Al Concentration In Roots Research Articles

Influence of parent material and soil type on the root chemistry of forest species grown on acid soils

The dissimilarities in soil pH and in aqueous Ca/Al and Mg/Al molar ratios in acid forest soils derived from either granite (GR) or amphibolite (AMP) materials are expected to have an influence on the root chemistry of forest species. Samples were taken from the A 1 and A 3 horizons of three GR soils (Typic Dystrudepts), under stands of Quercus robur L., Pinus radiata D. Don., and Eucalyptus globulus Labill., whereas A 1 and B horizons were sampled from three nearby AMP soils (Lithic Hapludands, Andic Dystrudept) under the same tree species. Fine roots were sequentially extracted with NH 4Cl (1 M) and HCl (1, 10, and 10 mM), and also digested with HNO 3. The distribution of Ca, Mg, and Al at the root exchange sites was mainly related to aqueous Ca and Mg concentrations in the rhizosphere, which in turn, were related to the type of parent material. This was more evident in the deeper horizons where the effect of the mineral solid phase on the soil solution composition was more intense. The fraction of Ca-extractable with HCl comprised 36–51% of the sum of HCl and NH 4Cl-extractable Ca, and that of Mg comprised 49–76% of the sum of HCl- and NH 4Cl-extractable Mg. A large fraction of the Al was more strongly bound to the root in an HCl soluble form (78–92%). Values of total Al concentration in roots (after HNO 3 digestion) indicated that less Al accumulated in roots of the GR A 1 horizons than in those of AMP A 1 horizons. The GR A 1 horizons had a more acidic (pH<4.2) and Al-undersaturated organic matter, which may have negatively affected the precipitation of Al compounds in roots. The acid forest soils studied have provided us with an opportunity to investigate the influence of a range of soil solutions under natural conditions (varying in pH, Ca/Al, and Mg/Al) and to confirm previous findings obtained under greenhouse conditions.

Growth and nutrient uptake of ectomycorrhizal Pinus sylvestris seedlings in a natural substrate treated with elevated Al concentrations.

Models of the effects of elevated concentrations of aluminum (Al) on growth and nutrient uptake of forest trees frequently ignore the effects of mycorrhizal fungi. In this study, we present novel data indicating that ectomycorrhizal mycelia may prevent leaching of base cations and Al. Mycorrhizal and non-mycorrhizal Pinus sylvestris L. seedlings were grown in sand obtained from the B-horizon of a local forest. In Experiment 1, non-mycorrhizal seedlings and seedlings inoculated with Hebeloma cf. longicaudum (Pers.: Fr.) Kumm. ss. Lange or Laccaria bicolor (Maire) Orton were provided with nutrient solution containing 2.5 mM Al. Aluminum did not affect growth of non-mycorrhizal seedlings or seedlings inoculated with L. bicolor. Seedlings colonized by H. cf. longicaudum had the highest biomass production of all seedlings grown without added Al, but the fungus did not tolerate Al. Shoots of seedlings colonized by L. bicolor had the lowest nitrogen (N) concentrations but the highest phosphorus (P) concentrations of all seedlings. The treatments had small but significant effects on shoot and root Al concentrations. In Experiment 2, inoculation with L. bicolor was factorially combined with the addition of a complete nutrient solution, or a solution lacking the base cations K, Ca and Mg, and solutions containing 0 or 0.74 mM Al. Seedling growth decreased in response to 0.74 mM Al, but the effect was significant only for non-mycorrhizal seedlings. Mycorrhizal seedlings generally had higher P concentrations than non-mycorrhizal seedlings. Aluminum reduced P uptake in non-mycorrhizal plants but had no effect on P uptake in mycorrhizal plants. Mycorrhizal colonization increased the pH of the soil solution by about 0.5 units and addition of Al decreased the pH by the same amount. We conclude that the presence of ectomycorrhizal mycelia decreased leaching of base cations and Al from the soil.

