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1.
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
2.
Two hydroponic experiments were conducted to determine the effectsof brief and prolonged AI3+ exposures on the hydraulic conductivity(Lp) of northern red oak (Quercus rubra L.) root systems. RootLp was determined using the pressure chamber method of Fiscus(1977). In the first experiment, 28- to 40-d-old seedlings weretreated for 4 d with complete nutrient solutions containingone of three Al concentrations (0.04, 1.85 or 3.71 mol m3)and either 0 or 50 mmol m3 P. Neither Lp nor daily transpirationwas affected by treatment. In Experiment II, seedlings were grown for 4863 d incomplete solutions containing one of three Al concentrations(0, 0.75 or 2.00 mol m3) and either 10 or 250 mmol m3Ca. Lp and leaf area to root length ratio (LA/RL) were reducedwhen (AI3+/ Ca2+), the solution activity ratio, was 2.9 andhigher. Lp and LA/RL were also negatively correlated with Alconcentration and Al/Ca concentration ratio in the roots. Lpwas positively correlated with LA/RL in both experiments. Itis unclear whether Lp in the second experiment was reduced directlyby solution and root chemistry or whether Lp changed in responseto altered leaf/root balance. Key words: Al phytotoxicity, Al x Ca interaction, Quercus rubra, root hydraulic conductivity 相似文献
3.
Jarvis, S. C. and Hatch, D. J. 1985. The effects of aluminiumon the growth of white clover dependent upon fixation of atmosphericnitrogen.J. exp. Bot. 36: 10751086. The effects of aluminium (Al3 +) on the growth of white cloverdependent upon symbiotic fixation of atmospheric nitrogen wereexamined at concentrations that may be encountered in solutionsfrom soils of low pH. Well established plants were grown inflowing solution culture with carefully maintained concentrationsof Al and of P and with pH held constant at a value (4.5) atwhich insoluble precipitates are unlikely to form. After 3 weeksof treatment, there were major visual differences between treatmentsin both shoots and roots. Although added Al at 25, 50 and 100mmol m3 reduced dry weight, the differences between theplants were not significant. There were, however, some considerabledifferences in P and Ca contents between the treatments. Muchof the Al held by the roots was displaced when plants were transferredto solutions containing either scandium or gallium. As wellas the effects on the plant, Al had a considerable influenceon the fixation of atmospheric nitrogen. At concentrations of50 and 100 mmol m3 Al3+ nodule initiation was reducedand there was a much reduced nodule nitrogenase activity perunit of root. Even at 25 mmol m3 Al3+, when nodule numberswere not reduced, nitrogenase activity was adversely affected. Key words: Aluminium, Trifolium repens, nitrogen fixation 相似文献
4.
Apparent uptake and transport of H232PO4 from nutrientsolutions containing 100 mmol m3 phosphate were characterizedasfunctions of time, concentration and pH in ryegrass seedlings.On a log/log plot, concentration versus uptake to the root resolvedintotwo linear phases, suggesting a change in uptake mechanism orefflux at the break. These results were compared with thosefor 32P uptake and transport in solutions containing Al rangingfrom 0185 mmol m3. Al addition depressed pH, butbecauseuptake of P was unaffected by pH below 50, noadjustments were attempted. Uptake time-courses revealed clearlythe usualinitial adsorption shoulder in the uptake curve, increasingwith Al concentration up to 37 mmol m3. Beyond about2 h, P uptaketo the root became linear, at rates increasingwith external Al concentration up to 37 mmol m3. Concentrationsof Al muchabove 100 mmol m3 were toxic. Al treatmentsdid not affect P transport to the shoot and absorbed Al wasconfined to the root.The quantities of P and Al taken up intothe root indicated storage in cortex cell vacuoles, lockingup significant amounts of P.Experiments with tillering plantsshowed similar characteristics to those with seedlings. Sequesteringof P with Al within the rootcortex cells was evident, particularlyin plants which had been grown in nutrient containing Al fromsoon after germination. Aland P solution chemistry is discussedin the context of this work and the consequences of effectson P uptake for the economy ofphosphate poor upland soils wereconsidered. Key words: Phosphate, aluminium, adsorption, uptake, Lolium perenne L 相似文献
5.
