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1.
The pigment changes that occur during transformation of etioplaststo fully developed chloroplasts have been studied in seedlingsof barley (Hordeum vulgare L.) by greening with white lightof low (1525 µmol m2 s1) and medium(150 µmol m2 s1) intensity. At least 24h longer was required in the low light regime for the same concentrationof pigment to be accumulated in the seedlings. The increasein pigment content was mainly due to the synthesis of chlorophyllsa and b. Of the carotenoids present, the increases in the levelsof neoxanthin and, especially, ß-carotene were muchgreater than those observed for the other carotenoids. Levelsof lutein also increased but this change was small by comparisonto those observed for neoxanthin and ß-carotene. Inthe long-term the concentration of violaxanthin remained unalteredalthough significant transient changes were recorded. The levelsof antheraxanthin and zeaxanthin were markedly reduced duringgreening. The rate of pigment synthesis decreased with increasingcell age, i.e. from the base to the tip of the primary leaf.Overall, carotenoid levels increased by approximately 100% atthe base of the seedling but hardly at all at the tip. Key words: Hordeum vulgare, carotenoids, violaxanthin-cycle, etiolation 相似文献
2.
Laminar pulvini of bean (Phaseolus vulgaris L.) contain numerouschloroplasts in cells of their motor tissue. The quantitativerelationships of the chloroplast pigments, chlorophyll a andb, ß-carotene, lutein, neoxanthin as well as the xanthophyllcycle carotenoids (violaxanthin, antheraxanthin and zeaxanthin)were similar to those of mesophyll chloroplasts from leafletlaminae. Exposure of pulvinules to light caused deepoxidationof violaxanthin to zeaxanthin, showing that the xanthophyllcycle is functioning. Chlorophyll fluorescence analysis of pulvinulesconfirmed that their chloroplasts are capable of both photosyntheticelectron transport and non-photochemical fluorescence quenching,showing that they build up a considerable transthylakoid protongradient in the light. Application of DCMU to excised pulvinulesand laminar discs, as well as to pulvinules of intact, attachedterminal leaflets blocked electron transport and fluorescencequenching. Application of the uncoupler CCCP to intact pulvinulesalso prevented non-photochemical fluorescence quenching. Therate of movement of the low-light-adapted terminal leaflet inresponse to exposure of its pulvinule to overhead red light(500 µmol m2 s1) was reduced when the pulvinulewas pretreated with DCMU. The pulvinar response to overheadblue light (50 µmol 2 s1), which is morepronounced than to red light, was not affected by similar pretreatmentwith DCMU. Pretreatment with CCCP caused a short lag in theresponse to red light, but did not affect its subsequent rate.The results suggest that the pulvinar response to red, but notto blue light, requires non-cyclic electron transport and theresulting generation of ATP Key words: Leaf movements, light, non-cyclic electron transport, Phaseolus, pulvinar chloroplasts 相似文献
3.
Astle, M. and Rubery, P. 1987. Carrier-mediated ABA uptake bysuspension-cultured Phaseolus coccineus L. cells: Stereospecificityand inhibition by ionones and ABA esters.J. exp. Bot.38: 150163. The substrate for the abscisic acid (ABA) carrier in Phaseoluscoccineus L. suspension-cultured cells is shown to be the (S)ABAenantiomer, Km = 1?0 mmol m3. The methyl (MeABA) andphenyl (PheABA) esters of ABA inhibit carrier-mediated uptakeof ABA with half-maximal inhibition achieved at about 7?0 mmolm3 and 10 mmol m3 respectively: with (S)MeABAthis value is decreased to about 2?0 mmol m3. There isno demethylation of radioactive MeABA by the cells during 5min incubations. Although MeABA reversibly inhibits the ABAcarrier, it is not a transport substrate: association of radioactiveMeABA with living cells is unaffected by non-radioactive MeABAor ABA and, by comparison with frozen-and-thawed cells, it isshown that the radioactivity remains extracellular. It is proposedthat MeABA binds to the carrier to form an abortive complexthat is not translocated. The terpenoid ABA analogue LAB 144143also inhibits carrier-mediated ABA uptake. At concentrationsup to about 20 mmol m3 - and ß-ionone specificallyinhibit the ABA carrier with the half-maximal effect at about0?6 mmol m3 ß-ionone. However, at higher iononeconcentrations, the uptake of ABA, indol-3-yl acetic acid andof 5,5-dimethyloxazolidine-2,4-dione (DMO) are all stimulated:this may reflect general permeabilization of the membrane toweak acids by ionone. Key words: Uptake carrier, abscisic acid, methyl and phenyl esters of ABA, ionone, Phaseolus coccineus L. suspension culture 相似文献
4.