Effect of water stress on aluminum toxicity in pitch pine seedlings

A decrease in soil water content during droughts may increase aluminum (Al) to concentrations that are toxic to the growth of trees. The effects of water stress (WS) on the response of ectomycorrhizal pitch pine (Pinus rigida Mill.) seedlings to aluminum was determined by growing seedlings in sand irrigated with nutrient solution (pH 3.8) containing 0, 5, or 10 mg L‐1 Al. Water stress was imposed for 41 days by withholding nutrient solution for five consecutive days each week. At harvest time, seedlings at high WS had 72% of mean gravimetric water contents of seedlings at low WS. Aluminum decreased growth of seedlings at high WS, but had no effect on growth of seedlings at low WS. Aluminum toxicity symptoms in roots (e.g., dark thickened tips) were observed at lower Al levels at high WS than at low WS. Stem dry weight was the only plant part decreased by water stress alone. Across Al levels, Al concentration in roots was higher at low WS than at high WS. Water stress alone reduced root [phosphorus (P), potassium (K), and calcium (Ca)] and foliar [P, K, and magnesium (Mg)] concentrations of mineral nutrients. Decreases of nutrients in roots with increasing Al was greater at low than at high WS. Calcium was the only foliar nutrient decreased by Al treatment.

Effects of aluminum toxicity on nutrient accumulation in maize shoots: Implications on photosynthesis

The physiological characterization of aluminum (Al) toxicity in C4 plants prompted this study, having maize (Zea mays cv. XL‐72.3) used as a test system. Two weeks after germination, maize plants were submitted to increasing Al concentrations (from 0 up to 81 mg L‐1) for 20 days in a growth medium with low ionic strength, after which several analyses were carried out. In root tissues, Al concentrations significantly increased between the 0 and the 81 mg L‐1 Al treatment. In the shoots nitrogen (N), phosphorus (P), and iron (Fe) significantly decreased with increasing Al concentrations, but at different rates. Magnesium (Mg) showed a tendency to decrease for Al treatments higher than 9 mg L‐1, the opposite occurring with manganese (Mn) contents. Chlorophyll a fluorescence parameters Fo and Fv/Fm showed non‐significant changes, while photosynthetic capacity, electron transport rate associated with photosystem I and cytochromes (cyt) f and b563 contents decreased above the 9 mg L‐1 Al treatment. Aluminum concentrations were correlated to phenol and quinone contents. In isolated chloroplasts, acyl lipid peroxidation increased continuously until the 81 mg L‐1 Al treatment, whereas ethylene production in intact leaves showed a sharp rise already for the 9 mg L‐1 Al treatment. Increasing Al concentrations significantly inhibited copper (Cu), zinc (Zn)‐SOD, catalase and glutathione reductase activities, whereas those of ascorbate peroxidase and dehydroascorbate reductase increased, in Al treatments with 9 mg L‐1 or higher. It was concluded that Al toxic effects in the shoot metabolism were mostly indirect, being mediated/modulated by the interactions between root Al concentrations and the concurrent inhibition of nutrients translocation mechanism(s). It was further concluded that an increasing production of chloroplastic hydroxyl radicals is coupled to the initial targets of Al mediated/modulated toxicity, being the intrachloroplastic production of H2O2, superoxide and singlet oxygen limited. It was also found, a decreased efficiency on the control of superoxide and H2O2 accumulation, since Cu,Zn‐SOD activity was ihibited and because the in vivo ascorbate peroxidase activity was limited by that of glutathione reductase. Additionally, as catalase activity was inhibited, the control of the concentration of photosynthetically‐generated H2O2 that might diffuse out of the chloroplast was also found to be less effective.

PH influence on root growth and nutrient uptake of Pinus pinaster seedlings

Two-week old Pinus pinaster seedlings were grown at four pH values ranging from 3.5 to 6.5. Root elongation rate progressively decreased with the duration of treatment at 3.5 and 6.5 pH. After 4 weeks 3.5 pH gron roots showed the lowest lenth and the highest biomass because of their marked thickening. The pH of the culture solution did not influence lateral root initiation, whereas it affected their length, that was highest at 3.5 pH and lowest at 6.5 pH. Mineral nutrition was affected by the pH of the culture solution. The P, Fe and Al concentration in roots was higher in the 3.5 pH and 4.5. pH solutions. On the contrary a lower K, Ca, Mg and especially Mn content of roots was measured in the 3.5 pH grown seedlings. These results suggest that P pinaster is able to grow on a wide range of acidic soils changing the morphology of the root system in relation to soil conditions.

Influence of phosphorus on the growth and ergot alkaloid content of Neotyphodium coenophialum-infected tall fescue (Festuca arundinacea Schreb.)

