Subcellular compartmentation of strontium and zinc in mulberry idioblasts in relation to phytoremediation potential

The cellular compartmentation of heavy metals was analyzed using mulberry leaves, in which CaCO₃-forming idioblasts are situated in the epidermal layer. Germinated mulberry seedlings were grown on hydroponic culture medium containing strontium (Sr), zinc (Zn), and cadmium (Cd) with and without supplemental calcium (Ca). After ten weeks of growth, toxic effects of these metals were assessed by measuring shoot length and chlorophyll content of leaves. Sr and Cd treatment at a higher dose (4 mM for Sr, 25 μM for Cd) resulted in signs of toxicity, whereas no distinct phytotoxicity was observed at 500 μM Zn. Elemental mapping of leaves using an energy-dispersive X-ray microanalysis system fitted to variable-pressure scanning electron microscope showed that Sr and Zn were preferentially accumulated in the idioblasts and Cd was not detected in any type of leaf cell. The deposition site of Sr was confined to cell wall sacs developing in idioblasts. The Sr sink capacity in leaves was more than 30 mg/g dry weight, which equaled the Ca sink capacity. Exposure of Sr + Ca led to the co-localization of Sr and Ca in the same cell wall sac, in which Ca and Sr deposition were each estimated to be 60–80 ng. The localization site of Zn was cell walls of a dome-shaped protrusion (cap) of idioblasts, together with silicon (Si) originating as a contaminant in tap water used for culturing. Mulberry idioblasts were unique in showing metal-dependent distribution to two subcellular sites (cell wall sac and cap region) of idioblasts. In conclusion, mulberry plant is a candidate for phytoremediation of radiostrontium because of their Sr-hyperaccumulating capacity with sufficient leaf biomass production.     

Surface chemical properties of purified root cell walls from two tobacco genotypes exhibiting different tolerance to manganese toxicity

Surface chemical characteristics of root cell walls extracted from two tobacco genotypes exhibiting differential tolerance to Mn toxicity were studied using potentiometric pH titration and Fourier transform infrared spectroscopy. The Mn-sensitive genotype KY 14 showed a stronger interaction of its cell wall surface with metal ions than did the Mn-tolerant genotype Tobacco Introduction (T.I.) 1112. This observation may be attributed to the relatively higher ratio of COO⁻ to COOH in KY 14 cell walls than that found in the cell walls of T.I. 1112 in the pH range of 4 to 10. For both genotypes, the strength of binding between metal ions and cell wall surface was in the order of Cu > Ca > Mn > Mg > Na. However, a slightly higher preference of Ca over Mn was observed with the T.I. 1112 cell wall. This may explain the high accumulation of Mn in the leaves of Mn-tolerant genotype T.I. 1112 rather than the high accumulation of Mn in roots, as occurred in Mn-sensitive KY 14. It is concluded that surface chemical characteristics of cell walls may play an important role in plant metal ion uptake and tolerance.     

Calcium deprivation disrupts enlargement of Chara corallina cells: further evidence for the calcium pectate cycle

Pectin is a normal constituent of cell walls of green plants. When supplied externally to live cells or walls isolated from the large-celled green alga Chara corallina, pectin removes calcium from load-bearing cross-links in the wall, loosening the structure and allowing it to deform more rapidly under the action of turgor pressure. New Ca(2+) enters the vacated positions in the wall and the externally supplied pectin binds to the wall, depositing new wall material that strengthens the wall. A calcium pectate cycle has been proposed for these sub-reactions. In the present work, the cycle was tested in C. corallina by depriving the wall of external Ca(2+) while allowing the cycle to run. The prediction is that growth would eventually be disrupted by a lack of adequate deposition of new wall. The test involved adding pectate or the calcium chelator EGTA to the Ca(2+)-containing culture medium to bind the calcium while the cycle ran in live cells. After growth accelerated, turgor and growth eventually decreased, followed by an abrupt turgor loss and growth cessation. The same experiment with isolated walls suggested the walls of live cells became unable to support the plasma membrane. If instead the pectate or EGTA was replaced with fresh Ca(2+)-containing culture medium during the initial acceleration in live cells, growth was not disrupted and returned to the original rates. The operation of the cycle was thus confirmed, providing further evidence that growth rates and wall biosynthesis are controlled by these sub-reactions in plant cell walls.     

