甘蓝型油菜根系突变体lrn1、prl1和野生型根系显微结构的差异

油菜外源细胞分裂素不敏感突变体lrn1和prl1表现为磷高效。营养液培养0.2μmol/L细胞分裂素(6-BA)处理,与甘蓝型油菜野生型‘宁油7号’(WT)相比,突变体lrn1侧根较多,prl1主根较长。本研究利用体式显微技术、非切片压片法以及石蜡切片等技术,对3个基因型在ddH2O和0.2μmol/L 6-BA处理下的根毛、根表皮细胞分化及根尖解剖结构的差异进行了观察,结果表明:ddH2O处理,种子发芽后第1、3、6、9 d,lrn1、prl1和WT根尖成熟区根毛较少。0.2μmol/L 6-BA处理,种子发芽后第3 d,lrn1、prl1和WT根尖形成大量根毛,其中WT根毛最多、密度最大;prl1根毛最少,密度也最小;lrn1处于两者之间。种子发芽后第6 d,lrn1、prl1和WT分生区和伸长区明显缩短,lrn1和prl1分生区面积无显著差异,但两者均显著大于WT;lrn1和prl1根冠细胞结构较正常,而WT根冠细胞结构畸形;lrn1皮层原细胞之间排列较WT和prl1紧密。种子发芽后第9 d,lrn1已有4条侧根,但prl1与WT无侧根形成。6-BA处理,prl1主根较长,与其根尖分生区面积较大密切相关;lrn1侧根较多,可能与中柱原细胞排列密度较高密切相关。     

Identification of quantitative trait loci associated with low boron stress that regulate root and shoot growth in Brassica napus seedlings

Brassica napus (Brassicaceae) is among the most important oil crops and a promising biofuel. In the tropics and subtropics, boron (B) deficiency is a major factor limiting Brassica yields. The effect of B on the regulation of root and shoot growth in a doubled haploid (DH) population was evaluated in experiments that utilized hydroponic culture. Strong genetic variability for traits of interest at normal and low B concentrations was demonstrated. Quantitative trait loci (QTL) were analyzed for seven plant growth parameters: increment of primary root length (IPRL), shoot dry weight (SDW), root dry weight (RDW), ratio of RDW to SDW (R/S), shoot B accumulation (SBA), root B accumulation (RBA), and ratio of RBA to SBA [(R/S)BA] in the population. Twenty-seven QTL were detected at normal B levels: four for IPRL, seven for SDW, three for RDW, two for R/S, six for SBA, two for RBA, and three for (R/S)BA. At low B, 18 QTL were detected: four for IPRL, three for SDW, two for RDW, two for R/S, five for SBA, one for RBA, and one for (R/S)BA. Three QTL for adaptability were detected: one A_IPRL and two A_SDW. No putative QTL was detected at both low and normal B. B-related genes were mapped in silico and their locations compared with the QTL identified. The present analyses show the profound and varied effects of B on B. napus and studies on QTL related to B efficiency will help to locate candidate genes and elucidate possible functions of B-efficiency-related QTL.     

Aluminum induces low phosphate adaptive responses and modulates primary and lateral root growth by differentially affecting auxin signaling in Arabidopsis seedlings

Aims

The aims of this work were to investigate the aluminum (Al) and phosphate (P) interactions in the regulation of root system architecture of Arabidopsis thaliana seedlings and the contribution of auxin signaling in primary and lateral root growth in response to Al toxicity.

Methods

Detailed analyses of root system architecture and cell division were performed in Arabidopsis WT seedlings and in low phosphorus insensitive mutants lpi1-3 and lpr1-1 lpr2-1 in response to Al. Expression studies of P-deficiency regulated phosphate transporter AtPT2 were also conducted. The role of auxin as a mediator of root morphogenetic changes by Al was evaluated by using the auxin-signaling mutants tir1, tir1 afb2 afb3, and arf7 arf19.

Results

Al inhibited primary root growth by affecting cell cycle progression and causing differentiation of cells in the root meristem. These effects were reduced in low phosphorus insensitive lpi1-3 and low phosphate resistant lpr1-1 lpr2-1 Arabidopsis mutants. Al also activated the expression of the low phosphate-induced P transporter AtPT2 in roots. Lateral root formation by Al decreased in tir1 afb2 afb3 while arf7 arf19 mutants were highly resistant to Al in both primary root inhibition and lateral root induction.