Intact chloroplasts were isolated from mesophyll and bundlesheath protoplasts of a C4 plant, Panicum miliaceum L., to measurethe uptake of [1-14C]pyruvate into their sorbitol-impermeablespaces at 4?C by the silicone oil filtering centrifugation method.When incubated in the dark, both chloroplasts showed similarslow kinetics of pyruvate uptake, and the equilibrium internalconcentrations were almost equal to the external levels. Whenincubated in the light, only mesophyll chloroplasts showed remarkableenhancement of the uptake, the internal concentration reaching1030 times of the external level after 5 min incubation.The initial uptake rate of the mesophyll chloroplasts was enhancedabout ten fold by light and was saturated with increasing pyruvateconcentration; Km and Vmax were 0.20.4 mM and 2040µmol(mg Chl)1 h1, respectively. The lightenhancement was abolished by DCMU and uncoupling reagents suchas carbonylcyanide-m-chlorophenylhydrazone and nigericin. Theseresults indicate the existence of a light-dependent pyruvatetransport system in the envelope of mesophyll chloroplasts ofP. miliaceum. The uptake activity of mesophyll chloroplastsboth in the light and the dark was inhibited by sulfhydryl reagentssuch as mersalyl and p-chloromercuriphenylsulfonate, but thebundle sheath activity was insensitive to the reagents. Thesefindings are further evidence for the differentiation of mesophylland bundle sheath chloroplasts of a C4 plant with respect tometabolite transport. (Received July 3, 1986; Accepted October 8, 1986) 相似文献
5.
Tentoxin and, to a lesser extent, dihydrotentoxin (both at 10mmol m3) reduce stomatal opening in epidermal stripsof Commelina communis in the light but not in darkness. Thiseffect was significantly greater in normal air than in CO2-freeair. Fusicoccin overcame the tentoxin effect. However, tentoxindid not inhibit stomatal opening in the light in epidermal stripsof Paphiopedilum harrisianum, a species which lacks guard cellchloroplasts. It is concluded that tentoxin exerts its actionon stomata not by an ionophorous effect in the plasmalemma ofguard cells but by the inhibition of photophosphorylation intheir chloroplasts. The effects of DCMU and tentoxin on guardcells are discussed in terms of their effects on chloroplastsand the extent to which energy is supplied from this organelleduring stomatal opening in the light. The results indicate thatneither photophosphorylation nor non-cyclic electron transportin guard cell chloroplasts are essential for stomatal opening. Key words: Commelina, epidermal strips, Paphiopedilum, photophosphorylation, stomata, tentoxin 相似文献
6.
Various nitrate concentrations (0, 1, 2, 4, 8, 20, 50 mol m3)were applied at weekly intervals for 10 weeks to the caesalpinioidlegume Chamaecrista fasciculata. Microscopic techniques andgeneral growth studies showed that nitrate affected both theplant and its rhizobial symbiosis. As the nitrate concentrationwas increased, nodule structure became increasingly disruptedeven though nitrate remained limiting to plant growth until8 mol m3. Poly-ß-hydroxybutyrate (PHB) was observedusing transmission electron microscopy; as nitrate increasedfrom 0 to 2 mol m3, the PHB stores were utilized Key words: Chamaecrista fasciculata, poly-ß-hydroxybutyrate, nitrogen fixation 相似文献
7.
