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1.
Bertl, A. and Felle, H. 1985. Cytoplasmic pH of root hair cellsof Sinapsis alba recorded by a pH-sensitive micro-electrode.Does fusicoccin stimulate the proton pump by cytoplasmic acidification?J. exp. Bot. 36: 11421149. pH-sensitive micro-electrodes, filled with ion-exchanger resinhave been fabricated with a turgorinsensitive tip and have beenapplied to test the intracellular pH and changes thereof inroot hair cells of Sinapis alba. (1) The cytoplasmic pH of Sinapisroot hairs was determined to be 7.3 ±0.2 (at neutralexternal pH). (2) 10 mol m3 sodium azide depolarizesthe membrane potential by about 100 mV and acidifies the cytoplasmby 0.8 pH-units. (3) The change from 1.0 mol m3 to 10mol m3 external potassium causes a depolarization ofabout 45 mV, but no change in internal pH. (4) At an externalpH of 5.0, sodium acetate hyperpolarizes the plasmalemma byabout 60 mV and acidifies the cytoplasmic pH by 0.2 to 0.3 units.(5) 2.0 mmol m3 fusicoccin (FC) hyperpolarizes the plasmalemmaby 2025 mV, acidifies the cytoplasm by 0.1 to 0.2 pH-units,and acidifies the external medium by about 03 pH-units.It is concluded that cytoplasmic acidification stimulates theelectrogenic proton pump in Sinapis root hairs, and it is suggestedthat the FC-induced effects, viz. hyperpolarization and externalacidification, can also be interpreted in this way. Key words: Cytoplasmic pH, pH-sensitive micro-electrode, fusicoccin 相似文献
2.
Behavioural and electrophysiological taste responses in theblowfly (Calliphora vicina) are measured in successive experiments,using the same flies twice. Inter-individual variations in behaviourare at least partly due to differences in the functioning ofthe tarsal taste hairs; flies with low behavioural thresholdvalues have taste hairs firing with higher rates. The percentageof taste hairs responding with spike trains is not important.Behavioural responses are predominantly influenced by the bestfiring hair. The most effective of the parameters describingspike trains seems to beft, the firing rate after an infinitelength of stimulation time. 相似文献
3.
The Role of the Plasma Membrane Proton Pump in Short-term pH Regulation in the Aquatic Liverwort Riccia fluitans L. 总被引:2,自引:0,他引:2
The question is raised, to what extent is the plasma membraneproton pump involved in short-term pH regulation of plant cells?For this purpose the cytosolic pH (pHc) of Riccia fluitans rhizoidand thallus cells has been measured continuously using pH-sensitivemicroelectrodes (Felle and Bertl, 1986a). It is demonstratedthat pH perturbations (light, weak acids, external pH) in bothdirections are completely or at least partly eliminated withinminutes. The pHc recovery occurs regardless of the activationstate of the proton pump. The proton pump reacts to changesin cytosolic pH as expected, namely with increased proton extrusionto decreased pHc; however, changes in pump activity (fusicoccin,CCCP, cyanide) do not necessarily result in cytosolic pH shifts.These results suggest that several proton transport mechanisms(including the proton pump) co-operate in the restoration ofa perturbed cytosolic pH. It is concluded, however, that theproton pump, although most important for the energization ofthe plasma membrane, does not regulate cytosolic pH. 相似文献
4.
