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1.
Shelp, B. J. 1987. The composition of phloem exudate and xylemsap from broccoli (Brassica oleracea var. italica) suppliedwith NH+4, NO3 or NH4NO3.J. exp. Bot. 38: 16191636. The detailed composition of xylem sap and exudate from stemincisions of attached inflorescences of broccoli (Brassica oleraceavar. italica) was compared in plants supplied with NH+4, NO3or NH4NO3. A phloem origin for the exudate was suggested fromthe high levels of sugars (71133 mg cm-3), amino acids(8·1-26·7 mg cm3) and K. (2·33·8mg cm3), the low levels of NO3 and Ca, the high C: N (w/w) ratios(8·333), and the alkaline pH (7·27·3).In contrast, the xylem sap was mildly acidic (pH 5·66·0),and possessed lower levels of all organic and inorganic solutesbut NO3 and Ca, and lower ratios of K: Ca, Mg: Ca and C: N (0·64·4). Glutamine was the predominant o-phthalaldehyde-reactive aminocompound in both transport fluids with the next most abundantamino acids dependent on sap type and N-form. Together witharginine, -aminobutyric acid, which was found only in the xylemstream, was enhanced by NH+4compared to NO3 -nutrition suggestingthat glutamate metabolism was stimulated in the roots. Underlimiting N the amino acid concentrations in the transport fluidswere greater with NH+4 than with NO3. NO3 reduction occurredin both the root and shoot with the latter site predominatingover the entire N range (0-300 mol m3). Even though the compositionof nitrogenous solutes in the xylem was dependent on cultivarand N source, the composition of the phloem streams supplyingthe developing inflorescence was relatively unaffected. The data on the element composition of organs and phloem sapare interpreted to suggest that, in spite of the restrictedmobility of some elements such as B and Mn, a significant proportionof their total supply to developing sinks is carried in thephloem stream. Key words: Transport fluid composition, plant nutrition, phloem mobility. 相似文献
2.
LOBODA T.; KLECZKOWSKI L. A.; TARLOWSKI J.; NALBORCZYK E. 《Journal of experimental botany》1988,39(12):1765-1770
The effects of -hydroxy-2-pyridinemethanesulphonic acid (-HPMS)upon net photosynthesis (Pn, the CO2 compensation point (),post-lower illumination burst of CO2 (PLIB) and post-lower temperatureburst of CO2 (PLTB) in detached rye (Secale cereale L.) leaveswere investigated. At low concentrations ( 0.5 mol m3),-HPMS initially stimulated Pn and decreased the magnitude ofboth PLIB and PLTB. The decreased at all concentrations of-HPMS (0.055.0 mol m3. The effects of -HPMS onPn and were time-dependent and, after a few minutes, the Pnwas inhibited while values increased considerably. At a higherconcentration (5.0 mol m 3), the transient effects of-HPMS were shorter () or not observed at all (Pn. Both PLIBand PLTB, when expressed in relation to Pn, increased at higherlevels of this compound. Similar data with respect to the effectsof -HPMS on PLIB and PLTB were found for leaves of dandelion(Taraxacum officinale L.). The results suggest that -HPMS may stimulate Pn by inhibitingphotorespiration, as originally suggested by Zelitch (1966),but only at low concentrations and over a short time span. Thedecrease of PLIB and PLTB values at low -HPMS levels is consistentwith these processes being a residual activity of the glycolatepathway. Key words: CO2 compensation point, -hydroxy-2-pyridinemethanesulphonic acid, photorespiration, photosynthesis 相似文献
3.
