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1.
Abstract

Two cultivars of cotton (Gossypium spp.) were grown in Yolo loam soil in a glasshouse to determine phytotoxicity effects of excesses of Ni and Cd. A 200 μg/g level of Ni in soil reduced yield by 60% in Acala SJ‐2 and by 83% in Giza 45. The leaf Ni concentrations, respectively, were 146 and 165 μg/g‐ The 300 μg/g level of Cd decreased leaf yields by 60% and 75% for the two cultivars, respectively. Leaf concentrations of Cd, respectively, were 43 and 63 μg/g. There was a stem to leaf gradient of Cd for all cases. High Cd did not depress Mn concentrations in plants . as in other species but there were many mineral element interactions.  相似文献   

2.
Abstract

Two cultivars of cotton (Gossypium spp.) were grown in Yolo loam soil (soil pH about 6) in pots in a glasshouse to determine phytotoxic effects of excesses of Cu, Zn, Co, and Mn. Leaf yields of cv. Acala SJ‐2 were depressed 35% by 400 μg Cu/g soil, 54% by 400 μg Zn/g soil, 98% by 400 μg Co/g soil, and 84% by 2000 μg Mn/g soil. Leaf metal concentrations at these application levels in μg/g leaf were 12.0 Cu, 520 Zn, 243 Co, and 14780 Ma, respectively. Plants were tolerant of in / dry leaves of 10 Cu, 157 Zn and 444 Mn. The concentration for Co could not be ascertained. Leaf yields of cv. Giza 70 were depressed 53% by 400 μg Cu/g soil, 25% by 400 μg Zn/g soil, 92% by 400 μg Co/g soil and 90% by 2000 μg Mn/g soil. This cv. was more tolerant of Zn than Acala SJ‐2. Leaf metal concentrations at these application levels in μg/g leaf were 11.8 Cu, 312 Zn, 224 Co, and 18300 Mn respectively. Gradients of these four elements existed from leaves to stems. Many interactions with other elements were observed.  相似文献   

3.
Abstract

Two cultivars of cotton (Gossypium spp.) were grown in solution culture in a glasshouse to determine phytotoxicity effects of excesses of Ni and Cd. Leaf yield was depressed 94% by 10‐4 M NiSO4(with 198μg Ni/g leaf) in Acala SJ‐2 and 93% (with 167μg Ni/g) in Plma PS‐5. The Ni gradient was roots > stems > leaves in both cultivars. At 10‐5 M, CdSO4 gave more phytotoxicity than NiSO4. The 10‐4 M CdSO4 resulted in about the same amount of phytotoxicity as did the Ni for both cultivars. The Pima PS‐5 plant parts, however, contained less Cd than did the Acala SJ‐2 at the highest Cd concentration. At 10‐5 M CdSO4 the reverse held in leaves and stems. Interactions held for both metals but the inverse effect between Cd and Mn was less pronounced than for other species. Many other interactions were present.  相似文献   

4.
Abstract

The toxicity of Li to three plant species was studied to determine if there were interactions with other elements and to determine if a chelating agent modified Li toxicity. Bush beans (Phaseolus vulgarls L. C.V. Improved Tendergreen), grown in solution culture, were sensitive to 0.5 X10‐3Li which resulted in 10 μg/g in leaves, 48 in stems, and 24 in roots. Higher concentrations of Li produced marked reductions in plant yield accompanied by increased Li concentrations in leaf, stem, and root tissues. For most treatments, root concentrations of Li were lower than those in shoots, but those in stems were higher than those in leaves. Higher levels of Li decreased Zn in leaves, increased Ca in stems, and generally increased Fe and Mn in all plant tissues. Ethylenediamine tetraacetic acid (EDTA) resulted in slightly increased Ii levels in leaves, stems, and roots. Bush bean plants were injured slightly with 25 μg Li/g of Yolo loam soil applied as LiCl; 50 μg Li/g soil caused more severe injury. Leaf concentrations of about 200 μg Li/g resulted in significant yield reduction and around 600 μg//g of leaves resulted in severe toxicity. There were some interactions of Li with other elements which resulted in an increase of them in both leaf and stem tissues. Barley plants (Hordeum vulgare L. C.V. Atlas 57) were severely stunted when grown with 500 and 1000 μg Li/g soil as Li oxalate. Increasing the soil pH even further with lime and decreasing it with S had no influence on the toxicity. Shoot concentrations of Li ranged from 800 to over 2000 in the various treatments resulting in severe disruption of the Ca and K balance. Leaf concentrations of Li were higher than those for stems in cotton (Gossypium hirsutum L. C.V. Acala 442). Cotton was tolerant of a leaf concentration of 587 μg Li/g. High levels of Li increased concentrations of several elements in cotton leaves and in stems. Cotton leaves accumulated more Li than did bush beans.  相似文献   