In the aquatic liverwort Riccia fluitans the regulation of theplasma membrane H+/amino acid symport has been investigated.Cytosolic pH (pHc), membrane potential (Em) and membrane conductancehave been measured and related to transport data, (i) The releaseof [14C]amino acids is strongly stimulated by cytosolic acidification,induced by the external addition of acetic acid, a decreasein external K+, and in the change from light to dark. On average,a decrease in pHc of 0.5 to 0.6 units corresponded with a 4-foldstimulation in amino acid efflux. (ii) External pH changes havefar less effect on substrate transport than the cytosolic pHshifts of the same order. (iii) The inwardly directed positivecurrent, induced by amino acids, is severely inhibited by cytosolicacidification. (iv) Fusicoccin (FC) stimulates amino acid uptakewithout considerable change in proton motive force. (v) Whenthe proton motive force is kept constant, the uptake of aminoacids into Riccia thalli is much lower than when the pump isdeactivated. It is suggested that both the proton pump activityand cytosolic pH are the dominant factors in the regulationof the H+/amino acid symport across the plasma membrane of Ricciafluitans, and it is concluded that the proton motive force isnot a reliable quantity to predict and interpret transport kinetics. Key words: Amino acid, cytosolic pH, pH-sensitive electrode, proton motive force, regulation, Riccia fluitans 相似文献
5.
Proton Transport and pH Control in Sinapis alba Root Hairs: A Study carried out with Double-Barrelled pH Micro-electrodes 总被引:3,自引:0,他引:3
Continuous measurements of cytoplasmic pH (pHc) in Sinapis roothairs have been carried out with double-barrelled pH-micro-electrodesin order to gain information on translocation of protons acrossthe plasmalemma and cytoplasmic pH control. (i) The cytoplasmicpH of Sinapis (733 ? 012, standard conditions)changes no more than 0.1 pHc, per pHo-unit, regardless of whethercyanide is present or not. (ii) Weak acids rapidly acidify pHcand hyperpolarize, while weak bases alkalize pHc and depolarizethe cells, (iii) 1.0 mol M,3 NaCN acidifies the cytoplasm by0.4 to 0.7 pH-units, but alkalizes the vacuole. (iv) 20 mmolm3 CCCP has no significant effect on pHc, if added atpH 9.6 or 7.2, but acidifies pHc by 1.3 units at pH 4.3. Inthe presence of CCCP, cyanide acidifies the cytoplasm, (v) Chloridetransiently acidifies pHc, while K+, Na+, and have no significant effects, (vi) Cytoplasmic buffer capacityforms a bell-shaped curve versus pHc with an optimum of about50 mol m3 H+pHc-unit. The modes of proton re-entry and the effects of active and passiveproton transport on cellular pH control are critically discussed.It is suggested that the proton leak, consisting of H+-cotransport(e.g. H+/Cl) rather than H+-uniport, is no threat topHc. The proton export pump, although itself reacting to changesin pHc, influences pHc only to a minor extent. It is concludedthat buffer capacity and membrane transport play moderate rolesin pHc control in Sinapis, while the interlocked H+-producingand -consuming reactions of cellular metabolism are the mainregulating factors. This makes pH control in Sinapis quite differentfrom bacterial and animal cells. Key words: Cytoplasmic pH, double-barrelled pH micro-electrode, pH control, proton transport, Sinapis 相似文献
6.
MUSCHINEK GYORGYI; ALSCHER RUTH; ANDERSON LOUISE E. 《Journal of experimental botany》1987,38(6):1069-1075
Muschinek, G., Alscher, R. and Anderson, L. E. 1987. The sensitivityof light modulation of enzyme activity to arsenite and sulphiteand of photosynthetic induction to arsenite is determined bya cytoplasmic geneJ. exp. Bot. 38: 10691075. The membrane component of the light modulation system was moresensitive to arsenite and to sulphite in the Pisum cultivarNugget than in the cultivar Progress No.9. Likewise, the induction phase of CO2 fixation wasmore arsenite sensitive in chloroplasts isolated from Nuggetplants. Sensitivity was controlled by a cytoplasmic gene. Key words: Induction, light modulation, arsenite sensitivity 相似文献
7.
