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1.
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
2.
Munns, R. 1985. Na+, K+ and Cl in xylem sap flowing toshoots of NaCl-treated barley.J. exp. Bot. 36: 10321042. Na+, Cl and K+ concentrations were measured in xylemsap obtained by applying pressure to the roots of decapitatedbarley plants grown at external [NaCl] of 0, 25, 50, 100, 150and 200 mol m3. For any given NaCl treatment, ion concentrationsin the xylem sap were hyperbolically related to the flux ofwater. Ion concentrations in sap collected at very low volumefluxes (without applied pressure) were 510 times higherthan in sap collected at moderate fluxes (under pressure). Fora given moderate volume flux, Na+ concentration in the xylemsap, [Na+]x, was only 4.0 mol m3 at external [NaCl] of25150 mol m3, and increased to 7.0 mol m3at 200 mol m3. [Cl-]x showed a similar pattern. Thisshows there would be little difference in the rate of uptaketo the shoot of plants at 25150 mol m3 externalNaCl and indicates little change even at 200 mol m-3 NaCl becausetranspiration rates would be much lower. Thus the reduced growthof the shoot of plants at high NaCl concentrations is not dueto higher uptake rates of Na+ or Cl. The fluxes of Na+, Cl and K increased non-linearlywith increasing volume flux indicating little movement of saltin the apoplast. The flux of K+ increased even when [K+]x wasgreater than external [K+], indicating that membrane transportprocesses modify the K+ concentration in the transpiration streamas it flows through the root system. Key words: -Xylem sap, Na+, K+, Cl fluxes, salinity, barley 相似文献
3.
Ricinus communis L. (castor bean) plants were grown in the absence(control) and in the presence of 100molm3NaCl with areciprocal split-root system, in which K+ was supplied to oneand NO3 to the other part of the root system. In theseplants shoot and, to a lesser extent, total root growth wereinhibited compared to plants with non-split roots. Without andwith NaCl, growth of roots receiving NO3 but noK+ (minusK/plus N-roots) was substantially more vigorous thanunder the reverse conditions (plus K/minus N-roots1).100mol m3 NaCl inhibited growth of minus K/plus N-roots1to the same extent as that of non-split roots, indicating thatexternally supplied K+ was not required for root growth undersaline conditions. In growth media without added K+ the rootdepleted the external low K + levels resulting from chemicalsdown to a minimum value Cmln (1.0 to 1.4 mmol m3); inthe presence of 100 mol m3 NaCl, Cmin, was higher (1018mmol m3) and resulted from an initial net loss of K +.Cmin, was pH-dependent The distribution of K+, Na+ and Mg2+along the root was measured. In meristematic root tissues, K+ concentrations were scarcely affected by external K+ or byNaCl, where Na + concentrations were low, but somewhat elevatedat low external K+ and/or high NaCl. In differentiated, vacuolatedtissues K + concentrations were low and Na+ concentrations high,if K + was not supplied externally and/or NaCl was present.The longitudinal distribution of ions within the root was usedto estimate cytoplasmic and vacuolar ion concentrations. Thesedata showed a narrow homoeostasis of cytoplasmic K+ concentrations(100140 mol m3) independent of external K + supplyeven in the presence of 100 mol m 3 NaCl. CytoplasmicNa + concentrations were maintained at remarkably low levels.Hence, external K+ concentrations above Cmin, were not requiredfor maintaining K/Na selectivity, i.e. for controlling Na+ entry.The results are discussed with regard to mechanisms of K/Naselectivity and to the importance of phloem import of K+ forsalt tolerance of roots and for cytoplasmic K+ homoeostasis. Key words: Ricinus communis, nitrate, potassium, root (split-root), salt tolerance, phloem transport 相似文献
4.
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
5.