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
6.
From compartmental analysis of 32P elution measurements, concentrationsand fluxes of phosphate were estimated for root cortical cellsof intact Lolium perenne L. plants, when in complete nutrientsolution containing 0.1 mol m3 phosphate with and without37 mmol m3 Al during loading and elution. Failure ofthe data, when plotted as ct. min1 remaining in the tissueas a function of time, to meet the criteria for first orderkinetics led to a discussion of the relative importance of transportto the shoot, assimilation, and complexation in the vacuole,in causing this discrepancy. It was concluded that complexationwas the most important factor. Transformation of the data tomeet the criteria for first order kinetics gave corrected valuesfor compartmental concentrations and fluxes of phosphate, andestimates of the size of the otherwise unresolved slowly exchangingcompartment within the vacuole equated with condensed phosphate.In the control this was 2.5 mol m3 P but in Al treatmentsa much larger amount of phosphate was complexed with Al (6.5mol m3 P). Phosphate transport to the shoot was unaffectedby Al. Instead, levels of Al, common in solution in upland soils,sequestered in the root vacuoles quantities of phosphate significantfor stressing the phosphate economy of nutrient-poor grassland. Key words: Lolium perenne L. phosphate, aluminium, compartmentation, complexation 相似文献
7.
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
8.
Partitioning of shoot and root dry matter and carbohydrates in bean plants suffering from phosphorus, potassium and magnesium deficiency 总被引:17,自引:2,他引:15
Cakmak Ismail; Hengeler Christine; Marschner Horst 《Journal of experimental botany》1994,45(9):1245-1250
The influence of varied supply of phosphorus (10 and 250 mmolP m3) potassium (50 and 2010 mmol K m3) and magnesium(20 and 1000 mmol Mg m3) on the partitioning of dry matterand carbohydrates (reducing sugars, sucrose and starch) betweenshoots and roots was studied in bean (Phaseolus vulgaris) plantsgrown in nutrient solution over a 12 d period. Shoot and rootgrowth were quite differently affected by low supply of P, K,and Mg. The shoot/root dry weight ratios were 4.9 in the control(sufficient plants), 1.8 in P-deficient, 6.9 in K-deficientand 10.2 in Mg-deficient plants. In primary (source) leaves,but not in trifoliate leaves, concentrations of reducing sugars,sucrose and starch were also differently affected by low nutrientsupply. In primary leaves under K deficiency and, particularlyMg deficiency, the concentrations of sucrose and reducing sugarswere much higher than in control and P-deficient plants. Magnesiumdeficiency also distinctly increased the starch concentrationin the primary leaves. In contrast, in roots, the lowest concenfrationsof sucrose, reducing sugars and starch were found in Mg-deficientplants, whereas the concentrations of sucrose and starch wereparticularly high in P-deficient plants. There was a close relationshipbetween shoot/root dry weight ratios and relative distributionof total carbohydrates (sugars and starch) in shoot and roots.Of the total amounts of carbohyd rates per plant, the followingproportions were parti tioned to the roots: 22.7% in P-deficient,15.7% in control, 3.4% in K-deficient and 0.8% in Mg-deficientplants. The results indicate a distinct role of Mg and K in the exportof photosynthates from leaves to roots and suggest that alterationin photosynthate partitioning plays a major role in the differencesin dry matter distribution between shoots and roots of plantssuffering from mineral nutrient deficiency. Key words: Bean, carbohydrates, magnesium nutrition, phosphorus nutrition, potassium nutrition, shoot/root growth 相似文献
9.
