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1.
Summary The effect of silicon on manganese tolerance of bean plants (Phaseolus vulgaris L. var. ‘Red Kidney’) grown in water culture was studied at different levels of manganese supply.
Without silicon, growth depression and toxicity symptoms occurred already at 5 × 10−4 mM Mn in the nutrient solution. After addition of Aerosil (0.75 ppm Si), the plants tolerated 5 × 10−3 mM Mn and, at a higher silicon supply of 40 ppm, as much as 10−2 mM Mn in the nutrient solution without any growth depression. This increase in manganese tolerance was not caused by a depressing
effect of silicon on uptake or translocation of manganese but rather by an increase in the manganese tolerance of the leaf
tissue. In absence of silicon, 100 ppm Mn was already toxic for the leaf tissue, whereas with a supply of 40 ppm Si, this
‘critical level’ in the leaves was increased to more than 1000 ppm Mn.
At lower manganese levels in the leaf tissue, a molar ratio Si/Mn of 6 within the tissue was sufficient to prevent manganese
toxicity. Above 1000 ppm Mn, however, even a much wider Si/Mn ratio (> 20) could not prevent growth depression by manganese
toxicity.
With54Mn and autoradiographic studies, it could be demonstrated that, in absence of silicon, even at optimal manganese supply (10−4 mM), the distribution of manganese within the leaf blades was inhomogeneous and characterized by spot-like accumulations. In
presence of silicon, however, the manganese distribution was homogeneous in the lower concentration range of manganese and
still fairly homogeneous in the high concentration range.
This effect of silicon on manganese distribution on the tissue level was also reflected on the cellular level. In the presence
of silicon, a higher proportion of the leaf manganese could be found in the press sap,i.e., had been transported into the vacuoles, than in the absence of silicon. The increase in manganese tolerance of bean leaves
by silicon therefore seems to be primarily caused by the prevention of local manganese accumulation within the leaf tissue
which leads to local disorders of the metabolism and, correspondingly, growth depression. 相似文献
2.
K. Ohki 《Plant and Soil》1987,98(2):195-202
Summary Sorghum plants were grown in the greenhouse in modified Steinberg nutrient solution containing ten Al rates (0 to 297 μM) and harvested 28 days after transplanting. Top and root dry weight were not affected by added Al up to 74 μM; but decreased sharply at concentration of 148 μM and greater. Aluminum concentrations in blade 1 (recently matured blade) and plants remained constant from 0 to 297 μM added Al. Root Al concentration increased as added Al increased. No correlation existed between top dry weight and Al concentration
in blade 1 or in plant. Root Al concentration was related to top dry weight and root dry weight to estimate the Al critical
toxicity level. The Al critical toxicity levle in the root was 54 mmol kg−1 root dry weight basis for either top or root dry weight. In blade 1 Cu concentration negatively correlated with Al while
Fe and P were positively correlated. In roots Ca, Mg, Mn and Fe concentrations were negatively correlated with Al while Zn,
Cu, P, and K were positively correlated with Al concentration. 相似文献
3.
Summary Soybean (Glycine max (L) Merr. cv. Bragg) seedlings were grown in nutrient solutions to evaluate the response to manganese nutrition as affected by potassium supply. In solutions containing 275 M manganese, increasing the solution concentration of potassium from 1 mM to 10 mM alleviated symptoms of manganese toxicity, decreased manganese concentrations in the leaves and increased dry matter yields of the plants. The reduction in manganese toxicity was brought about by a reduced rate of root absorption of manganese at high potassium supply levels.Increasing the supply of either potassium or manganese decreased the leaf concentration of magnesium although there were no apparent symptoms of magnesium deficiency in any treatment. The reduced concentration of magnesium in the leaves was due to effects of potassium and manganese on the rate of root absorption of magnesium.Under manganese deficiency conditions, growth was reduced and manganese concentrations in plant parts were very low; there was no effect of potassium supply when manganese was absent from the nutrient solution. 相似文献
4.
