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Schematic illustration of the longitudinal section of a mature rice stem and crown root. 109Cd was supplied to a mature rice plant through one crown root for 30min (shown at lower left). The shoot was then sliced into sections at the incision lines (A–R) to trace the 109Cd transport pathway inside the stem. The areas between the central cavities are the nodes. CC, central cavity; CR, crown root; LB, large vascular bundles; LSB, laterally running small vascular bundles; NV, nodal vascular anastomoses; PV, peripheral cylinder of longitudinal vascular bundles; VSB, vertically running small vascular bundles.
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Participation of the intervascular transport system within the rice stem during cadmium (Cd) partitioning was investigated
by characterizing 109Cd behaviour in the shoot. In addition, 45Ca, 32P, and 35S partitioning patterns were analysed for comparison with that of 109Cd. Each tracer was applied to the seedling roots for 15min, and the shoots were...
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... distribution in sequential sections of the mature plant shoot A series of sections corresponding to the positions illus- trated in Fig. 4 are shown in Fig. 5, from the lowest to the uppermost section. 109 Cd was detected in and around the treated crown root, with the maximum amount in the cen- tre (Fig. 5A). 109 Cd signals were also detected in one vascular bundle inside the stem and nodal vascular anastomoses (NV) at the centre of the stem (Fig. 5A). NV are connected to ...Context 2
... the maximum amount in the cen- tre (Fig. 5A). 109 Cd signals were also detected in one vascular bundle inside the stem and nodal vascular anastomoses (NV) at the centre of the stem (Fig. 5A). NV are connected to the large vascular bundles (LB) and the vertically running small vascular bundles (VSB), and NV ascend upwards around the central cavity (Fig. 4). Both LB and VSB are linked to the PV via the laterally running small vascular bundles (Fig. 4). In the second section (Fig. 5B), the 109 Cd-treated crown root is visible beneath the surface of the shoot tissue. 109 Cd signals were detected around the treated crown root and in tissues inside the stem, similar to those seen in Fig. 5A ...Context 3
... bundle inside the stem and nodal vascular anastomoses (NV) at the centre of the stem (Fig. 5A). NV are connected to the large vascular bundles (LB) and the vertically running small vascular bundles (VSB), and NV ascend upwards around the central cavity (Fig. 4). Both LB and VSB are linked to the PV via the laterally running small vascular bundles (Fig. 4). In the second section (Fig. 5B), the 109 Cd-treated crown root is visible beneath the surface of the shoot tissue. 109 Cd signals were detected around the treated crown root and in tissues inside the stem, similar to those seen in Fig. 5A (Fig. 5A, B). The 109 Cd-treated crown root was further inwards in the stem in sections from ...Context 4
... section images of a mature rice stem after applying 109 Cd to one crown root for 30 min. 109 Cd signals are illustrated by heat maps superimposed on bright-field images (top panels). The original bright-field images are shown in the bottom panels. The positions of the sections illustrated in (A-R) correspond to the incision lines indicated in Fig. 4. 109 Cd signals found in the centre of the treated crown root (red arrows), peripheral cylinder of longitudinal vascular bundles in the stem (white arrowheads), nodal vascular anastomoses (blue arrowheads), the small vascular bundle heading to the leaf (blue arrows), and the large vascular bundle (red arrowheads) are marked as noted. ...Context 5
... of the tracer into the stem; this approach resulted in clear images showing the downward Cd transport, which was observed as 109 Cd distribution in PV tissue below the connection point of the treated crown root (Fig. 5A-E and Fig. 6). Considering that the PV in which the crown root was formed was connected to the completely expanded upper leaves (Fig. 4), the xylem flow inside was directed upwards. Therefore, downward Cd transport indicated phloem trans- port of Cd following xylem-to-phloem transfer. Furthermore, the 109 Cd distribution pattern around the PV was clearly restricted to a few vascular bundles ( Fig. 5C-E) originating from the crown root connection point (Fig. 5F). Based ...Similar publications
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Citations
... Similarly, in wheat, 50-60% Cd in mature grains was found to have occurred by re-mobilization through phloem from leaves and stem [62]. Rice nodes, especially the first node, are the important transfer stations where Cd can be loaded into the rice phloem [63]. In addition, it was suggested that OsHMA2, highly expressed in the nodes and close to the vascular bundles, could be involved in mediating Cd transference from the xylem sap to the phloem [64]. ...