5.
Abstract

The essential trace elements Fe, Mn, Zn, Cu, and B in high concentrations can produce phytotoxicities. Iron toxicity resulted from 5 × 10‐4 M and 10‐3 M FeSO4, but not from equivalent amounts of FeEDDHA (ferric ethylenediamine di (o‐hydroxyphenylacetic acid) ). Leaf concentrations in bush beans of 465 μg Mn/g, 291 μg B/g, and 321 μg Zn/g all on the dry weight basis resulted in 27%, 45%, and 34% reduction in yields of leaves, respectively. Zinc was concentrated in roots while Mn and B concentrated in leaves. Solution concentrations of MnS04 of 10‐3 and 10‐2 M depressed leaf yields of bush beans by 63% and 83%, respectively, with 5140 and 10780 μg Mn/g dry weight of leaves. Copper concentrations were simultaneously increased and those of Ca were decreased. Bush bean plants grown in Yolo loam soil with 200 μg Cu/g soil had a depression in leaf yield of 26% (with 28. 8 μg Cu/g leaf); plants failed to grow with 500 μg Cu/g soil. A level of 10‐3 M H2MoO4 was toxic to bush beans grown in solution culture. Leaves, stems, and roots, respectively, contained 710, and 1054, and 5920 μg Mo/g dry weight.  相似文献   

6.
Abstract

Cadmium in solution culture at 10‐4 M decreased Mn concentrations in bush beans (Phaseolus vulgaris L. C.V. Improved Tendergreen) at both low and high concentrations of Mn (noncompetitive inhibition). When Mn was decreased, the concentrations of Fe and several other ions were simultaneously increased, particularly in leaves and roots. Toxicity due to the 10‐6 M Cd and the 10‐4 M Mn was additive in the experiment. When barley (Hordeum vulgare L. Atlas57)was grown in amended soil, 15μg Fe as DTPA (diethylene triamine pentaacetic acid) per g soil resulted in increased uptake of Cd and in somewhat greater yield depression for soil pH of 3.9, 6. 0, and 7.6. Acidification of soil without DTPA also increased Cd uptake to high levels with associated yield decrease. The Cd decreased the uptake of Mn and Cu most when CaCO3 had also been added to the soil. When salts were added to soil with Cd before bush beans were grown, KCl (200 μg K/g soil), and equivalent KH2PO4 increased Cd concentrations of leaves while CaSO4 and KCl did so for roots. In bush beans with different levels of Cd and Zn, there were no yield interactions, but some interactions of Cd on Zn concentrations in leaves, stems, and roots at the high Zn level.  相似文献   

7.
Abstract

Earlirose rice (Oryza sativa L. ) and Hawkeye soybeans (Glycine max L.) were grown in solution culture with A12(SO4)3 in concentrations of 0, 10‐6, 10‐5, 10‐4, 10‐3 M. Only at 10‐4 (slightly) and at 10‐3 M were there yield depressions due to Al. The threshold concentration of Al for toxicity was about 20 μg/g in rice shoots and about 30 μg/g in soybean leaves. The solution level necessary for these concentrations was 8 μg Al/ml. Plant concentrations which caused severe toxicity were 70 μg Al/g plant with 81 μg Al/ml solution. Most Al remained in roots, but leaves contained more than did stems of soybeans. The high Al decreased Fe, Cu, and Mn concentrations in shoots of rice and decreased Fe, Cu, and Zn in roots of rice. The high Al resulted in decreased Fe and Zn in leaves of soybeans. No Fe deficiency symptoms were present due to the high Al.  相似文献   

