Root Tolerance Index Research Articles

Seedling root response of some Kenyan bread wheat cultivars grown in acid nutrient culture solution containing aluminum

The objective of this study was to determine whether a series of Kenyan bread wheat cultivars differed in tolerance to aluminum toxicity. Fourteen Kenyan wheat cultivars representing current and former widely grown cultivars of diverse pedigree origin, and two control cultivars, Maringa (Al-tolerant) and Siete Cerros (Al-susceptible), were tested in solution cultures with 0 (control), 148, 593, and 2370 μM Al at pH 4.6. Highly significant (p≤0.01) differences in seedling growth were observed among cultivars for root mass, root length and root tolerance index (RTI). Significant (p≤0.05) cultivar × treatment interactions were observed for root mass and RTI. All characters were negatively affected by increased Al concentration, with root length and root mass being affected the most. RTI is a commonly used index which measures the relative performance of individual cultivars with and without aluminum stress. High levels of tolerance to Al were identified in the Kenyan cultivars by evaluating RTI with this simple nutrient solution technique. Romany and Kenya Nyumbu had RTI values approaching those of the Al tolerant Brazilian cultivar Maringa, a spring wheat standard that has been used for high Al tolerance.

Differential aluminum tolerance in some tropical rice cultivars: I. Growth performance

Abstract Ten‐day‐old seedlings of 22 rice (Oryza sativa.L) cultivars originated from various tropical countries were subjected to six levels of aluminum (Al) [0, 74, 148, 222, 296, and 370 μM] to test their tolerance to Al toxicity in nutrient solutions at pH 4.0±0.l. Seedlings were grown in the presence of Al under controlled environmental conditions in growth chambers. The nutrient solutions were replenished once a week. After 30 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), root tolerance index (RTI) and shoot tolerance index (STI) have been used as markers of Al toxicity. Rice cultivars studied exhibited wide range of responses in their tolerance to Al. Though, the rice cultivars were subjected to six levels of Al, a good degree of separation in their responses was observed only at 222 μM Al. Therefore, this concentration wa...

Potassium/Magnesium Ratio Effects on Aluminum Tolerance and Mineral Composition of Wheat Forage

AbstractKnowledge of cation amelioration of Al toxicity may improve our understanding of differential Al‐tolerance mechanisms among winter wheat (Triticum aestivum L.) forage genotypes, and the causes of tetany in grazing cattle. A solution culture experiment was conducted using two winter wheat cultivars (Atlas 66 and Scout 66), two Al levels (0 and 50 μM), and three K/Mg ratios (0.1, 0.7 and 2.3, on a mol Lc−1 basis). Root dry weights were decreased significantly by Al for Al‐sensitive Scout 66, but not for Al‐tolerant Atlas 66. Increasing the K/Mg ratio in the presence of Al significantly decreased root dry weight, root length, and the root tolerance index for Scout 66, but not for Atlas 66. Shoot and root Mg concentrations were always significantly lower for Scout 66 than for Atlas 66. Without Al, shoot K and Ca concentrations for the two cultivars were not significantly different. With Al, shoot K, Ca and Mg concentrations were depressed more for Scout 66 than for Atlas 66. The K(Ca + Mg) ratios increased significantly in Scout 66 with added Al, thereby causing an increased tetany hazard. Adding Al reduced shoot Cu and Zn concentrations in both cultivars, and Fe and Mn concentrations in Scout 66. Increasing the proportion of Mg in solution increased the Al tolerance for Scout 66, indicating that an appropriate K/Mg ratio is important in selecting for Al‐tolerant wheat cultivars.

Characterization of differential aluminum tolerance among rice genotypes cultivated in South India

Abstract Six genotypes of rice (Oryza sativa L.) commonly cultivated in South India have been subjected to screening for their tolerance to Al toxicity in hydrocultures. Ten‐day‐old seedlings were exposed to six levels of Al (0, 74, 148, 222, 296, and 370 μmol/L) supplied in the nutrient solutions at pH 4.0. The seedlings were grown under controlled environmental conditions in growth chambers and the nutrient solutions were replenished once a week. After three weeks of Al stress, growth characteristics of the rice genotypes were compared. The recommended growth parameters such as root and shoot growth, number of roots, leaf tip scorching, dry matter (biomass) production by roots and tops, relative growth reduction in roots (RGRR) and shoots (RGRS), and root tolerance index (RTI) and shoot tolerance index (STI) have been used as markers of Al response. The rice genotypes tested revealed a wide range of responses to Al. Although only six levels of Al were employed, a good degree of separation in the respons...

Evaluation of crop resistance to aqueous oil pollution

Root and shoot tolerance indices and photosynthesis characteristics (CO2-dependent-O2 evolution; H2O→MV electron transport; whole-leaf photosynthesis by infrared gas analyzer) indicated that ADT-36 and CR-1009 rice varieties were more tolerant than other varieties (IR-50, IR-20, and Ponni). Vigna varieties (T-9 and Krishna) were most susceptible to aqueous oil pollution. Since the oil-polluted soil contained a potentially toxic concentration of cadmium, tolerant (ADT-36) and susceptible (IR-50) varieties of Oryza were further analyzed for cadmium-binding components. Higher accumulations of cadmium were found in the roots than in the leaves of both rice varieties. Cadmium is associated with proteins of about 50,000 and 33,000-dalton in molecular mass, of which the 33-kdalton protein was significantly induced only in ADT-36. It is suggested by the present study that the ADT-36 rice variety is most tolerant to aqueous oil pollution, as evidenced by higher STI (shoot tolerance index) and RTI (root tolerance index) values, induction of Cd-binding proteins, and comparatively normal photosynthesis rates.