Guard cell protoplasts were isolated enzymatically from theepidermis of Vicia faba L. and their photosynthetic activitieswere investigated. Time courses of light-induced changes inthe chlorophyll a fluorescence intensity of these protoplastsshowed essentially the same induction kinetics as found formesophyll protoplasts of Vicia. The transient change in thefluorescence intensity was affected by DCMU, an inhibitor ofphotosystem II; by phenylmercuric acetate, an inhibitor of ferredoxinand ferredoxin NADP reductase; and by methyl viologen, an acceptorof photosystem I. Low temperature (77 K) emission spectra ofthe protoplasts had peaks at 684 and 735 nm and a shoulder near695 nm. A high O2 uptake (175 µmol mg1 Chl hr1)was observed in guard cell protoplasts kept in darkness, whichwas inhibited by 2 mM KCN or NaN3 by about 60%. On illumination,this O2 uptake was partially or completely suppressed, but itssuppression was removed by DCMU, which indicates that oxygenwas evolved (150 µmol mg1 Chl hr1) photosynthetically.We concluded that both photosystems I and II function in guardcell chloroplasts and that these protoplasts have high respiratoryactivity. (Received January 30, 1982; Accepted May 15, 1982) 相似文献
8.
Protoplasts were successfully isolated from internodal callustissues of both Oxalis glaucifolia and O. rhombeo-ovata whenthey were digested in a solution containing 0.1% (w/v) MacerozymeR-10, 0.5% (w/v) cellulase Onozuka R-10 and 0.3 mmol m3sucrose. Protoplasts proliferated to give cell colonies on Gamborget al.'s B5 medium supplemented with 0.3 mmol m3 mannitol,0.5 mg dm32, 4-D, and 2.0 mg dm3 kinetin. Calluswas produced upon transfer of cell colonies to Murashige andSkoog medium containing 2.0 mg dm3 l-naphthaleneaceticacid (NAA) and 0.1 mg dm3 kinetin for O. glaucifolia,or with 5.0 mg dm3 NAA and 0.5 mg dm3 6-benzylaminopurine,for O. rhombeo-ovata. Plants were regenerated from O. glaucifoliaprotoplasts on a medium containing 0.1 mg dm3 NAA, 1.0mg dm3 kinetin and 1.0 mg dm3 gibberellic acid,but only vascular nodules were differentiated by O. rhombeo-ovataprotoplast-derived calli. Key words: Tissue culture, protoplasts, plant regeneration, Oxalis spp 相似文献
9.
GEHL KATHARINA A.; COOK CATHERINE M.; COLMAN BRIAN 《Journal of experimental botany》1987,38(7):1203-1210
The carbon dioxide compensation point of the unicellular greenalga, Chloretla saccharophila, was determined in aqueous mediumby a gas chromatographic method. Compensation points decreasedmarkedly from 63 cm3 m3 at an external pH of 4.0 to 3.2cm3 m3 at pH 8.0 and were not affected by the O2 concentrationof the medium. The calculated CO2 concentration required tosupport the half-maximum photosynthetic rate of the algal cellsranged from 6.0 mmol m3 at an external pH of 60 to 1.5mmol m3 at pH 8.0 and these values were not affectedby O2 concentration. The Km(CO2) of nbulose-l,5-bisphosphatecarboxylase isolated from cells grown either at pH 4.0 or pH8.0 was determined to be 64 mmol m3. These results indicatethat loss of CO2 by photorespiration does not occur in C. saccharophilacells at acid pH and the disparity between the apparent affinityfor CO2 of the intact cells and that of the carboxylase indicatesthe operation of a CO2 concentrating mechanismin this alga at acid pH. Key words: Acidophilic alga, bicarbonate transport, Chlorella saccharophila, compensation point, CO2 affinity, PH, RuBP carboxylase 相似文献
10.