Phosphorus Deficiency Impairs Early Nodule Functioning and Enhances Proton Release in Roots of Medicago truncatula L. 总被引:10,自引:0,他引:10
The effect of phosphorus supply (115 µM) on protonrelease and the role of P in symbiotic nitrogen fixation inmedic (Medicago truncatula L. Jemalong) was investigated.As P concentration in the nutrient solution increased, shootand root growth increased by 19 and 15%, respectively by day35, with maximal growth at 4 µM P. A P concentration of15 µM appeared to be toxic to plants. Phosphorus supplyhad no influence on nodule formation by day 12 but increasednodule number by day 35. Nitrogenase activity was estimatedby in situ measurement of acetylene reduction activity (ARA)in an open-flow system. During the assay, a C2H2-induced declineof ARA was observed under all P concentrations except 4 µM.Specific ARA (per unit nodule weight) doubled when P supplywas increased from 1 to 8 µM. This effect of P was muchgreater than the effects of P on nodulation and host plant growth.Concentrations of excess cations in plants decreased with increasingP concentration in the nutrient solution. Phosphorus deficiencystimulated uptake of excess cations over anions by the plantsand hence enhanced proton release. The results suggest thatP plays a direct role in nodule functioning in medic and thatP deficiency increases acidification which may facilitate Pacquisition. Copyright 2001 Annals of Botany Company Medicago truncatula L. (medic), P deficiency, C2H2-ID, nitrogenase activity, proton release, cation-anion balance, open-flow system 相似文献
8.
Developmental control of xylem hydraulic resistances and vulnerability to embolism in Fraxinus excelsior L.: impacts on water relations 总被引:3,自引:0,他引:3
Welbaum G.E.; Bian D.; Hill D.R.; Grayson R.L.; Gunatilaka M.K. 《Journal of experimental botany》1997,48(3):655-663
The freezing tolerance of many plants, such as pea (Pisum sativum),is increased by exposure to low temperature or abscisic acidtreatment, although the physiological basis of this phenomenonis poorly understood. The freezing tolerance of pea shoot tips,root tips, and epicotyl tissue was tested after cold acclimationat 2C, dehydration/rehydration, applications of 104M abscisic acid (ABA), and deacclimation at 25C. Tests wereconducted using the cultivar Alaska, an ABA-deficientmutant wil, and its wildtype. Freezinginjury was determined graphically as the temperature that caused50% injury (T50) from electrical conductivity. Endogenous ABAwas measured using an indirect enzyme-linked immunosorbant assay,and novel proteins were detected using 2-dimensional polyacrylamidegel electrophoresis. The maximum decrease in T50 for root tissuewas 1C for all genotypes, regardless of treatment. For Alaskashoot tips and epicotyl tissue, exogenous ABA increased thefreezing tolerance by 1.5 to 4.0C, while coldtreatment increased the freezing tolerance by 7.5 to14.8C. Cold treatment increased the freezing toleranceof shoot tips by 9 and 15C for wiland wild-type, respectively. Cold acclimationincreased endogenous ABA concentrations in Alaskashoot tips and epicotyls 3- to 4-fold. Immunogold labeling increasednoticeably in the nucleus and cytoplasm of the epicotyl after7 d at 2C and was greatest after 30 d at the time of maximumfreezing tolerance and soluble ABA concentration. Cold treatmentinduced the production of seven, three, and two proteins inshoot, epicotyl, and root tissue of Alaska, respectively.In Alaska shoot tissue, five out of seven novelproteins accumulated in response to both ABA and cold treatment.However, only a 24 kDa protein was produced in wiland wild-type shoot and epicotyl tissues aftercold treatment. Abscisic acid and cold treatment additivelyincreased the freezing tolerance of pea epicotyl and shoot tissuesthrough apparently independent mechanisms that both resultedin the production of a 24 kDa protein. Key words: Pisum sativum, cold acclimation, immuno-localization 相似文献
9.
