The effects of aluminium on root cap function and root development in Zea mays L.

Bennet, R. J.; Breen, C. M.; Fey, M. V.

doi:10.1016/0098-8472(87)90059-1

Cited by 83 publications

(38 citation statements)

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“…In agreement with a previous study with barley (31) the apical portion of control roots did not extrude protons, but this alkaline region became progressively shorter as Al toxicity symptoms increased. This may explain the occasionally enhanced proton extrusion (and polarity) in Al-cultured roots observed in the present study and by Bennett et al (2).…”

Section: Discussionsupporting

confidence: 68%

Proton Extrusion by Wheat Roots Exhibiting Severe Aluminum Toxicity Symptoms

Kinraide

1988

Plant Physiol.

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ABSTRACIrThe mechanisms of Al rhizotoxicity are not known, but disruption of membrane function has been a persistent hypothesis. The objective of this study was to establish whether cells of Al-cultured wheat roots (Triticum aestivum L. cv Tyler) exhibiting severe Al toxicity symptoms were capable of vigorous proton extrusion. The membrane electrical potential difference (Em) was measured in individual cells throughout the first centimeter of root tips during perfusion with Al solutions similar to or more concentrated than those of the culture medium. For both Alcultured and control roots the resting Em was -100 millivolts, and 1 millimolar acetic acid induced cyanide-sensitive hyperpolarizations to -180 millivolts at a maximum rate of -30 millivolts per minute. Al, like Ca2", enhanced the negativity of the Em of cells already treated with acetic acid. Both acetic acid and fusicoccin stimulated net proton extrusion from Al-cultured and control roots, both of which also extruded protons in the absence of these stimulants. These results demonstrate that wheat roots exhibiting severe Al toxicity symptoms had an undiminished capacity to extrude protons, that the membranes were intact, and that ATP synthesis was sufficient to supply the proton-translocating ATPases.Al"3 is a rhizotoxic ion that is often present in acidic soils at activities sufficiently high to seriously inhibit root elongation (32). At least one unstable polynuclear hydroxy-Al species is even more toxic than Al3" (20), but its presence in soils has not been confirmed. The mononuclear hydroxy-Al species, which are in equilibrium with Al3", are probably nontoxic (20), and some other Al complexes are demonstrably nontoxic (3, 11, 24). Since no Al species of charge < +3 has been shown to be toxic, Al rhizotoxicity may simply be an instance ofthe apparently general rhizotoxicity of polyvalent cations (4,20).These considerations bear upon the unelucidated mechanisms of Al toxicity. It is unknown whether the primary lesion is intracellular or extracellular, but according to equilibrium computations the cytoplasmic levels of OH-and other ligands for Al would reduce A13+ to an extremely small fraction of the intracellular Al (14). An intracellular lesion is also hard to reconcile with the nontoxicity of AlSO4+ (11) and other species which would also quickly respeciate intracellularly and therefore be indistinguishable from Al3+. Perhaps the polyvalent cations are the only species of Al to enter the cell, but that contradicts the general principle that membranes are more permeable to ions of lower charge (18). Nevertheless, hypotheses for an intracellular lesion have been advanced (16,19,21), and the differences in varietal sensitivity to Al have been considered in terms of Al exclusion by plasma membranes (29) or intracellular detoxification by Al- binding organic ligands (1, 24).The alternative view-that the primary lesion is extracellular-is easier to reconcile with the general rhizotoxicity of polyvalent cations, some ofwhich are reportedly impermeant, at...

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Section: Discussionsupporting

confidence: 68%

Proton Extrusion by Wheat Roots Exhibiting Severe Aluminum Toxicity Symptoms

Kinraide

1988

Plant Physiol.

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“…Results on Al effects on proton extrusion measured in vivo on Triticum aestivum roots are somewhat contradictory because Kinraide (1988) reported undiminished proton extrusion, while Miyasaka et al (1989) observed inhibition of net H"" efflux in an Al-sensitive (but not in an Al-tolerant) cultivar. In other in vivo experiments, Al increased net H^ efflux from Zea mays roots (Bennet et al, 1987) and also in Sorghum bicolor concomitantly with increased NH4"â nd decreased NO3" uptake (Keltjens & Ulden, 1987). Even though in experiments in vivo the composition of nutrient solution in which plants were grown might have masked the real effect of Al on H^-ATPase activity by influencing cation/anion uptake ratio, it appears that the hypothesis of Al interference with wall acidification through direct effect on H"^-ATPases that would result in reduction of the amount of H^ ions pumped into the apoplasm may not be valid.…”

Section: Cell Wall Extensibilitymentioning

confidence: 99%

“…Calmodulin is present at high levels in root caps (Allan & Trewavas, 1985) which have been suggested as a primary site of Al injury (Bennet et al, 1987;Bennet & Breen, 1991a, b). Upon binding of Ca^^ (signal input) calmodulin undergoes conformational changes necessary for signal amplification and output to the respective response elements.…”

Section: Calmodulinmentioning

confidence: 99%

“…In addition, stimulus-response coupling, rather than a direct effect, has recently been evoked to explain deleterious Al effects on Zea mays root growth (Bennet & Breen, 1991 a, b). Perception of aluminium levels and subsequent physiological responses through altered growth pattern have been spatially divided between root cap (signal perception) and root meristem growth responses (Bennet & Breen, 1991a) with secretory activity of Golgi apparatus of root cap cells involved in stimulus transduction (Bennet, Breen & Fey, 1987;Bennet & Breen, 1991 a, b). Removal of the root cap, however, does not change the root response to Al (Ryan & Kochian, 1991), casting some doubts on the great importance that is given to root cap in the model of Bennet & Breen (1991 a).…”