Cyanobacteria have two protochlorophyllide (Pchlide) reductasescatalyzing the conversion of Pchlide to chloro-phyllide, a keystep in the biosynthetic pathway of chlorophylls (Chls); a light-dependent(LPOR) and a light-independent (DPOR) reductase. We found anopen reading frame (ORF322) in a 2,131-bp EcoRI fragment fromthe genomic DNA of the cyanobacterium Plectonema boryanum. Becausethe deduced amino acid sequence showed a high similarity tothose of various plant LPORs and the LPOR activity was detectedin the soluble fraction of Esche-richia coli cells over-expressingthe ORF322 protein, ORF322 was defined as the por gene encodingLPOR in P. boryanum. A por-disrupted mutant, YFP12, was isolatedby targeted mutagenesiss to investigate the physiological importanceof LPOR. YFP12 grew as well as wild type under low light conditions(10-25 µE m2 S1). However, its growth wassignificantly retarded as a result of a significant decreasein its Chl content under higher light conditions (85-130 µEm2 s1). Furthermore, YFP12 stopped growing andsuffered from photobleaching under the highest light intensity(170 µE m2 s1). In contrast, a chlL-dis-rupted(DPOR-less) mutant YFC2 grew as well as wild type irrespectiveof light intensity. From these phenotypic characteristics, weconcluded that, although both LPOR and DPOR contribute to Chlsynthesis in the cells growing in the light, the extent of thecontribution by LPOR increases with increasing light intensity;without it, the cells are unable to grow under light intensitiesof more than 130 µ Em2s-. (Received September 26, 1997; Accepted November 21, 1997) 相似文献
11.
Perennial ryegrass (Lolium perenne L.) was grown from seed for29 d in flowing solution culture containing 0.1, 0.4 or 6.4mmol m3 P before the concentrations were changed (0.1and 0.4 raised to 6.4; 6.4 lowered to 0.4; controls unchanged)for an experimental period of two weeks to test the hypothesisthat after the seedling stage, the maximum rate of plant growthcould be sustained by a lower concentration of phosphate atthe root/solution interface than was necessary for the maximumrate of seedling growth. During the 29 d seedling period growthwas greatest on 6.4 mmol m3 P achieving 179 mg per plantdry weight compared with 122 and 26 mg on 0.4 and 0.1 mmol m3P respectively. During the experimental period growth on thetreatment 6.4 lowered to 0.4 mmol m3 P continued at thesame rate as the 6.4 control achieving 981 and 983 mg per plantdry weight respectively. Similarly growth of the treatment 0.4raised to 6.4 mol m3 P was unaffected by the change inconcentration and was comparable with the 0.4 control. Bothresults support the hypothesis for seedlings exceeding about100 mg per plant dry weight. In contrast the small plants ofthe treatment 0.1 raised to 6.4 mmol m3 P behaved similarlyto seedlings and responded rapidly to the increased concentrationof phosphate in solution, achieving high rates of phosphateuptake and increasing the growth of shoot more than the growthof root so that the ratio of root: shoot declined from 065 to0.34, a value similar to that for the seedlings grown on 6.4mmol m3 P. Key words: Lolium perenne L, Phosphate concentration, Seedling growth 相似文献
12.
The use of chlorate as an analogue for NO3 during nitrateuptake into Chara corallina cells has been investigated. NO3inhibits 36C1O3 influx into Chara over the concentrationrange 01000 mmol m3. Lineweaver-Burke plots ofthe data are characteristic of competitive inhibition by NO3in the low concentration range (0300 mmol m3 ClO3)and apparent KINO3 is 140 mmol m3 which is of a similarorder of magnitude as apparent KmCIO3- 180 mmol m3. Athigher substrate concentrations the inhibition by NO3was not characteristic of competitive or uncompetitive inhibition. 36C1O3/NO3 influx was dependent on K+ and Ca2+in the external medium and inhibited by FCCP. NO3 pretreatmentor N starvation increased subsequent 36C1O3/NO3influx into Chara. A comparison between rates of net NO3uptake and 36C1O3/NO3 influx supported the previoushypothesis that NO3 efflux is an important componentin the determination of overall uptake rates. Key words: Nitrate, Chara, 36CIO3 相似文献
13.