The Combined Effects of Salinity and Root Anoxia on Growth and Net Na+ and K+-accumulation in Zea mays Grown in Solution Culture 总被引:2,自引:0,他引:2
The effects of excess salinity and oxygen deficiency on growthand solute relations in Zea mays L. cv. Pioneer 3906 were examinedin greenhouse experiments. The roots of plants 14 d old growingin nutrient solution containing additions of NaCl in the range1.0200 mol m3 were either exposed to a severedeficiency of O2 by bubbling with nitrogen gas (N2 treatment),or maintained with a supply of air (controls), for a periodof 17 d. The threshold NaCl concentration resulting inappreciable inhibition of leaf extension, and shoot f. wt gainin controls was between 10 and 25 mol m3. At 25 mol m3NaCl the ratio of Na+/K+ transported to shoots was about 20times greater than in plants in 1.0 mol m3 NaCl. Theeffect of addition of NaCl to the nutrient solution was to enhanceNa+ movement but simultaneously depress the rate of K+ transportto shoots (per g f. wt roots). Interactions between NaCl levels and aeration treatment wereshown by analyses of variance to be statistically significantfor leaf extension, shoot and root f. wt gains, Na+ and K+ concentrationsin shoots and roots. When roots were N2-treated, shoot and rootgrowth were depressed, the effect of aeration treatment beinggreatest at NaCl concentrations of 50 mol m3 or less.Additionally, N2-treatment greatly accelerated Na- transportto shoots while depressing K+ transport still further, so thatat 10 mol m3 NaCl the ratio Na+/K+ acquired by the shootswas 230 times greater than in controls. Over the concentrationrange 1.0 to 50 mol m3 NaCl, the ratio Na+/K+ transportedto shoots by anoxic roots increased by a factor of 860. Mechanisms controlling changes in solute flux to the shoot,and the significance in relation to plant tolerance of excesssalts or oxygen deficiency are discussed. Anaerobic, corn, flooding, maize, oxygen-deficiency, salinity 相似文献
10.
Explants of stem, leaves, roots, and cotyledons from etiolatedaxenically grown Vicia faba seedlings were cultured on a rangeof media. Shoot organogenesis was only obtained with nodal stemand cotyledonary node explants when cultured on MS medium with3% sucrose, 2.0 mg 11 BAP and 02 mg 11 NAA. Callusproliferation accompanied shoot organogenesis from nodal stemexplants. Successive subculture of nodal stem callus resultedin proliferation of regenerative callus which contained severalshoot bud initials. The capacity for shoot regeneration fromthis callus was maintained for 9 months. Histological studiesreveal de novo formation of meristematic centres in callus andtheir further development into bud primordia. High frequencyrooting of these adventitious shoots was obtained on half-strengthMS medium with 1.5% sucrose, 0.1 mg 11 NAA and 0.5 mg11 kinetin. Key words: Vicia faba, adventitious shoots, axillary shoots, de novomeristem formation, organogenesis, tissue culture 相似文献
11.
Macklon A.E.S.; Lumsdon D.G.; Sim A.; McHardy W.J. 《Journal of experimental botany》1996,47(6):793-803
From compartmental analysis of 32P elution measurements, concentrationsand fluxes of orthophosphate were estimated for root corticalcells of intact seedlings of the indigenous grass Agrostis capillarisL. cv. Highland when in complete nutrient solution containing10 mmol m3 or 100 mmol m3 phosphate with or without3.7 and 37 mmol m3 Al, respectively, during loading andelution. When plotted as counts min1 remaining in thetissue as a function of time, the data failed to meet the criteriafor first order kinetics. Transformation of the data to meetthe kinetic criteria gave corrected values for compartmentalconcentrations and fluxes of phosphate, and estimates of theotherwise unresolved slowly exchanging compartment within thevacuole considered to be the cause of the discrepancy in fluxanalysis. In the control, the discrepancy was considered dueto sequestration of phosphate with Ca in the vacuole and a small,but not significant, increase in sequestered P occurred in thepresence of Al, the presence of which was confirmed by X-raymicroanalysis. A chemical speciation model was used to demonstrate,for various values of pH and carboxylic acid concentration,the possibility that phosphate was precipitated in root cellvacuoles as Ca and Al phosphates (hydroxy-apatite and variscite).The ecological significance of the ability of A. capillarisplants to make efficient use of scarce P resources by minimizingthe sequestration of P by Al in vacuoles, compared with Loliumperenne, was recognized. Key words: Phosphate sequestration, phosphate use efficiency, X-ray microanalysis, super-saturation 相似文献
12.