Interaction of Salinity and Anaerobiosis in Barley and Rice 总被引:3,自引:0,他引:3
Barley and rice at the early tillering stage were exposed simultaneouslyto anaerobiosis and high [NaCl]. Barley was grown at 0.5, 70,and 125 mol m3 NaCl, and rice at 2, 20, 40, and 80 molm3 NaCl. Surprisingly, anaerobiosis only slightly aggravatedthe adverse effects of high [NaCl] on root and shoot growthof both species. For rice and barley grown under aerobic conditions, high [NaCl]increased [Na+] and [Cl] and decreased [K+] in both rootsand shoots. However, the changes in ion concentrations in theshoots were smaller for rice than for barley. For roots of barley, anaerobiosis decreased [Na+], [Cl],and [K+] at both low and high [NaCl], possibly as a result ofinhibition of active ion accumulation. For barley shoots, anaerobiosisincreased [Na+] and [Cl], but only at high salinity;in contrast, [K+] was reduced by anaerobiosis at both low andhigh [NaCl]. These results indicate that anaerobiosis slightlyincreased the permeability of the barley root system to Na+and Cl. For rice, the most important interaction between salinity andanaerobiosis occurred in the shoots, where anaerobiosis increased[Na+] and decreased [K+], particularly at 40 and 80 mol m3NaCl, while there was no interaction between anaerobiosis andsalinity for Cl uptake. It is therefore suggested thatanaerobic treatment of rice decreased the selectivity for K+over Na+ of cation transport to the shoots, at least for plantsgrown at high salinities. 相似文献
6.
This paper reports the effects of low O2 concentration (001,0055, and 0.115mol m3) in nutrient solutions onK+/Na+ selectivity of growing and mature root tissues of 6-to 8-d-old, intact, wheat (Triticum aestivum cv. Gamenya) seedlings. Increases in anaerobic catabolism and decreases in O2 uptake,K+ uptake and K+/Na+ selectivity were all more pronounced and/oroccurred at higher external O2 concentrations in the apex (02mm) than in the expanding tissues (24 mm); these growingtissues were, in turn, more affected than the expanded tissuesof the roots (412 mm). Selectivity for K+ over Na+ in roots and shoots was particularlysensitive to O2 deficiency. For example, in apical tissues (02mm) K + /Na+ selectivity was already reduced at 0.115 mol m3O2, yet at this O2 concentration there was no effect on eithergrowth or (K+/Na+) uptake. Upon transfer from 0.01 to 0.26 mol m3 O2, a detailedstudy of the 12 mm root tips showed that 70% of these tips regainedhigh (K+ + Na+) concentrations and K+/Na+ ratios. In contrast,there was no recovery in the remaining 30% of the 12 mm roottips. Net K+ transport to the shoots during the period afterre-aeration was negative for the population as a whole. Theseverity of these effects supports the view that the root tipsand the stele were more susceptible to O2 deficiency than wasthe cortex of the fully-developed root tissues. Key words: Hypoxia, K+/Na+ selectivity, expanded and expanding tissues 相似文献
7.
Endogenous abscisic acid contents were measured by gas-liquidchromatography in shoots of Suaeda maritima growing both inthe steady state over a range of salinities and over a time-coursefollowing an increase in the culture solution salinity of betweenapproximately 100 and 400 mol m3 NaCl. In steady-stateplants, the ABA content was maximal in the absence of salt at41 ng g1 fr. wt., declining to a minimum at 200 mol m3NaCl of 24 ng g1 fr. wt. Increase of culture solutionsalinity resulted in a marked increase in shoot ABA which wasmaximal after 6 h or 24 h in plants previously growing at 200mol m3 NaCl and in the absence of salt, respectively.Additionally, culture solution water potentials were loweredby 1.0 MPa (equivalent to raising the salt concentration byaround 200 mol m3); this resulted in a similar increasein endogenous ABA content to that brought about by an iso-osmoticsalt increase. Results are discussed in relation to the possiblerole of ABA in halophyte salt tolerance mechanisms. Key words: Suaeda, halophyte, abscisic acid, salt tolerance 相似文献
8.