LARQUE-SAAVEDRA A.; RODRIGUEZ M. T.; TREJO C.; NAVA T. 《Journal of experimental botany》1985,36(11):1787-1792
Larqué-Saavedra, A., Rodriguez, M. T., Trejo, C. andNava, T. 1985. Abscisic acid accumulation and water relationsof four cultivars of Phaseolus vulgaris L. under drought.J.exp. Bot 36: 17871792. Plants of four cultivars of Phaseolus vulgaris L. differingin drought resistance were grown in pots under greenhouse conditionsand prior to flowering water was withheld from the pots untilthe mid-day transpiration rate reached values below 1.0 µgH2O cm2 s1 (designated the droughtstage). At this point leaves were harvested on 3 or 4 occasionsover 24 h to determine the abscisic acid (ABA) concentration,total water potential (), solute potential (1) and turgor potential(p). Results showed that values of , 1, and p differed between cultivarswhen they reached the drought stage. The stomatalsensitivity to changes in and p, was as follows: Michoacán12A3 > Negro 150 Cacahuate 72 > Flor de Mayo. These datacorrelated well with the pattern of drought resistance reportedfor the cultivars. ABA accumulation at the drought stage differedbetween cultivars at each sampling time, but overall differencesin ABA level between cultivars were not significant. ABA levelsdid not, therefore, correlate with the drought resistance propertiesreported for the cultivars. Results are discussed in relationto and hour of the day when bean samples were taken for ABAanalysis. Key words: Phaseolus vulgaris L., drought resistance, abscisic acid 相似文献
4.
This work aimed to study the impacts of acquisition and assimilationof various nitrogen sources, i.e. NO3, NH4+ or NH4NO3,in combination with gaseous NH3 on plant growth and acid-basebalance in higher plants. Plants of C3 Triticum aestivum L.and C4 Zea mays L. grown with shoots in ambient air in hydroponicculture solutions with 2 mol m3 of nitrogen source asNO3, NH4+ or NH4NO3 for 21 d and 18 d, respectively,had their shoots exposed either to 320 µg m3 NH3or to ambient air for 7 d. Variations in plant growth (leaves,stubble and roots), and OH and H+ extrusions as wellas the relative increases in nitrogen, carbon and carboxylatewere determined. These data were computed as H+/N, H+/C, (C-A)/N,and (C-A)/C to analyse influences of different nitrogen sourceson acid-base balance in C3 Triticum aestivum and C4 Zea maysplants. Root growth in dry weight gain was significantly reduced bytreatment with 320 µg m3 NH3 in Triticum aestivumand Zea mays growing with different N-forms, whereas leaf growthwas not significantly affected by NH3. In comparison with C3Triticum aestivum, non-fumigated C4 Zea mays had low ratiosof OH/N in NO33-grown plants and of H+/N in NH4+- and NH 4NO3-grown plants. Utilization of NH3 from the atmospherereduced both the OHN ratios in NO3 -grown plantsand the H+/N ratio in NH4+ - and NH4NO3 -grown plants of bothspecies. Furthermore, Zea mays had higher ratios of (C-A)/Nin NH4+ - and NH4NO3-grown plants than Triticum aestivum. Thismeans that C4 Zea mays had synthesized more organic anion perunit increase in organic N than C3 Triticum aestivum plants.Within both species, different nitrogen sources altered theratios of (C-A)/N in the order: NH4NO3>NH4+>NO3.Fumigation with NH3 increased organic acid synthesis in NO3- and NH4+ - grown plants of Triticum aestivum, whereas it decreasedorganic acid synthesis in Zea mays plants under the same conditions.Furthermore, these differences in acid-base regulation betweenC3 Triticum aestivum and C4 Zea mays plants growing with differentnitrogen sources are discussed. Key words: Acid-base balance, ammonia, ammonium, nitrate, ammonium nitrate, C3 Triticum aestivum L., C4 Zea mays L. 相似文献
5.
Smith, J. R. 1987. Potassium transport across the membranesof Chara. II. 42K fluxes and the electrical current as a functionof membrane voltage.J. exp. Bot. 38: 752777. The current required to clamp the trans-membrane voltage ofinternodal cells of Chara australis at different levels wasmeasured simultaneously with either the 42K influx or efflux.Examination of the voltage-dependence of the ratio of the electricalcurrent to the unidirectional tracer fluxes yielded no evidenceof any amplification of the electrical driving force on theK+ ions. There was thus no evidence for the interaction of K+ions with themselves or any other species during their passageacross the membrane. These measurements allow the determinationof , the fraction of the electrical current carried by K+ ions.When the external [K+] = 10 mol m3, the average valueof was 0?85 for Vm > 125 mV and 07?5 for Vm <150 mV. When the external [K+] = 0?1 mol m3, was 0?6 for Vm < 80 mV and 0?1 for Vm > 250mV. It was also found that the conductance associated with K+transport was inhibited by hyperpolarization. Key words: Potassium, conductance, flux-ratio 相似文献
6.