Increase in fluence rates of white light over the range of 5to 80 µmol m2 s1 brought about a correspondingincrease in amounts of anthocyanin production in shoots of Zeamays L. seedlings. Roots also exhibited a similar relationshipbetween increased fluence rate and increased anthocyanin productionover the range of 5 to 40 µmol m2 s1 whereasfluence rates above 40 µmol m2 s1 broughtabout decreases in anthocyanin production. Rates of productionand amounts of accumulation of anthocyanin in both shoots androots were found to vary with the age of the seedlings at thetime of exposure to light. Age, fluence rates, anthocyanin, seedlings, Zea mays 相似文献
13.
BREEZE V. G.; WILD A.; HOPPER M. J.; JONES L. H. P. 《Journal of experimental botany》1984,35(8):1210-1221
The effect of phosphate concentration in flowing solution cultureat a range between 0.04 and 32 mmol m3 P on the growthof perennial ryegrass was studied in two experiments, each lastingabout 45 d after sowing. Phosphorus contents of seedlings wereaffected by the concentration in solution within about 5 d fromgermination, and dry weight differences were first observedat about 6 d after this. The rate of uptake of phosphate byseedlings was affected by the concentration in solution beforethe root fresh weight or root/emdash shoot ratio had changed.Young plants (less than 4 weeks old) were more sensitive tophosphate concentration in solution than older ones. In conditionsof high rate of growth, older plants required a solution concentrationbetween 0.1 and 0.4 mmol m3 P to achieve maximum potentialgrowth rate, whereas for plants of similar age but less dryweight, 0.04 mmol m3 P was adequate. Towards the endof the experimental period, plants growing at a nominal solutionconcentration of 0.04 mmol m3 P were able to obtain phosphatefrom a solution of about 0.01 mmol m3P. Phosphate toxicity was not observed, nor were there visual symptoms(other than reduced growth) of phosphate deficiency in plantswhose growth was limited by phosphate concentration in solution. Key words: Lolium perenne, Phosphate uptake 相似文献
14.
Effect of Salinity on Growth, Nodulation and Nitrogen Yield of Chickpea (Cicer arietinum L.) 总被引:2,自引:0,他引:2
Chickpea cultivar ILC 482 was inoculated with salt-tolerantRhizobium strain Ch191 in solution culture with different saltconcentrations added either immediately with inoculation or5 d later. The inhibitory effect of salinity on nodulation ofchickpea occurred at 40 dS m1 (34.2 mol m3 NaCl)and nodulation was completely inhibited at 7 dS m1 (61.6mol m3 NaCl); the plants died at 8 dS m1 (71.8mol m3 NaCl). Chickpea cultivar ILC 482 inoculated with Rhizobium strain Ch191spcstrwas grown in two pot experiments and irrigated with saline water.Salinity (NaCl equivalent to 14 dS m1) significantlydecreased shoot and root dry weight, total nodule number perplant, nodule weight and average nodule weight. The resultsindicate that Rhizobium strain Ch191 forms an infective andeffective symbiosis with chickpea under saline and non-salineconditions; this legume was more salt-sensitive compared tothe rhizobia, the roots were more sensitive than the shoots,and N2 fixation was more sensitive to salinity than plant growth. Key words: Cicer arietinum, nodulation, N2 fixation, Rhizobium, salinity 相似文献
15.