Effect of modification of cell calcium status on lectin activity

Effects of oryzalin (10 microM), an inhibitor of microtubule polymerization, on the activity of soluble and cell wall lectins were studied in 7 day-old seedlings of unhardened (23 degrees C) and cold acclimated (7 days at 2-3 degrees C) winter wheat (Triticum aestivum L.). Seedlings were grown in the presence of 25 microM and 1 mM Ca2+, 500 microM verapamil, 250 microM chlorpromazine or without modifiers of calcium status in the medium. Inhibitor of the microtubule polymerization inhibitor, likely as inhibitors of Ca(2+)-signal, decreased the activity of soluble lectins and increased that of cell wall lectins. Apparently, injury of microtubule phosphorylation results in a more considerable microtubule disorganization, than that observed after oryzalin effect. A low Ca2+ concentration (25 microM) depressed, while a high concentration (1 mM) prompted microtubule sensibility to oryzalin. Such an effect of high Ca2+ concentration may be related to destabilizative action of Ca(2+)-calmodulin in these conditions, because chlorpromazine decreased oryzalin-induced increase in the activity of cell wall lectins with 1 mM Ca2+. It is concluded that the activity of cell wall lectins depends on the microtubule status that is regulated by calcium signal.     

Use of secondary ion mass spectrometry to image44calcium uptake in the cell walls of apple fruit

Summary Calcium, an important agent in regulating cell wall autolysis during fruit ripening, interacts with pectic acid polymers to form cross-bridges that influence cell separation. In the present study, secondary ion mass spectrometry (SIMS) was used to determine whether the cell walls of apple fruit were able to take up exogenously applied⁴⁴Ca, which was infiltrated into mature fruit. SIMS, which has the ability to discriminate between isotopes, allowed localization of the exogenously applied⁴⁴Ca and the native⁴⁰Ca. The results indicated that the total amount of calcium present in the cell walls was enriched with⁴⁴Ca and that heterogeneity of⁴⁴Ca distribution occurred in the pericarp. Isotope ratio images showed microdomains in the cell wall, particularly in the middle lamella intersects that oppose the intercellular spaces. These domains may be the key areas that control cell separation. These data suggest that exogenously applied calcium may influence cell wall autolysis.Abbreviations SIMS secondary ion mass spectrometry     

Relationship of strontium and calcium concentrations with the parameters of cell structure in Siberian spruce and fir tree-rings

This study addressed distribution of calcium and strontium in Siberian spruce (Picea obovata Ledeb.) and Siberian fir (Abies sibirica Ledeb.) tree-rings and its dependence on these woody species cell structure. Calcium concentration was found to decrease gradually from earlywood to latewood, whereas strontium showed an opposite trend. However, their trends at the scale of several rings are co-directed in the samples analyzed. A strong linear relationship was identified between the distribution of Sr/Ca concentration ratio and tree-ring density profile for both woody species. Radiographic density of Siberian spruce tree-ring cell walls and Ca and Sr concentrations in them were determined to have negative correlation with cell wall thickness. In earlywood of annual rings of a spruce the radiographic density of cell wall reaches 2.0 g/cm³ and decreases to 1.2 g/cm³ in latewood. The hypothesis put forward in this study to explain these strontium and calcium distributions in the tree-rings is that the concentrations of the element ions change with development of different cell wall layers. The high value of radiographic density of a cellular wall in earlywood and its relationship with cell wall thickness can be explained by the presence of ions of calcium in a cellular wall. Ions of calcium absorb X-ray radiation more strongly in comparison with light chemical elements. It can become the reason of observable relationship between radiographic density of cell wall and cell wall thickness.     

Calcium deficiency in potato (Solanum tuberosum ssp. tuberosum) leaves and its effects on the pectic composition of the apoplastic fluid