Welbaum G.E.; Bian D.; Hill D.R.; Grayson R.L.; Gunatilaka M.K. 《Journal of experimental botany》1997,48(3):643-654
The freezing tolerance of many plants, such as pea (Pisum sativum),is increased by exposure to low temperature or abscisic acidtreatment, although the physiological basis of this phenomenonis poorly understood. The freezing tolerance of pea shoot tips,root tips, and epicotyl tissue was tested after cold acclimationat 2C, dehydration/rehydration, applications of 104M abscisic acid (ABA), and deacclimation at 25C. Tests wereconducted using the cultivar Alaska, an ABA-deficientmutant wil, and its wildtype. Freezinginjury was determined graphically as the temperature that caused50% injury (T50) from electrical conductivity. Endogenous ABAwas measured using an indirect enzyme-linked immunosorbant assay,and novel proteins were detected using 2-dimensional polyacrylamidegel electrophoresis. The maximum decrease in T50 for root tissuewas 1C for all genotypes, regardless of treatment. For Alaskashoot tips and epicotyl tissue, exogenous ABA increased thefreezing tolerance by 1.5 to 4.0C, while coldtreatment increased the freezing tolerance by 7.5 to14.8C. Cold treatment increased the freezing toleranceof shoot tips by 9 and 15C for wiland wild-type, respectively. Cold acclimationincreased endogenous ABA concentrations in Alaskashoot tips and epicotyls 3- to 4-fold. Immunogold labeling increasednoticeably in the nucleus and cytoplasm of the epicotyl after7 d at 2C and was greatest after 30 d at the time of maximumfreezing tolerance and soluble ABA concentration. Cold treatmentinduced the production of seven, three, and two proteins inshoot, epicotyl, and root tissue of Alaska, respectively.In Alaska shoot tissue, five out of seven novelproteins accumulated in response to both ABA and cold treatment.However, only a 24 kDa protein was produced in wiland wild-type shoot and epicotyl tissues aftercold treatment. Abscisic acid and cold treatment additivelyincreased the freezing tolerance of pea epicotyl and shoot tissuesthrough apparently independent mechanisms that both resultedin the production of a 24 kDa protein. Key words: Pisum sativum, cold acclimation, immuno-localization 相似文献
10.
Influence of Flooding on Net CO2Assimilation, Growth and Stem Anatomy of Annona Species 总被引:1,自引:0,他引:1
NUNEZ-ELISEA ROBERTO; SCHAFFER BRUCE; FISHER JACK B.; COLLS ANGEL M.; CRANE JONATHAN H. 《Annals of botany》1999,84(6):771-780
A series of experiments was conducted to assess net CO2assimilationand growth responses to waterlogging of grafted and seedlingtrees in the genus Annona. Seedlings of A. glabra, A. muricataandA. squamosa L., and scions of Gefner atemoya(A. squamosaxA. cherimola Mill.), 49-11 (GefneratemoyaxA. reticulata L.), 4-5 (PriestleyatemoyaxA. reticulata), A. reticulata grafted onto either A.glabra, A. reticulata orA. squamosa rootstocks were floodedfor up to 60 d. Soil anaerobiosis occurred on the third dayof flooding. Seedlings ofA. glabra and A. muricata, and thescions 49-11, Gefner atemoya, andA. reticulata grafted onto A. glabra rootstock were consideredflood tolerant based on their ability to survive and grow inflooded conditions. Scions of the normally flood-sensitive A.reticulata, Gefner atemoya, and 49-11tolerated root waterlogging when grafted onto the flood-tolerantspecies, A. glabra. In contrast, flooding of A. squamosa seedlingsand rootstocks, and A. reticulata rootstocks greatly reducedgrowth and net CO2assimilation rates, and resulted in 2080%tree mortality. Stem anatomical responses to long-term flooding(12 continuous months) were assessed in seedlings of A. glabraand A. muricata, and trees of 49-11 grafted ontoA. glabra. Flooded trees developed hypertrophied stem lenticels,particularly in A. glabra, and enlarged xylem cells resultingin thicker stems with reduced xylem density. Flooding did notincrease air spaces in pre-existing xylem near the pith or inxylem tissue that was formed during flooding. Thus, flood tolerancedid not involve aerenchyma formation in the stem. Copyright1999 Annals of Botany Company Flood tolerance, net CO2assimilation, photosynthesis, stem anatomy, shoot growth, anaerobiosis, Annonaceae. 相似文献
11.
