似文献   

20.
We studied the course of early leaf area expansion and specificleaf area (SLA) in potato (Solanum tuberosum L.) and wheat (Triticumaestivum L.) genotypes and tested whether air temperature explainsdifferences in these courses within different environments.Such knowledge can be used to improve crop growth modelling.The relative rate of leaf area expansion (RL) of potato andwheat decreased with thermal time, but was nearly linear upto a leaf area index (L) of 1.0. TheRL (L < 1; mean: 17.9x 10-3°C-1 d-1) of potato showed an interaction betweengenotype and environment, and varied with year. TheRL (L <1; mean: 7.1 x 10-3°C-1 d-1) of winter wheat was lower thanthat of spring wheat (mean: 10.9 x 10-3°C-1 d-1), and bothvaried with year. SLAof potato increased nearly linearly withthermal time from 5 to 15 m2 kg-1at 50% emergence, to 20 to25 m2 kg-1at 155°Cd, and then decreased slightly. The SLAofboth winter and spring wheat began at 16 to 23 m2 kg-1and inmost cases increased slightly with thermal time. In potato,regression parameters of SLAwith thermal time were affectedby environment (management conditions and year) and genotype;in wheat they were affected by environment (year and site).Treatment effects on RLof potato were not correlated with thoseon SLA , and were only partly correlated for wheat. Thereforewe conclude that the early foliar expansion of potato is associatedwith a strong increase in SLA , and not so for wheat. For bothcrops the course of early leaf area expansion and ofSLA withair temperature is not robust over environments and genotypes.The consequences of these results for modelling are discussed.Copyright 2000 Annals of Botany Company Triticum aestivum, spring wheat, winter wheat, Solanum tuberosum, leaf area expansion, specific leaf area, early growth, genotype, environment, modelling  相似文献   

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