Potato plants (Solanum tuberosum ssp. tuberosum cv. Adelheid), multiplied in vitro, were cultivated in growth chambers on nutrient solution at calcium regimes of 1000, 90, 60 or 30 μM Ca. An absolute Ca deficiency, particularly at the low Ca‐supply levels of 30 and 60 μM Ca, manifested itself initially in the form of marginal necrosis in younger, but not in the youngest, leaves of the potato plants. Further symptoms were rolling of the leaf lamina, browning of veins and roots, and finally necrosis also of the youngest leaves. Only in an advanced stage of Ca deficiency, the meristem of the shoots died. Ca‐deficiency symptoms could be expected at a Ca content in the leaves of less than 5 mg Ca (g dry weight)^?1. However, there was no close negative correlation between the extent of leaf damage and the total Ca content of the leaves. In order to obtain information about the Ca concentration in the apoplast fluid of the leaves, apoplastic washing fluid was extracted by an infiltration‐centrifugation technique. A low Ca supply reduced the Ca concentration both in the apoplast fluid of the leaves and in the cell walls. Up to 60% more diffusible pectin fragments were then found in the apoplast of younger leaves, as compared to the control supplied with an optimum Ca level of 1000 μM. The amount of diffusible pectins accounted for 1–2% of the total pectin content of younger potato leaves. The size of the existing pectin fragments varied depending on the Ca supply. Compared with an optimum Ca supply of 1000 μM, fewer monomers and up to 7 times more diffusible pectin fragments with a degree of polymerization 9–20 were present at the low Ca‐supply level (30 μM). In addition, polygalacturonase activity in tissue homogenates increased remarkably with Ca deficiency. Thus it appears that one major effect of Ca deficiency was a stimulation of the activity of polygalacturonase, which could control the breakdown of pectic polysaccharides in the cell wall. Whether the release of potentially biologically active pectic fragments in cell walls might be involved in the occurrence of Ca‐deficiency symptoms is discussed.     

The effects of enhanced levels of calcium on the gravireaction of sunflower hypocotyls

A current hypothesis states that there is a redistribution of wall calcium from the lower to the upper sides of horizontal shoots during gravireaction, and because calcium stiffens walls, the unequal calcium distribution results in differential wall extensibility on the upper and lower sides, and thus, causes unequal growth. If this hypothesis is valid, then saturating the cell walls with calcium should minimize the effect of calcium redistribution, and thereby inhibit gravicurvature and stiffen the walls. To test this hypothesis, sunflower seedlings were grown on agar containing 0 to 50molm^-3 CaCl₂. The wall-bound calcium content of the tissues increased as the external concentration of CaCl₂ increased, and the epidermal layers were saturated with calcium by the 10molm^-3 CaCl₂ treatment. Contrary to the predictions from the hypothesis, the vertical growth and the gravicurvature rate of plants grown in 10molm^-3 CaCl₂ were actually accelerated, and wall extensibility, as measured by the Instron technique, was unaffected. These results contradict the hypothesis, and provide further evidence that wall-bound calcium is not involved in the reaction phase of gravicurvature.     

Cytochemical Localization of Calcium in Cap Cells of Primary Roots of Zea mays L.

The distribution of calcium (Ca) in caps of vertically- andhorizontally-oriented roots of Zea mays was monitored to determineits possible role in root graviresponsiveness. A modificationof the antimonate precipitation procedure was used to localizeCa in situ. In vertically-oriented roots, the presumed graviperceptive(i.e., columella) cells were characterized by minimal and symmetricstaining of the plasmalemma and mitochondria. No precipitatewas present in plasmodesmata or cell walls. Within 5 min afterhorizontal reorientation, staining was associated with the portionof the cell wall adjacent to the distal end of the cell. Thisasymmetric staining persisted throughout the onset of gravicurvature.No staining of lateral cell walls of columella cells was observedat any stage of gravicurvature, suggesting that a lateral flowof Ca through the columella tissue of horizontally-orientedroots does not occur. The outermost peripheral cells of rootsoriented horizontally and vertically secrete Ca through plasmodesmata-likestructures in their cell walls. These results are discussedrelative to proposed roles of root-cap Ca in root gravicurvature. Key words: Antimonate, calcium, columella cell, peripheral cell, root gravitropism, Zea mays L.     

Calcium effect on the mycelial cell walls of Botrytis cinerea

The goal of this study was to determine whether calcium ion, (one of the electrolytes released after plant cell attack), may have a direct effect on fungal growth and chemistry of the fungal cell wall. B. cinerea was grown on Richard's solution containing different amounts of CaCl₂, and the cell walls were extracted from the mycelium after 7 days of growth. Mineral, neutral and aminosugar, protein and uronic acid contents were determined. At 1 g l⁻¹ CaCl₂, only the aminosugar content increased. At 2 g l⁻¹ CaCl₂, neutral sugar synthesis was reduced, whereas the uronic acid content increased. For higher CaCl₂ concentrations, the calcium ion content of the cell wall increased, resulting in reduced protein and neutral sugar contents. Meanwhile, the cell wall proportion of the mycelia increased on a dry weight basis due to an increase in uronic acid, Ca, P, Na and neutral sugar contents of the cell wall with increasing CaCl₂ in the media. The resulting thickening of the fungal cell wall caused by calcium ion may be an important factor in the host-pathogen relationship.     