Nodulated white clover plants (Trifolium repens L. cv. Huia)were grown as simulated swards for 71 d in flowing nutrientsolutions with roots at 11 C and shoots at 20/15 C, day/night,under natural illumination. Root temperatures were then changedto 3, 5, 7, 11, 13, 17 or 25 C and the total N2, fixation over21 d was measured in the absence of a supply mineral N. Alltreatments were subsequently supplied with 10 mmol m2NO2 in the flowing solutions for 14 d, and the relativeuptake of N by N2, fixation and NO3 uptake was compared.Net uptake of K+ was measured on a daily basis. Root temperature had little effect on root d. wt over the 35-dexperimental period, but shoot d. wt increased by a factor of3.5 between 3 and 25 C, with the sharpest increase occurringat 711 C. Shoot: root d. wt ratios increased from 25to 68 with increasing temperature at 725 C. N2-fixationper plant (in the absence of NO2 ) increased with roottemperature at 313C, but showed little change above13 C. The ratios of N2 fixation: NO2 uptake over 14d (mol N: mol N) were 0.470.77 at 37 C, 092154at 1117 C, and 046 at 25 C, reflecting the dominanceof NO3 uptake over N2 fixation at extremes of high andlow root temperature. The total uptake of N varied only slightlyat 1125 C (095110 mmol N plant1),the decline in N2 fixation as root temperature increased above11 C was compensated for by the increase in NO 3 uptake.The % N in shoot dry matter declined with decreasing root temperature,from 32% at 13 C to 15% at 3 C. In contrast, concentrationsof N expressed on a shoot water content basis showed a modestdecrease with increasing temperature, from 345 mol m3at 3 C to 290 mol m3 at 25 C. Trifolium repens L, white clover, root temperature, N2 fixation, potassium uptake, nitrate uptake, flowing solution culture 相似文献
9.
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
10.
Salt Tolerance in the Triticeae: K/Na Discrimination in Barley 总被引:5,自引:4,他引:1
GORHAM J.; BRISTOL A.; YOUNG E. M.; JONESH R. G. WYN; KASHOUR G. 《Journal of experimental botany》1990,41(9):1095-1101
Concentrations of ions were measured in the youngest fully-expandedleaves of Triticum aestivum, T. durum, Hordeum vulgare, H. spontaneum,Secale cereale, and Aegilops squarrosa accessions grown in hydroponicculture in the presence of salt (NaCl+CaCl2). Triticum aestivum,Secale cereale, and Ae. squarrosa had the low leaf Na and highleaf K concentrations typical of plants which contain the enhancedK/Na discrimination character originally found in Ae. squarrosa.T. durum and the Hordeum species did not have this character.The better growth of H. vulgare than of T. durum with similarsalt concentrations in the youngest fully-expanded leaves maybe a result of better compartmentation of Na, Cl, and K betweendifferent tisssues or between different compartments withincells. The enhanced K/Na discrimination character was expressedin disomic addition lines of H. vulgare chromosomes in Triticumaestivum. The H. vulgare variety Herta and its slender mutantboth had similar leaf cation concentrations, although they differedin growth rate when grown at 60 mol m3 NaCl. H. vulgareand T. durum seedlings grown in the absence of monovalent cationsaccumulated more 22Na in their shoots than seedlings of otherspecies when incubated in 1.0 mol m3 NaCl labelled with22Na. Key words: Salt, ion transport, I genome, barley, wheat 相似文献
11.