A membrane fraction from flax cells was able to incorporate[14C]galactose from UDP-D-[14C]galactose in vitro. The productsof the reaction, characterized by methylation analysis, consistedof a rß-1,4-galactan (solubilized mainly in water)and a rß-1,3- rß-1,6-galactan (solubilizedmainly in alkali). These results indicated the presence of severalgalactan synthase complexes, as did a profile of the relationshipbetween pH and activity which revealed both a maximum at pH6.5 and a shoulder at pH 8. Moreover, galactan synthase activitieswere found at two densities: 1.125 g cm3 (Golgi membranes)and 1.071.08 g cm3 (corresponding to low-densityvesicles). Partial characterization of one enzymatic system (maximaly activeat pH 8 in the presence of 5 mM MgCl2) was achieved. The Kmfor UDP-galactose and Vmax were 38 µM and 4.5 nmol h1(mg protein)1, respectively. (Received June 6, 1993; Accepted September 22, 1993) 相似文献
14.
Investigations on the effects of low levels of Al on P adsorption,uptake and translocation in seedlings of the indigenous grassAgrostis capillaris were undertaken. Apparent uptake and transportof H2 32PO4 from nutrient solutions containing 10 or 100mmolm3 phosphate were characterized as functions of timeand concentration. Experiments on 32P uptake and transport insolutions containing no Al (control) or Al ranging from 3.7to 185 mmol m3 at pH ranging from 4.3 to 4.6, showedthat in 10 mmol m3 P, effects of Al at 3.7 and 37 mmolm3 on the size of the initial uptake shoulder were small,but some increase in subsequent P uptake to the roots was observed,though transport to the shoots was suppressed. With 37 mmolm3 Al in nutrient solution containing 100 mmol m3P, the uptake shoulder was much increased above the control.Subsequent root uptake was stimulated but transport was unaffected.Lack of toxicity of the Al concentrations used was indicatedby a lack of significant effect on plant fresh weight. AbsorbedAl was almost totally retained in the root in all treatments.Speciation calculations showed that the major species in Alamended nutrient solution at pH 4.4 were H2PO4, AI3+and AIHPO4+, together with substantial amounts of AISO4+ andsoluble aluminium hydroxy complexes (AIOH2+, AI(OH)2+), dependingon the relative concentrations of P and Al. The effects of Al,with 10 mmol m3 P, on adsorption of complexed P werepartly accounted for in terms of preferential cell wall adsorptionof Al complexes not containing P. Conclusions were drawn aboutthe P-economy of A. capillaris plants growing on soils withlow levels of P and Al. Key words: Phosphorus, aluminium, speciation, Agrostis capillahs L 相似文献
15.
MACDUFF J. H.; JARVIS S. C.; LARSSON C-M.; OSCARSON P. 《Journal of experimental botany》1993,44(9):1475-1484
Two approaches to quantifying relationships between nutrientsupply and plant growth were compared with respect to growth,partitioning, uptake and assimilation of NO3 by non-nodulatedpea (Pisum sativum L. cv. Marma). Plants grown in flowing solutionculture were supplied with NO3 at relative addition rates(RAR) of 0·03, 0·06, 0·12, and 0·18d1, or constant external concentrations ([NO3)of 3, 10, 20, and 100 mmol m3 over 19 d. Following acclimation,relative growth rates (RGR)approached the corresponding RARbetween 0·030.12 d-1, although growth was notlimited by N supply at RAR =0.18 d-1. Growth rates showed littlechange with [NO3] between 10100 mmol m3(RGR=0·15 0·16 d-1). The absence of growthlimitation over this range was suggested by high unit absorptionrates of NO3, accumulation of NO3 in tissues andprogressive increases in shoot: root ratio. Rates of net uptakeof NO3 from 1 mol m3 solutions were assessed relativeto the growth-related requirement for NO3, showing thatthe relative uptake capacity increased with RGR between 0·030·06d1 , but decreased thereafter to a theoretical minimumvalue at RGR 相似文献
16.