8.
Abstract

The phytotoxicity of five nonessential elements (Co, V, Ti, Ag, Cr) to higher plants was studied in solution culture experiments with bush beans (Phaseolus vulgaris L. C.V. Improved Tendergreen). All, but in varying degrees, tended to concentrate in roots with a decreasing gradient to stems and leaves. Cobalt was one of the more mobile of the five trace metals. Its toxicity was expressed as severe chlorosis; 43 (with 10‐5 M) and 142 (with 10‐4 M) μg Co/g dry weight in leaves resulted in severe chlorosis. Vanadium as 10‐4 M vanadate resulted in smaller plants but not in chlorosis. Leaf, stem, and root V, respectively, were 13, 8, and 881 μg/g dry weight. Titanium was somewhat mobile with considerable yield decrease at 10‐4 M; leaf, stem, and root Ti concentrations, respectively, were 202, 48, and 2420 μg/g. Symptoms were chlorosis, necrotic spots on leaves, and stunting. Silver was very lethal at 10‐4 M AgNO3; at 10‐5 M yields were greatly decreased, but plants were grown without symptoms. Leaf, stem, and root concentrations of Ag for this treatment, respectively, were 5.8, 5.1, and 1760 μg/g dry weight. Plants grown with 10‐5 N Cr2O7 were decreased in yield by about 25% with or without EDTA (ethylenediamine tetraacetic acid) while the same level of Cr2(SO4)3 was essentially without effect. For the two salts, the leaf, stem, root concentrations for Cr, respectively were 2.2 and 1.3, 0.7 and 0. 7, and 140 and 104 μg/g. Most of the trace metals studied here had interactions in the uptake and/or distribution of other elements.  相似文献   

9.
Abstract

In a field experiment conducted during three years in a sandy‐loam, calcareous soil, one aerobically digested sewage sludge (ASL) and another anaerobically digested sewage sludge (ANSL) were applied at rates of 400, 800, and 1,200 kg N/ha/year, and compared with mineral nitrogen fertilizer at rates of 0, 200, 400, and 600 kg N/ha/year in a cropping sequence of potato‐corn, potato‐lettuce, and potato, the first, second, and third year, respectively. Results showed that the highest values of soil extractable metals were obtained with aqua regia, whereas the lowest levels with DTPA. All metal (Zn, Cu, Cd, Ni, Pb, and Cr) gave significant correlations between metal extracted with the different extractants and metal loading applied with the sludges. The metal extractable ion increased over the control for Zn, Cu, Cd, Ni, Pb, and Cr extracted with DTPA, EDTA (pH 8.6) and 0.1 N HC1, for Zn, Cd, Ni, Pb, and Cr extracted with EDTA (pH 4.65) and AB‐DTPA, and for Zn, Cd, Ni, and Cr extracted with aqua regia. The level of metal‐DTPA extractable resulted highly correlated with that obtained by the other methods, except the Ni‐aqua regia extractable. The soil extractable elements which showed significant correlations with metals in plant were: Zn, Cu, Cd, and Ni in potato leaves, Cd, Ni, and Pb in corn grain, and Zn and Cd for lettuce wrapper leaves. In general, all the chelate based extractants (DTPA, EDTA pH 4.6, EDTA pH 8.6, AB‐DTPA) were equally useful as indicator of plant available metals in the soil amended with sludge.  相似文献   

10.
Abstract

The main objective of this study was to ascertain effects of some edaphic factors on the uptake and influence of Ni on plant growth sinee Ni is a common trace element contaminant as well as an important component of serpentine soils. Corn (Zea mays L. inbred Ys1/Ys1) was rown in Yolo loam soil amended to give soil pH values of 4.2, 5.6, 7.5, and 8.2. A level of 100 μg Ni/g soil was not toxic to the corn. Shoot concentrations of Ni increased as soil pH decreased for both application rates of Ni. A level of 250 μg Ni/g soil decreased yields more at soil pH below 7 than above 7. Iron, Zn, and Mn levels in shoots did not appear to be directly related to the Ni applications although Fe levels tended to increase as a result of smaller plant size. PI54619–5–1 soybeans (Glycine max L. ) were grown in soil at two different pH values (with and without CaCO3) and with and without a level of 1000 μg Ni/g added as the sulfate and thoroughly mixed with the soil and equilibrated for 1 month prior to transplanting the soybeans with and without application of a chelating agent, DTPA (diethylene triamine pentaacetic acid), commonly used to correct Fe deficiency in plants. Plants were killed in the soil of pH 6.2 when the 1000 μg Ni/g soil was added. The pH 7.2 soil decreased the toxicity of Ni. The DTPA had little effect on yields, but increased the amount of Ni in plants. Nickel decreased the Fe, Zn, Cu, and Mn concentrations of the plants. Stems contained less Ni than did leaves. In another experiment, EDTA (ethylenediamine tetraacetate) greatly increased Ni concentrations in bush beans (Phaseolus vulgaris L. C.V. Improved Tendergreen) and in barley (Hordeum vulgare L.C.V. Atlas 57) grown in Yolo loam soil, and simultaneously increased Fe concentrations. Lime (CaCO3 or MgCO3) decreased toxicity of Ni in bush beans. DTPA increased Ni transport in bush beans and increased the ratio of Ni in leaves to that in stems at soil pH 7.5 and 8.2, but not at pH 4.0 and 5.8.  相似文献   