Possible reasons for relative salt stress tolerance in nodules of white lupin cv. Multolupa 总被引:5,自引:2,他引:3
Fernndez-Pascual M.; de Lorenzo C.; de Felipe M.R.; Rajalakshmi S.; Gordon A.J.; Thomas B.J.; Minchin F.R. 《Journal of experimental botany》1996,47(11):1709-1716
The effects of different NaCl concentrations on the growth andnitrogen fixation activity of white lupin (Lupinus albus [L.])was studied over a 6 d period. Plant growth parameters, photosynthesisand shoot respiration were unaffected by NaCl concentrationsup to 150 mol m3. However, nitrogenase activity decreasedwith increased NaCl concentration up to 100 mol m3, whilstthe O2 diffusion resistance increased with 100 mol m3NaCl, but showed no further change when 150 mol m3 NaClwas applied for 6 d. Increases in NaCl concentration decreasednodular starch content while increasing sucrose content, suggestingan osmotic regulation. These changes were associated with a77% decrease in sucrose synthase activity. The effect on theO2 diffusion resistance was paralleled by changes in glycoproteincontent of the nodules, as determined by immunogold localizationand ELISA. X-ray microanalysis studies of nodules showed that,following a 6 d exposure to 150 mol m3 NaCl, Na+ ionswere largely excluded from the infected zone, whilst only lowlevels of Cl- ions penetrated into this region. Na+ entry intoroots and leaves was also at a low level. Leghaemoglobin contentdecreased with saline stress, as did superoxide dismutase; whichdecreased by 36% following exposure to 100 mol m3 saltfor 6 d. These results are discussed in relation to the relativesalt tolerance of the Multolupa/ISLU-16 symbiosis. Key words: Salt stress, nodules, nitrogen fixation, oxygen diffusion, carbohydrates, Lupinus albus 相似文献
12.
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
13.
Salt Stress Causes Acceleration of Purine Catabolism and Inhibition of Pyrimidine Salvage in Zea mays Root Tips 总被引:1,自引:0,他引:1
PETERSON TODD A.; LOVATT CAROL J.; NIEMAN RICHARD H. 《Journal of experimental botany》1988,39(10):1389-1395
Nucleotide metabolism was studied in apical 5.0 mm root tipsof corn plants (Zea mays L., cv. Pioneer 3906) hydroponicallycultured for 7 d and then salinized for 19 d at a rate calculatedto reduce the osmotic potential (o) of the solutions by O.1MPad1 to a final o = -0.4 MPa. Saline treatments withtwo different molar ratios of Ca2+/Na+ were employed, viz.,003 (2.5 mol m3 CaCl2 + 86.5 mol m3 NaCl)for the NaCl treatment and 0.73 (31.5 mol m3 CaCl2 +43.1 mol m3 NaCl) for the NaCl + CaCl2 treatment. Bothsalt treatments reduced root growth by more than 30%. The capacityof roots to provide purine nucleotides either by de novo synthesisor by re-utilization of existing bases, e.g. salvage of hypoxanthineto adenine nucleotides, was not affected by either salt treatment.However, catabolism of hypoxanthine was accelerated more than3.5-fold by both salt treatments, demonstrating an increasedcapacity for purine catabolism which would shift the normal1: 1 ratio of synthesis: degradation of purine nucleotides observedfor the roots of healthy control plants to less than 0.2 duringsalt stress. The ratio of pyrimidine nucleotide synthesis: degradationwas also reduced. In this case, the unfavourable shift towardnucleotide degradation resulted because both salt treatmentsreduced salvage capacity by more than 25%, but had no compensatingeffect on de novo synthesis or catabolism of pyrimidines. Key words: Salinity, osmotic potential, nucleotide metabolism 相似文献
14.
Spatial and Temporal Aspects of Growth in the Primary Root of Cotton Seedlings: Effects of NaCl and CaCl2 总被引:1,自引:0,他引:1
Seedlings of cotton (Gossypium hirsutum L. cv. Acala SJ-2) weregrown in modified Hoagland nutrient solution with various combinationsof NaCl and CaCl2. Marking experiments and numerical analysiswere conducted to characterize the spatial and temporal patternsof cotton root growth at varied Na/Ca ratios. At 1 mol m3Ca, 150 mol m3 NaCl reduced overall root elongation rateto 60% of the control, while increasing Ca to 10 mol m3at the same NaCl concentration restored the elongation rateto 80% of the control. Analysis of the spatial distributionof elongation revealed that the presence of 150 mol m3NaCl in the medium shortened the growth zone by about 2 mm fromthe approximate 10 mm in the control and also reduced the relativeelemental elongation rate (i.e. the longitudinal strain rate,defined as the derivatives of displacement velocity of a cellularparticle with respect to position on root axis). Supply of 10mol m3 Ca at the high salt condition restored partiallythe relative elemental elongation rate, but not the length ofthe growth zone. Compared to the control, the growth trajectoriesshowed that at 1 mol m3 CaCl2 it took more time for acellular particle to move through the growth zone at 150 molm3 NaCl, while at 10 mol m3 CaCl it took lesstime and there was no difference between the NaCl treatments Key words: Gossypium hirsutum, salinity stress, root growth kinematics 相似文献
15.