Effects of Priming and Endosperm Integrity on Seed Germination Rates of Tomato Genotypes: II. GERMINATION AT REDUCED WATER POTENTIAL 总被引:3,自引:0,他引:3
Seed germination rates (GR =inverse of time to germination)are sensitive to genetic, environmental, and physiological factors.We have compared the GR of tomato (Lycopersicon esculentum Mill.)seeds of cultivar T5 to those of rapidly germinating L. esculentumgenotypes PI 341988 and PI 120256 over a range of water potential(). The influence of seed priming treatments and removal ofthe endosperm/testa cap enclosing the radicle tip on germinationat reduced were also assessed. Germination time-courses atdifferent 's were analysed according to a model that identifieda base, or minimum, allowing germination of a specific percentage(g) of the seed population (b(g)), and a hydrotime constant(H) indicating the rate of progress toward germination per MPa.h.The distribution of b(g) determined by probit analysis was characterizedby a mean base (b) and the standard deviation in b among seeds(b). The three derived parameters, b, b) and H, were sufficientto predict the time-courses of germination of intact seeds atany . A normalized time-scale for comparing germination responsesto reduced is introduced. The time to germination at any (tg())can be normalized to be equivalent to that observed in water(tg(0)) according to the equation tg(0)=[l(/b(g))]tg().PI 341988 seeds were more tolerant of reduced and had a morerapid GR than T5 seeds due to both a lower b and a smaller H.The rapid germination of PI 120256, on the other hand, couldbe attributed entirely to a smaller H. Seed priming (6 d in1.2 MPa polyethylene glycol 8000 solution at 20 ?C followedby drying) increased GR at all >b(g), but did not lower theminimum allowing germination; i.e. priming reduced H withoutlowering b. Removing the endosperm/testa cap (cut seeds) markedlyincreased GR and lowered the mean required to inhibit germinationby 0.7 to 0.9 MPa. However, this resulted primarily from downwardadjustment in b during the incubation of cut seeds at low inthe test solutions. The difference in b between intact and cutseeds incubated at high was much less (0.l MPa), indicatingthat at the time of radicle protrusion, the endosperm had weakenedto the point where it constituted only a small mechanical barrier.In the intact seed, endosperm weakening and the downward adjustmentin embryo b ceased at < 0.6 MPa, while the reductionin H associated with priming proceeded down to at least 1.2MPa. Based on these data and on the pressure required to pushthe embryos from the seeds at various times after imbibition,it appears that the primary effect of priming was to shortenthe time required for final endosperm weakening to occur. However,as priming increased GR even in cut seeds, priming effects onthe embryo may control the rate of endosperm weakening. Key words: tomato, Lycopersicon esculentum Mill., water potential, germination rate, seed priming, genetic variation 相似文献
7.
Thomas, H. 1987. Physiological responses to drought of Loliumperenne L.: Measurement of, and genetic variation in, waterpotential, solute potential, elasticity and cell hydration.J.exp. Bot. 38: 115125. Clonally-replicated genotypes of Loiium perenne L. were grownin a controlled environment. Leaf water potential (w) osmoticpotential (s), turgor potential (p = w s), elasticity(E), leaf hydration (g water per g dry matter, H) and numberof green leaves per tiller (NGL) were measured before and duringa 42 d drought treatment. A simplified method of estimating E (at w < 1?0 MPa) usingonly six measurements was developed to permit a measurementrate of 8 leaves per hour. Measurement errors in all characterswere 3% or less. During drought, w and s (at w = 0?5 MPa) decreased significantly,p and E increased significantly, and H decreased slightly. Plantsize during drought was negatively correlated with s, and Hand positively correlated with p, osmotic adjustment, E andNGL. Measurements made on the genotypes before draughting didnot give a reliable indication of their physiological conditionafter adaptation to drought. Genetically controlled variation (broad sense heritability)of drought-adapted plants for E was 15%, w 23%, s, 34%, p, 35%,H 34% and NGL 64%. The possibilities for, and effectivenessof, divergent selection of genotypes with high and low expressionof the characters are discussed. Key words: Water relations, Lolium, genetic variation 相似文献
8.
