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1.
Two genotypes of Old world bluestems from the species Bothriochloa intermedia (R. Br.), A. Camus, shown earlier to differ in tolerance to acid, Al‐toxic Tatum subsoil at pH 4.1, were characterized further with respect to growth in pots of Tatum soil over a wider pH range and tolerance to Al in nutrient solutions. The two genotypes studied were acid‐soil tolerant P. I. 300860 (860) and acid soil sensitive P. I. 300822 (822).

The soil experiment confirmed earlier rankings of acid soil tolerance in these two genotypes. For example, with 0, 375 or 750 ug CaCO3 g‐1 soil (final pH 4.0, 4.3 and 4.6), the 860 genotype produced significantly more dry top weight than 822, but these differences were precluded with 1500 or 3000 ug g‐1 CaCO3 added (pH 4.7 and 5.4). At pH 4.3 and 4.6, the root dry weights of the two genotypes were also significantly different and weights were equalized at pH 4.7 and 5.4. The 860 genotype made fairly good top growth (67% of maximum) at pH 4.3 and a soil Al saturation of 63%; this situation was lethal for 822. When grown in greenhouse pots, the acid‐soil tolerant 860 genotype required only about one fourth as much CaCO3 as 822 to produce good growth of forage on acid Tatum subsoil. If confirmed under field conditions, such a difference could be economically significant in reclaiming acidic marginal land and in producing forage at low cost.

Differential Al tolerance in the two genotypes was confirmed in nutrient solutions. For example, with 8 mg Al L‐1 added, both top and root dry weights of 860 were significantly higher than those of 822, but with no Al added, these growth differences disappeared.

Mineral analyses of plants did not shed much light on mechanisms of differential acid soil or Al tolerance. For example, Al concentrations in plant tops associated with toxicity varied from 33–43 ug g‐1 in nutrient solutions containing Al to 119–283 ug g‐1 in acid soil It appears that elucidation of Al‐adaptive mechanisms will require physiological and biochemical studies at the cellular level.  相似文献   

2.
Alleviation by calcium (Ca) of inhibition of soybean [Glycine max (L.) Merr. cv. ‘Ransom'] root elongation by hydrogen (H) and aluminum (Al) was evaluated in a vertical split‐root system. Roots extending from a limed and fertilized soil compartment grew for 12 days into a subsurface compartment containing nutrient solution with treatments consisting of factorial combinations of either pH (4.0, 4.6, and 5.5) and Ca (0.2, 2.0, 10, and 20 mM), Al (7.5, 15, and 30 μM) and Ca (2.0,10, and 20 mM) at pH 4.6, or Ca (2, 7, and 12 mM) levels and counter ions (SO4 and Cl) at pH 4.6 and 15 μM Al. Length of tap roots and their laterals increased with solution Ca concentration and pH value, but decreased with increasing Al level. Length of both tap and lateral roots were greater when Ca was supplied as CaSO4 than as CaCl2, but increasing Ca concentration from 2 to 12 mM had a greater effect on alleviating Al toxicity than Ca source. In the absence of Al, relative root length (RRL) of tap and lateral roots among pH and Ca treatments was related to the Ca:H molar activity ratio of solutions (R2≥0.82). Tap and lateral RRL among solutions with variable concentrations of Al and Ca at pH 4.6 were related to both the sum of the predicted activities of monomeric Al (R2≥0.92) and a log‐transformed and valence‐weighted balance between activities of Ca and selected monomeric Al species (R2≥0.95). In solutions with 15 μM Al at pH 4.6, response of tap and lateral RRL to variable concentrations of CaSO4 and CaCl2 were related to predicted molar activity ratios of both Ca:Al3+ (R2≥0.89) and Ca:3 monomeric Al (R2≥0.90), provided that AISO4 and AI(SO4)2 species were excluded from the latter index. In all experiments H and Al inhibited length of lateral roots more than tap roots, and a greater Ca:H or Ca:Al concentration ratio was required in solutions to achieve similar RRL values as tap roots.  相似文献   