The effects of varying solution concentrations of manganese (Mn), zinc (Zn), copper (Cu), boron (B), iron (Fe), gallium (Ga) and lanthanum (La) on plant chemical concentrations, plant uptake and plant toxicity were determined in wheat (Triticum aestivum L.) grown in a low ionic strength (2.7×10–3
M solution culture). Increasing the solution concentration of Mn, Zn, Cu, B, Fe, Ga and La increased plant concentrations of that ion. Asymptotic maximum plant concentrations were reached for Zn (10 mg kg DM–1 in the roots), Ga (2 mg kg DM–1 in the tops and 18 mg kg DM–1 in the roots) and La (0.4 mg kg DM–1 in the tops and 4 mg kg DM–1 in the roots). Plant ion concentrations were, on average, 3 times higher in the roots than the tops for Mn and Zn, 7 times for Cu, 9 times for Fe, 12 times for Ga and 15 times for La. In contrast, B concentrations were higher in the tops than the roots by, on average, 2 times. The estimated toxicity threshold (plant concentration at which a rapid decrease in yield occurred) in the tops was 0.4 mg g DM–1 for B, 2 for Zn, 0.075 for Cu and 0.09 for La and in the roots 0.2 mg g DM–1 for B, 5 for Zn, 0.3 for Cu and 3 for La. Plant uptake rates of the ions (as estimated by the slope of the relationship between solution ion concentrations and plant ion concentrations) was in the order B 250 mg kg DM–1 M
–1). Plant toxicity was estimated as the reciprocal of the plant concentration that reduced yield by 50% (change in relative yield per mg ion kg DM–1). The plant toxicity of the ions tested was in the order Mn相似文献
5.
The effects of aluminium (Al), manganese (Mn), zinc (Zn), copper (Cu), boron (B), iron (Fe), gallium (Ga), scandium (Sc) and lanthanum (La) on growth of an Al-tolerant and an Al-sensitive line of wheat (Triticum aestivum L.) were measured in solution culture. The concentrations of nutrients in the basal nutrient solution were (M) 500 Ca, 100 Mg, 300 K, 600 N (150 NH4, 450 NO3), 600 SO4, 2.5 P, 3 B, 2.5 Fe, 0.5 Zn, 0.5 Mn, 0.1 Cu at a pH of 4.7. The major solution nutrient concentrations were maintained at the nominal concentration with monitoring, frequent additions and weekly renewal. Differentiation in yield between the Al-tolerant and Al-sensitive line only occurred in the presence of Al indicating that, in the long term, none of the other metals tested could be used as an analog for Al. The visual symptoms in the roots of Cu toxicity (in both lines) and Al toxicity (in the sensitive line) were similar. The solution concentration (M) at which yield of the roots of the tolerant line was reduced by 50% was, in order of increasing tolerance, Cu 0.5, Sc 1.1, La 7.1, Ga 8.6, Al 15, Zn 19, Fe 84, B 490 and Mn 600. 相似文献
6.
The effects of silicon (Si) supply on manganese (Mn) toxicity symptoms and Mn and Si concentrations in the leaf apoplast in a Mn-sensitive cowpea cultivar (Vigna unguiculata (L.) Walp. cv. TVu 91) were investigated in solution culture experiments. When 1.44 mM Si was supplied concurrently with 50 M Mn, the Mn toxicity symptoms were clearly avoided without decreasing the total Mn concentration. On the other hand, the symptoms were not completely alleviated when the plants were pretreated with 1.44 mM Si and then exposed to 50 M Mn without concurrent Si supply. Plants of both of these treatments exhibited lower Mn concentrations in the apoplastic washing fluids but higher amounts of adsorbed Mn on the cell walls than the plants treated with 50 M Mn without Si supply. However, the difference in Mn concentration between plants with continuous and interrupted Si supply was not significant. Moreover, the Mn concentration in the apoplastic washing fluids of the plants with continuous supply of 1.44 mM Si and 50 M Mn and not showing Mn toxicity symptoms was higher than that of the plants grown at 10 M Mn without Si supply which showed distinct Mn toxicity symptoms. These results show that Si supply alleviates Mn toxicity not only by decreasing the concentration of soluble apoplastic Mn through the enhanced adsorption of Mn on the cell walls. A role of the soluble Si in the apoplast in the detoxicification of apoplastic Mn is indicated. 相似文献
7.