Northern red oak (Quercus rubra L.) seedlings were grown for63 d in a complete nutrient solution (pH 3.8) containing oneof three concentrations of Al (0, 0.75 or 2-0 mol m3)and either 10 or 250 mmol m3 Ca. Of all solution variables,the In of (Al3+)/(Ca2+), the solution activities ratio, wasmost closely correlated with declines in shoot and root growth.Ln (Al3+)/(Ca2+) also most closely predicted leaf and root [Mg],[Al], and [Al]/[Ca]. These three variables in turn were closelyrelated to growth. Toxic levels of (Al3+) and (Al3+)/(Ca2+)in solution are compared to levels in forest soils. Key words: Al phytotoxicity, Al x Ca interaction, Quercus rubra 相似文献
16.
Sodium Exclusion from the Shoots by Roots of Zea mays (cv. LG 11) and its Breakdown with Oxygen Deficiency 总被引:1,自引:0,他引:1
The effects of sodium chloride salinity and root oxygen deficiency(anoxia) were studied in 11-12d old maize plants (Zea mays L.cv. LG 11) in nutrient solution culture. Transport of 22Na bythe roots to the shoot in 24 h was markedly increased by anoxiawhen the external concentration of NaCl was in the range 0·1-10·9mol m3. Anoxia severely inhibited uptake of 42K by rootsand its transport to the shoot, so that the ratio of Na+/K+moving into the shoot was increased by a factor of approximately10. When the external concentration of NaCl was increased to2.4 mol m3, the roots showed much less ability to excludeNa+ under aerobic conditions, and anoxia caused no further increasein the movement of Na+ to the shoot. It is concluded that atthe higher concentration the ability of the roots to excludeNa+, presumably through an active mechanism in the xylem parenchymacells or in the root cortex and transporting Na+ to the outersolution, is saturated by excessive inward diffusion of Na+.The ratio of Na+/K+ transported to the shoot increased by afactor of 600 when the concentration of NaCl was increased from2·4 mol m3 to 40 mol m3 and roots weremade anoxic. Such imbalances in the supply of cations to theshoot, particularly when roots are oxygen-deficient, may contributeto salinity damage. Key words: Anaerobic, Anoxic, Oxygen deficiency, Roots, Salinity, Salt stress, Sodium chloride, Zea mays 相似文献
17.
The effects of 0, 50, 100, 200, 300, 400 and 500 mol m3NaCl on growth and ion accumulation in the succulent, coastalhalophyte Sarcocornia natalensis (Bunge ex Ung.-Sternb.) A.J. Scott were investigated. Increase in salinity from 0 to 300 mol m3 NaCl stimulatedproduction of fresh, dry, and organic dry mass, increased succulenceand shifted resource allocation from roots to shoots. Growthwas optimal at 300 mol m3 and decreased with furtherincrease in salinity. Water contributed to a large proportion of the increase in freshmass. Inorganic ions, especially Na+ and Cl contributedsubstantially to the dry mass. At 300 mol m3 NaCl inorganicions contributed to 37% of total dry mass and NaCl concentrationin the shoots was 482 mol m3. Expressed sap osmotic potentialsdecreased from 2.10 to 3.95 MPa as salinity increasedfrom 0 to 300 mol m3 NaCl. Massive accumulation of inorganicions, especially Na+ and Cl, accounted for 86% of theosmotic adjustment at 300 mol m3 NaCl. Salinity treatments decreased the concentrations of K+ in shoots.Plant Na+ :K+ ratios increased steadily with salinity and reacheda maximum of 16.6 at 400 mol m3 NaCl. It is suggested that the exceptional salt tolerance of S. natalensisis achieved by massive inorganic ion accumulation which providessufficient solutes for osmoregulation, increased water fluxand turgor-induced growth. Key words: Sarcocornia natalensis, salt tolerance, halophyte 相似文献
18.