3.
Abstract

Precipitation of Al(OH)3 and aluminum phosphate may occur in nutrient solution if a large amount of Al and P have been added to a relatively high pH. The objective of this study was to develop and test a supernatant‐solution method for Al phytotoxicity studies with large and/or old plant seedlings. Effects of pH and additions of Al and P on ionic strength and concentrations of Al and P in supernatant nutrient solutions were investigated. Two sets of supernatant nutrient solutions at two pH levels were prepared. The pH 4.0 set and 4.5 set contained seven levels of Al (maximum Al concentration of 6355 and 378 μM) and similar P concentration about 32 and 6 μM P, respectively. The Al concentrations in supernatant solutions were dependent on preparation procedure. The pH 4.0 set was tested in the greenhouse study with 6‐month‐old citrus seedlings and found to be successful as culture solutions for Al phytotoxicity studies. These two sets are suitable for growth of large (about 0.3 m) and/or old (about 6 mon.) seedlings. This supernatant‐solution method makes it possible to study Al phytotoxicity of large and/or old seedlings, to avoid the confounding effects of P on Al with respect to plant growth, and to report the actual concentrations of Al and P in growth solutions.  相似文献   

4.
Kentucky bluegrass, Poa pratensis L., is generally regarded as an acid‐soil‐sensitive species. However, previous studies in our laboratory showed that cultivars within the species differed widely in tolerance to acid Tatum subsoil (pH 4.6) which is used routinely to screen plants for aluminum (Al) tolerance. In the early studies, specific differential Al tolerance was not demonstrated. The objective of the current study was to test the hypothesis of differential Al tolerance more precisely in nutrient solutions. In one experiment, acid‐soil‐tolerant Victa and Fylking and acid‐soil‐sensitive Windsor and Kenblue cultivars were grown for 35 days in nutrient solutions containing 0, 2, 4, 6, 12, and 24 mg Al L‐1, at initial pH 4.5, with no subsequent adjustment. In a second experiment, Victa and Windsor were grown for 30 days in solutions containing 0, 4, and 6 mg Al L‐1, at initial pH 4.5, with no further adjustment. For Victa and Windsor, tolerance to Al in nutrient solution corresponded with tolerance to acid Tatum subsoil, however, the cultivar difference in tolerance, based on relative root dry weight, was only about 2‐fold, compared with 20‐fold in acid Tatum subsoil. Fylking and Kenblue cultivars, which showed a wide difference in tolerance to acid Tatum subsoil, did not show distinct differences in tolerance to Al in nutrient solutions. Possible reasons for this discrepancy are discussed. Superior Al tolerance of Victa (compared with Windsor) was associated with a greater plant‐induced increase in the pH of its nutrient solutions and a corresponding decrease in concentrations of soluble Al in the filtered solutions at the end of the experiments. Greater Al sensitivity in Windsor (compared with Victa) was not related to reduced uptake of phosphorus (P) or excessive uptake of Al; neither cultivar accumulated appreciable Al concentrations in its shoots. The observed differential acid soil and Al tolerance among bluegrass cultivars appears worthy of further study. Improved understanding of Al tolerance mechanisms would contribute to fundamental knowledge of plant mineral nutrition and could aid plant breeders in tailoring plants for greater tolerance to acid subsoils.  相似文献   

5.
Five winter cultivars of Triticum aestivum L., representing a known range of tolerance to aluminum (Al), were grown in nutrient solutions with and without Al for 41 days to determine long‐term changes in solution pH. Plant‐induced pH of the nutrient solutions declined for 16 to 17 days. Subsequently, the pH induced by Al‐sensitive plants grown without Al and Al‐tolerant plants grown with Al and without Al increased rapidly, presumably reflecting depletion of NH4 + from the nutrient solutions. Aluminum‐sensitive plants grown with Al showed a less pronounced pH rise after 16 to 17 days of treatment.

After nutrient solutions were renewed on days 26 and 34, plant‐induced pH patterns were similar to those during days 1 to 26. However, the time required for the onset of the rapid rise in pH decreased. In these subsequent pH cycles, the pH patterns induced by Al‐tolerant plants grown with Al progressively approximated those induced by plants grown without Al. Aluminum‐sensitive plants grown with Al did not induce a rapid rise In pH of nutrient solutions.