Light-induced changes in membrane potential in Spirogyra 总被引:2,自引:0,他引:2
Spirogyra cells exhibited changes in membrane potential whenthey were exposed to light. Cells made chloroplast-free didnot show any light-induced potential change (LPC) upon illuminationwith white light and also monochromatic red (680 nm) and farred (720 nm) light. LPC was observed when the cell containedonly a small fragment of chloroplast, whether the cell had anucleus or not. The magnitude of LPC depended on the amountof chloroplast in the cell. DCMU at 105 M, CCCP at 105 M and DNP at 104M at pH 5.5 suppressed LPC, while CCCP at 15 ? 106M, NH4Cl at 5 ? 102 M and DNP at 104 M at pH 7.0stimulated LPC. PMS at 104 M stimulated LPC and couldinduce LPC which was completely inhibited by DCMU. These factssuggest that LPC is related to noncyclic and cyclic electronflows. The influences of light and dark conditions and various metabolicinhibitors (DCMU, DNP, CCCP, NH4Cl) on ATP level have been investigated.No significant difference in the ATP level was observed betweencells in the light and dark. DNP at 104 M (pH 5.5) andCCCP at 5 ? 106 M decreased the ATP level significantly,while DCMU and NH4Cl only slightly. Good correlation was notfound between the total ATP level and LPC in Spirogyra. LPC occurred even when the external medium contained only asingle salt such as KCl, NaCl or CaSO4. LPC was also recorded in chloroplasts in situ and in vitro.The mode of LPC of chloroplasts was quite different from thatof the cell. On illumination, the chloroplast potential changedvery rapidly and transiently in the positive direction thenrecovered spontaneously to almost the original potential level. Possible causes of LPC are discussed in relation to the electrogenicion pump.
1 Present address: Department of Botany, Faculty of Science,University of Tokyo, Hongo, Bunkyo, Tokyo 113, Japan. (Received November 9, 1977; ) 相似文献
17.
The development of a medium for studying aluminium toxicityin plant cell cultures is described. To prevent the precipitationof Al added to the standard cell culture medium, it was necessaryto lower the phosphate concentration from 1250 mmol m3to10 mmol m3, and the pH from 5.8 to 4-0. Two additionalmodifications were the use of unchelated iron and a reductionin the calcium concentration from 3.0 mol m3 to 0.1 molm3. Since the gelling properties of agar are inhibitedat pH 4.0, cells were cultured on filter paper supported bypolyurethane foam sturated with liquid medium. The only limitationto the growth of plated Nicotiana plumbaginifolia Viv. cellson the modified medium was the reduced phosphate concentration.This was partly overcome by preloading the cellswith phosphate prior to each experiment. In addition, the filterpaper with adhering cells was transferred to fresh medium everysecond day to replenish phosphate, and to re-establish the initialpH of4.0 (which otherwise drifts upward). With the modifiedmedium, Al toxicity was observed in plated N. plumbaginifoliacells at both 200 mmol m3 and 400 mmol m3 Al.There was no toxicity at these Al concentrations when the normalphosphate concentration or pH were restored to the modifiedmedium. Partial alleviation of Al toxicity occurred with restorationof the normal calcium concentration or chelated iron. Chelationof Al with citrate or EDTA also mitigated Al toxicity. In additonto Al toxicity, the modified medium should also prove usefulfor studying other metal toxicities in plant cell culture. Key words: Al toxicity, Cell culture, Nicotiana plumbaginifolia 相似文献
18.