The effects of Cl and pretreatment on 36Clinflux and influx into Characorallina cells were examined. Both treatments reduced 36Clinflux into C. corallina cells in the acid pH range (4.57.0). pretreatment stimulated influx into C. corallina cells, but Cl pretreatment hadno effect. There was a direct inhibitory effect of CI on influx into C. corallina cells, but no apparenteffect on net NO uptake. The time course of 36Cl accumulation into cytoplasmic and vacuolarcompartments during incubation of the cells with showed that significant radioactivity appeared in the vacuolarsap after 30 min. There was a linear increase in the percentageof total 36CI which crossed the tonoplast (c-v). There was noeffect of Cl or pretreatment on accumulation of radioactivity in the vacuole. Thin layer chromatography ofthe vacuolar sap showed that after 2 h only one component waspresent which had an RF which was similar to 36CI. Therate of accumulation of 36C1 in the vacuole could beused to estimate rates of reduction. Key words: Chloride, Chlorate, Chara, Nitrate 相似文献
9.
Carbon Metabolism in Seagrasses: I. THE UTILIZATION OF EXOGENOUS INORGANIC CARBON SPECIES IN PHOTOSYNTHESIS 总被引:2,自引:0,他引:2
Four species of seagrasses, Halophila stipulacea, Thalassodendronciliatum, Halodule uninervis, and Syringodium isoetifolium,were investigated for their ability to utilize and CO2 as exogenous carbon sources for photosynthesis. Ratesof photosynthesis were measured as rates of O2 evolution ina closed system in which the pH was continuously controlled.A computer program was written to calculate the concentrationsof different carbon species as a function of pH and other specifiedexperimental conditions. Bicarbonate as well as CO2 were readily assimilated by all fourseagrass species. Saturating concentrations of , at saturating light intensities, were 0.51.8 mM dependingon the species. Rates of photosynthesis under such conditionswere 0.10.55 µmol O2 min1 mg1 chlorophyll.At saturating CO2 concentrations, i.e. 0.51.3 mM, ratesof photosynthesis were 0.221.4 µmol CO2 min1mg1 chlorophyll. Photosynthetic rates in each specieswere considerably higher when CO2 rather than was supplied at saturating concentrations. The concentration of in natural seawater was found to be saturating, and that of CO2 insufficient forconsiderable photosynthetic rates in these plants under thegiven conditions It was thus concluded that is the major carbon source for photosynthesis in seagrasses. 相似文献
10.
The vacuolar pH (pHv) and the cytoplasmic pH (pHc) of the marinegiant-celled green alga Chaetomorpha darwinii were measuredby pH microelectrode techniques on extracted vacuolar sap, andby the [I4C]DMO distribution method respectively. Equilibrationof DMO occurred with a half-time of about 2 h, with an apparentPDMO of 3.6 x 105 cm s1, but the vacuolar concentrationof free, undissociated DMO was always less than the externalconcentration. The explanation offered for freshwater giant-celledalgae of net DMO leakage across the plasmalemma cannotapply to Chaetomorpha darwinii, since electrically-driven DMOexit from the cytoplasm should be similar across the plasmalemmaand the tonoplast in these cells with large, vacuole-positivepotential differences across the tonoplast. pHc was accordinglycomputed assuming either tonoplast or plasmalemma equilibrationof DMO, with correction for DMO metabolism within the cell.pHc was 8.08.3 in the light in artificial seawater (pHoabout 8.0), was some 0.5 units lower in the dark, and was slightlylower with an external pH of 7. Vacuolar pH was 6.56.9,without consistent effects of illumination or of external pHof 7 rather than 8. While µH+ at the tonoplast was similarto that in giant-celled freshwater algae (although with a greatercontribution from relative to pH), µH+ at the plasmalemmawas less than 8 kJ mol1, i.e. less than one-third ofthe value in freshwater green algae. µNa+ was some 13kJ mol1 at the plasmalemma. The possibility that theprimary active transport process at the plasmalemma of Chaetomorphadarwinii (and certain other marine algae) is Na+ efflux ratherthan H+ efflux is discussed. 相似文献
11.