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 effects on micronutrient uptake by annual ryegrass

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

MECHANISMS OF ALUMINUM TOLERANCE IN TRITICUM AESTIVUM L. (WHEAT). II. DIFFERENTIAL PH INDUCED BY SPRING CULTIVARS IN NUTRIENT SOLUTIONS

Twenty spring cultivars of Triticum aestivum L. (wheat) were grown in solution culture with and without aluminum (Al) (74 μM, 2.0 mg L‐1) for 14 days. Root growth and shoot growth were depressed in all cultivars grown with Al; however, symptoms of Al toxicity were most evident on roots. Based on a root tolerance index (RTI = weight of roots grown with Al/weight of roots grown without Al), cultivar tolerance ranged from 0.18 ± 0.02 to 0.85 ± 0.03. Aluminum‐affected roots were relatively short, thick, and had numerous undeveloped laterals. Leaves of some cultivars showed chlorosis resembling iron deficiency and others showed purple stems typical of phosphate deficiency.Plants of all cultivars induced a progressive decline in nutrient solution pH from the outset of the experiment until Days 10–14. After this initial period, some cultivars rapidly increased solution pH, while others continued to depress solution pH throughout the experiment. Cultivar tolerance expressed as the RTI was negatively correlated with the negative log of the mean hydrogen ion (H+) concentration, the minimum pH, and the slope of the pH decline, each calculated from pH data collected during the first 9 days of the experimental period before any sharp rises in pH. The relationship between solution pH and Al tolerance was similar to that reported previously for winter cultivars of T. aestivum, suggesting that the Al tolerance of a given cultivar is a function of its ability to resist acidification of the nutrient solution and hence to limit the solubility and toxicity of Al.

MECHANISMS OF ALUMINUM TOLERANCE IN TRITICUM AESTIVUM L. (WHEAT). I. DIFFERENTIAL PH INDUCED BY WINTER CULTIVARS IN NUTRIENT SOLUTIONS

Twenty winter cultivars of Triticum aestivum L. (wheat) were grown in solution culture with and without aluminum (Al) (74 μM, 2.0 mg L‐1) for 14 days. Exposure to Al increased root growth of the most tolerant cultivar, while both root and shoot growth were depressed in all other cultivars. On the basis of a root tolerance index (RTI = weight of roots grown with Al/weight of roots grown without Al), cultivar tolerance to Al ranged 9‐fold, from 0.13 ± 0.01 to 1.16 ± 0.10. Symptoms of Al toxicity were most evident on roots. Aluminum‐affected roots were relatively short and thick and had numerous undeveloped laterals. Leaves of some cultivars showed chlorosis resembling iron deficiency, and others showed purple stems typical of phosphate deficiency.Plants of all cultivars grown with and without Al depressed the pH of nutrient solutions, presumably until NH4+ was depleted, at which point the pH increased. Cultivar tolerance, expressed both as the root tolerance index and a shoot tolerance index, was negatively correlated with the negative log of the mean hydrogen ion (H+) concentration, the minimum pH, and the slope of the pH decline, each calculated from pH data collected during the first 9 days of the experimental period before any sharp rises in pH occurred. These results are consistent with the hypothesis that the Al tolerance of a given cultivar is a function of its ability to resist acidification of the nutrient solution and hence to limit the solubility and toxicity of Al.

Mechanisms of Aluminum Tolerance in Triticum aestivum L. (Wheat). I. Differential pH Induced by Winter Cultivars in Nutrient Solutions

Twenty winter cultivars of Triticum aestivum L. (wheat) were grown in solution culture with and without aluminum (Al) (74 μM, 2.0 mg L-1) for 14 days. Exposure to Al increased root growth of the most tolerant cultivar, while both root and shoot growth were depressed in all other cultivars. On the basis of a root tolerance index (RTI = weight of roots grown with Al/weight of roots grown without Al), cultivar tolerance to Al ranged 9-fold, from 0.13 ± 0.01 to 1.16 ± 0.10. Symptoms of Al toxicity were most evident on roots. Aluminum-affected roots were relatively short and thick and had numerous undeveloped laterals. Leaves of some cultivars showed chlorosis resembling iron deficiency, and others showed purple stems typical of phosphate deficiency. Plants of all cultivars grown with and without Al depressed the pH of nutrient solutions, presumably until NH4+ was depleted, at which point the pH increased. Cultivar tolerance, expressed both as the root tolerance index and a shoot tolerance index, was negatively correlated with the negative log of the mean hydrogen ion (H+) concentration, the minimum pH, and the slope of the pH decline, each calculated from pH data collected during the first 9 days of the experimental period before any sharp rises in pH occurred. These results are consistent with the hypothesis that the Al tolerance of a given cultivar is a function of its ability to resist acidification of the nutrient solution and hence to limit the solubility and toxicity of Al.