《Journal of experimental botany》1960,11(2):150
On page 235, Table I: Equation (1) for Node 4 should read A/Ac=0·840+0·0006Ac;Equation (2) for Node 4 should read A=0·89Acand Equation (2) for Node 510 should read A=0·813Ac. 相似文献
12.
SINGH N; SINGH S N; SRIVASTAVA K; YUNUS M; AHMAD K. J; SHARMA S C.; SHARGA A N 《Annals of botany》1990,65(1):41-44
Five Gladiolus cultivars, namely Aldebaran, BrightEye, Illusion, Manisha andManmohan, were exposed to 1 and 2 µg l1sulphur dioxide to test their relative-sensitivity toleranceto the pollutant Plants were fumigated experimentally for 2h daily Foliar injury symptoms were observed first in Manishafollowed by Aldebaran and Illusionat the higher dose Photosynthetic pigments and leaf extractpH were significantly decreased, particularly in Manishaand Illusion Overall disturbances in the plantmetabolism due to SO2 treatment led to retarded growth of plants,as evident from decreased shoot length and phytomass valuesThe order of sensitivity of the five Gladiolus cultivars toSO2 was as follows, with the greatest first Manisha, Illusion,Aldebaran, Bright Eye, Manmohan Cultivars, Gladiolus, sensitivity, sulphur dioxide, tolerance 相似文献
13.
《Journal of experimental botany》1977,28(6):1247
Effects of coupled solute and water flow in plant roots withspecial reference to Brouwer's experiment. Edwin L. Fiscus. p. 71 Abstract: Line 3 delete interval insertinternal. p. 73 Materials and Methods: line 6: delete diversion insert division line 9 equation should read Jv=Lp PRT(C0C1). 74 Last line of figure legend: 101 should read 1011. 75 Line 11: delete seems insert seem. le 1 column heading106 should read 1011. 77 delete ...membrane in series of... insert membranein series or... Delete final paragraph. 相似文献
14.
The Sensitivity of Net Photosynthesis in Several Plant Species to Short-term Fumigation with Sulphur Dioxide 总被引:4,自引:0,他引:4
The effects of exposure of up to 2 h with sulphur dioxide ona range of plant species was observed by measuring changes inthe rate of net photosynthesis under closely controlled environmentalconditions. Ryegrass, Lolium perenne S23 was thespecies most sensitive to SO2; significant inhibition was detectedat 200 nl l1. Fumigations at 300 nl l1 also inhibitedphotosynthesis in field bean (Vicia faba cv. Three FoldWhite and Blaze) and in barley (Hordeumvulgare cv. Sonja). No effect was detected inwheat (Triticum aestivum cv. Virtue) at concentrationsup to 600 nl l1 SO2, or in oil-seed rape (Brassica napuscv. Rafal) except at 800 nl l1 SO2). Recoverycommenced immediately after the fumigation was terminated andwas complete within 2 h when inhibition had not exceeded 20%during the SO2 treatment. Key words: Sulphur dioxide, short-term fumigation, photosynthesis 相似文献
15.