Conclusions

Our results suggest that lateral root formation in response to Al toxicity and P deficiency may involve common signaling mechanisms, while a pathway involving ARF7 and ARF19 is important for primary root growth inhibition by Al.     

In situ localization of Paenibacillus polymyxa HKA-15 in roots and root nodules of soybean (Glycine max.L.)

Background and aims

Bacterial endophytes can colonize various plants and organs. However, endophytic bacteria (other than rhizobia) colonizing root nodules in legumes have been rarely analyzed. The present study aimed to examine the colonization and spread of gfp-tagged Paenibacillus polymyxa in soybean plants under gnobiotic conditions.

Methods

Inoculation with gfp-tagged Paenibacillus. polymyxa HKA ?15 alone and in combination with Bradyrhizobium japonicum were done on soybean seedlings. In situ localization was detected through confocal microscopy and PCR.

Results

Inoculation with P. polymyxa-gfp strain alone and in combination with B. japonicum DS-1 had a stimulatory effect on the plant growth. There was an increase in shoot (7.2 %) and root dry weights (14.5 %) when the two strains were co - inoculated over that of B. japonicum inoculation alone. In vivo simultaneous visualization using Confocal Laser Scanning Microscopy (CLSM) showed the localization of the gfp-tagged P. polymyxa cells in the root nodules and its spread in the root tissue, both tap as well as lateral roots. Systemic spread into aerial tissue did not occur as indicated by the absence of bacteria. CLSM observations of the presence of gfp-tagged P. polymyxa in the nodule and roots tissues was corroborated with PCR amplification of the gfp-gene from these tissues.

Conclusions

CLSM and PCR methods confirmed that P. polymyxa invades roots and root nodules of soybean, but the spread is restricted to root tissue only. The strain improves plant growth when inoculated singly or in combination with B. japonicum.     

Interaction between root growth allocation and mycorrhizal fungi in soil with patchy P distribution

Aims and Background

Many plants preferentially grow roots into P-enriched soil patches, but little is known about how the presence of arbuscular mycorrhizal fungi (AMF) affects this response.

Methods

Lotus japonicus (L.) was grown in a low-P soil with (a) no additional P, (b) homogeneous P (28 mg pot^?1), (c) low heterogeneous P (9.3 mg pot^?1), and (d) high heterogeneous P (28 mg pot^?1). Each P treatment was combined with one of three mycorrhiza treatments: no mycorrhizae, Glomus intraradices, indigenous AMF. Real-time PCR was used to assess the abundance of G. intraradices and the indigeneous AMF G. mosseae and G. claroideum.

Results

Mycorrhization and P fertilization strongly increased plant growth. Homogeneous P supply enhanced growth in both mycorrhizal treatments, while heterogeneous P fertilization increased biomass production only in treatments with indigenous AMF inoculation. Preferential root allocation into P-enriched soil was significant only in absence of AMF. The abundance of AMF species was similar in P-enriched and unfertilized soil patches.

Conclusion

Mycorrhization may completely override preferential root growth responses of plants to P- patchiness in soil. The advantage of this effect for the plants is to give roots more freedom to forage for other resources in demand for growth and to adapt to variable soil conditions.     

The effect of phosphorus on cluster-root formation and functioning of Embothrium coccineum (R. et J. Forst.)

Background and aims

Embothrium coccineum (R. et J. Forst.) is a Proteaceae species from the southern part of South America. South-central Chilean soils are younger and contain more phosphorus (P) than soils in Australia and South Africa, where Proteaceae are common. Phosphorus deficiency is the main factor promoting cluster-root formation in Proteaceae. It is not known, however, whether this also applies to E. coccineum, which grows on soils with higher P content.

Methods

Four-month-old seedlings were grown for 4 weeks in hydroponic cultures with 1 μM P or 50 μM P. The number of cluster roots, relative height increment, biomass distribution, cluster root/total root biomass ratio, foliar P concentration, root acid phosphatase activity and root carboxylate-exudation rates were determined.

Results

Seedlings growing at 50 μM P showed a 10?, 1.3? and 3.3-fold greater increase in relative height, total dry mass and foliar P concentration, respectively, compared with those grown at1 μM P. However, seedlings grown at 1 μM P showed a 5?, 16?, 1.7? and 1.3-fold greater number of cluster roots, cluster root/total root biomass ratio, phosphatase activity and total carboxylate exudation, respectively, as compared with those grown at 50 μM P.

Conclusions

A low P supply promotes the initiation, growth and metabolic activity of cluster roots which is in accordance with reports on Proteaceae species occurring in ancient and highly weathered soils.     