Differential tolerance to Al was apparent visually after three to five days growth. Cultivar tolerance to Al was correlated with the initial rate of the pH decline (days 1 to 26) as well as final pH of solutions discarded on days 26, 34, and 41. These results support the hypothesis that differential uptake of NH4 + and NO3 ‐ causes cultivar differences in plant‐induced pH of nutrient solutions and affects the relative growth of cultivars in Al‐toxic nutrient solutions.  相似文献   


6.
Aluminum (Al) plant tolerance has been frequently associated with a pH increase in the rhizosphere. The changes in pH are dependent on plant genotypes and ionic composition and strength of nutrient solutions. This work was performed in order to study in triticale (Triticosecale Wittm.) the association of pH change with nitrogen (N) uptake and growth performance in acid conditions. Three‐day‐old seedlings were treated with Al (185 μM) in solutions having different proportion nitrate/ammonium (NO3/NH4), 15/1 and 8/1, but the same total N content. Along the period with Al treatment, several measurements have been made: pH, every day; NO3 and NH4 uptake from the solution as well as shoot and root biomass production every two days (five and seven days of plant age). The maximum growth inhibition (30%) of fresh weight was found in roots of plants in the 15/1 (NO/NH,) nutrient solution. The presence of a higher proportion of NH4 (8/1 solution) had a protective effect on Al damage as shown by less growth inhibition and less reduction in NO3 uptake. Changes in pH apparently were not relevant for the tolerance. The results suggest that NH4 fertilization may be useful for alleviating Al toxicity in triticale.  相似文献   

7.
Abstract

Four ryegrass (Lolium multiflorumLam.) cultivars were grown in 1/5 Steinberg nutrient solution supplemented with six Al levels (0, 37, 74, 148, 296, or 592 umol L‐1) at pH initially adjusted to 4.2. Average net Fe influx was stimulated at low nutrient solution Al levels. This stimulation was larger for more Al‐tolerant cultivars Marshall and Gulf. Decreases in average net Mn and Zn influxes were brought about by increasing Al levels in the nutrient solution. The average net influx of Fe, Mn, and Zn was positively correlated with the root tolerance index (relative root yield of plants grown with and without Al added to the nutrient solution). For more Al‐tolerant cultivars, increased total uptake of Fe and Cu was brought about by increased nutrient solution Al levels up to 74 umol L‐1. Decreases in total uptake of Mn and Zn were generally noted with increased nutrient solution Al levels. Percentage inhibition of total Fe, Mn, Zn, and Cu uptake was negatively correlated with the mean pH of the Al‐containing nutrient solutions. The higher average net influx and the smaller percentage inhibition of total Fe uptake at nutrient solution Al levels up to 74 umol L‐1can be used as indicators in ranking ryegrass cultivars as more Al‐tolerant  相似文献   

8.
Aluminum (Al) has many detrimental effects on plant growth, and shoots and roots are normally affected differently. A study was conducted to determine differences among sorghum [Sorghum bicolor (L.) Moench] genotypes with broad genetic backgrounds for growth traits of plants grown at 0,200,400,600, and 800 μM Al in nutrient solutions (pH 4.0). Genotypes were categorized into “Al‐sensitive”, “intermediate Al‐tolerant”, “Al‐tolerant”, and SC 283 (an Al‐tolerant standard). As Al increased, shoot and root dry matter (DM), net main axis root length (NMARL), and total root length (TRL) became lower than controls (0 Al). Aluminum toxicity and/or nutrient deficiency symptoms become more severe, and shoot to root DM ratios and specific RL (TRL/root DM) values also changed as Al in solution increased. Root DM had greater changes among genotypes than shoot DM, and NMARL at 400 μM Al, and TRL at 200 μM Al had greater differences among genotypes than root DM, ratings for toxicity and/or deficiency symptoms, and other DM and RL traits. The wide differences among genotypes for NMARL and TRL could be used more effectively to evaluate sorghum genotypes for tolerance to Al toxicity than the other growth traits.  相似文献   