Section: Fmportance Of Calcium In Environmental Stressesmentioning

confidence: 99%

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Role of calcium in aluminium toxicity

1992

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summary Aluminium is the most important growth‐limiting factor in many acid soils throughout the world. Physiological effects of Al toxicity and mechanisms of tolerance are not well understood. An initial uptake of Al is confined to the apoplasm. Aluminium complexes (whose exact identification is beyond current experimental techniques) enter the cytosol slowly and only after prolonged exposure. Electrochemical properties of the cell wall Donnan free space as well as the plasma membrane of root cells are altered by the presence of Al ions that are polyvalent cations in acidic environments. The primary Al effects are very fast (taking only seconds to several minutes to develop) and may therefore occur while Al is still in the Donnan free space and on the apoplasmic side of the plasma membrane. Resumption of root growth upon removal of Al ions supports such a claim. Aluminium affects membrane permeability for both electrolytes and non‐electrolytes; it reduces accumulation of divalent cations (especially Ca and Mg) by interfering with the membrane transport. Aluminium alters the pattern of Ca2+ fluxes across the plasma membrane, thus supposedly disturbing symplasmic Ca2+ homeostasis. Supplemental Ca2+ can greatly alleviate deleterious Al effects. Frequently observed changes in the secretory activity of root cells exposed to Al are mediated through altered cell Ca2+ homeostasis; they result in cessation of cell wall growth and stoppage of root elongation. Involvement of calmodulin in the Al‐related phenomena is suggested to be indirect, at least in the initial stages of the Al treatment when Al is likely to be confined to the apoplasm. The role of growth substances, at least auxins and cytokinins, in the Al toxicity syndrome appears to be related to the Ca‐Al interactions that may alter the pattern of auxin transport as well as cytokinin biosynthesis and transport. Disturbance of the cell Ca2+ homeostasis appears to be an important feature of ion‐related environmental stresses in general (salt, heavy metals, aluminium).

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“…Aluminum can inhibit plant root development, water and nutrient uptake, and overall plant growth (Delhaize and Ryan, 1995). Aluminum toxicity has been reported to stunt growth in several crops, including wheat (Miyasaka et al, 1989), barley (Ali et al, 2011), soybean (Abo et al, 2010), and corn (Bennet et al, 1987). However, since the soils in the area around the ATK test site are neutral or alkaline, the mobility of aluminum within soils and its availability to plants are expected to be very low.…”

Section: Introductionmentioning

confidence: 99%

The sky is falling II: Impact of deposition produced during the static testing of solid rocket motors on corn and alfalfa

Doucette¹,

Mendenhall²,

McNeill³

et al. 2014

Science of The Total Environment

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This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. H I G H L I G H T S• Static rocket motor tests deposit entrained soil and combustion products on crops.• High deposition exposures could impact corn and alfalfa germination and growth.• High chloride in the deposition is the main cause of the observed impacts.• Depositional impacts can be mitigated with rainfall or additional irrigation water. Tests of horizontally restrained rocket motors at the ATK facility in Promontory, Utah, USA result in the deposition of an estimated 1.5 million kg of entrained soil and combustion products (mainly aluminum oxide, gaseous hydrogen chloride and water) on the surrounding area. The deposition is referred to as test fire soil (TFS). Farmers observing TFS deposited on their crops expressed concerns regarding the impact of this material. To address these concerns, we exposed corn and alfalfa to TFS collected during a September 2009 test. The impact was evaluated by comparing the growth and tissue composition of controls relative to the treatments. Exposure to TFS, containing elevated levels of chloride (1000 times) and aluminum (2 times) relative to native soils, affected the germination, growth and tissue concentrations of various elements, depending on the type and level of exposure. Germination was inhibited by high concentrations of TFS in soil, but the impact was reduced if the TFS was pre-leached with water. Biomass production was reduced in the TFS amended soils and corn grown in TFS amended soils did not develop kernels. Chloride concentrations in corn and alfalfa grown in TFS amended soils were two orders of magnitude greater than controls. TFS exposed plants contained higher concentrations of several cations, although the concentrations were well below livestock feed recommendations. Foliar applications of TFS had no impact on biomass, but some differences in the elemental composition of leaves relative to controls were observed. Washing the TFS off the leaves lessened the impact. Results indicate that the TFS deposition could have an effect, depending on the amount and growth stage of the crops, but the impact could be mitigated with rainfall or the application of additional irrigation water. The high level of chloride associated with the TFS is the main cause of the observed impacts. a b s t r a c t a r t i c l e i n f o

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The effects of aluminium on root cap function and root development in Zea mays L.

Cited by 83 publications

References 35 publications

Proton Extrusion by Wheat Roots Exhibiting Severe Aluminum Toxicity Symptoms

Proton Extrusion by Wheat Roots Exhibiting Severe Aluminum Toxicity Symptoms

Role of calcium in aluminium toxicity

The sky is falling II: Impact of deposition produced during the static testing of solid rocket motors on corn and alfalfa

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