Humez S Monet M van Coppenolle F Delcourt P Prevarskaya N 《American journal of physiology. Cell physiology》2004,287(6):C1733-C1746
In this study, we investigated ionic mechanisms involved in growth arrest induced by extracellular ATP in androgen-independent prostate cancer cells. Extracellular ATP reversibly induced a rapid and sustained intracellular pH (pHi) decrease from 7.41 to 7.11. Inhibition of Ca2+ influx, lowering extracellular Ca2+, and buffering cytoplasmic Ca2+ inhibited ATP-induced acidification, thereby demonstrating that acidification is a consequence of Ca2+ entry. We show that ATP induced reuptake of Ca2+ by the mitochondria and a transient depolarization of the inner mitochondrial membrane. ATP-induced acidification was reduced after the dissipation of the mitochondrial proton gradient by rotenone and carbonyl cyanide p-trifluoromethoxyphenylhydrazone, after inhibition of Ca2+ uptake into the mitochondria by ruthenium red, and after inhibition of the F0F1-ATPase with oligomycin. ATP-induced acidification was not induced by either stimulation of the Cl/HCO3 exchanger or inhibition of the Na+/H+ exchanger. In addition, intracellular acidification, induced by an ammonium prepulse method, reduced the amount of releasable Ca2+ from the endoplasmic reticulum, assessed by measuring change in cytosolic Ca2+ induced by thapsigargin or ATP in a Ca2+-free medium. This latter finding reveals cross talk between pHi and Ca2+ homeostasis in which the Ca2+-induced intracellular acidification can in turn regulate the amount of Ca2+ that can be released from the endoplasmic reticulum. Furthermore, pHi decrease was capable of reducing cell growth. Taken together, our results suggest that ATP-induced acidification in DU-145 cells results from specific effect of mitochondrial function and is one of the major mechanisms leading to growth arrest induced by ATP. prostate; cancer; acidification 相似文献
16.
The apoplastic pH of the Zea mays root cortex as measured with pH-sensitive microelectrodes: aspects of regulation 总被引:5,自引:0,他引:5
In the root cortex of Zea mays the apoplastic pH and
aspects of its regulation were investigated using pH-sensitive
microelectrodes. To measure the pH directly in different cell layers of the
apoplast sharp double-barrelled electrodes were applied, whereas blunt
pH-electrodes were used simultaneously to measure the pH at the root
surface. Recordings carried out 8-10 mm behind the root tip show that the
apoplastic pH is maintained between 5.1 and 5.6, depending on the given
experimental conditions, i.e. varying external [K+],
[Ca2+], pH, weak buffering, as well as perfusion of
the test medium. When the medium pH (bulk) differs considerably from the
apoplastic pH, a small pH gradient is built up between the root surface
(unstirred layer) and the outer cortex layers. In a standing medium these
gradients equilibrate. The apoplastic pH responds to increases in external
[K+] and [CA2+] with an
acidification, which is attributed to ion-exchange properties of the cell
wall constituents. Stimulation of proton pump activity with fusicoccin
acidifies the apoplast from pH 5.6 to pH 4.8, while deactivation of the
pump with cyanide/salicylhydroxamic acid increases the pH of the apoplast
from 5.6 to 6.2, and further to pH 6.6 with CCCP. The
Ca2+ channel antagonists nifedipine and
La3+ also increase the apoplastic pH. It is
suggested that not only the proton pump, but also the cation channels may
contribute to the regulation of the apoplastic pH.Keywords:
Apoplast, ion-selective microelectrodes, pH, unstirred layer,
Zea mays, root.
相似文献
17.
Simulated swards of each of two selection lines of Lolium perennecv. S23 with fast and slow ratesof mature tissue respiration were establishedin growth rooms at 20/15 °C day/night temperatures and studiedover four successive regrowth periods of 46, 30, 26 and 53 daysduration. The slow line outyielded the fast,both in harvestable shoot (above a 5 cm cut) and in root andstubble. Its advantage increased over successive regrowth periodsto 23 per cent (total biomass). Gas analysis measurements onthe entire communities (including roots), during the final regrowthperiod, showed that the slow line had a 2234per cent lower rate of dark respiration per unit dry weight.This enabled it to maintain its greater mass of tissue for thesame cost in terms of CO2 efflux per unit ground area. Halfthe extra dry weight produced by the slow line,relative to the fast, could be attributed to itsmore economic use of carbon. The rest could be traced to a 25per cent greater tiller number which enabled the slowline to expand leaf area faster (though not at a greater rateper tiller), intercept more light and fix more carbon, earlyin the regrowth period. Lolium perenne L., ryegrass, respiration, maintenance respiration, tiller production, simulated swards, canopy photosynthesis, carbon economy 相似文献
18.