Influence of external zinc and phosphorus supply on Cd uptake by rice (Oryza sativa L.) seedlings with root surface iron plaque 总被引:1,自引:0,他引:1
Rice seedlings were grown in hydroponic culture to determine the effects of external Zn and P supply on plant uptake of Cd
in the presence or absence of iron plaque on the root surfaces. Iron plaque was induced by supplying 50 mg l−1 Fe2+ in the nutrient solution for 2 day. Then 43-day-old seedlings were exposed to 10 μmol l−1 Cd together with 10 μmol l−1 Zn or without Zn (Zn–Cd experiment), or to 10 μmol l−1 Cd with 1.0 mmol l−1 P or without P (P–Cd experiment) for another 2 day. The seedlings were then harvested and the concentrations of Fe, Zn, P
and Cd in dithionite–citrate–bicarbonate (DCB) extracts and in roots and shoots were determined. The dry weights of roots
and shoots of seedlings treated with 50 mg l−1 Fe were significantly lower than when no Fe was supplied. Adsorption of Cd, Zn and P on the iron plaque increased when Fe
was supplied but Cd concentrations in DCB extracts were unaffected by external Zn or P supply levels. Cd concentrations in
shoots and roots were lower when Fe was supplied. Zn additions decreased Cd concentrations in roots but increased Cd concentrations
in shoots, whereas P additions significantly increased shoot and root Cd concentrations and this effect diminished when Fe
was supplied. The percentage of Cd in DCB extracts was significantly lower than in roots or shoots, accounting for up to 1.8–3.8%
of the plant total Cd, while root and shoot Cd were within the ranges 57–76% and 21–40% respectively in the two experiments.
Thus, the main barrier to Cd uptake seemed to be the root tissue and the contribution of iron plaque on root surfaces to plant
Cd uptake was minor. The changes in plant Cd uptake were not due to Zn or P additions altering Cd adsorption on iron plaque,
but more likely because Zn or P interfered with Cd uptake by the roots and translocation to the shoots. 相似文献
8.
Iron Enhances Aluminum-induced Leaf Necrosis and Plant Growth Inhibition in Eucalyptus camaldulensis
The combined effects of excess Fe and Al on Eucalyptus camaldulensis Dehnh. were studied by investigating time course and visible symptoms of leaf necrosis, plant biomass, the status of some
antioxidants and pigments and nutrient concentrations. Seedlings were grown hydroponically in nutrient solutions containing
0 or 500 μM AlCl3, each with a FeSO4 range of 1, 12 and 120 μM at pH 4.2. Leaf necrosis and plant growth inhibition were induced by Al and enhanced by the increase in Fe concentration.
The process from the first appearance of necrotic spots to leaf death (shedding) of a leaf proceeded from a few days to about
20 days after the leaf had fully expanded. Either 120 μM Fe without Al or Al reduced plant growth to a similar extent but 120 μM Fe without Al did not cause leaf necrosis. In leaves, excess Fe (12 and 120 μM) without Al reduced concentration of ASC and GSH, while concentration of Fe, DHA and GSSG and DHA:ASC and GSSG:GSH ratios
tended to increase with the increase in Fe concentration in treatment solution with or without Al. At 1 μM Fe, Al increased concentration of DHA and DHA:ASC and GSSG:GSH ratios. Catalase activity in leaves reduced with the increase
in leaf Al concentration. At 1 μM Fe, Al greatly reduced concentrations of Fe and chlorophylls in leaves but increase two times Fe concentration in stems.
These suggest that the enhancement effects of Fe on Al-induced leaf necrosis and plant growth inhibition can be discussed
in context of the excess Fe itself weakens antioxidant capability of ASC–GSH cycle in leaves and greatly reduces plant growth;
and the increase in Fe accumulation in stems is involved in Al-induced leaf chlorosis. 相似文献
9.