Effects of light flux density (LFD) during growth and uptakeassay on induction of transport system and kinetics of transport were studied using the Azolla pinnata-Anabaena azollae association (Azolla). Theinduction and uptake kinetics of the transport system were determined using an automated system that measuredthe NO3 concentration in the growth medium as a function oftime, using an on-line high performance liquid chromatograph(HPLC) with a UV-VIS detector. Full induction of the transport system required about 1.5 to 2.0 h and occurred without any apparent lag phase,regardless of the LFD provided. The level of induction of transport of Azolla grown at 600 µmol m2s1 LFD was higher than for that grown at 100 µmolm2 s1. Similarly, 600 µmol m1 s1LFD during the assay resulted in a higher level of inductionthan did 100 umol m2 s1. An increase in the LFDeither during the growth or the assay period increased the uptake rate; however, an increase in LFD duringthe latter period had greater effect. Azolla grown and assayedat 600 umol m2 s1 had the highest uptake rate. The uptake rate at 50 cm3 m3ambient CO2 concentration was initially higher than at 305 cm3m3, but the uptake rate decreased rapidly with time andeventually dropped below that at 305 cm3 m3 CO2. Thesedata suggest that the energy required for transport in Azolla may bypass the photosynthetic CO2 fixationand carbon-cycling. Key words: carbon dioxide, concentration dependence, light flux density, uptake 相似文献
12.
In Trifolium repens L. there were immediate transient depolarizationsof the membrane electropotential (Evo) when KH2PO4 was addedto phosphate-free media, but these were of the same magnitudeas the controls (K2SO4 and KCI). Furthermore, the extents ofdepolarization were the same as the expected effect of the addedK+ calculated using the Goldman equation. There was no significantdepolarization on adding H3PO4 to buffered media. Consequently,there was no evidence for a depolarization caused by phosphate.This result provides evidence that the H+H2PO4 symportin roots of T. repens operates with a stoichiometry of 1: 1. In a group of control plants ( + P plants) and a group whichwere stressed by reducing the supply of phosphate ( Pplants), the P plants had lower values for Evo than+P plants ( 118 mV and 130 mV, respectively).The absence of phosphate from the measurement media also reducedEvo (mean effect = 9 mV). A significant difference in Evo between P and + P plants persisted when phosphate was addedto P plants. The electropotential difference acrossthe tonoplast (Evo) in P plants became more positivewith time. Key words: White clover, membrane transport, roots, tonoplast, symport 相似文献
13.
Effects of soil moisture deficits on the water relations of bambara groundnut (Vigna subterranea L. Verdc.) 总被引:1,自引:0,他引:1
Collinson S.T.; Clawson E.J.; Azam-Ali S.N.; Black C.R. 《Journal of experimental botany》1997,48(4):877-884
The components of leaf water potential (l) and relative watercontent (RWC) were measured for stands of bambara groundnut(Vigna subterranea) exposed to three soil moisture regimes incontrolled-environment glasshouses at the Tropical Crops ResearchUnit, Sutton Bonington Campus. Treatments ranged from fullyirrigated (wet) to no irrigation from 35 days after sowing (DAS)(dry). RWC values varied between 9296% for the wet treatment,but declined from 93% to 83% in the dry treatment as the seasonprogressed. l at midday decreased in both the wet and dry treatments,but the seasonal decline was more pronounced in the latter:seasonal minimum values were 1.19 and 2.08 MPa,respectively. Plants in the wet treatment maintained turgor(p) at about 0.5 MPa throughout the season, whereas values inthe dry treatment approached zero towards the end of the season.There was a linear relationship between p and l9 with p approachingzero at a l of 2.0 MPa. Mean daily leaf conductance wasconsistently higher in the wet treatment (0.460.79 cm-1)than in the intermediate and dry treatments (0.130.48cm s-1 Conductances in the intermediate and dry treatments weresimilar, and the lower evapotranspirational water losses inthe latter were attributable to its consistently lower leafarea indices (L): L at final harvest was 3.3, 3.3 and 1.9 forthe wet, intermediate and dry treatments. Bambara groundnutwas apparently able to maintain turgor through a combinationof osmotic adjustment, reductions in leaf area index and effectivestomatal regulation of water loss. Key words: Vigna subterranea, water relations, soil moisture 相似文献
14.