华北落叶松花粉发育过程中的钙动态分布

运用焦锑酸钾沉淀法研究了华北落叶松(Larixprincipis-rupprechtiiMayr)小孢子发育过程中不同阶段Ca2 的分布情况。减数分裂时期,小孢子囊壁表皮和中层细胞的细胞壁及细胞间隙Ca2 分布较多,绒毡层只有外切向面的细胞膜有Ca2 分布,小孢子母细胞的各部位则很少有Ca2 ;四分体时期,包围四分小孢子的胼胝质壁上有大量的Ca2 分布,在四分孢子壁上也有较多沉淀;游离小孢子时期,钙离子在小孢子壁的分布较四分体时期有所减少,而到花粉成熟时又逐渐增多;从四分体到花粉成熟,乌氏体周围的Ca2 有增多的趋势。对四分体外壁Ca2 的大量分布与花粉壁的形成及信号物质在花粉表面贮存的关系,以及小孢子囊的外壁、绒毡层和乌氏体在Ca2 向花粉运输中所起的作用进行了讨论。     

Effects of boron deficiency and calcium supply on the calcium metabolism in tomato plant

Summary Tomato plants were grown in water-culture with a different supply of Ca (10, 100 ppm) and B (0, 0.2 ppm), and the effects of B deficiency on the translocation and subcellular distribution of Ca in tomato plants were studied by using⁴⁵CaCl₂ as a carrier of Ca. Boron deficiency slight increased the total Ca uptake by the plant and inhibited the Ca translocation to the upper leaves. The incorporation of⁴⁵Ca into the cell wall in the upper leaves was increased by B deficiency at both Ca levels. As Ca supply decreased, the distribution of⁴⁵Ca in the 1N NaCl fraction of the cell wall increased only at 0.2 ppm B. As B supply decreased, the distribution of⁴⁵Ca in the 0.6N HCl fraction increased at both Ca levels. These results suggest that B deficiency inhibit the translocation of Ca, and induce the abnormal changes of the Ca metabolism in the cell wall.     

Cell wall adaptations to multiple environmental stresses in maize roots

A municipal solid-waste bottom slag was used to grow maize plants under various abiotic stresses (high pH, high salt and high heavy metal content) and to analyse the structural and chemical adaptations of the cell walls of various root tissues. When compared with roots of control plants, more intensive wall thickenings were detected in the inner tangential wall of the endodermis. In addition, phi thickenings in the rhizodermis in the oldest part of the seminal root were induced when plants were grown in the slag. The role of the phi thickenings may not be a barrier for solutes as an apoplastic dye could freely diffuse through them. The chemical composition of cell walls from endodermis and hypodermis was analysed. Slag-grown plants had higher amounts of lignin in endodermal cell walls when compared to control plants and a higher proportion of H-type lignin in the cell walls of the hypodermis. Finally, the amount of aliphatic suberin in both endo- and hypodermal cell walls was not affected by growing the plants on slag. The role of these changes in relation to the increase in mechanical strengthening of the root is discussed.     

Cytochemical localization of calcium in cap cells of primary roots of Zea mays L

The distribution of calcium (Ca) in caps of vertically- and horizontally-oriented roots of Zea mays was monitored to determine its possible role in root graviresponsiveness. A modification of the antimonate precipitation procedure was used to localize Ca in situ. In vertically-oriented roots, the presumed graviperceptive (i.e., columella) cells were characterized by minimal and symmetric staining of the plasmalemma and mitochondria. No precipitate was present in plasmodesmata or cell walls. Within 5 min after horizontal reorientation, staining was associated with the portion of the cell wall adjacent to the distal end of the cell. This asymmetric staining persisted throughout the onset of gravicurvature. No staining of lateral cell walls of columella cells was observed at any stage of gravicurvature, suggesting that a lateral flow of Ca through the columella tissue of horizontally-oriented roots does not occur. The outermost peripheral cells of roots oriented horizontally and vertically secrete Ca through plasmodesmata-like structures in their cell walls. These results are discussed relative to proposed roles of root-cap Ca in root gravicurvature.     

Differential extractability of calcium and pectic substances in different wall regions of epicotyl cells in young flax plants.

