Aluminium interactions with K+(86Rb+) and 45Ca2+ fluxes in three cultivars of sugar beet (Beta vulgaris)

Lindberg, Sylvia

doi:10.1111/j.1399-3054.1990.tb06742.x

Cited by 53 publications

(26 citation statements)

References 43 publications

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“…It is also encouraging to note that the net current predicted from summing the ion fluxes in (5,30,32), and some evidence suggests a competitive interaction between Al and Ca2' at the membrane surface (6,10,18). However, in the present work, Al had no effect on Ca2+ influx in five of seven experiments.…”

Section: Identity Of the Current-carrying Ionssupporting

confidence: 62%

Aluminum Toxicity in Roots

Ryan

Shaff²,

Kochian³

1992

Plant Physiol.

105

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The inhibition of root growth by aluminum (Al) is well established, yet a unifying mechanism for Al toxicity remains unclear.The association between cell growth and endogenously generated ionic currents measured in many different systems, including plant roots, suggests that these currents may be directing growth. A vibrating voltage microelectrode system was used to measure the net ionic currents at the apex of wheat (Triticum aestivum L.) roots from Al-tolerant and Al-sensitive cultivars. We examined the relationship between these currents and Al-induced inhibition of root growth. In the Al-sensitive cultivar, Scout 66, 10 micromolar Al (pH 4.5) began to inhibit the net current and root elongation within 1 to 3 hours. These changes occurred concurrently in 75% of experiments. A significant correlation was found between current magnitude and the rate of root growth when data were pooled. No changes in either current magnitude or growth rate were observed in similar experiments using the Al-tolerant cultivar Atlas 66. Measurements with ion-selective microelectrodes suggested that H' influx was responsible for most of the current at the apex, with smaller contributions from Ca2" and Cl fluxes. In 50% of experiments, Al began to inhibit the net Ho influx in Scout 66 roots at the same time that growth was affected. However, in more than 25% of cases, Al-induced inhibition of growth rate occurred before any sustained decrease in the current or H' flux. Although showing a correlation between growth and current or H' fluxes, these data do not suggest a mechanistic association between these processes.We conclude that the inhibition of root growth by Al is not caused by the reduction in current or H' influx at the root apex.Al2 toxicity has been identified as one of the most important factors limiting plant growth in acid soils (5). Although a wide range of Al-related effects have been described in plants ' P.R.R.

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Section: Identity Of the Current-carrying Ionssupporting

confidence: 62%

Aluminum Toxicity in Roots

Ryan

Shaff²,

Kochian³

1992

Plant Physiol.

105

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“…However, the Al content in the mature regions of the sensitive roots was only twofold higher than in the mature regions of the tolerant roots (Fig. 4) (12,15,26,29). Wagatsuma (26) and Pettersson and Strid (15) suggested that DNP changed the plasma membrane permeability, increasing the passive transport of Al.…”

Section: Discussionmentioning

confidence: 98%

Aluminum Partitioning in Intact Roots of Aluminum-Tolerant and Aluminum-Sensitive Wheat (Triticum aestivum L.) Cultivars

Rincón¹,

Gonzales²

1992

Plant Physiol.

166

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Aluminum (Al) partitioning in intact roots of wheat (Triticum aestivum L.) cultivars that differ in sensitivity to Al was investigated. Roots of intact seedlings were exposed to Al for up to 24 hours and distribution of Al was assessed visually by hematoxylin staining or by direct measurement of concentration of Al by atomic absorption spectrophotometry or ion chromatography. Major differences in Al accumulation between Al-tolerant (Atlas 66) and Al-sensitive (Tam 105) cultivars were found in the growing regions 0 to 2 and 2 to 5 millimeters from the root apex. Al content was 9 to 13 times greater in the 0 to 2 millimeters root tips of cv Tam 105 than in the tips of cv Atlas 66 when exposed to 50 micromolar Al for 19 to 24 hours. The oxidative phosphorylation inhibitor carbonyl cyanide m-chlorophenylhydrazone and the protein synthesis inhibitor cycloheximide increased Al uptake by intact root tips of cv Atlas 66. Also, loss of Al from the roots of both cultivars was measured after the roots were "pulsed" with 50 micromolar Al for 2 hours and then placed in an Al-free nutrient solution for 6 hours. The 0 to 2 millimeter root tips of cv Tam 105 lost 30% of the absorbed Al, whereas the tips of cv Atlas 66 lost 60%. In light of these results, we conclude that the differential Al sensitivity in wheat correlates with the concentration of Al in the root meristems. The data support the hypothesis that part of the mechanism for Al tolerance in wheat is based on a metabolism-dependent exclusion of Al from the sensitive meristems.

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“…therein). In an Al-resistant sugar beet cultivar Lindberg (1990) speculated that a metabolically dependent efflux of Pi was occurring in the presence of Al. Also, Pettersson andStrid Plant Physiol.…”

mentioning

confidence: 99%

Multiple Aluminum-Resistance Mechanisms in Wheat (Roles of Root Apical Phosphate and Malate Exudation)

1996

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Although it is well known that aluminum (AI) resistance in wheat (Trificum aestivum) is multigenic, physiological evidence for multiple mechanisms of AI resistance has not yet been documented. l h e role of root apical phosphate and malate exudation in AI resistance was investigated i n two wheat cultivars (AI-resistant Atlas and AI-sensitive Scout) and two near-isogenic lines (AI-resistant E13 and AI-sensitive ES3). I n Atlas AI resistance is multigenic, whereas in E13 resistance is conditioned by the single Alfl locus. Based on rootgrowth experiments, Atlas was found to be 3-fold more resistant in 20 PM AI than ET3. Root-exudation experiments were conducted under sterile conditions; a large malate efflux localized to the root apex was observed only in Atlas and in ET3 and only i n the presence of AI (5 and 20 p~) .Furthermore, the more AI-resistant Atlas exhibited a constitutive phosphate release localized to the root apex. As predicted from the formation constants for the AI-malate and AI-phosphate complexes, the addition of either ligand to the root bathing solution alleviated AI inhibition of root growth in AI-sensitive Scout. These results provide physiological evidence that AI resistance in Atlas is conditioned by at least two genes. I n addition to the alf locus that controls AI-induced malate release from the root apex, other genetic loci appear to control constitutive phosphate release from the apex. We suggest that both exudation processes act in concert to enhance AI exclusion and AI resistance i n Atlas.A1 toxicity is one of the major factors that limits the productivity of crop plants in acid soils. A number of crop species and cultivars exhibit significant genetically based variability in their response to the toxic levels of soil A1 (Kochian, 1995). This variability has served as the basis for a considerable amount of recent research on the underlying mechanisms that result in crop A1 resistance. We are beginning to understand the cellular processes that confer A1 resistance in plants. Most of the recent work has focused on A1 exclusion from the root apex as a primary mechanism of A1 resistance (Kochian, 1995).Root exudation of organic acids that can chelate A13+ in the rhzosphere and, thus, detoxify A1 was first reported in an

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Aluminium interactions with K⁺(⁸⁶Rb⁺) and ⁴⁵Ca²⁺ fluxes in three cultivars of sugar beet (Beta vulgaris)

Cited by 53 publications

References 43 publications

Aluminum Toxicity in Roots

Aluminum Toxicity in Roots

Aluminum Partitioning in Intact Roots of Aluminum-Tolerant and Aluminum-Sensitive Wheat (Triticum aestivum L.) Cultivars

Multiple Aluminum-Resistance Mechanisms in Wheat (Roles of Root Apical Phosphate and Malate Exudation)

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