Cultures of nine potato genotypes (seven Solanum tuberosum oneS. sparsipilum and one S. oplocense genotypes) were examinedfor their response to growing on medium containing either 60mol m3, 40 mol m3 or 20 mol m3 nitrogen.Genotypes differed in their response to nitrogen. Reducing thenitrogen regime tended to produce taller plants with longerinternodes, shoots had larger leaves but contained less chlorophyll.No change in fresh weight or number of nodes was observed. Genotypex nitrogen interactions were significant for chlorophyll content,shoot length and internode length. Results suggest that thechanges observed were as a result of changes in the total nitrogenlevel rather than changes in the ammonium : nitrate ratio. Thisstudy suggests that for certain potato genotypes, nitrogen levelsin MS medium are too high for producing desirable microplantsin terms of leaf area and shoot length Key words: Solanum tuberosum, S. sparsipilum, S. oplocense, micropropagation, morphogenesis 相似文献
19.
Drew, M. C. and Lauchli, A. 1986. The role of the mesocotylin sodium exclusion from the shoot of Zea mays L. (cv. Pioneer3906).J. exp. Bot. 38: 409418. The mesocotyl, located between the root and shoot, can stronglyaccumulate Na+ from the ascending transpiration stream, therebypotentially acting as a sink to protect the shoot from excessNa+. To determine the quantitative importance of the mesocotylas a Na+ sink, we grew plants with either short (9·0mm) or long(21 mm) mesocotyls, the latter resembling the sizefound in field-grown plants. At 13 d, plants were transferredfrom Na + -free nutrient solution to a 22Na+ labelled solutionin which the concentration of NaCl was (mol m3) 1·0,10 or 100. The concentration of Na+ accumulated in the mesocotylin 24 h (g1 fr. wt.) exceeded that in the roots thatwere directly exposed to the nutrient solution. The amountsof 22Na+ retained in the long mesocotyl were about double thatin the short ones and increased with time of exposure and NaClconcentration. At 1·0 and 10 mol m3 NaCl, theamounts of 22Na+ retained in the mesocotyl were 619%of those reaching the shoot in 24 h, but with 100 mol m3NaCl, a damaging concentration for maize, this declined to 38%.The mesocotyl, even as a fully elongated structure is, therefore,unlikely to provide an appreciable alternative sink for Na+when NaCl reaches injurious concentrations. Key words: Ion transport, potassium, roots, salinity 相似文献
20.
The Response of Atriplex amnicola to the Interactive Effects of Salinity and Hypoxia 总被引:3,自引:0,他引:3
The growth of Atriplex amnicola, its water and ion relations,and carbohydrate use were investigated in response to the interactiveeffects of salinity and root zone hypoxia in an experiment conductedin nutrient culture. One week of hypoxia in the root zone atboth 50 and 400 mol m3 NaCl caused the cessation of rootgrowth, a reduction in shoot growth, and adversely affectedwater relations, but not ion relations or carbohydrate concentrations.Two weeks of hypoxia at 400 mol m3 NaCl resulted in thedeath of root tips, a 20fold increase in the resistanceto water flow from the exterior of the roots to the leaves,and a further deterioration in water relations. There was alsoa doubling of Cl concentrations in the xylem sap anda doubling of Na+ and Cl concentrations in the leaves.An increase in the concentration of starch in the leaves, andsugars in the leaves, stems and roots, indicated that therewere problems with carbohydrate use rather than supply. Underthe prevailing conditions of low vapour pressure deficit, iontoxicity was the most probable cause of injury to A. amnicolain hypoxic solutions at high salinity. The response of A. amnicolato the interactive effects of salinity and hypoxia were similarto those reported for non-halophytes, but occurred at highersalinities. Key words: Atriplex, hypoxia, salinity, water relations, ion transport, carbohydrate 相似文献