We applied the simultaneous use of a subtractive method and two imaging techniques (secondary ion mass spectrometry and electron microscopy after PATAg staining) to correlate the distribution of Ca2+ to pectic substances in cell walls of young flax plants. The calcium images were compared with the structural electron microscopy images. This suggests that the linkage of the pectic substances within the wall is mainly by calcium bridges in the intercellular junctions of most types of cells under study (epidermis, subepidermis, fiber layer, and endodermis) and in the outer part (close to the cuticle) of the wall of the epidermal cells. In the primary walls of the various types of cells under study and in the inner part (close to the cytoplasm) of the wall of the epidermal cells, the linkage of the pectic substances would be mainly by covalent bonds. In the middle lamellae of the various cells, and in the intercellular junctions within the cortical parenchyma, both types of linkages apparently coexist. The mechanism of "ionic condensation" may provide an interpretation for the chemical status of the Ca2+ ions which are associated with the pectic components solubilized in boiling water, and which do not seem to contribute to the linkage of these components within the wall.     

Calcium carbonate deposition in a cell wall sac formed in mulberry idioblasts

Summary. Although calcium carbonate is known to be a common biomineral in plants, very little attention has been given to the biological control of calcium carbonate deposition. In mulberry leaves, a subcellular structure is involved in mineral deposition and is described here by a variety of cytological techniques. Calcium carbonate was deposited in large, rounded idioblast cells located in the upper epidermal layer of mulberry leaves. Next to the outmost region (“cap”) of young idioblasts, we found that the inner cell wall layer expanded to form a peculiar outgrowth, named cell wall sac in this report. This sac grew and eventually occupied the entire apoplastic space of the idioblast. Inside the mature cell wall sac, various cellulosic membranes developed and became the major site of Ca carbonate deposition. Concentrated Ca²⁺ was pooled in the peripheral zone, where small Ca carbonate globules were present in large numbers. Large globules were tightly packed among multiple membranes in the central zone, especially in compartments formed by cellulosic membranes and in their neighboring membranes. The maximum Ca sink capacity of a single cell wall sac was quantified using enzymatically isolated idioblasts as approximately 48 ng. The newly formed outgrowth in idioblasts is not a pure calcareous body but a complex cell wall structure filled with substantial amounts of Ca carbonate crystals. Correspondence and reprints: Graduate School of Science and Technology, Kyoto Institute of Technology, Goshokaido, Matsugasaki, Sakyo, Kyoto 606-8585, Japan.     

Penicillin-induced changes in the cell wall composition of Staphylococcus aureus before the onset of bacteriolysis

To analyze if chemical cell wall alterations contribute to penicillin-induced bacteriolysis, changes in the amount, stability, and chemical composition of staphylococcal cell walls were investigated. All analyses were performed before onset of bacteriolysis i.e. during the first 60 min following addition of different penicillin G doses. Only a slight reduction of the amount of cell wall material incorporated after penicillin addition at the optimal lytic concentration was observed as compared to control cells. However, the presence of higher penicillin G concentrations reduced the incorporation of wall material progressively without bacteriolysis. Losses of wall material during isolation of dodecylsulfate insoluble cell walls were monitored to assess the stability of the wall material following penicillin addition. Wall material grown at the lytic penicillin concentration was least stable but about 30% of the newly incorporated wall material withstood even the harsh conditions of mechanical breakage and dodecylsulfate treatment. Dodecylsulfate insoluble cell walls were used for chemical analyses. While peptidoglycan chain length was unaffected in the presence of penicillin, other wall parameters were considerably altered: peptide cross-linking was reduced in the wall material synthesized after addition of penicillin; reductions from approx. 85% in controls to about 60% were similar for lytic and also for very high penicillin concentrations leading to nonlytic death. O-acetylation was also reduced after treatment with penicillin; this effect paralleled the occurence of subsequent bacteriolysis at different drug concentrations. The results are not consistent with hypotheses explaining penicillin-induced lysis as a result of an overall weakened cell wall structure or an overall activation of autolytic wall enzymes but not conflicting with the model that ascribes penicillin-induced bacteriolysis as the result of a very restricted, local perforation of the peripheral cell wall (murosome-induced bacteriolysis).Abbreviations CL Cross-linking - DNFB 2,4-dinitro-1-fluorobenzole - MIC Minimal inhibitory concentration - OD Optical density at 578 nm - PEN Penicillin G     