Tall fescue (Festuca arundinacea Schreb.) plants infected by the fungal endophyte Neotyphodium coenophialum (Morgan-Jones & Gams) (Glenn et al., 1996) often perform better than noninfected plants, especially in marginal resource environments. There is a lack of information about endophyte related effects on the rhizosphere of grasses. In a greenhouse experiment, four endophyte-infected (E+) tall fescue clones (DN2, DN4, DN7, DN11) and their endophyte-free (E−) forms were grown in limed (pH 6.3) Porter soil (low fertility, acidic, high aluminum and low phosphorus content, coarse-loamy mixed mesic Umbric Dystrochrept) at three soil P levels (17, 50, and 96 mg P kg-1 soil) for five months. Excluding the genotype effect, endophyte infection significantly increased cumulative herbage DM yield by 8% at 17 mg P kg-1 soil but reduced cumulative herbage DM yield by 12% at 96 mg P kg-1 soil. With increased P availability in the soil, shoot and root DM, and root/shoot ratio in E+ plants were significantly less when compared to E− plants. Endophyte infection increased specific root length at 17 and 50 mg P kg-1soil. At soil P level of 17 mg P kg-1soil, E+ plants had significantly higher P concentrations both in roots and shoots. Similar relationships were found for Mg and Ca. E+ plants had significantly higher Zn, Fe, and Al concentration in roots, and lower Mn and Al concentration in shoots when compared to E− plants. Ergot alkaloid concentration and content in shoot of E+ plants increased with increasing P availability in the soil from 17 to 50 mg P kg-1 but declined again at 96 mg P kg-1 soil. Ergot alkaloid accumulation in roots increased linearly with P availability in the soil. Results suggest that endophyte infection affects uptake of phosphorus and other mineral nutrients and may benefit tall fescue grown on P-deficient soils. Phosphorus seems also to be involved in ergot alkaloid accumulation in endophyte-infected tall fescue.

Aluminum sensitivity of loblolly pine and slash pine seedlings grown in solution culture.

To probe variation in Al sensitivity of two co-occurring pine species, seedlings from six full-sib families of loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) were grown in solution culture containing 4.4 mM (high-Al) or 0.01 mM (low-Al) AlCl(3) at pH 4 for 58 days. On average, both pine species had 41% less total dry weight in the high-Al treatment than in the low-Al treatment. Stem volume growth of slash pine was more sensitive to the high-Al treatment than that of loblolly pine. In both species, the high-Al treatment inhibited root dry weight more than shoot dry weight. Within-species variation in Al sensitivity among families was greater in loblolly pine (24 to 52% inhibition of seedling dry weight) than in slash pine (35 to 47% inhibition of seedling dry weight). Foliar Al concentration was positively correlated with Al sensitivity in slash pine but not in loblolly pine; however, in both species, the concentration of Al in roots was 20-fold greater than in foliage.

The influence of soil chemistry on fine root aluminum concentrations and root dynamics in a subalpine Spodosol, Washington State, USA

The relationship between root Al concentrations and Al fractions in the soil solution was examined in a mature Abies amabilis ecosystem in the Cascade Range of Washington State. The naturally acidic soils in these ecosystems lead to high concentrations of aqueous Al in soil solutions and contribute to the biocycling of Al by the A. amabilis/T. mertensiana stand. Root concentrations of Al were very closely related to aqueous Al3+ activities, but poorly correlated with total aqueous Al concentrations. The solution Al/Ca molar ratios followed a seasonal cycle with low values during the fall and high values during the spring. Ratios remained <1 throughout the year in the Oa horizon while they varied between 2 and 14 in the E and Bhs horizons. The vertical distribution of roots and the mortality of fine roots may be linked to the soil solution Al/Ca ratio. Root cation exchange capacity ranged between 180 and 225 μ mol g-1 and the exchangeable Al fraction represented from 12–17% of the total Al content in the root. Evidence for solid-phase co-precipitates of Al with PO4 and oxalate was indicated from selective dissolution of the root tissue. Sufficient quantities of PO4 and oxalate exist in the roots to tie up 20–40% of the Al present in the roots of the Oa and E horizons, but only 9% of that present in the Bhs horizon. Species differences in the distribution of Al between the above-ground and below-ground components may be dictated by these retention processes in the fine roots.