Cadmium (Cd) contamination in rice grains is posing a significant threat to global food security. To restrict the transport of Cd in the soil-rice system, an efficient way is to use the ionomics strategy. Since calcium (Ca) and Cd have similar ionic radii, their uptake and translocation may be linked in multiple aspects in rice. However, the underlying antagonistic mechanisms are still not fully understood. Therefore, we first summarized the current knowledge on the physiological and molecular footprints of Cd translocation in plants and then explored the potential antagonistic points between Ca and Cd in rice, including exchange adsorption on roots, plant cell-wall composition, co-transporter gene expression, and transpiration inhibition. This review provides suggestions for Ca/Cd interaction studies on rice and introduces ionomics research as a means of better controlling the accumulation of Cd in plants.
... Similarly in wheat, 50-60% Cd in mature grains was found by re-mobilization through phloem from leaves and stem [61]. Rice nodes were the important transfer stations when Cd can be loading Cd into the rice phloem, especially for the first node [62]. In addition, it was suggested that OsHMA2, highly expressed in the nodes and close to the vascular bundles, could be involved in mediating Cd transference from the xylem sap to the phloem [63]. ...
Cadmium (Cd) contamination in rice grains is posing a significant threat to global food security. To restrict the transport of Cd in the soil-rice system, an efficient way is to use the ionomics strate-gy. Since calcium (Ca) and Cd have similar ionic radii, their uptake and translocation may be linked in multiple aspects in rice. However, the underlying antagonistic mechanisms are still not fully understood. Therefore, we first summarized the current knowledge on the physiological and molecular footprints of Cd translocation in plants and then explored the potential antagonistic points between Ca and Cd in rice, including exchange adsorption on roots, plant cell wall compo-sition, co-transporter gene expression, and transpiration inhibition. This review provides sugges-tions for the Ca/Cd interacting study in rice and introduces the ionomics research to better control the accumulation of Cd in plants.
... Node I was preferentially enriched in heavier Cd isotopes than the stems (Δ 114/110 Cd node I-stem = 0.13 to 0.38 ‰). Stems contain xylem, phloem, and parenchyma cells (Yamaji and Ma, 2017), and most of the Cd inside the stem is distributed in vascular bundles and parenchyma cells (Kobayashi et al., 2013). A major pathway for Cd transport from the basal stem to node I requires xylem-to-phloem transfer in the nodes (Fujimaki et al., 2010;Yamaji and Ma, 2017), with heavy Cd isotopes being preferentially transported to node I via the OsLCT1 and OsHMA2 transporters. ...
... In straws, light Cd isotopes were preferentially transported from stem to total leaves, and from node I to the flag leaves (Δ 114/110 Cd flag leaves-node I = -0.82 to −0.24 ‰), as observed in previously reported soil-rice systems (−0.53 to −0.12 ‰) (Gao et al., 2022;Wiggenhauser et al., 2021b). The major driving force of transpiration or CAL1 protein generally promotes the movement of light Cd isotopes from node I to the flag leaves via xylem (Luo et al., 2018;Kobayashi et al., 2013). The magnitude of fractionation from nodes I to flag leaves was decreased upon flooding of grain filling. ...