Nitrogen utilization by plant species from acid heathland soils: I. Comparison between nitrate and ammonium nutrition at constant low pH 总被引:4,自引:2,他引:2
Seven heathland species, four herbaceous plants and three dwarfshrubs, were tested for their capacity to utilize NH4+ or NO3. When cultured in solution at pH 4.0 with 2mol m3 N,all species showed similar growth responses with respect toN source. Nitrate was assimilated almost equally well as ammonium,with relative growth rate generally averaging 58% lowerfor NO3 grown plants, albeit not always significantly.However, N source was significantly and consistently correlatedwith biomass partitioning, as NH4+-fed plants allocated moredry matter to shoots and less to roots when compared to NO3-fed plants. The strong difference in biomass partitioning mayrelate to the relative surplus of carbon per unit plant N (or,alternatively, the relatively suboptimal rate of N assimilationper unit plantC) in NO3-fed plants Inherently slow-growing dwarf shrubs accumulated virtually nofree nitrate in their tissues and reduction of nitrate was strictlyroot-based. Faster-growing herbaceous plants, however, partitionedthe assimilation of nitrate over both shoots and roots, therebyaccumulating relatively high tissue NO3 levels. Ion uptakerates depended clearly on the relative shoot demand.At similar shoot demands, especially in the herbaceous species,specific uptake rates for N and total inorganic (non-N) anionswere higher in NH4+ -fed plants, whereas the uptake rate fortotal (non-N) cations was higher in NO3-fed plants. Rateof P uptake was enhanced with increasing plant demand, but wasindependent of the N source. Net H+ extrusions ranged from 1.00to 1.34 H+ per NH4+, and from 0.48 to 0.77 H+per NO3 taken up. Key words: Ammonium, biomass partitioning, heathland plants, low pH, nitrate, nitrate reductase activity, relative shoot demand, specific absorption rate 相似文献
16.
When rye and triticale accessions were grown in saline hydroponicculture they exhibited the low Na and high K concentrationsin their leaves which are characteristic of the enhanced K/Nadiscrimination trait originally found in the D genome of wheat.This trait was not consistently improved by the presence ofthe D genome in octaploid triticale or in D genome substitutionlines of hexaploid triticale. The presence of the rye genomedid not significantly affect anion concentrations within theleaves. At high salt concentrations (250 mol m3 NaCl+12.5mol m3 CaCl2) the triticales were more tolerant thanthe rye accessions or a DDRR-genome tetraploid, with two triticalelines being almost as salt-tolerant as barley. Key words: Salt, ion transport, R genome, rye (Secale cereale L.) 相似文献
17.
Influence of the Form of Nitrogen Supply on Root Uptake and Translocation of Cations in the Xylem Exudate of Maize (Zea mays L) 总被引:1,自引:0,他引:1
Concentrations of inorganic cations are often lower in plantssupplied with NH4+ as compared with NO3. To examine whetherthis is attributable to impaired root uptake of cations or lowerinternal demand, the rates of uptake and translocation of K,Mg, and Ca were compared in maize plants (Zea mays L.) withdifferent growth-related nutrient demands. Plants were grownin nutrient solution with either 1·0 mol m3 NO3or NH4+ and the shoot growth rate per unit weight of roots wasmodified by varying the temperature of the shoot base (SBT)including the apical shoot meristem. The shoot growth rate per unit weight of roots, which was takenas the parameter for the nutrient demand imposed on the rootsystem, was markedly lower at 12°C than at 24°C SBT.As a consequence of the lower nutrient demand at 12°C SBT,uptake rates of NO3 and NH4+ declined by more than 50%Compared with NO3 supply, NH4+ nutrition depressed theconcentrations of K and particularly of Ca in the shoot, bothin plants with high and with low nutrient demand. This indicatesa control of cation concentration by internal demand ratherthan by uptake capacity of the roots. Translocation rates of K, Mg and Ca in the xylem exudate werelower in NH4+- than in NO3-fed plants. Net accumulationrates of Ca in the shoot were also decreased, whereas net accumulationrates of K in the shoot were even higher in NH4+-fed plants.It is concluded that reduced cation concentrations in the xylemsap of plants supplied with NH4+ are due to the lower demandof cations for charge balance. The lower K translocation tothe shoot is compensated by reduced retranslocation to the roots.For Ca, in contrast, decreased translocation rates in NH4+-fedplants result in lower shoot concentration. Key words: Nitrogen form, cation nutrition, charge balance, xylem exudate, recirculation 相似文献
18.