9.
The effect of elevated nitrate [(NO3‐nitrogen (N)] or ammonium (NH4)‐N on the response of nonmycorrhizal (NM) and ectomycorrhizal (ECM) pitch pine (Pintis rigida Mill.) seedlings to aluminum (Al) was determined in experiments in which N was increased three times above ambient levels. Seedlings with and without the mycorrhizal fungus Pisolithus tinctorius (Pers.) Coker & Couch were grown in sand irrigated with nutrient solution (pH 3.8) containing 0, 10, or 20 mg Al L‐1 (0, 370, or 740 μM Al). The nutrient solution simulated that for the sandy, nutrient‐poor soil of the New Jersey Pine Barrens. Elevated NO3‐N had no significant effect on Al toxicity in NM seedlings, but Al toxicity at ambient NH4‐N was ameliorated by elevated NH4‐N. Symptoms of Al toxicity in roots (thick and stunted) of ECM seedlings at ambient N levels were reduced by elevated NH4‐N and absent at elevated NO3‐N. When N was elevated by an increase in NO3‐N or NH4‐N, uptake of N and relative increases in total biomass were greater in ECM than in NM seedlings.  相似文献   

10.
Forty genotypes representing maize genetic diversity from the Island of Madeira were screened for resistance to aluminum (Al) in nutrient solution. Seeds of maize were obtained from local farmers from field plots spread around the island in a range of altitudes from 99 to 1000 m above sea level. The content of ionic aluminum and the pH of soils cultivated with maize were determined. The mean pH value of all examined soils was 4.9, while the mean ionic Al content was 0.76 cmol kg–1. Seventy‐two hours (h) exposure to 100 and 200 μM Al followed by a 48 h recovery period of 4‐day old seedlings revealed significant differences in Al resistance in the Madeiran maize germplasm. Root survival and regrowth exceeding 80 % of the seedlings were observed in 22 and 8 of the tested genotypes screened at 100 and 200 μM Al in nutrient solution. High Al resistance among Madeiran maize genotypes appeared not to be associated with the lower pH of soil, and did not correlate with the amount of soil Al3+ or the altitude at the site of collection. The high level of Al resistance of the maize cultivars indicates an initial genetic trait enhanced by open pollination of maize.  相似文献   

11.
Ten‐day‐old seedlings of four cowpea (Vigna unguiculata Walp) genotypes were subjected to six levels of aluminum (Al) (0, 74, 148, 222, 296, and 370 μM/L) to test their tolerance to Al toxicity in a nutrient solution at pH 4.0±0.1. Seedlings were grown in the presence of Al under controlled environmental conditions in a growth chamber. The nutrient solutions were replenished once a week. After 20 days, treatments were terminated and the differences in their growth patterns were compared. Standard growth parameters, such as plant growth, dry matter production, relative growth reduction in roots (RGRS) and shoots (RGRS), and root and shoot tolerance indices (RTI and STI) have been used as markers of Al toxicity. The cowpea genotypes studied exhibited a wide range of responses in their tolerance to Al. Though the genotypes were subjected to six levels of Al, a good degree of separation in their responses was observed only at the 222 μM Al/L treatment level. Therefore, this concentration was chosen to treat and compare the performances of the genotypes. The genotype Co 3 showed an increase in growth, while Paiyur 1 and other genotypes showed severe inhibitions in the presence of Al. Furthermore, for RTI and STI, Co 3 also registered its tolerance to Al by showing increased ratios in the presence of Al. Whereas, Paiyur 1 recorded severe reductions. The RGRR and RGRS data also substantiates this finding. Based on the growth parameters, the four cowpea genotypes were ranked based on their tolerance to Al: Co 3 > Co 4 > KM > Paiyur 1. Co 3 was the most Al‐tolerant genotype which performed extremely well in the presence of Al, while Paiyur 1was the most Al‐susceptible genotype. Therefore, the Al‐tolerant genotype can be used for future breeding programmes to produce Al‐tolerant genotypes, subsequently, can be recommended for acidic infertile soils in the tropics.  相似文献   

12.
Some plants respond to Fe‐deficiency stress by inducing Fe‐solubilizing reactions at or near the root surface. In their ability to solubilize Fe, dicotyledonous plants are more effective than monocotyledonous plants. In this study we determined how representative plants differ in their response when subjected to Fe‐deficiency stress in a calcareous soil and in nutrient solutions. Iron‐inefficient genotypes of tomato, soybean, oats, and corn all developed Fe chlorosis when grown in soil, whereas Fe‐efficient genotypes of these same species remained green. The same genotypes were grown in complete nutrient solutions and then transferred to nutrient solutions containing N (as NO3 ‐) and no Fe.