Grain filling is the key period that causes excess cadmium (Cd) accumulation in rice grains. Nevertheless, uncertainties remain in distinguishing the multiple sources of Cd enrichment in grains. To better understand the transport and redistribution of Cd to grains upon drainage and flooding during grain filling, Cd isotope ratios and Cd-related gene expression were investigated in pot experiments. The results showed that the Cd isotopes in rice plants were much lighter than those in soil solutions (∆114/110Cdrice-soil solution = -0.36 to -0.63 ‰) but moderately heavier than those in Fe plaques (∆114/110Cdrice-Fe plaque = 0.13 to 0.24 ‰). Calculations revealed that Fe plaque might serve as the source of Cd in rice (69.2 % to 82.6 %), particularly upon flooding at the grain filling stage (82.6 %). Drainage at the grain filling stage yielded a larger extent of negative fractionation from node I to the flag leaves (∆114/110Cdflag leaves-node I = -0.82 ± 0.03 ‰), rachises (∆114/110Cdrachises-node I = -0.41 ± 0.04 ‰) and husks (∆114/110Cdrachises-node I = -0.30 ± 0.02 ‰), and significantly upregulated the OsLCT1 (phloem loading) and CAL1 (Cd-binding and xylem loading) genes in node I relative to that upon flooding. These results suggest that phloem loading of Cd into grains and transport of Cd-CAL1 complexes to flag leaves, rachises and husks were simultaneously facilitated. Upon flooding of grain filling, the positive fractionation from the leaves, rachises and husks to the grains (∆114/110Cdflag leaves/rachises/husks-node I = 0.21 to 0.29 ‰) is less pronounced than those upon drainage (∆114/110Cdflag leaves/rachises/husks-node I = 0.27 to 0.80 ‰). The CAL1 gene in flag leaves is down-regulated relative to that upon drainage. Thus, the supply of Cd from the leaves, rachises and husks to the grains is facilitated during flooding. These findings demonstrate that the excess Cd was purposefully transported to grain via xylem-to-phloem within nodes I upon the drainage during grain filling, and the expression of genes responsible for encoding ligands and transporters together with isotope fractionation could be used to tracking the source of Cd transported to rice grain.
... With respect to Cd, Cd contaminated soils often result in elevated wheat grain Cd concentrations simply due to the transport mechanisms that carry Cd through the soil-root-shoot-grain continuum (Clemens et al., 2013;Rizwan et al., 2016;Li et al., 2020;Rezapour et al., 2022). Wheat can directly or indirectly absorb heavy metals from atmospheric deposition on foliar surfaces through cuticular cracks, stomata, lenticel, ectodesmata and aqueous pores (Shahid et al., 2017;Rossi et al., 2019); it has been confirmed that foliar absorbed Pb contributed to wheat grain Pb accumulation (Fujimaki et al., 2010;Kobayashi et al., 2013;Ma et al., 2021b;Zhang et al., 2022). ...
Atmospheric deposition of Cd, from anthropogenic activities, can be directly deposited onto and absorbed into wheat plants, yet, how foliar absorbed Cd is translocated in wheat plants is not well understood. A pot experiment investigated foliar Cd application on the accumulation and distribution of heavy metals in various wheat parts. Wheat was grown in a Cd/heavy metal contaminated soil, and from grain heading to the filling stage, 0, 10, 20, 30 and 40 mg kg-1 Cd solution was sprayed repeatedly on leaves (grain heads were covered). Foliar Cd application had no effect on grain yield and Cd concentration (3.01-3.51 mg kg-1 for all treatments), while increased flag leaf blade and sheath Cd concentrations by 1.06-2.77 and 0.00-0.66 times, respectively. Cadmium concentration in the center of the peduncle, from the 40 mg kg-1 Cd solution treatment, was 1.41 times that of the control (10.3 vs 7.30 mg kg-1). Foliar Cd application also increased Cd accumulation (concentration × mass) of the flag leaf blade and sheath. Rachis and grain Pb concentrations were reduced, while stem Pb concentration was increased by Cd application. Cadmium application negatively affected whole plant Ni accumulation and concentration of certain wheat parts; Ni absorption inhibition may have occurred in roots via the downward transport of Cd. Overall results implied that the predominant portion of foliar applied Cd was retained in leaves, while lesser portions migrated to peduncle or root and affected the absorption/distribution of other metals in wheat plants. These results are important for further discerning the mechanism of wheat grain Cd accumulation, especially when grain is raised in areas where atmospheric deposition of Cd (e.g., near smelting facilities) is an issue from an environmental and human health perspective.
10.1016/j.chemosphere.2023.138177
... With respect to Cd, Cd contaminated soils often result in elevated wheat grain Cd concentrations simply due to the transport mechanisms that carry Cd through the soil-root-shoot-grain continuum (Clemens et al., 2013;Rizwan et al., 2016;Li et al., 2020;Rezapour et al., 2022). Wheat can directly or indirectly absorb heavy metals from atmospheric deposition on foliar surfaces through cuticular cracks, stomata, lenticel, ectodesmata and aqueous pores (Shahid et al., 2017;Rossi et al., 2019); it has been confirmed that foliar absorbed Pb contributed to wheat grain Pb accumulation (Fujimaki et al., 2010;Kobayashi et al., 2013;Ma et al., 2021b;Zhang et al., 2022). ...