11.
Abstract

Chloride (Cl) toxicity was suspected in corn (Zea mays L.) growing in a poorly‐drained Atlantic Coast Flatwoods soil where Cl toxicity of soybean {Glycine max (L.) Merr.} was a problem. Field and greenhouse research was conducted with rates of applied Cl in an effort to induce Cl toxicity in corn.

‘Trojan 114’ corn was grown in the greenhouse with Cl rates (KCl) of 0, 364, and 728 ug/g and in the field with rates of 0, 85, 170, and 340 kg/ha. Potassium sulfate (K2SO4) treatments were included to supply equivalent amounts of K as that in KCl.

Phytotoxicity of corn did not occur in greenhouse or field experiments with any fertilizer treatment. In the greenhouse Cl concentrations in 26‐day old corn plants grown in a poorly‐drained Flatwoods soil (Leefield sand ‐ arenic Plinthaquic Paleudult) for the 0 and 728 ug Cl/g treatments were 5.0 and 32.7 g/kg in shoots, 1.6 and 14.9 g/kg in ear leaves, and 1.3 and 16.5 g/kg in stalks, respectively. In the field, Cl treatments applied to corn grown in a poorly‐drained Flatwoods soil (Alapaha sand ‐ arenic Plinthic Paleaquults) were not as effective in increasing Cl concentrations in shoots and ear leaves as that for corn grown in a well‐drained soil (Tifton loamy sand ‐ thermic Plinthic Paleudult) apparently because of the greater amount of residual soil Cl in the poorly‐drained soil. Concentrations of Cl in shoots of corn receiving O and 340 kg Cl/ha were 3.8 and 18.0 g Cl/kg, respectively, for corn grown in the well‐drained soil and 16.1 and 18.0 g Cl/kg, respectively, for corn grown in the poorly‐drained soil. Grain yields were not affected by fertilizer treatments on either soil and Cl concentration in grain for corn grown in the Tifton soil was not different among treatments. These data indicate that corn is not very susceptible to high levels of soil Cl.  相似文献   

12.
Abstract

Lvcium andersonii A. Gray is an accumulator of Li. Assays were made of 200 samples of it collected from six different locations within the Northern Mojave Desert. Mean concentrations of Li varied from location to location and tended not to follow loge normal distribution, and to follow a normal distribution only poorly. There was some negative skewness tp the loge distribution which did exist. The results imply that the variation in accumulation of Li depends upon native supply of Li. Possibly the Li supply and the ability of L. andersonii plants to accumulate it are both loge normally distributed. The mean leaf concentration of Li in all locations was 29 μg/g, but the maximum was 166 μg/g.  相似文献   

13.
Abstract

Radlands Crimson strawberries were grown in a glasshouse with 7 rates of applied boron. Wood shavings mulches with different boron concentrations were also applied as separate treatments. Boron toxicity symptoms were produced in leaves by boron rates of 0.32 kg ha‐1 and greater on a soil containing 1.6 ug B g‐1 of hot water extractable boron. Concentrations greater than 123 μg B g‐1 in old leaves were associated with boron toxicity symptoms.

In the B rate experiment, soil boron concentrations greater than 1.9 μg B g‐1 soil were associated with leaf toxicity symptoms which increased in severity with increasing soil boron concentrations up to 4.1 μg B g‐1 soil. Wood shavings mulch containing 17 μg B g‐1 caused boron toxicity symptoms in older leaves whereas mulches containing less than 6 μg B g‐1 did not produce toxicity symptoms.  相似文献   