Iron nutrition affects cadmium accumulation and toxicity in rice plants 总被引:12,自引:0,他引:12
Guosheng Shao Mingxue Chen Weixia Wang Renxiang Mou Guoping Zhang 《Plant Growth Regulation》2007,53(1):33-42
The effect of iron (Fe) nutrition on cadmium (Cd) toxicity and accumulation in rice plants was studied using a hydroponic
system. The inhibitory effect of Cd on plant growth and chlorophyll content (SPAD value) was dependent on Fe level and the
genotype. Malondialdehyde (MDA) content in leaves and roots was not much affected by an increased Cd stress at 0.171 mg l−1 Fe, but it showed a rapid increase when the plants were exposed to moderate (1.89 mg l−1) and high (16.8 mg l−1) Fe levels. High Fe nutrition caused a marked reduction in Cd content in both leaves and roots. Fe content in plants was
lower at high Cd (5.0 μM) stress than at low Cd (<1.0 μM) stress. Cd stress increased both superoxide dismutase (SOD) and
peroxidase (POD) activities at low and moderate Fe levels. However, with high Fe level, it increased the POD activity, but
reduced the SOD activity. Our results substantiate the hypothesis that cell membrane-bound iron transporter (carrier) involved
in high-affinity iron transport systems can also transport Cd, and both these ions may compete for this common carrier. The
study further showed that there were significant correlations between MDA and Fe contents in leaves and roots of rice plants.
It is suggested that the occurrence of oxidative stress in plants exposed to Cd stress is mediated by Fe nutrition. The present
results also show that Cd stress affects the uptake of Cu and Zn. 相似文献
10.
Summary The effect of Ca on the absorption and translocation of Mn, Zn and Cd in excised barley roots was studied using a multi-compartment
transport box technique. A radioisotope (54Mn,65Zn or115mCd)-labelled test solution was supplied to the apexes of excised roots and the distribution pattern in the roots was examined
in the absence or presence of Ca. Results obtained were as follows.
Addition of Ca to the test solution reduced the absorption of Mn and inhibited drastically its translocation in excised roots.
With increasing concentrations of Ca in test solutions, its inhibitory effects on the absorption and translocation of Mn became
severe.
Similar results were observed for the absorption and translocation of Zn. Ca in the test solution decreased the absorption
and inhibited drastically the translocation of Zn; as in the case of Mn, higher concentrations of Ca had severe effects on
these functions.
It was also evident that the addition of Ca to the test solution reduced the absorption of Cd at all levels of Cd concentration
(1, 10, and 100 μM). Cd absorption decreased with increasing concentrations of Ca in the test solution. However, Ca accelerated the translocation
of Cd in excised roots supplied with test solutions containing up to 10μM Cd. At 100μM Cd, addition of Ca caused a negligibly small acceleration of Cd translocation.
The accelerating effect of Ca on Cd translocation, especially “xylem exudation”, decreased markedly with the addition of 2,4-dinitrophenol,
but not with the addition of chloramphenicol or p-chloromercuribenzene sulphonic acid. When barley plants were supplied with
only CaSO4 during the entire growing period, that is, plants were not supplied with nutrient solution on the last day of this period,
Ca had no accelerating effect on Cd translocation in excised roots. 相似文献
11.
After aluminum toxicity, manganese (Mn) toxicity is probably the second most important growth limiting factor in acid soils.
The purpose of this study was to determine the feasibility of using chlorophyll content and leaf elongation rate (LER) for
regrowth of Mn stressed seedlings as a rapid seedling based screening bioassay for Mn tolerance in segregating populations
of wheat (Triticum aestivum L.). In one experiment, chlorophyll was determined for the cultivars Norquay (Mn-tolerant) and Columbus (Mn-sensitive) subjected
to twelve Mn levels (2 to 2000 μM) in nutrient solutions. As Mn concentration increased, chlorophyll ‘a’ and ‘b’ contents of the Mn-tolerant cultivar decreased
up to 9%, while in the Mn-sensitive cultivar it was reduced by as much as 43%. The chlorophyll ‘a/b’ ratio did not differ
among Mn concentrations for either cultivar. In a second experiment, chlorophyll content and LER for regrowth of Mn stressed
seedlings (1000 μM) was determined for Columbus and Katepwa (Mn-sensitive), Oslo (Mn-intermediate), and Norquay and Laura (Mn-tolerant). Manganese
tolerance as assayed by chlorophyll ‘a’ and ‘b’ and LER was significantly correlated with Mn tolerance as assayed by the relative
root weight methodology (RRW). Thus, chlorophyll content of Mn-stressed seedlings and LER of seedling regrowth appear to be
suitable techniques for screening unreplicated selections of segregating populations for tolerance to Mn. 相似文献
12.
