Exclusion of metals from the symplasm: A possible mechanism of metal tolerance in higher plants

Taylor, Gregory J.

doi:10.1080/01904168709363649

Cited by 63 publications

(22 citation statements)

References 17 publications

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“…Clarkson (4) and Huett and Menary (7) also suggested a minor accumulation of Al in the cytosol of B. oleracea, L. sativa, P. clandestinum, and H. vulgare, emphasizing that most (70-90%) absorbed Al was located in cell wall. Although the supernatant fraction was not well defined here, our results are consistent with studies which suggest that the plasma membrane and cell wall play an important role in restricting entry of Al into the cytoplasm (19) A dual pattern of Al uptake (a rapid saturable phase superimposed over a linear phase) in excised and whole roots has been reported by several authors (7,16,24), and the linear phase has been suggested to represent uptake in the symplasm (11,16). However, this interpretation of the identity of the linear phase is not consistent with our results.…”

Section: Test Of Cell Wall Puritysupporting

confidence: 81%

Kinetics of Aluminum Uptake in Triticum aestivum L

Zhang¹,

Taylor²

1990

Plant Physiol.

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The identity of a linear phase of aluminum (Al) uptake in Triticum aestivum was investigated by analysis of the kinetics of Al uptake by excised roots and purified cell wall fractions. Classical interpretation of kinetic data suggests that a linear phase of uptake with time reflects uptake across the plasma membrane; however, in studies with Al the possibility that the linear phase of uptake includes accumulation of Al in both the symplasm and the apoplasm has not been discounted. direct experimental evidence is lacking, these two phases have been interpreted as representing passive accumulation in the apoplasm (rapid phase) and transport across the plasma membrane into the symplasm (linear phase) (11,16).Pettersson and Strid (16), and Zhang and Taylor (24) compared uptake ofAl by roots ofAl-tolerant and Al-sensitive cultivars of T. aestivum and failed to observe differences in uptake between cultivars. While these results could suggest that Al tolerance is not linked to initial uptake of Al (16), Zhang and Taylor (24) acknowledged that the precise identity of the linear phase is still in doubt. They reported that the apparent size of the apoplasmic compartment for Al was larger when estimated by extrapolation of the linear phase of uptake to time zero than when estimated by extrapolation of the linear phase of desorption to time zero (24). If the linear phase of uptake represents accumulation of Al in both symplasmic and apoplasmic compartments (not just accumulation of Al in the symplasmic compartment), then differences between Al-tolerant and Al-sensitive cultivars in the uptake of Al across the plasma membrane might be obscured by differences in accumulation of Al in the cell wall. This would be particularly true if exclusion ofAl at the plasma membrane leads to increased polymerization or precipitation of Al in the cell wall.This study was designed to determine if the linear phase of Al uptake by excised roots of Al-tolerant and Al-sensitive cultivars of T. aestivum includes accumulation of Al in the cell wall. Our results support a novel view of the identity of the linear phase of Al uptake. MATERIALS AND METHODS Preparation of Plant MaterialSeeds of two Al-tolerant cultivars (Atlas-66 and PT-74 1) and two Al-sensitive cultivars (Neepawa and Scout-66) of Triticum aestivum L. (wheat) were surface sterilized in 1.2% sodium hypochlorite for 20 min, and germinated overnight in a solution of 0.005 g L' Vitavax to prevent fungal growth. Seedlings were grown for 7 d on nylon mesh suspended over 16 L of nutrient solution containing (mM) 1.0 Ca(NO3)2. 4H20, 0.3 Mg(NO3)2.6 H20, 0.3 NH4NO3, 0

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Section: Test Of Cell Wall Puritysupporting

confidence: 81%

Kinetics of Aluminum Uptake in Triticum aestivum L

Zhang¹,

Taylor²

1990

Plant Physiol.

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“…Resistance to Cd is thought to involve metal-chelating complexes called phytochelatins (Jackson et al, 1987) whereas Cu resistance might involve root cell-wall selectivity (Taylor, 1987). These physiological adaptations can be selected on exposure to contaminated soils, and depend on the prior possession of the appropriate genetic variability within plant populations.…”

Section: N T R O D I' C T 1 O Nmentioning

confidence: 99%

Acclimation of Salix to metal stress

1997

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SUMMARYNine different clones of six species of Salix (Salix cordata Muhlenb. non Michaux, 5. fragilis L., S. caprea L., S. cinerea h., S. burjatica Nazarov. and 5. viminalis L.) and one hybrid (S. x calodendron Wimm.) were exposed to heavy metals in solution culture in an attempt to increase innate metal resistance. Resistance was estimated using comparative root measurements, and metal uptake was also studied. The first experiment entailed pretreatments with background nutrient solution, or 0-25 and 050 mg Cu 1"^ amendments, and re-exposure to each of the same concentrations. In a second experiment clones were exposed to sub-toxic concentrations of single metals (0-15 mg Cu 1"', O-lSmgCdl"' or 2-5mgZnl'') and dual-combination treatments (0-075mgCu|-'-l-0-O75mgCdl-', O'O75 mg Cu 1"'+ 1 25 mg Zn I"' or 0'075 mg Cd 1"'+ 1-25 mg Zn 1" = )' with concentrations gradually raised 10-fold over 128 d. Plants tested in the first experiment, following pre-exposure to Cu, were no more resistant to subsequent exposure to this metal. In the second experiment, gradual cumulati^ e doses resulted in reduced phytotoxicity and increased resistance, most notably to Cd. There appeared to be an inverse relationship between metal uptake and resistance. Copper uptake was restricted to the roots, whereas Cd and Zn were more evenly distributed throughout the plant. Exposure to dual combinations of metals resulted in several interaction effects on uptake: increased root-bound Cu in all combinations, and the increase in uptake of both Cd and Zn into the root tissues when supplied with Cu. The implications of these results for the use of willows in phytoremediation programmes are discussed.

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“…Lower levels of bolewood Ca, Mg, and Ca/Mn and higher levels of bolewood Mn are thought to be indicators of increased stress in trees. Although soil acidification may cause increased Al in soil solution, increased levels of Al in bolewood are generally not found due to exclusion at the soil-root interface (Taylor 1987) or retention by the root cortex (Tomlinson 1990).…”

Section: Introductionmentioning

confidence: 99%