The T3238 FER tomato (Lycopersican esculentum Mill.) Fe‐efficient) was the only genotype that released significant amounts of H from the roots (the pH was lowered to 3.9) and concomitantly released reductants. Under similar conditions, Hawkeye soyhean [Glycine max (L.) Merr.] released reductants but the solution pH was not lowered. Both Fe‐inefficient and Fe‐efficient genotypes of oats (Avena sativa L.) and corn (Zea mays L.) released insufficient H or reductant from their roots to solubilize Fe; as a result, each of these genotypes developed Fe‐deficiency (chlorosis).

The marked differences observed among these genotypes illustrate the genetic variability inherent within many plant species. A given species or genotype may accordingly not be adapted to a particular soil. Conversely, a given species or genotype may be found (or developed) that is precisely suited for a particular soil. In this event, the need for soil amendments may be reduced or eliminated.  相似文献   

13.
Standard white oat genotypes were subjected to different methods and aluminum (Al) levels under hydroponic conditions to verify the relationship between plantlet characteristics and their Al tolerance using multivariate analyses. A completely randomized design with three replications was used, adopting three evaluation protocols: “complete nutrient solution” with 0, 8, 16, and 32 mg L?1 of Al supplied as aluminum sulfate [Al2(SO4)3·18H2O]; “complete nutrient solution” with 0, 8, 16 and 32 mg L?1 of Al supplied as aluminum chloride (Al2Cl3?6H2O); and the “minimum nutrient solution” with 0, 1, 3, and 5 mg L?1 of Al supplied as Al2Cl3?6H2O. The performance of white oat plantlet genotypes subjected to excess Al in hydroponic conditions is greatly associated with root length, where the nutrient solution composition and the Al sources interfere in these associations. The study based on the joint analysis of characteristics at plantlet level does not allow an efficient discrimination of Al-tolerant and Al-sensitive white oat genotypes.  相似文献   

14.
Abstract

Growing evidence of positive crop responses to gypsum or phosphogypsum (PG) application in acid soils strongly support the use of these amendments as an ameliorant of subsoil acidity. Although gypsum improves Ca availability in subsoils, its role in alleviation of Al toxicity needs careful attention. In the current study, either PG, CaSO4.2H2O or CaCl2.2H2O was added (to supply 12 mM Ca) to solutions containing 40 μM Al at pH 4.1 + 0.1. Solution pH was gradually raised to 4.5, 4.8 and then to 5.3 at various time intervals during 25 d aging of the solutions at 25 + 1OC.

Concentration of Al measured by aluminon method without preacidification and preheating, referred to as “reactive Al”; in this paper, was 16 μM in 2 g L‐1PG solution without added Al. This accounted 38% of total soluble Al in PG solution. Addition of 2 g L‐1PG to solution containing 40 μM Al, resulted in only 42% of total Al in solution present in forms reactive with aluminon. According to MINTEQ speciation model, Al in solution was present as an entirely complexed form with F‐. An increase in solution pH up to 5.3 had no effect on measured concentration of reactive Al or predicted distribution of Al species.

Addition of CaSO4.2H2O to 40 μMAl solutions had no effect on the concentration of reactive Al within pH 4.1 ‐4.8, however, up to 62% of total Al was in a form complexed with SO4 2‐, as predicted by MINTEQ model. The concentration of reactive Al decreased by 60% at pH 5.3. Addition of CaCl2.2H2O also had no effect on the concentration of reactive Al within pH 4.1 ‐ 4.8. Nearly 73 ‐ 94% of total Al was present in Al3+form. An increase in pH to 5.3, decreased the concentration of reactive Al by 27%. The results suggest that ion‐pairing of Al with F‐would appear to be a possible mechanism for alleviation of Al toxicity by PG at pH range 4.1 ‐ 5.3. With regard to CaSO4.2H2O, at pH 4.1 ‐ 4.8 ion‐pairing with SO.4 2‐appears to be possible mechanism for the alleviation of Al toxicity. In addition, at pH 5.3 a considerable decrease in reactive Al was evident which would further alleviate Al toxicity.  相似文献   