Understanding of the mechanisms of Mn supply from the soil and uptake by the plants can be improved by using simulation models
that are based on basic principles. For this, a pot culture experiment was conducted with a sandy clay loam soil to measure
Mn uptake by summer wheat (Triticum aestivum L. cv. Planet), maize (Zea mays L. cv. Pirat) and sugar beet (Beta vulgaris L. cv. Orbis) and to simulate Mn dynamics in the rhizosphere by means of a mechanistic model. Seeds of three crops were sown
in pots containing 2.9 kg soil in a controlled growth chamber. Root and shoot weight, Mn content of plants, root length and
root radius were determined 8 (13 days in case of sugar beet) and 20 days after germination. Soil and plant parameters were
determined to run nutrient uptake model calculations. Manganese content of the shoot varied from 25 mg kg-1 for sugar beet to 34 mg kg-1 for maize. Sugar beet had the lowest root length/shoot weight ratio but the highest relative shoot growth rate, resulting
in the highest shoot demand on the root. This is reflected by the Mn influx which was 0.9 × 10-7, 1.7 × 10-7 and 2.5 × 10-7 nmol cm-1 s-1 for wheat, maize and sugar beet, respectively. Nutrient uptake model calculations predicted similar influx values. Initial
Mn concentration of 0.2 μM in the soil solution decreased to only 0.16 μM for wheat, 0.13 μM for maize and 0.11 μM for sugar beet at the root surface. This shows that manganese transport to the root was not a limiting step. This was confirmed
by the fact that an assumed 20 times increase in maximum influx (Imax) increased the calculated Mn influx by 3.7 times. Sensitivity analysis demonstrated that for controlling Mn uptake the initial
soil solution concentration (C
Li), the root radius (r0), Imax and the Michaelis constant (K
m) were the most sensitive factors in the listed order.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
A. C. B. de A. Monteiro E. N. Higashi A. N. Gonçalves A. P. M. Rodriguez 《In vitro cellular & developmental biology. Plant》2000,36(6):527-531
Summary Mineral deficiency symptoms were observed in leaves of yellow passionfruit plantlets grown in MS medium (Murashige and Skoog,
1962) with 1.0 mg l−1 (3.0 μM) gibberellic acid. Initially, leaves showed interveinal chlorosis, followed by bleaching of the leaves and retarded growth.
Leaf mineral analysis was done and compared to mineral requirements suggested for passionfruit in the literature. Several
modifications were made to the inorganic composition of MS medium, according to mineral deficiencies, mainly of Fe and Ca,
and possible toxicity of Cl. The concentration of the elements in the new medium (MSM) was based on the mineral composition
of leaves of healthy plants. The chemical equilibrium was checked using the software Geochem (Sposito and Mattigod, 1980)
and final adjustments were made to ensure good availability of nutrients. To test the efficiency of the modified medium nodal
segments were cultured in both MS and MSM supplemented with 3.0 mg l−1 (13.3 μM) 6-benzyladenine. After three subcultures mineral analysis of the leaves was done. Severe mineral deficiency was observed
on the leaves of plantlets cultured in MS, while plantlets cultivated in MSM had green leaves. A comparison of the mineral
analysis of plantlets in both media showed a fairly large increase in Ca, Cu, Fe, Mg and S and decrease in levels of B and
Cl in plantlets cultivated in MSM. A slight increase or decrease in other elements was also observed. Subculture of the chlorotic
plantlets into MSM showed that the visual symptoms of mineral deficiency disappeared in 2–4 wk. 相似文献
14.