Interactive effects of soil nutrient heterogeneity and belowground herbivory on the growth of plants with different root foraging traits

Aims

Plants with precise root foraging patterns can proliferate roots preferentially in nutrient-rich soil patches. When nutrients are distributed heterogeneously, this trait is often competitively advantageous in pot experiments but not field experiments. We hypothesized that this difference is due to belowground herbivory under field conditions.

Methods

We performed pot experiments using seedlings of Lolium perenne (a more precise root foraging species) and Plantago lanceolata (a less precise root foraging species). The experiment had a two-way factorial randomized block design, with nutrient distribution pattern (homogeneous or heterogeneous) and belowground herbivore (present or absent) as the two factors. Each pot contained one seedling of each species.

Results

With no herbivore present, plant biomass was smaller in the heterogeneous nutrient treatment than in the homogeneous treatment in P. lanceolata, but not in L. perenne. Under homogeneous nutrient distribution, plant biomass was lower in both species with a herbivore present than with no herbivore. Under heterogeneous nutrient distribution, biomass reduction due to herbivory occurred only in L. perenne.

Conclusions

Roots of the precise root foraging species were grazed more under the heterogeneous nutrient distribution, suggesting that the herbivore more efficiently foraged for roots in nutrient-rich soil patches.     

Growth of tree roots in hostile soil: A comparison of root growth pressures of tree seedlings with peas

Background and Aims

As part of a study on growth of tree roots in hostile soil, we envisaged that establishment and survival of trees on hard, dry soil may depend on their ability to exert axial root growth pressures of similar magnitude to those of the roots of agricultural plants (with significant root thickening when roots grow across an air gap or cracks and biopores). We selected tree species originating from a range of different soil and climatic conditions to evaluate whether their relative success on harsh soil (in an evolutionary sense) might be related to the magnitude of root growth pressures they could exert, or how they performed in the very early stages of growth after germination.

Methods

We measured the maximum axial root growth force (F_max) on single lateral root axes of 3- to 4- month old seedlings of 6 small-seeded eucalypts from 2 different habitats and 2 contrasting soil types. Root growth rate, root diameter and F_max were also measured on the primary root axes of a large-seeded acacia and a domesticated annual (Pisum sativum) seedling for up to 10 days following germination.

Results

The lateral roots of the 6 eucalypts and the primary roots of the acacia were considerably smaller than the primary roots of P. sativum and they exerted average forces of similar magnitude to one another (0.198 to 0.312 N). The maximum axial root growth pressures were all in the range 150 to 250 kPa but E. leucoxylon, E. loxophleba and A. salicina exerted the greatest pressures among the trees, and comparable pressures to those exerted by the primary roots of 2-day-old P. sativum (211-252 kPa). Although the primary roots of acacia seedlings exerted increasing axial root growth pressures over a 10-day period following germination, the pressures were still only slightly greater than those of the domesticated plant, P. sativum.

Conclusions

The lack of any very large differences in axial root growth pressures between trees and domesticated plants suggests that trees that grow well in harsh soil don’t do so by exerting higher root growth pressures alone but by also exploring the network of cracks and pores more effectively than do other plants that are less successful.     

Response of Populus tremula to heterogeneous B distributions in soil

Background

Poplars accumulate inordinate amounts of B in their leaves and are candidate plants for the remediation of B contaminated soil. We aimed to determine the effect of heterogeneous B distribution in soil by comparing the growth and B accumulation of young Populus tremula trees growing in soil with heterogeneous and homogeneous B distributions.

Methods

The first of two experiments focused on the tolerance and B accumulation of P. tremula under heterogeneous soil B distributions, while the second was designed to study fine root growth under such conditions in detail.

Results

Growth and B accumulation of P. tremula were unaffected by the spatial distribution of B. Root and shoot growth were both reduced simultaneously when leaf B concentrations increased above 800 mg kg^?1. In the heterogeneous soil B treatments, root growth was more reduced in spiked soil portions with B concentrations >20 mg kg^?1. Fine root length growth was stronger inhibited by B stress than secondary growth.

Conclusions

The root growth responses of P. tremula to B are primarily a systemic effect induced by shoot B toxicity and local toxicity effects on roots become dominant only at rather high soil B concentrations. Local heterogeneity in soil B should have little influence on the phytoremediation of contaminated sites.     