Acclimation in Seedlings of a Tropical Tree, Bischofia javanica, Following a Stepwise Reduction in Light 总被引:2,自引:0,他引:2
Acclimation of fully developed leaves of Bischofia javanicaBlume to shadelight was examined. Seedlings were grown undersimulated daylight (1000 µmol m2 s1), thentransferred to a simulated shadelight (40 µmol m2s1). When a high-light leaf was transferred to low light, large negativenet photosynthetic rates (Pm) were recorded. This decrease wasrapid, but within 7 d the rate increased and became equal tothe low-light control leaf. These changes in photosynthesisdid not follow the pattern of changes in stomatal conductance(gs). Transfer to the low light resulted in a dramatic decreasein leaf weight per unit area (Lw), and most of the decreasesin Lw occurred within 3 d of transfer when the Pm of the transferredleaf was well below that of the low-light control leaf. There was a significant decrease in chlorophyll a in the transferredleaf without an appreciable change in chlorophyll b resultingin a large decrease in the chlorophyll a to chlorophyll b ratio.Leaf chlorophylls per unit area were higher in the transferredleaf than the low-light control leaf. Maximum photosyntheticrate in the transferred leaf was decreased by 40% compared tothat for the high-control leaf, but was almost at the same extenthigher than the low-light control leaf The results are discussedin the context of carbon gain capacity of its seedlings underlight-limiting forest understorey habitats. Bischofia, chlorophylls, light, photosynthesis, shade acclimation, tree seedlings, tropical tree 相似文献
19.
At low light intensities (less than 50 µmol m2s1) illumination evokes transient depolarization of membranepotential in mesophyll cells of the leaf-trap of Dionaea muscipulaEllis. Darkening causes hyperpolarization approximately symmetricto the response to illumination. The amplitude as well as therate of potential changes depend on light intensity. After exceedinga definite threshold (usually between 50 and 80 µmol m2s1)the depolarization plays the role of a generator potential andan all-or-none action potential (AP) is released. Switchinglight off in a depolarization phase of an AP does not changeits shape and the amplitude. When the light intensity is increasedto 80150 µmol m2 s1 a single lightstimulus triggers two successive APs. The time interval betweenthe two APs decreases with increasing stimulus strength andreaches the minimum between 300 and 400 µmol m2s1. At higher light intensities the interval increasesagain, and finally only a single AP is triggered. It was shownthat the effect was evoked by light but not by temperature changeaccompanying illumination. An inhibitor of the photosyn-theticelectron transport chain, DCMU, blocked the generator potentialsmediating between light absorption and APs. Residual responsesto light stimuli in plants treated with DCMU had reverse polarityand strongly reduced the amplitudes. (Received September 16, 1997; Accepted January 16, 1998) 相似文献
20.
THORNTON F. C.; SCHAEDLE M.; RAYNAL D. J.; ZIPPERER C. 《Journal of experimental botany》1986,37(6):775-785
Honeylocust (Gleditsia triacanthos L.) seedlings were grownin solution culture at pH 4.0) with 50, 150, 600 and 1500 mmolm3 aluminium. All levels of aiuminium reduced the sizeand weight of roots, shoots and leaves with the exception ofroot elongation at 50 mmol m3 Al. Aluminium content ofroots was 50 to 100 times that of shoots. With increasing concentrationof aluminium, aluminium content of leaves and roots increasedexponentially while a linear increase was observed for stems.The nutrient content of seedlings was improved in 50 mmol m3where increases in shoot calcium, magnesium, and phosphorusconcentrations were observed. Aluminium concentrations greaterthan 50 mmol m3 reduced shoot nutrient content. Presenceof aluminium increased the root phosphorus and calcium levelsbut had no effect on potassium and magnesium concentrations.Results show that honeylocust is an aluminium sensitive treespecies whose growth may be reduced by high soil Al levels. Key words: Aluminium toxicity, Gleditsia triacanthos, nutrient solution 相似文献