Nitrate Effects on Pre-emergence Growth and Emergence Percentage of Wheat (Triticum aestivum L.) from Different Sowing Depths 总被引:1,自引:0,他引:1
The effects of a range of applied nitrate (NO3) concentrations(020 mol m3) on germination and emergence percentageof Triticum aestivum L. cv. Otane were examined at 30, 60, 90and 120 mm sowing depths. Germination percentage was not affectedby either sowing depth or applied NO3 concentration whereasemergence percentage decreased with increased sowing depth regardlessof applied NO3 concentration. Nitrate did not affectemergence percentage at 30 mm sowing depth, but at 60 to 120mm depth, emergence percentage decreased sharply with an increasedapplied NO3 concentration of 0 to 1·0 mol m3then decreased only slightly with further increases in appliedNO3 of about 5·0 mol m3. Root and shoot growth, NO3 accumulation and nitrate reductaseactivity (NRA) of plants supplied with 0, 1·0 and 1·0mol m3 NO3 at a sowing depth of 60 mm were measuredprior to emergence. The coleoptile of all seedlings opened withinthe substrate. Prior to emergence from the substrate, shootextension growth was unaffected by additional NO3 butshoot fr. wt. and dry wt. were both greater at 1·0 and1·0 mol m3 NO3 than with zero NO3.Root dry wt. was unaffected by NO3. Nitrate concentrationand NRA in root and shoot were always low without NO3.At 1·0 and 10 mol m3 NO3, NO3 accumulatedin the root and shoot to concentrations substantially greaterthan that applied and caused the induction of NRA. Regardlessof the applied NO3 concentration, seedlings which failedto emerge still had substantial seed reserves one month afterplanting. Coleoptile length was substantially less for seedlingswhich did not emerge than for seedlings which emerged, but wasnot affected by NO3. It is proposed that (a) decreasedemergence percentage with increased sowing depth was due tothe emergence of leaf I from the coleoptile within the substrateand (b) decreased emergence percentage with additional NO3was due to the increased expansion of leaf 1 within the substrateresulting in greater folding and damage of the leaf. Key words: Triticum aestivwn L., nitrate, sowing depth, seedling growth, seedling emergence 相似文献
19.
The Partitioning of Nitrate Assimilation Between Root and Shoot of a Range of Temperate Cereals and Pasture Grasses 总被引:2,自引:1,他引:1
Nitrate reductase activity (NRA, in vivo assay) and nitrate(NO-3) content of root and shoot and NO-3 and reduced nitrogencontent of xylem sap were measured in five temperate cerealssupplied with a range of NO-3 concentrations (0·120mol m3) and three temperate pasture grasses suppliedwith 0·5 or 5 0 mol m3 NO-3 For one cereal (Hordeumvulgare L ), in vitro NRA was also determined The effect ofexternal NO-3 concentration on the partitioning of NO-3 assimilationbetween root and shoot was assessed All measurements indicatedthat the root was the major site of NO3 assimilation in Avenasatwa L, Hordeum vulgare L, Secale cereale L, Tnticum aestivumL and x Triticosecale Wittm supplied with 0·1 to 1·0mol m3 NO-3 and that for all cereals, shoot assimilationincreased in importance as applied NO-3 concentration increasedfrom 1.0 to 20 mol m3 At 5.020 mol m3 NO3,the data indicated that the shoot played an important if notmajor role in NO-3 assimilation in all cereals studied Measurementson Lolium multiflorum Lam and L perenne L indicated that theroot was the main site of NO-3 assimilation at 0.5 mol m3NO-3 but shoot assimilation was predominant at 5.0 mol m3NO-3 Both NRA distribution data and xylem sap analysis indicatedthat shoot assimilation was predominant in Dactylis glomerataL supplied with 0.5 or 5.0 mol m3 NO-3 Avena sativa L., oats, Hordeum vulgare L., barley, Secale cereale L., rye, x Triticosecale Wittm., triticale, Triticum aestivum L., wheat, Dactylis glomerata L., cocksfoot, Lolium multiflorum Lam., Italian ryegrass, Lolium perenne L., perennial ryegrass, nitrate, nitrate assimilation, nitrate reductase activity, xylem sap 相似文献
20.