15.
Common bean (Phaseolus vulgaris L.) proved to be very sensitive of low pH (4.3), with large genotypic differences in proton sensitivity. Therefore, proton toxicity did not allow the screening of common bean genotypes for aluminium (Al) resistance using the established protocol for maize (0.5 mM CaCl2, 8 μM H3BO3, pH 4.3). Increasing the pH to 4.5, the Ca2+ concentration to 5 mM, and addition of 0.5 mM KCl fully prevented proton toxicity in 28 tested genotypes and allowed to identify differences in Al resistance using the inhibition of root elongation by 20 μM Al supply for 36 h as parameter of Al injury. As in maize, Al treatment induced callose formation in root apices of common bean. Aluminium‐induced callose formation well reflected the effect of Ca supply on Al sensitivity as revealed by root‐growth inhibition. Aluminum‐induced callose formation in root apices of 28 bean genotypes differing in Al resistance after 36 h Al treatment was positively correlated to Al‐induced inhibition of root elongation and Al contents in the root apices. However, the relationship was less close than previously reported for maize. Also, after 12 h Al treatment, callose formation and Al contents in root apices did not reflect differences in Al resistance between two contrasting genotypes, indicating a different mode of the expression of Al toxicity and regulation of Al resistance in common bean than in maize.  相似文献   

16.
Aluminum (Al) toxicity to plants in complete nutrient solutions is difficult to relate to Al activity in solution because of precipitation and complexation. Aluminum toxicity was studied for two seedling crops, sorghum (Sorghum bicolor L. Moench) and wheat (Triticum aestivum L. em Thell), at low levels (≤10 μM) in two incomplete nutrient solutions to study plant response to Al alone, Al+PO4 3‐, Al+OH‐, and Al+PO4 3‐+OH‐. Relative root length was the bioassay for Al toxicity. ‘Monomeric’ Al was measured using Aluminon and both root length and measured Al were compared to the theoretical Al in solution predicted by the MINTEQA2 equilibrium model.

Low levels of Al were toxic to plant roots with sorghum showing a decrease in relative root length from 1 to 10 μM Al, and wheat showing a decrease from 4 to 10 μM. A mono‐salt background solution (400 μM CaCl2) and a more complex base solution (CaCl2, KNO3, and MgCl2) gave similar root lengths and measured Al values. Phosphate and hydroxyl ameliorated Al toxicity and lowered measured Al in solution, but not to the extent predicted by the model. Adding phosphate (PO4 3‐) or hydroxyl (OH‐) raised the pH, but again not as high as the model predicted. The difference in toxicity and measured Al were most likely the result of polymers (Al+3) which are toxic, but not measured by the procedure used, or included in the model which showed the Al as being removed from solution by precipitation.  相似文献   

17.
Abstract

Considerable uncertainty prevails concerning a suitable measure that can adequately describe Al phytotoxicity in nutrient and soil solutions. A study was conducted to evaluate the ability of a modified aluminon technique to discriminate between phytotoxic and non‐phytotoxic Al in solutions containing 80 μM Al with varying levels of CaSO4(625 to 10000 μM), at two pH levels (4.2 and 4.8). The concentration of Al measured by the modified aluminon technique ranged from 18.3 to 77.7 μM,thereby indicating substantial polymerization in some of the solutions. The greatest amount of polymerization occurred at pH 4.8 in the presence of 625 μM CaSO4. Increasing additions of CaSO4resulted in an increase in predicted activity of AlSO4 +at both pH levels. However, with increasing addition of CaSO4, the predicted activity of Al3+decreased at pH 4.2 or remained relatively constant at pH 4.8. The relationship between the sum of predicted activities of monomeric Al (SaAl mono.) in solution and tap root length of soybean [Glvcine max(L.) Merr.] cv. Lee was extremely poor, thereby indicating the inability of the modified aluminon technique to measure phytotoxic Al in solutions employed in the current study. This difficulty was due to failure of the modified aluminon technique to exclude lesser phytotoxic AlSO4 +species. The activity of Al3+was closely related to tap root length (R2= 0.865). The prediction of root length response to Al was further improved (R2= 0.899) by considering the solution Al index as: S[3aA13+ + 2aAl(OH)2+ + aA1(OH)+]. There was a poor relationship between tap root length and the concentration of polymeric Al, thus suggesting the lower phytotoxicity of this component under the prevailing solution conditions.  相似文献   