MACDUFF J. H.; HOPPER M. J.; WILD A.; TRIM F. E. 《Journal of experimental botany》1987,38(10):1589-1602
Macduff, J. H., Hopper, M. J., Wild, A. and Trim, F. E. 1987.Comparison of the effects of root temperature on nitrate andammonium nutrition of oilseed rape (Brassica napusL.) in flowingsolution culture. II. Cation-anion balance.J. exp. Bot.38: 1589-1602. The effects of root temperature and form of N nutrition (NH4or NOJ) on the mineral composition of the plant, the balanceof inorganic cation-anion uptake and on the apparent net effluxof H +/OHions from the roots were studied with 49-d-oldoilseed rape (Brassica napusL. cv. Bien venu) in flowing solutionculture. Plants were pre-treated for 14 d at a root temperatureof 5 °C prior to constant root temperatures of 3, 7, 11or 17°C for 14 d, with a common shoot temperature of 20/15°Cday/night. Nitrogen was supplied as NH+44 or NO3 at 10mmol m3. Values of Q10 (7-17°C) for mean unit absorptionrates of all the major nutrient ions (K+ , Mg++ , NH+4, SO4,H2PO4, NO3), except Ca++, were > 2.0 over the first 5 d oftreatment but thereafter were < 1.5; the apparent effectof temperature on uptake rates diminished with time. Under NH+4nutrition, inorganic cation uptake (Mg+ + + K++Ca+ + +NH+4)exceeded inorganic anion uptake (SO4 4+ H2PO4) over 14d at all temperatures, with the proportion of cation uptakeas NH4 remaining constant (0.67-0-68) irrespective of root temperature.The net efflux of H + from the roots approximately balancedNH+4 uptake (1:1) over 14 d at each temperature and also balancedthe difference between the total uptake of inorganic cationsand inorganic anions. Under NO3 nutrition, the sum of the netefflux of OH and the change in the carboxylate contents of plantsover 14 d approximately balanced the sum of NO3 and SO 4reduced in the plant. The majority of the negative charge associatedwith the reduction of NO3 and SO 4 was apparently effluxedas OH, but this fraction was lower at low root temperatures.The results are discussed in terms of mechanisms that have beenproposed to regulate the internal pH of plants. Key words: Brassica napus, oilseed rape, root temperature, cation-anion balance, H+/OH efflux. 相似文献
15.
Nitrate Transport Characteristics in Hordeum vulgare L. Seedlings using Three Different Tracer Techniques 总被引:2,自引:0,他引:2
Deane-Drummond, C. E. and Thayer, J.R. 1986. Nitrate transportcharacteristics in Hordeum vulgare L. seedlings using threedifferent tracer techniques.J. exp. Bot. 37: 429439. and have been used to investigate various properties of nitrate uptake and translocation intoHordeum vulgare L seedlings. Short term / influx into seed lings grown in CaSO4 was stimulated by after a lag of 2 h. The apparent kinetics of shortterm / influx over the concentration range 0?00?7mol m fitted Michaelis-Menten equations The apparent Vmax didnot change when seedlings were used that had been pretreatedin 10 or 100 mmol m3 and Vmax=3.77 and 3?56µmol g1 fr. wt. h1respectively. The apparent Michaelis constants were also similarand Km=0?47 and 0?45 mol m3 respectively. Longer term pulse chase experiments with the heavy isotope 15Nhave shown that feeding roots with resulted in the preferential appearance of 15N labelled aminoacids in the xylem sap. Pulse chase experiments with the radioisotope13N have shown that feeding shoots with resulted in a radial pattern of distnbution of labelin the leaf veins, which can be detected using autoradiography. The limitations and advantages of all three techniques are comparedby reference to other known experimental data. Key words: 36Chlorate, 13nitrate, 15nitrate, Hordeum vulgare 相似文献
16.