The relationships between CO2 concentrating mechanisms, photosyntheticefficiency and inorganic carbon supply have been investigatedfor the aquatic macrophyte Littorella uniflora. Plants wereobtained from Esthwaite Water or a local reservoir, with thelatter plants transplanted into a range of sediment types toalter CO2 supply around the roots. Free CO2 in sediment-interstitial-waterranged from 101 mol m3 (Esthwaite), 0.79 mol m3(peat), 0.32 mol m3 (silt) and 017 mol m3(sand), with plants maintained under PAR of 40 µmol m2s1. A comparison of gross morphology of plants maintained underthese conditions showed that the peat-grown plants with highsediment CO2 had larger leaf fresh weight (069 g) andtotal surface area (223 cm2 g1 fr. wt. including lacunalsurface area) than the sand-grown plants (0.21 g and 196 cm2g1 fr. wt. respectively). Root fresh weights were similarfor all treatments. In contrast, leaf internal CO2 concentration[CO2], was highest in the sand-grown plants (269 molm3, corresponding to 6.5% CO2 in air) and lowest inthe Esthwaite plants (108 mol m3). Expressionof CAM in transplants was also greatest in the low CO2 regime,with H+ (measured as dawn-dusk titratable acidity) of 50µmolg fr. wt., similar to Esthwaite plants in natural sediment.Assuming typical CAM stoichiometry, decarboxylation of malatecould account largely for the measured [CO2]1 and would makea major contribution to daytime CO2 fixation in vivo. A range of leaf sections (02, 10, 50 and170 mm) was used to evaluate diffusion limitation andto select a suitable size for comparative studies of photosyntheticO2 evolution. The longer leaf sections (17.0 mm), which weresealed and included the leaf tip, were diffusion-limited witha linear response to incremental addition of CO2 and 10mol m3 exogenous CO2 was required to saturate photosynthesis.Shorter leaf sections were less diffusion-limited, with thegreatest photosynthetic capacity (36 µmol O2 g1 fr. wt. h1) obtainedfrom the 1.0 mm size and were not infiltrated by the incubatingmedium. Comparative studies with 1.0 mm sections from plants grown inthe different sediment types revealed that the photosyntheticcapacity of the sand-grown plants was greatest (45 µmolO2 g1 fr. wt. h1) with a K0.5 of 80 mmol m3.In terms of light response, saturation of photosynthesis intissue slices occurred at 8501000 µmol m2s1 although light compensation points (611 µmolm2s1) and chlorophyll a: b ratios (1.3) were low.While CO2 and PAR responses were obtained using varying numbersof sections with a constant fresh weight, the relationshipsbetween photosynthetic capacity and CO2 supply or PAR were maintainedwhen the data were expressed on a chlorophyll basis. It is concludedthat under low PAR, CO2 concentrating mechanisms interact inintact plants to maintain saturating CO2 levels within leaflacunae, although the responses of the various components ofCO2 supply to PAR require further investigation. Key words: Key words-Uttorella uniflora, internal CO2 concentration, crassulacean acid metabolism, root inorganic carbon supply, CO2 concentrating mechanism 相似文献