Atmospheric deposition of Cd, from anthropogenic activities, can be directly deposited onto and absorbed into wheat plants, yet, how foliar absorbed Cd is translocated in wheat plants is not well understood. A pot experiment investigated foliar Cd application on the accumulation and distribution of heavy metals in various wheat parts. Wheat was grown in a Cd/heavy metal contaminated soil, and from grain heading to the filling stage, 0, 10, 20, 30 and 40 mg kg-1 Cd solution was sprayed repeatedly on leaves (grain heads were covered). Foliar Cd application had no effect on grain yield and Cd concentration (3.01-3.51 mg kg-1 for all treatments), while increased flag leaf blade and sheath Cd concentrations by 1.06-2.77 and 0.00-0.66 times, respectively. Cadmium concentration in the center of the peduncle, from the 40 mg kg-1 Cd solution treatment, was 1.41 times that of the control (10.3 vs 7.30 mg kg-1). Foliar Cd application also increased Cd accumulation (concentration × mass) of the flag leaf blade and sheath. Rachis and grain Pb concentrations were reduced, while stem Pb concentration was increased by Cd application. Cadmium application negatively affected whole plant Ni accumulation and concentration of certain wheat parts; Ni absorption inhibition may have occurred in roots via the downward transport of Cd. Overall results implied that the predominant portion of foliar applied Cd was retained in leaves, while lesser portions migrated to peduncle or root and affected the absorption/distribution of other metals in wheat plants. These results are important for further discerning the mechanism of wheat grain Cd accumulation, especially when grain is raised in areas where atmospheric deposition of Cd (e.g., near smelting facilities) is an issue from an environmental and human health perspective.
... Cd, which has high mobility in the soil, enters plants through the roots and moves through all parts of plants and causes multiple symptoms of toxicity [23]. The level of Cd accumulation in plants depends on many factors, such as its total content in the soil, biological availability, genetic features of plants, soil properties, and the rhizosphere [24][25][26]. Cd negatively affects the growth and development of plants, and it has a negative impact on various physiological and biochemical processes, but plants have developed various resistance mechanisms to reduce Cd toxicity [27]. Under Cd stress, growth parameters decrease and physiological and biochemical processes are disrupted-the content of photosynthetic pigments and the intensity of photosynthesis decrease, and water absorption, mineral nutrition, and carbohydrate metabolism are disrupted [28][29][30]. ...
... Cd, which has high mobility in the soil, enters plants through the roots and moves through all parts of plants and causes multiple symptoms of toxicity [23]. The level of Cd accumulation in plants depends on many factors, such as its total content in the soil, biological availability, genetic features of plants, soil properties, and the rhizosphere [24][25][26]. Cd negatively affects the growth and development of plants, and it has a negative impact on various physiological and biochemical processes, but plants have developed various resistance mechanisms to reduce Cd toxicity [27]. Under Cd stress, growth parameters decrease and physiological and biochemical processes are disrupted-the content of photosynthetic pigments and the intensity of photosynthesis decrease, and water absorption, mineral nutrition, and carbohydrate metabolism are disrupted [28][29][30]. ...
Due to the environment pollution by cadmium (Cd) near industrial metallurgic factories and the widespread use of phosphorus fertilizers, the problem of toxic Cd effect on plants is well discussed by many authors, but the phytotoxicity of Cd under iron (Fe) deficiency stress has not been sufficiently studied. The aim of the work was to study comprehensively the effect of Cd under Fe deficiency conditions on physiological, biochemical, and anatomical parameters of rice varieties, to identify varietal differences in plant response to the effect of double stress. Relative resistance and sensitivity to the joint effect of Cd and Fe deficiency stress rice varieties have been identified. Double stress decreased a linear growth and biomass accumulation of roots and shoots (by 36-50% and 33-46% and 32-56% and 32-48%, accordingly), content of photosynthetic pigments (Chla, Chlb, and carotenoids by 36-51%, 32-47%, and 64-78%, accordingly), and relative water content (by 18-26%). Proline content increased by 28-103% in all rice varieties, but to a lesser extent in sensitive varieties. The thickness of the lower and upper epidermis and the diameter of vascular bundles of leaves decreased by 18-50%, 46-60%, and 13-48%, accordingly. The thickness of the root endodermis and exodermis and diameter of the central cylinder mainly decreased. The thickness of the exodermis increased slightly by 7%, and the diameter of the central cylinder remained at the control level in resistant Madina variety while in sensitive Chapsari variety, these indicators decreased significantly by 50 and 45%, accordingly. Thus, the aggravation of adverse effect of Cd under Fe deficiency conditions and the varietal specificity of plants’ response to double stress were shown. It creates the need for further study of these rice varieties using Fe to identify mechanisms for reducing the toxic effect of Cd on plants as well as the study of Fe and Cd transporter genes at the molecular level.