Henson, I. E. 1985. Solute accumulation and growth in plantsof pearl millet (Pennisetum americanum [L.] Leeke) exposed toabscisic acid or water stress.J. exp. Bot. 36: 18891899.Experiments were conducted to investigate whether abscisic acid(ABA) elicits the accumulation of solutes and lowering of osmotic(solute) potential (2) which occurs in leaves of pearl millet(Pennisetum americanum [L.] Leeke) exposed to water stress.When (?)ABA was injected into the base of the shoot of15dold plants, 2 of the fifth leaf was reducedsignificantly below controls 2772 h after treatment.The reductions, however, were small (< 0.10 MPa) and wereaccompanied by a significant inhibition of shoot growth. Incontrast, no significant reduction in 2 or in growth occurredwhen the hormone was introduced directly into leaf five viaits midrib. ABA concentrations in leaf five were highshortly after direct injection, but declined to control levelswithin 48 h. Injecting ABA into the shoot base resulted in lowerleaf five ABA concentrations. Hence, the ABA concentration inthe leaf was not the most critical factor for its effect on2. ABA also reduced 2 of shoots when applied to seedlings 48h or 72 h after sowing via the roots. As with older plants,the effects of ABA on 2 were small ( 02 MPa) and wereaccompanied by inhibition of shoot growth. A water stress treatmentand an ABA treatment were compared. Although both treatmentsresulted in a similar degree of growth inhibition, the stresstreatment was much more effective than was ABA in reducing 2. Key words: Pennisetum americanum [L.], pearl millet, abscisic acid, water stress, osmotic 相似文献
17.
By analysing the relationship between inverse water potential(1), and relative water content (RWC) measured on leavesof roses (Rosa hybrida cv. Sonia), grown soilless, it was foundthat a non-linear (NL) model was better suited than a linearmodel to reproduce values observed in the non-turgid region.To explain this apparent curvature, it is assumed that a reductionof the non-osmotic water fraction (Ap) takes place when decreases.Osmotic potentials () measured on fresh and frozen leaf discstend to support this hypothesis. A method for exploiting PVcurves, which takes into account the variation of Ap, is described.It delivers values for the turgor pressure (p), the relativeosmotic water content, and the mean bulk volumetric elasticitycoefficient, lower than those given by the linear model. Onthe other hand, it gives higher estimates for Ap and for . Whenapplying the traditional model to obtain estimates for waterrelations characteristics of rose leaves, and comparing resultsfrom two distinct salinity treatments (electrical conductivitiesof 1·8 mS cm1 and 3·8 mS cm1, respectively),one deduces a significant reduction of at turgor-loss in thehigh salinity treatment. The NL method is, in addition, ablesimultaneously to reveal a reduction of and a significant increasein p at RWC=100% this proves that soillessgrown roseplants are able to osmoregulate when subjected to a constantand relatively high degree of salinity. Key words: Apoplastic water, non-linear regression, pressure-volume curves, tissue-water relations 相似文献
18.
Salt-Stimulated Bicarbonate-Dependent Photosynthesis in the Marine Angiosperm Zostera muelleri 总被引:1,自引:0,他引:1
Millhouse, J. and Strother, S. 1986. Salt-stimulated bicarbonate-dependentphotosynthesis in the marine angiosperm Zostera muelleri.J.exp. Bot. 37: 965976. Photosynthetic oxygen evolution in the seagrass Zostera muelleriIrmisch ex Aschers. was inhibited in iso-osmotic sucrose. Theapparent affinity of the leaves for CO2 in seawater increasesfrom pH 8?2 to 8?9 indicating that as well as CO2 may act as a substrate for photosynthesis. Theaffinity for CO2 was lower in iso-osmotic sucrose and was notaffected by pH. Under these conditions was not a substrate for photosynthesis. The differencebetween the photosynthetic rate in seawater and iso-osmoticsucrose at the same concentration of CO2 was used to estimate assimilation. The Briggs-Maskell equation, which allows for an unstirred layer around the tissuewas more appropriate than the Michaelis-Menten theory for calculatingthe apparent affinity of the leaf slices for CO2. The apparentKm CO2 was calculated as 116 mmol m3 at pH 8?2 by Michaelis-Mentenkinetics but only 8?10 mmol m3 by the Briggs-Maskellequation. The stimulation by various ions in Seawater of use was investigated. The cations,in decreasing order of effectiveness were Ca2+, Mg2+, K+ andNa+ Anions were ineffective. No single cation at its concentrationin seawater was capable of supporting use at the rate observed in seawater. Acetazolamide,an inhibitor of carbonic anhydrase, inhibited the use of for photosynthesis but had littleeffect on CO2 photosynthesis. Thus, carbonic anhydrase activityis required for -dependent photosynthesis. Key words: Zostera muelleri, photosynthesis, salinity 相似文献
19.