Four experiments were conducted to determine the effect of tradewinds in Guam, USA, on growth and gas exchange of three papaya(Carica papaya L.) cultivars. Known You 1, Sunrise,and Tainung 2 papaya seedlings at two differentstages of development were exposed to 0, 36 or 100% ambientwind. Wind exposure reduced stem height and leaf or stem dryweight in most cases, but had little influence on root growth.Net CO2assimilation (ACO2) at midday was lower for seedlingsexposed to wind than for those protected from wind. Dark respirationof exposed seedlings increased as much as 120% above that ofthe protected seedlings during the night. Wind exposure decreasedwhole plant evapotranspiration by up to 36% during the photoperiod,but increased evapotranspiration by 5887% during thenocturnal period. Responses to wind exposure were similar amongcultivars, except that growth of Tainung 2 seedlingswas less affected by wind than that of the other cultivars.Seedlings that were exposed to the various wind treatments fromgermination onwards were less influenced by wind exposure thanwere seedlings that were grown in a protected nursery beforebeing exposed to the various wind treatments. These data indicatethat: (1) ambient trade winds in Guam are strong enough to decreasethe growth of papaya seedlings; (2) plant age influences theresponse; (3) stem and leaf growth are more influenced thanroot growth; and (4) decreasedACO2 and increased dark respirationmay be partly responsible for growth reduction. Copyright 2001Annals of Botany Company Carica papaya, gas exchange, wind 相似文献
19.
Diverse Responses of Maple Saplings to Forest Light Regimes 总被引:7,自引:1,他引:6
Seedlings of 11 species of forest maples (AcerL.) were grownoutdoors from budburst to senescence under three light regimes:gap centre under clear skies (approx. 20% opensky irradiance; red:far-red ratio=1.12); gap centre undercloudy skies (1.5%, ratio=1.03); and gap edge(2.5%, ratio=0.6). Seedlings grown under the gap centre (clearsky) regime had significantly greater height growth, greaterspecific leaf mass, higher root:shoot ratio, greater investmentin roots, higher leaf nitrogen concentrations, greater chlorophylla:bratio,lower photosynthetic rates under dim light, higher maximum photosyntheticrate, higher stomatal conductance, and lower leaf internal CO2concentrationscompared with those grown in either gap edge or gap centre (cloudy)regimes. Responses to the gap edgevs.gap centre (cloudy) treatmentsdiffer little, suggesting that shade acclimation in forest mapleseedlings is mainly a response to light intensity rather thanspectral quality. The ubiquitous and, except for leaf internalCO2concentration, highly significant interspecific variationin traits was broad-ranging and continuous. These results suggestthat (1) the responses to light quality found in shade intolerantherbaceous and woody species growing in more open habitats maynot have a selective advantage in seedlings of shade tolerantforest trees, and (2) the adaptive plastic response to understoreyvs.gapenvironments in forest maples, which is qualitatively consistentacross species, is founded on co-ordinated, small shifts insets of functionally inter-related traits.Copyright 1998 Annalsof Botany Company Acer,forest gap heterogeneity, plasticity, specific leaf mass, photosynthesis, leaf chlorophyll, nitrogen, stomatal density, root growth, root:shoot ratio, growth form. 相似文献
20.
The Presence of Gibberellins in Excised Tomato Roots 总被引:1,自引:0,他引:1
Substances having similar physiological properties to the gibberellins(located by the Meteor dwarf pea bio-assay) havebeen detected in extracts from excised tomato root. The chromatographicbehaviour of the most active zone is similar to that of gibberellinA1. Experiments using the d-1 and d-5 mutants of mazie did not indicatethe presence of substances with differential effects on thesetwo mutants. 相似文献