Effects of aluminium and mineral nutrition on growth and chemical composition of hydroponically grown seedlings of five different forest tree species

Forest die-back and impaired tree vitality have frequently been ascribed to Al-toxicity and Al-induced nutritional disorders due to increased acidification of forest soils. Therefore, in this experiment effects of Al were studied on growth and nutrient uptake with seedlings of five different forest tree species. During growth in culture solutions with and without Al all five species proved to be very Al-tolerant, despite high accumulation of Al in roots. In the coniferous evergreens Douglas-fir and Scots pine shoot as well as root Al concentrations were significantly higher than in the deciduous broad-leaved species oak and birch. Larch showed intermediate Al levels.

Aluminum Effects on Growth and Macronutrient Uptake by Annual Ryegrass

AbstractAnnual ryegrass (Lolium multiflorum Lam.) is an important forage crop in the southeastern USA, often grown on acid soils with potentially high levels of soluble Al. Effects of Al on growth and nutrient relationships in ryegrass are poorly understood. In this study four ryegrass cultivars were grown in a growth chamber in nutrient solutions at 0, 37, 74, 148, 296, and 592 µmol L−1 Al. The pH was initially adjusted to 4.2 and subsequent changes were monitored daily. More Al‐tolerant cultivars induced higher nutrient solution pH than more sensitive cultivars. For more Al‐tolerant cultivars, these pH changes were positively correlated with root and shoot tolerance indexes and negatively correlated with percent inhibition of Ca, Mg, K, and Na uptake. Root (shoot) tolerance index was defined as dry weight (wt.) of roots (shoots) grown with Al/dry wt. of roots (shoots) grown without Al. Changes in nutrient solution pH were effects rather than causes of differential Al tolerance, but once induced, differences in pH intensified cultivar differences in Al tolerance. An Al concentration of 37 µmol L−1 in solution significantly increased root Al concentrations, but very little Al was translocated to shoots. Higher shoot Al concentrations were found more often in the less Al‐tolerant cultivars Wilo and Urbana than in the more tolerant cultivars Gulf and Marshall. Larger root and shoot tolerance indexes, and lower percentages of inhibition of total Ca and Mg uptake were observed more often for more Al‐tolerant cultivars Marshall and Gulf than for more sensitive cultivars Wilo and Urbana. The average net influx of Ca and Mg was decreased where Al was added. Total uptake of K (quantity factor) was decreased by Al, while net K influx (intensity factor) increased for plants grown in the nutrient solution containing up to 74 µmol L−1 Al. Short exposure to Al increased net influx and total Na uptake. Longer exposure to higher concentrations of Al (at least 74 µmol L−1) inhibited both total uptake and net influx of Na. The root tolerance index was positively correlated with net influx of Ca, Mg, K, and Na. Increasing the nutrient solution Al level to 148 µmol L−1 greatly increased K/(Ca+Mg) ratio of shoots, thus increasing the grass tetany potential of the ryegrass forage.

Aluminum stress on sorghum growth and nutrient relationships

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.

Aluminium toxicity and induced nutrient disorders involving the uptake and transport of P, K, Ca and Mg inZea maysL.

Chemical analysis of plant fractions of maize cultivars TX 24 and HL 1 grown in liquid culture containing Al showed that the action of Al was directed at the uptake of Ca and Mg and the transport of P and K. Highly significant cultivar differences in the pattern of Al uptake, notably at low solution Al concentrations were identified. P transport between roots and shoots diminished with increased root Al concentrations. An Al-induced decline in root metabolism was found to occur in intact roots (20 h) and cultivar differences in the ability to maintain root respiration in the presence of Al coincided with cultivar differences in P transport. In the absence of Al, both cultivars responded to low Mg levels by taking up correspondingly more Ca and K without significantly affecting yield. It is therefore suggested that a major requirement for these ions involves charge neutralization. Furthermore, since the root Mg concentrations recorded in these experiments were comparable to those found in plants showing a ...