14.
Abstract

Barley, Hordeum vulgare L., is extremely sensitive to excess soluble or exchangeable aluminum (Al) in acid soils having pH values below about 5.5. Aluminum tolerant cultivars are needed for use in rotations with potatoes which require a soil pH below 5.5 for control of scab disease. They are also potentially useful in the currently popular “low input, sustainable agriculture (LISA)”; in which liming even the plow layer of soil is not always possible or cost effective, or in situations where surface soils are limed but subsoils are acidic and Al toxic to roots. Ten barley cultivars were screened for Al tolerance by growing them for 25 days in greenhouse pots of acid, Al‐toxic Tatum subsoil (clayey, mixed, thermic, typic Hapludult) treated with either 750 or 4000 μg?g‐1 CaCO3 to produce final soil pH values of 4.4 and 5.7, respectively. Based on relative shoot dry weight (weight at pH 4.4/weight at pH 5.7 X 100), Tennessee Winter 52, Volla (England), Dayton and Herta (Denmark) were significantly more tolerant to the acid soil than Herta (Hungary), Kearney, Nebar, Dicktoo, Kenbar and Dundy cultivars. Relative shoot dry weights averaged 28.6% for tolerant and 14.1% for sensitive cultivar groups. Comparable relative root dry weights were 41.7% and 13.7% for tolerant and sensitive cultivars, respectively. At pH 4.4, Al concentrations were nearly three times as high in shoots of sensitive cultivars as in those of the tolerant group (646 vs. 175 μg?g‐1), but these differences were reduced or absent at pH 5.7. At pH 4.4, acid soil sensitive cultivars also accumulated phosphorus concentrations that were twice as high as those in tolerant cultivars (1.2% vs. 0.64%). At pH 5.7, these P differences were equalized at about 0.7% for both tolerant and sensitive groups. At pH 4.4, shoots of the Al‐sensitive cultivar Nebar contained 1067 μg?g‐1 Al and 1.5% P. Concentrations of Al and P in the shoots of acid soil sensitive cultivars grown at pH 4.4 exceeded levels reported to produce toxicity in barley. The observed accumulation of such concentrations of Al and P in the shoots of plants grown under Al stress is unusual and deserves further study.  相似文献   

15.
Abstract

A 9‐kg quantity of Yolo loam soil was contaminated in sequence with (In μg/g soil) 100 Cd, 100 Zn, 100 Co, 12.5 Li, and 100 Ni. Corn (Zea mays L. C. V. Golden Cross N. C. ) was grown together in the soil for 22 days from seed. Seventy‐two harvested plants were assayed separately. Several different trace metals were tested for normal and loge frequency distribution patterns. Some followed loge normal distribution more closely than a normal distribution as indicated by kurtosis values. Two followed normal distribution more closely than loge normal distribution. Some negative skewness was observed with the loge normal distribution, but only that for Co was significant. The yields of the plants were significantly and negatively correlated with the concentrations of Ni, Co, Cu, and Cd in shoots. Stepwise regression analysis indicated that it was reasonably Possible to determine which of the trace metals of the mixture caused phytotoxicity. Some pairs of trace metals were highly and positively correlated: Zn‐Cu, Zn‐Cd, Cu‐Cd, Mn‐Li, Co‐Ni, Co‐Cd are examples. The mixed trace metals decreased shoot concentrations of P and Mo and increased Al and Ti relative to control plants not receiving added metals. The Si was also decreased by trace metals and was positively related to yields.  相似文献   

16.
Abstract

Because farmers use mixtures of leaves and stems as a soil amendment, data of leaves, stems, and a leaf/stem mixture of Indigofera constricta and Mucuna pruriens from a 20‐week litterbag study were analyzed to assess their decomposition, nutrient release, and possible interactions within mixtures. Decomposition and nitrogen (N)–release patterns were leaves≥mixtures≥stems, whereas phosphorus (P)–release patterns were the opposite (P<0.05). Leaves released 110–130 Kg N ha?1, and mixtures released 30% less. A similar ratio was obtained for P release. This suggests that nutrient release from leaf/stem mixtures is overestimated when only leaves are considered. Decomposition and nutrient‐release patterns of mixtures occasionally differed from estimated patterns by 2–5% (P<0.05), indicating that minor interactions took place. However, estimations based on the amount of released nutrients generally showed non significant interactions. This suggests that the impact of low‐magnitude interactions within mixtures during its decomposition on soil fertility are negligible when considering total nutrient release.  相似文献   