Potential phosphorus release from catch crop shoots and roots after freezing-thawing

Background and aims

Catch crops used for mitigating nutrient losses to water can release phosphorus (P) when exposed to repeated freezing-thawing cycles (FTCs). This study sought to evaluate potential P losses from shoots and roots of eight catch crops.

Methods

Shoots and roots sampled from perennial ryegrass (Lolium perenne L.), cocksfoot (Dactylis glomerata L.), chicory (Cichorium intybus L.), phacelia (Phacelia tanacetifolia L.), red clover (Trifolium pratense L.), white mustard (Sinapis alba L.), oilseed radish (Raphanus sativus var. oleiformis L.) and white radish (R. sativus var. longipinnatus L.) were treated with no freezing, one single FTC, four continuous FTCs and four discontinuous FTCs. All samples were analysed for water-extractable P (WEP), and root samples also for characteristics such as specific root surface area (SSA).

Results

Freezing-thawing significantly increased potential P losses from both shoots and roots compared with no freezing. The two radish species and white mustard contained significantly higher concentrations of WEP than the other species, among which chicory and phacelia had the lowest WEP. On average, shoots had 43 % higher WEP than roots. Cumulative P release from shoots and roots was strongly correlated with their total-P content (p?=?0.006 and p?=?0.002, respectively). Cumulative release of P from taproots was correlated with SSA (p?=?0.03).

Conclusions

Chicory, and possibly phacelia, appear to be promising catch crops for P.     

Relation of fine root distribution to soil C in a Cunninghamia lanceolata plantation in subtropical China

Background and aims

Growth and distribution of fine roots closely depend on soil resource availability and affect soil C distribution in return. Understanding of relationships between fine root distribution and soil C can help to predict the contribution of fine root turnover to soil C accumulation.

Methods

A study was conducted in a subtropical Cunninghamia lanceolata plantation to assess the fine root mass density (FRMD), fine root C density (FRCD) of different fine root groups as well as their relations with soil C.

Results

The FRMD and FRCD of short-lived roots, dead roots and herb roots peaked in the 0–10 cm soil layer and decreased with soil depth, while FRMD, FRCD of long-lived roots peaked in the 10–20 cm soil layer. Soil C was positively related to FRMD and FRCD of total fine roots (across all three soil layers), dead roots (0–10 cm) and herb roots (10–20 cm) as well as FRCD of short-lived roots (20–40 cm) (P <0.05).

Conclusions

Soil C was mainly affected by herb roots in upper soil layers and by woody plant roots in deeper soil layers.     

Anisohydric behaviour in grapevines results in better performance under moderate water stress and recovery than isohydric behaviour

Aims

Arbuscular mycorrhizal fungi (AMF) can control root-knot nematode infection, but the mode of action is still unknown. We investigated the effects of AMF and mycorrhizal root exudates on the initial steps of Meloidogyne incognita infection, namely movement towards and penetration of tomato roots.

Methods

M. incognita soil migration and root penetration were evaluated in a twin-chamber set-up consisting of a control and mycorrhizal (Glomus mosseae) plant compartment (Solanum lycopersicum cv. Marmande) connected by a bridge. Penetration into control and mycorrhizal roots was also assessed when non-mycorrhizal or mycorrhizal root exudates were applied and nematode motility in the presence of the root exudates was tested in vitro.

Results

M. incognita penetration was significantly reduced in mycorrhizal roots compared to control roots. In the twin-chamber set-up, equal numbers of nematodes moved to both compartments, but the majority accumulated in the soil of the mycorrhizal plant compartment, while for the control plants the majority penetrated the roots. Application of mycorrhizal root exudates further reduced nematode penetration in mycorrhizal plants and temporarily paralyzed nematodes, compared with application of water or non-mycorrhizal root exudates.

Conclusions

Nematode penetration was reduced in mycorrhizal tomato roots and mycorrhizal root exudates probably contributed at least partially by affecting nematode motility.     

High-throughput root phenotyping screens identify genetic loci associated with root architectural traits in Brassica napus under contrasting phosphate availabilities

Background and Aims

Phosphate (Pi) deficiency in soils is a major limiting factor for crop growth worldwide. Plant growth under low Pi conditions correlates with root architectural traits and it may therefore be possible to select these traits for crop improvement. The aim of this study was to characterize root architectural traits, and to test quantitative trait loci (QTL) associated with these traits, under low Pi (LP) and high Pi (HP) availability in Brassica napus.