... During early grain filling stage in rice, many essential nutrients are remobilized from different plant organs toward grains (Kobayashi et al., 2013). Cd and other mineral elements are generally accumulated in rachises of panicles that form the bases for the termination of vascular bundles in the stem (Fujimaki et al., 2010). ...
Cadmium (Cd) has detrimental effects on crop plants, whereas, jasmonates (JAs) play a vital role in abiotic stress tolerance in plants. The present study investigated the effects of exogenous application of methyl jasmonate (MeJa) on the physio-biochemical attributes, yield, and quality of two fragrant rice cultivars, i.e., Xiangyaxiangzhan and Meixiangzhan-2 under Cd stress. The experiment was comprised of four treatments, i.e., CK, control (normal conditions); Cd: 100 mg Cd kg–1 of soil; MeJa: exogenous application of MeJa at 20 mM; and Cd + MeJa: 100 mg Cd kg–1 of soil + exogenous MeJa application at 20 mM. Results depicted that Cd toxicity resulted in a substantial reduction of enzymatic activities and non-enzymatic antioxidants, chlorophyll contents, while enhanced oxidative damage in the terms of lipid peroxidation (higher malondialdehyde (MDA) contents), H2O2, and electrolyte leakage. Proline contents were found higher whereas protein and soluble sugars were lower under Cd stress as compared with Ck and Cd + MeJa. Exogenous MeJa application further improved the panicles per pot, spikelets per panicle, seed setting (%), 1,000 grain weight, and yield per pot under Cd stress conditions as compared with non-MeJa applied plant under Cd stress. In addition, exogenous MeJa application enhanced the accumulation of macro (N, P, K, Mg, and Ca) and micronutrients (Mn, Zn, Fe, and Cr) in both cultivars under Cd stress, while reduced the Cd contents in different plant parts. Overall, the contents of Cd in different plant organs were recorded as: root > stem > leaves > grains for all treatments. Comparing both cultivars, the grain Cd contents were higher in Meixiangzhan 2 than Xiangyaxianzhan under Cd contaminated conditions. Conclusively, Cd toxicity impaired growth in rice by affecting physio-biochemical attributes, however, Xiangyaxiangzhan performed better than Meixiangzhan-2 cultivar.
... The highest Cd accumulation was found in the youngest leaves because the youngest leaves showed the highest biomass, although their Cd concentrations were lower than those in the older leaves (Fig. 1c). This is consistent with previous findings that Cd is preferentially transported towards the newest leaf due to a higher transpiration rate and greater demand for nutrients for leaf development in young leaves (Page and Feller, 2015;Kobayashi et al., 2013). Free Cd 2+ is reported to be the major transport form in the xylem sap (Alvarez-Fernández et al., 2014;Clemens and Ma, 2016). ...
... The increasing enrichment of heavier Cd isotopes from the bottom leaf to the second leaf under flooded conditions may be partially ascribed to the Cd 2+ transported to the upper leaves via the xylem . In addition, Cd in the xylem of stems can be immediately loaded onto the phloem after Cd is transported from the root, and Cd may bind to thiol-containing ligands such as GSH and PCs in the phloem sap of rice (Kato et al., 2010;Kobayashi et al., 2013;Yamaji and Ma, 2014). Such an intervascular transfer process can be mediated by OsHMA2 (Yamaji et al., 2013), but no resolvable isotope fractionation has been observed in transgenic yeast expressing TcHMA2 from the cacao plant (Moore et al., 2020). ...