18.
After a 35 days growth on nutrient solutions with NO‐ 3 NH4NO3 and NH+ 4 as nitrogen source (pH 4.2) dry matter yield of the sorghum genotype SC0283 was much less affected by Al (1.5 mg‐1) than that of the genotype NB9040. With NO‐ 3 as the sole nitrogen source only growth of the NB9040 plants was significantly reduced. Since OH‐ efflux, shoot Al content and concentrations of all major nutrients of both genotypes were almost equal, a higher sensitivity to Al may underlie the lower Al tolerance of the NB9040 genotype. In the presence of NH.‐N Al again lowered d.m. yield of the NB plants. With SCO283 significant Al effects on d.m. yield were observed only with NH4NO3. Aluminum drastically increased the amount of protons released per unit of root surface area, especially with the NB9040 line. This shift in proton flux density was partly the result of a decrease of the specific root surface area and partly due to enhanced excess of catlonic nutrients taken up. With NH4NO3‐fed plants the latter could almost completely be attributed to a changed N preference brought about by inhibited uptake of NO‐ 3 and a simultaneous enhanced NH, absorption. Although both proton efflux and NH+ 4 preference of the NB plants were severely increased by Al, relative yields of this genotype were not lowered by NH+ 4. This can probably be explained by (1) the high NH, sensitivity of this cultivar through which Al effects can be masked and (2) the continuous adjustment of the solution pH through which rhizosphere conditions were prevented.  相似文献   

19.
Aluminum tolerant oat cultivars are needed for use on acid soil sites where neutralization of soil acidity by liming is not economically feasible. Oat germplasm in Poland has not been examined for range of Al tolerance. Eleven Polish oat cultivars were screened for Al tolerance in nutrient solutions containing 0, 5 and 15 mg L‐1 Al. Three of these cultivars showing high to moderate tolerance to Al in nutrient solutions were also grown in greenhouse pots of soil and in field plots of soil over a pH range of 3.8 to 5.5 as determined in 1 N KC1.

The eleven oat cultivars differed significantly in tolerance to Al in nutrient solutions. Based on relative root yield (15 mg L‐1 Al/no A1%), the cultivars ‘Solidor’ and ‘Diadem’ were most tolerant and ‘Pegaz’ and ‘B‐20’ were least tolerant. For these three cultivars, the order of tolerance to acid soil agreed with the order of tolerance to Al in nutrient solution ‐ namely, Solidor > Diadem > Leanda. Hence, for these cultivars, the nutrient solution methods used appear adequate for selecting plants that are more tolerant to Al in strongly acid soils. Additional study is needed to assess the value of this method for screening a broad range of germplasm.

Superior tolerance of the Solidor cultivar to acid soil was associated with significantly higher concentrations of N in the grain. Hence, results suggest that selecting for acid soil or Al tolerance may increase N efficiency in oats.  相似文献   

20.
Previous studies showed that limpograss, Hemarthria altissima (Poir), Stapf & C. E. Hubb (PI 364344) was tolerant to low temperature and to high concentrations of Al in acid soil, mine spoil and nutrient solution. Additional experiments were conducted to test the tolerance of this limpograss clone to excess Mn, another potential growth‐limiting factor in acid soils.

Cuttings from a single plant were grown in pots of Mn‐toxic Zanesville soil with no lime (pH 5.1) and 1250 ppm CaCO (pH 6.3) and in nutrient solutions containing 0, 4, 8, 16, 32 or 64 ppm Mn at pH 4.0. The grass was highly tolerant to excess Mn in both media. Liming the soil from pH 5.1 to 6.3 did not significantly affect top dry weight of the first harvest and significantly decreased that of the second. In nutrient solutions at pH 4.0 top dry weights were not significantly affected by Mn concentrations up to 64 ppm. Root dry weights were significantly increased by Mn additions of 16, 32 and 64 ppm. Limpograss (PI 364344) was not injured when Mn concentrations were as high as 930 and 9152 ppm in tops and roots, respectively. High Mn tolerance is yet another trait that should enhance the potential use of this grass in revegetating acid mine spoils and other acid sites.  相似文献   


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