17.
Abstract

Mature leaves of naturally occurring Jatropha curcas plants and soils samples were collected from four different populations to determine the soil characteristics, soil‐available nutrients, and leaf nutrient contents. This study provides a reliable account of the endogenic concentrations of nutrients present in jatropha leaves. Soil manganese [diethylenetriamine pentaacetic acid (DTPA)‐Mn] was the only soil‐available nutrient significantly correlated with its content in the plant. Relationships between soil characteristics, available nutrient in soil, and their content in plant leaves were also attempted.  相似文献   

18.
ABSTRACT

Phosphorus (P) efficiency (shoot dry weight at low P/shoot dry weight at high P) of a cultivar is the ability to produce a high yield in a soil that is limited in that element for a standard genotype. The large variation in P efficiency of different crops provides opportunities for screening crop species that perform well on low phosphorus soil. To explain the differences in P efficiency of sunflower (Helianthus annuus L.) cultivars a glasshouse pot experiment was conducted by using P-deficient soil [0.5 M sodium bicarbonate (NaHCO3)-extractable P 8.54 mg kg?1] treated with 0 (low P) and 100 mg P kg?1 soil (high P). The relationship between P efficiency and P, calcium (Ca), iron (Fe), zinc (Zn), and manganese (Mn) nutrition and anthocyanin accumulation was investigated in ten sunflower cultivars. Phosphorus deficiency resulted in significant decreases in the shoot and root yield. Phosphorus-efficient cultivars have the ability to produce higher yield than the inefficient cultivars in a limited P conditions. Our results showed that P-efficient cultivars had lower P concentrations, but higher P content in low P conditions. Phosphorus-efficient cultivars also have lower Ca and Fe concentrations in low P conditions but not in P-sufficient conditions. Applied P resulted in significant decreases in Zn concentrations in the shoots of the cultivars. Anthocyanin concentrations showed an accumulating pattern in all cultivars under P deficiency. The results demonstrated that phosphorus efficiency of the sunflower cultivars depends on their ability to produce higher yield and take up more P, and lower the concentration of Ca and Fe in shoots under low P conditions.  相似文献   

19.
This study determines the impact of biochar, as a supplement, on soil nutrient availability and yields for three crops within commercial management systems in a temperate environment. Central to the suggestion of biochar benefits is an increase in soil nutrient availability, and here, we test this idea by examining crop nutrient uptake, growth and yields of field‐grown spring barley, strawberry and potato. Biochar produced from Castanea sativa wood was incorporated into a sandy loam soil at 0, 20 and 50 t/ha as a supplement to standard crop management practice. Fertilizer was applied normally for each of the three crops. The biochar contained substantial concentrations of Ca, Mg, K, P, but only K occurred at high concentration in water‐soluble analysis. The large concentration of extractable K resulted in a significant increase of extractable K in soil. The increased availability of K in biochar‐treated soil, with the exception of spring barley grain and the leaves of strawberry during the second year, did not induce greater tissue concentrations. In general, biochar application rate had little influence on the tissue concentration of any nutrient, irrespective of crop or sampling date. There was, however, evidence of a biochar‐induced increase in tissue Mo and a decrease in Mn, in strawberry, which could be linked to soil alkalinization as could the reduction in extractable soil P. These experiments show a single rotational application of biochar to soil had no effect on the growth or harvest yield of any of these field‐grown crops. Heavy metal analysis revealed small concentrations in the biochar (i.e. <10 μg/g biochar), with the largest levels for Ni, V and Cu.  相似文献   

20.
Abstract

The tolerance of rice (Oryza sativa L. C.V. Earlirose) to various trace metal excesses was tested to determine if high levels of the trace metals found in some field‐grown plants were at toxicity levels. In one experiment, levels of 2200 μg Zn/g dry weight, 44 μg Cu/g dry weight, 4400 μg Mn/g dry weight, and 32 μg Pb/g dry weight in shoots of young plants had no adverse effects on vegetative yields. A level of 3160μgZn/ g dry weight decreased yields about 40% (P = . 05). In another test 51 μg Cu/g dry weight or 94 μg Pb/g dry weight did not decrease vegetative yields. Boron supplied at 10‐3 MH3BO3 not only caused no toxicity but resulted in only 144 μg B/g dry weight in shoots. Root levels of Zn were about equal to those in shoots; Mn levels were lower in roots than in shoots (1/4 to 1/10); B levels were generally low in both shoots and roots with roots 1/10 that of shoots; Cu levels were higher in roots than in shoots. Rice was tolerant of a high level of Cr. The tolerance of rice to high levels of some trace metals in these experiments may be related to high P levels in plants.  相似文献   

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