甾醇生物合成抑制剂粉锈宁对苹果黑星病菌发育的影响

采用电子显微镜和细胞化学技术,研究了杀菌剂粉锈宁（甾醇生物合成抑制剂）对苹果黑星病菌在苹果叶片上发育的影响。观察结果表明,接种前24h施药对病菌入侵有明显的影响。表现为分生孢子的萌发受阻,推迟萌发及萌发率降低;并引起芽管畸形,不能形成附着胞。接种后6天（显症前）施药,可引起叶片角质层下菌丝细胞和子座细胞的原生质坏死、细胞壁不规则增厚及液泡增大, 从而使菌丝进一步发育受阻。接种后12天（显症后）施药,不仅导致菌丝、子座细胞发生上述变化, 而且引起分生孢子和分生孢子梗塌陷、畸形,阻止了病菌的进一步产孢和扩展。细胞化学定位分析结果表明,?-1,3-葡聚糖和几丁质这两种胞壁主要成分在对照菌丝和药剂处理后的菌丝细胞壁内含量有很大差异。在药剂处理的菌丝细胞壁中,这两种成分的标记密度明显高于对照菌丝,表明杀菌剂对病菌质膜透性的不利影响使?-1,3-葡聚糖和几丁质在菌丝细胞壁中过度累积。     

Characterization of the Sclerotinia sclerotiorum cell wall proteome

We used a proteomic analysis to identify cell wall proteins released from Sclerotinia sclerotiorum hyphal and sclerotial cell walls via a trifluoromethanesulfonic acid (TFMS) digestion. Cell walls from hyphae grown in Vogel's glucose medium (a synthetic medium lacking plant materials), from hyphae grown in potato dextrose broth and from sclerotia produced on potato dextrose agar were used in the analysis. Under the conditions used, TFMS digests the glycosidic linkages in the cell walls to release intact cell wall proteins. The analysis identified 24 glycosylphosphatidylinositol (GPI)‐anchored cell wall proteins and 30 non‐GPI‐anchored cell wall proteins. We found that the cell walls contained an array of cell wall biosynthetic enzymes similar to those found in the cell walls of other fungi. When comparing the proteins in hyphal cell walls grown in potato dextrose broth with those in hyphal cell walls grown in the absence of plant material, it was found that a core group of cell wall biosynthetic proteins and some proteins associated with pathogenicity (secreted cellulases, pectin lyases, glucosidases and proteases) were expressed in both types of hyphae. The hyphae grown in potato dextrose broth contained a number of additional proteins (laccases, oxalate decarboxylase, peroxidase, polysaccharide deacetylase and several proteins unique to Sclerotinia and Botrytis) that might facilitate growth on a plant host. A comparison of the proteins in the sclerotial cell wall with the proteins in the hyphal cell wall demonstrated that sclerotia formation is not marked by a major shift in the composition of cell wall protein. We found that the S. sclerotiorum cell walls contained 11 cell wall proteins that were encoded only in Sclerotinia and Botrytis genomes.     

镉在旱柳中亚细胞分布及存在的化学形态

以2个旱柳无性系幼苗为材料,通过营养液培养并结合差速离心与化学试剂提取法,分析了不同浓度Cd2+胁迫下旱柳叶和根中Cd的亚细胞分布及其存在的化学形态.结果显示,(1)随着培养介质Cd2+浓度升高,旱柳无性系幼苗叶和根中各亚细胞组分Cd含量随之增加.叶片的Cd主要富集于细胞壁、叶绿体和可溶性部分,它们的含量分别占65%～69%、14%～22%、6.8%～7.7%,仅少量Cd发现于膜部分;而根中Cd主要积累于细胞壁和可溶性部分,其中含量分别占59%～66%和14%～25%,Cd在根亚细胞组分中积累量依次为细胞壁>可溶性部分>质体>膜部分.(2)旱柳体内Cd以不同的化学形态存在,大部分为HCl(FHCl)、NaCl(FNaCl)、醋酸(HAC,FHAC)提取态,极少部分为乙醇(EtOH,FEtOH)和水提取态(Fwater),叶和根中5种Cd提取态含量依次为FHCl>FNaCl>FHAC>Fwater>FEtOH,而叶和根中HCl和NaCl提取态Cd占有比例大于30%以上.研究表明,旱柳无性系中Cd主要与蛋白质和有机酸螯合或以金属磷酸盐沉淀的形态存在,其根、叶的细胞壁和液泡在Cd忍耐与解毒中起到重要作用.