Aluminum Tolerance of Spring Rye Inbred Lines1

Three hundred seventeen spring rye (Secale cereale L.) inbred lines, 15 cultivars of wheat (Triticum aestivum L.), and three lines of triticale (✕ trlticosecale Wittmack) were tested for Al tolerance. The seedlings were grown in solution‐paper medium and the roots were exposed for 48 hours to Al at different concentrations. The ability of roots to regrow after Al treatment was assessed. Approximately 75% of the rye lines tested showed root regrowth after exposure to Al concentrations of at least 30 ppm. The irreversible inhibition of root growth at a particular level of Al concentration in nutrient solution was associated with a significant increase in Al concentration in roots. The more tolerant rye lines were able to tolerate a significantly higher concentration of Al in their roots than those less tolerant. Variability in the reaction to Al was found within some inbred rye lines even though thye were S5 to S8 inbreds. No rye lines showed a greater tolerance to Al than the most tolerant wheat cultivars. Alumininm concentration in roots of tolerant wheat cultivars was lower than in rye lines. Two of the three triticale lines tested were highly tolerant to Al. The screening method is suitable for selecting homozygous tolerant lines.

Aluminum Accumulation and Tolerance of Triticale and Wheat in Relation to Root Cation Exchange Capacity

AbstractSince plant characteristics associated with Al tolerance vary from one species to another, the objective this study was to relate Al tolerance, Al accumulation, root Cation Exchange Capacity (CEC), and exchangeable Al in triticale (X Triticosecale, Witt Mack) and wheat (Triticum aestivum L.). Ten cultivars of the two species were grown in nutrient solutions with 0 or 6 ppm Al added. The solutions were adjusted to pH 4.8 either at transplanting or daily during plant growth. Aluminum accumulation and displacement by Ca and K from roots exposed to Al for up to 24 hours were also determined. With the solution pH adjusted only at transplanting, the relative root lengths (Al/no Al) indicated that the order of Al tolerance was 6TA 298 and 6TA 131 &gt; 6TA 385 &gt; 6TA 203 triticale and Atlas 66 &gt; Thorne and Seneca &gt; Monon &gt; Redcoat and Arthur wheats. Similar Al tolerance ratings were obtained when solutions were adjusted daily to pH 4.8. Correlation coefficients between relative root lengths and root Al concentrations were −0.93** and −0.90** for triticale and −0.85** and −0.063 for wheat, respectively with pH unadjusted and pH adjusted. Correlation coefficients between plant‐induced pH values and root Al concentrations were −0.19 for triticale and −0.79** for wheat. The root CEC values were generally lower in Al‐tolerant than Al‐sensitive cultivars. The results also suggested that the CEC of roots may be a factor in controlling Al absorption in the first 6 hr of plant exposure before the exchange sites are Al‐saturated at longer periods.

Effect of Soil Al Saturation on Nutrient Concentration of Soybean Tops, Roots, and Nodules1

AbstractA small amount of information is available on the effects of Al saturation on the nutrient concentration of different plant components. This manuscript presents data showing the former relative to the soybean [Glycine max (L.) Merr.]. To study the effects of varying exchangeable Al saturation on the concentration of P, Ca, Mg, and Al in the tops, primary roots, lateral roots, and nodules of soybeans, a randomized complete block greenhouse experiment using 12 soybean cultivars and three soil Al saturation levels was established. The soil was a Lynchburg sandy loam (Aeric Ochraquult). Soil Al saturation levels were established by adding various amounts of lime. Soil Al saturation had no effect on the P concentration of the tops. Root P concentration was significantly higher at 81% Al saturation than at 28 and 4%. Nodules had a much higher P concentration than the other plant parts. The calcium concentration of all plant parts was increased with increasing additions of CaCO3. Tops contained the highest Ca concentration and nodules the lowest. Aluminum saturation levels of 81 and 28% did not significantly affect the Mg concentration of the tops and primary roots. The Mg concentration of the nodules decreased as AI saturation decreased due primarily to a dilution effect. Tops and nodules contained approximately twice as much Mg as the root components. Top and root Al concentration was reduced by 53 and 30%, respectively, when the Al saturation was reduced from 81 to 28%. Aluminum concentration of tops was 6, 2, and 8% of the primary roots, lateral roots, and nodules, respectively at 81% Al saturation. Top growth and nodule number increased as the Al saturation was reduced from 28 to 4%, however, very little change occurred in the Al concentration of the tops over this range. Thus, growth responses of soybeans to reduction of soil Al saturation below 28% appears to be due to pH effects and/or Ca supply.