A study has been made on the effect of primary leaves on iron (Fe) distribution in the shoot. Bean (Phaseolus vulgaris L.) seedlings were precultured in nutrient solution with 8×10-5
M FeEDTA for 4 days, and then grown further with either 8×10-5
M FeEDTA (+Fe) or without Fe supply (-Fe) for another 5 days. Thereafter, both +Fe and -Fe plants were treated in three different ways: undisturbed; one primary leaf removed; or one primary leaf shaded, starting two hours before supply 59FeEDTA to the roots. The +Fe plants were supplied with 8×10-5
M
59FeEDTA, and the -Fe plants with only 1×10-6
M
59FeEDTA. After 1 to 8 hour uptake periods, plants were harvested and 59Fe in different organs was determined. Removal or shading of one primary leaf did not affect 59Fe uptake by roots and 59Fe translocation to the shoot in +Fe plants. In the -Fe plants, however, removal of one primary leaf decreased 59Fe uptake by roots, whereas shading of one primary leaf had no effect on 59Fe uptake but slightly enhanced 59Fe translocation from roots to the shoot. The quantity of 59Fe in primary leaves was positively correlated with quantity of 59Fe in the stem in the -Fepplants, but not in the +Fe plants. In both, the +Fe and -Fe plants, the quantity of 59Fe in the shoot apex was positively correlated with 59Fe in primary leaves. The results suggest that irrespective of the Fe nutritional status of plants, the source of Fe for the shoot apex is Fe retranslocated from primary leaves. 相似文献
15.
Distribution and mobility of manganese in the hyperaccumulator plant Phytolacca acinosa Roxb. (Phytolaccaceae) 总被引:2,自引:0,他引:2
Xianghua Xu Jiyan Shi Yingxu Chen Xincai Chen Hui Wang Anton Perera 《Plant and Soil》2006,285(1-2):323-331
The distribution and mobility of manganese (Mn) in the hyperaccumulator plant species Phytolacca acinosa Roxb. (Phytolaccaceae) were investigated in a hydroponic system. The plants were exposed to 2 or 5 mM Mn for up to 28 days. For any given plant, the Mn content in the mature leaves (nos. 5–9) was always higher than that in the old (nos. 1–4) and young leaves (nos. 10–14). Within the different parts of a leaf, Mn was preferentially accumulated in the leaf marginal area, where the observed level was threefold higher than that in the midrib. Cross-sectional analysis of the leaf revealed that the concentration of Mn was higher in the leaf epidermis than in the mesophyll. Cell fractionation analysis with P. acinosa leaves showed that most of the Mn (78.4%) was present in the final supernatant fraction (following centrifugation at 20,000 g for 45 min). The distribution of Mn in the leaves of P. acinosa was controlled mainly by the transpiration rate. Our investigation demonstrated that Mn was readily transported from the roots to shoots of P. acinosa but that it could not be remobilized readily after it reached leaves. 相似文献
16.
Physiological responses of wheat genotypes grown in chelator-buffered nutrient solutions with increasing concentrations of excess HEDTA 总被引:1,自引:0,他引:1
The chelator-buffered nutrient solutions containing excess chelator have been used frequently in the micronutrient research,
but potential toxicity of the excess chelator has not been ascertained. The present study was conducted to test effects of
four concentrations of excess HEDTA [ N-(2-hydroxyethyl)ethylenedinitrilotriacetic acid] and two levels of total Zn on growth,
root exudation, and nutrient uptake and transport by Triticum aestivum L. (cv. Aroona) and Triticum turgidum L. conv. durum
(Desf.) MacKey (cv. Durati) genotypes differing in tolerance to Zn deficiency. Excess HEDTA at 50 μM reduced root and shoot
growth and caused visual toxicity symptoms (necrotic lesions) on leaves; these effects were generally absent at lower concentrations
of excess HEDTA. Root exudation of phytosiderophores increased with increasing concentrations of excess HEDTA at deficient
and sufficient Zn levels, and was higher in Zn-deficiency-tolerant Aroona than in Zn-deficiency-sensitive Durati wheat. Shoot
and root Zn concentrations showed a saturable response to increasing Zn2+ activities in solution. Excess HEDTA at 50 μM caused an increase in shoot concentrations of Fe and a decrease in concentrations
of Mn and Cu. An average rate of Zn uptake increased with an increase in Zn2+ ionic activity in solution, with Zn-deficiency-tolerant Aroona having a higher rate of Zn uptake than Zn-deficiency-sensitive
Durati in the deficiency range of Zn2+ activities. Average uptake rates of Mn and Cu decreased with an increase in concentration of excess HEDTA. Similar observations
were noted for transport of Mn and Cu to shoots, while Zn transport to shoots was proportional to Zn2+ activities in solution. It was concluded that excess HEDTA at 50 μM adversely affects wheat growth and physiology, while
excess of 25 μM or less does not cause measurable toxicity.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
17.