CLOUX H. C. DU; ANDRE M.; DAGUENET A.; MASSIMINO J. 《Journal of experimental botany》1987,38(9):1421-1431
Du Cloux, H. C, André, M., Daguenet, A. and Massinuno,J. 1987. Wheat response to CO2 enrichment: Growth and CO2 exchangesat two plant densities.J. exp. Bot. 38: 14211431. The vegetative growth of wheat (Triticum aestivum L., var. Capitole)was followed for almost 40 d after germination in controlledconditions. Four different treatments were carried out by combiningtwo air concentrations of CO2, either normal (330 mm3 dm 3)or doubled (660 mm3 dm 3) with two plant densities, either 200plants m 2 or 40 plants m 2. Throughout the experiment the CO2gas exchanges of each canopy were measured 24 h d1. These provideda continuous growth curve for each treatment, which were comparedwith dry weights. After a small stimulation at the start (first13 d), no further effect of CO2 enrichment was observed on relativegrowth rate (RGR). However, RGR was stimulated throughout theexperiment when plotted as a function of biomass. The finalstimulation ol dry weight at 660 mm3 dm 3 CO2 was a factor of1·45 at high density and 1·50 at low density,contrary to other studies, no diminution of this CO2 effecton dry weight was observed over time. Nevertheless, at low density,a transient additional enhancement of biomass (up to 1·70)was obtained at a leaf area index (LAI) below 1. This effectwas attributed to a different build up of the gain of carbonin the case of an isolated plant or a closed canopy. In theformer, the stimulation of leaf area and the net assimilationrate are both involved; in the latter the enhancement becomesindependent of the effect on leaf area because the canopy photosynthesisper unit ground area as a function of LAI reaches a plateau. Key words: Triticum aestuum, L. var. Capitole, Vegetative growth, Canopy 相似文献
20.
Cl and ions interact apparently competitively during influx across the plasmalemma of carrot root cells. Cl,however, reduces influx much less than predicted from the effect of on Cl influx.Cl and plasmalemma influxes both increase with time after excision of carrot tissue. Cland may therefore be transported by a common mechanism. The effect of pH changes on the influx of malate across theplasmalemma in barley roots shows that malate crosses the plasmalemmaas the singly charged anion. Stimulations of influx by bothK2SO4 and KCl suggest that the malate anion crosses in associationwith. K+. If malate entry is passive, Pmal- is about 2?108cm s1, but it is thought that malate entry is partlyan active process. A slight, apparently competitive inhibition by Cl ofmalate flux into the vacuole of barley root cells suggests thatthe two anions may be transported by a common process at thetonoplast, but this is not thought to be physiologically significant. The accumulation of 14C from 1 mM is drastically reduced by 10 mM Cl. A quantitative analysis of the kineticsof 14C exchange shows that Cl directly inhibits the formationof malate from . The decreased influx of endogenously produced malate to the vacuole in the presenceof Cl is probably a secondary consequence of the fallin the cytoplasmic concentration. The nature of the Clinhibition of malate formation is discussed. In KCl-loaded tissue the influx of external malate and the accumulationof 14C from external are reduced. The location of these effects is not certain, but the effects suggest thatregulation of malate synthesis and accumulation may be relatedto the negative-feedback regulation of Cl and transport. 相似文献