Multiple processes are involved in Cd transfer in rice plants, including root uptake, xylem loading, and immobilization. These processes can be mediated by membrane transporters and can alter Cd speciation by binding Cd to different organic ligands. However, it remains unclear which processes control Cd transport in rice in response to different watering conditions in soil. Herein, Cd isotope fractionation and Cd-related gene expression were employed to investigate the key regulatory mechanisms during uptake, root-to-shoot, and stem-to-leaf transport of Cd in rice grown in pot experiments with Cd-contaminated soil under flooded and non-flooded conditions, respectively. The results showed that soil flooding decreased the Cd concentration in soil porewater and, thereby, Cd uptake and transport in rice. Cd isotopes fractionated negatively from soil porewater to the whole rice (flooded: ∆114/110Cdrice-porewater = −0.15‰, non-flooded: ∆114/110Cdrice-porewater = −0.39‰), suggesting that Cd transporters preferentially absorbed light Cd isotopes. The non-flooded treatment revealed an upregulated expression of OsNRAMP1 and OsNRAMP5 genes compared to the flooded treatment, which may partially contribute to its more pronounced porewater-to-rice fractionation. Cd isotopes fractionated positively from roots to shoots under flooded conditions (∆114/110Cdshoot-root = 0.19‰). However, a reverse direction of fractionation was observed under non-flooded conditions (∆114/110Cdshoot-root = −0.67‰), which was associated with the substantial upregulation of CAL1 in roots, facilitating xylem loading of Cd-CAL1 complexes with lighter isotopes. After being transported to the shoots, the majority of Cd were detained in stems (44%–55%), which were strongly enriched in lighter isotopes than in the leaves (∆114/110Cdleaf-stem = 0.77 to 1.01‰). Besides the Cd-CAL1 transported from the roots, the expression of OsPCS1 and OsHMA3 in the stems could also favor the enrichment of Cd-PCs with lighter isotopes, leaving heavier isotopes to be transported to the leaves. The higher expression levels of OsMT1e in older leaves than in younger leaves implied that Cd immobilization via binding to metallothioneins like OsMT1e may favor the enrichment of lighter isotopes in older leaves. The non-flooded treatment showed lighter Cd isotopes in younger leaves than the flooded treatment, suggesting that more Cd-CAL1 in the stems and Cd-PCs in the older leaves might be transported to the younger leaves under non-flooded conditions. Our results demonstrate that isotopically light Cd can be preferentially transported from roots to shoots when more Cd is absorbed by rice under non-flooded conditions, and isotope fractionation signature together with gene expression quantification has the potential to provide a better understanding of the key processes regulating Cd transfer in rice.
... The movement of an element results from the combination or balance between xylem and phloem flow and is very complicated, similar to water flow [11]. Therefore, the only method to solve these problems in the dynamic movement of elements is the application of radioisotopes for tracer work. ...
For the first stage of the study of the elements, the distribution of the element within the plant tissue was presented employing neutron activation analysis (NAA). Since NAA allows nondestructive analysis of the elements in the sample, this is the only method to measure the absolute amount of elements in the sample. The results showed that the element-specific profile varied throughout the whole plant, and this distribution tendency remained similar throughout development. There were many junctions of element-specific concentrations between the tissues, suggesting barriers to the movement of the elements. Generally, heavy elements tended to accumulate in roots, except for Mn and Cr. Of the elements measured, Ca and Mg showed changes in concentration with the circadian rhythm. Since the amount of the element in a plant reflects the features of the soil where the plant grows, multielement analysis of the plant could specify the site of the agricultural products produced. Before addressing the development of a real-time RI imaging system (RRIS), the production of RIs for essential elements for plant nutrition, 28Mg and 42K, is presented. The reason why concentrating on RIs is because when we examine the history of plant research, physiological research on the elements without available radioisotopes has not been well developed. For example, the boron (B) transporter was recently found and the study of B in plants is far behind compared to the other elements. Therefore, we developed a preparation method for elements whose available RIs were not previously employed in plant research, 28Mg and 42K. They are the radioisotopes we prepared and a root absorption study using 28Mg as a tracer is presented as an example. It was found that the orientation of Mg transfer was different according to the site of the root where Mg was absorbed. The specific role of Mg has not yet been clarified by florescent imaging because the overwhelming amount of Ca makes it difficult to distinguish Mg and Ca.