Summary The effects of P and Mn on growth response and uptake of Fe, Mn and P by grain sorghum were investigated using nutrient culture. High P and Mn concentrations in solution (greater than 40 and 1 mg/l for P and Mn, respectively) markedly reduced plant height and shoot and root dry weight of 4-week-old sorghum plants. High Mn concentrations in solution increased the concentrations of Mn and P in shoot tissue and uptake of Mn, but depressed the uptake of P. High levels of P enhanced Mn uptake by sorghum and accentuated Mn toxicity at low Mn levels. The tissue Fe and total uptake of Fe were both reduced markedly by the high levels of P and Mn concentrations in solution. The increases of P, Mn and Fe concentrations in root tissue with a concomitant decrease of Fe in shoots suggested that the translocation of Fe from roots to shoots was hindered under high P and Mn conditions. Since coating occurred on root surfaces and intensified with increasing Mn concentrations in the substrate, part of the reduction of Fe in shoots could be attributed to the formation of high valent manganese oxides on the root surfaces which may retain Fe and reduce its absorption by sorghum.Contribution from the Department of Agronomy and Range Sci., University of California, Davis, CA. 相似文献
18.
The objective of this study was to determine if plant roots have to take up nitrate at their maximum rate for achieving maximum
yield. This was investigated in a flowing-solution system which kept nutrient concentrations at constant levels. Nitrate concentrations
were maintained in the range 20 to 1000 μM. Maximum uptake rate for both species was obtained at 100 μM.
Concentrations below 100 μM resulted in decreases in uptake rate per cm root (inflow) for both spinach and kohlrabi by 1/3 and 2/3, respectively. However,
only with kohlrabi this caused a reduction in N uptake and yield. Thus indicating that this crop has to take up nitrate at
the maximum inflow. Spinach, however, compensated for lower inflows by enhancing its root absorbing surface with more and
longer roots hairs. Both species increased their root length by 1/3 at low nitrate concentrations. 相似文献
19.
J. Le Bot M. J. Goss M. J. G. P. R. Carvalho M. L. Van Beusichem E. A. Kirkby 《Plant and Soil》1990,124(2):205-210
Results are reported for tomato (Lycopersicon esculentum L. var. Ailsa craig) and wheat (Triticum aestivum L. cv. Mara) which demonstrate that increasing concentrations of Mg in the plant raises plant tolerance to Mn toxicity.Water culture experiments with tomato show that under conditions of high Mn supply (200 µM, Mn), not only does increasing Mg application (0.75 mM to 15 mM) depress Mn uptake, but the higher Mg concentrations in the shoot counteract the onset of Mn toxicity when the concentrations of Mn in the shoot are also high. The ratio of Mg: Mn in the tissues is a better indicator of the appearance of toxicity symptoms than Mn concentration alone. Toxicity symptoms were observed when the Mg:Mn ratio in the shoot tissue was from 1.13 to a value between 3.53 and 6.54. The corresponding Mg: Mn ratio in the older leaves was from 0.82 to between 2.27 and 3.51.For wheat grown in soil, analyses of leaves revealed that growth could be expressed by the following relationship: Y=A+B exp(-kX), where Y=growth, X=Mg:Mn ratio, A, B and k=constants. Growth was significantly reduced when the Mg:Mn ratio fell below 20:1. From a measurement of this ratio it is therefore possible to predict the appearance of Mn toxicity and its influence on growth. 相似文献
20.
This study was conducted to determine effects of nitrogen supply (75 and 150 kg(N) ha−1) and CO2 enrichment on partitioning of macro and micro nutrients in wheat (Triticum aestivum L. cv. HD-2285). Plants were grown from seedling emergence to maturity inside open top chambers under ambient CO2 (CA, 350 ± 50 μmol mol−1) and elevated CO2 (CE, 600 ± 50 μmol mol−1). Leaves, stems and roots of the same physiological age were analyzed for carbon, nitrogen, calcium, copper, iron, zinc and
manganese content at 40, 60 and 90 d after germination. C, Cu, Mn and Zn content was higher in the stem, leaves and roots
on dry mass basis under CE than CA. However, N and Fe contents decreased in CE grown plants. Ca content was unaffected due
to CE and variable N supplies.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献