Methods

Root architectural traits were characterized in seedlings of a double haploid (DH) mapping population (n = 190) of B. napus [‘Tapidor’ × ‘Ningyou 7’ (TNDH)] using high-throughput phenotyping methods. Primary root length (PRL), lateral root length (LRL), lateral root number (LRN), lateral root density (LRD) and biomass traits were measured 12 d post-germination in agar at LP and HP.

Key Results

In general, root and biomass traits were highly correlated under LP and HP conditions. ‘Ningyou 7’ had greater LRL, LRN and LRD than ‘Tapidor’, at both LP and HP availability, but smaller PRL. A cluster of highly significant QTL for LRN, LRD and biomass traits at LP availability were identified on chromosome A03; QTL for PRL were identified on chromosomes A07 and C06.

Conclusions

High-throughput phenotyping of Brassica can be used to identify root architectural traits which correlate with shoot biomass. It is feasible that these traits could be used in crop improvement strategies. The identification of QTL linked to root traits under LP and HP conditions provides further insights on the genetic basis of plant tolerance to P deficiency, and these QTL warrant further dissection.     

Modelling root plasticity and response of narrow-leafed lupin to heterogeneous phosphorus supply

Background & Aims

Searching for root traits underpinning efficient nutrient acquisition has received increased attention in modern breeding programs aimed at improved crop productivity. Root models provide an opportunity to investigate root-soil interactions through representing the relationships between rooting traits and the non-uniform supply of soil resources. This study used simulation modelling to predict and identify phenotypic plasticity, root growth responses and phosphorus (P) use efficiency of contrasting Lupinus angustifolius genotypes to localised soil P in a glasshouse.

Methods

Two L. angustifolius genotypes with contrasting root systems were grown in cylindrical columns containing uniform soil with three P treatments (nil and 20 mg P kg^?1 either top-dressed or banded) in the glasshouse. Computer simulations were carried out with root architecture model ROOTMAP which was parameterized with root architectural data from an earlier published hydroponic phenotyping study.

Results

The experimental and simulated results showed that plants supplied with banded P had the largest root system and the greatest P-uptake efficiency. The P addition significantly stimulated root branching in the topsoil, whereas plants with nil P had relatively deeper roots. Genotype-dependent root growth plasticity in response to P supply was shown, with the greatest response to banded P.

Conclusions

Both experimental and simulation outcomes demonstrated that 1) root hairs and root proliferation increased plant P acquisition and were more beneficial in the localised P fertilisation scenario, 2) placing P deeper in the soil might be a more effective fertilisation method with greater P uptake than top dressing, and 3) the combination of P foraging strategies (including root architecture, root hairs and root growth plasticity) is important for efficient P acquisition from a localised source of fertiliser P.     

Root growth in biopores—evaluation with in situ endoscopy

Background and aims

The significance of biopores for nutrient acquisition from the subsoil depends on root-soil contact, which in turn is influenced by root architecture. The aim of this study was to detect differences regarding the architecture and root-soil contact of homorhizous barley roots (Hordeum vulgare L.) and allorhizous oilseed rape roots (Brassica napus L.) growing in biopores.

Methods

In situ endoscopy was used as a technique that allows non-destructive display of pore wall characteristics and root morphology inside large biopores under field conditions.

Results

For both crops, about 85 % of all roots did establish contact to the pore wall. However, according to their different root architecture, the two crops varied in their strategy of resource acquisition: While barley was characterized by thin vertical or ingrowing roots, most of them in direct contact to the pore wall, oilseed rape established contact to the pore wall predominantly via lateral roots.

Conclusions

Root morphological and pore wall assessment with in situ endoscopy in combination with detailed studies of soil biochemical and soil physical parameters of the pore wall is considered an essential prerequisite for more precise future modelling of nutrient acquisition and uptake.     

Spatial variation in root system activity of tomato (Solanum lycopersicum L.) in response to short and long-term waterlogging as determined by 15N uptake

Background and aim

Root system activity is affected by abiotic stresses, which often creates spatial differences in root conditions. This is expected to influence plants ability to cope with suboptimal conditions.

Methods

Changes in root system activity were determined as ¹⁵N root uptake in top and bottom layers of potted tomato plants (Solanum lycopersicum L.), after waterlogging the bottom layer for 24 h or 5 d. The plants were grown in peat-based media; non-compacted or highly-compacted, resulting in differences in gas diffusion, air permeability and oxygen availability.

Results

The roots were affected by short-term waterlogging (24 h) by decreasing uptake in the bottom layer and increasing uptake in the pot top layer. Long-term waterlogging (5 d) decreased the ¹⁵N root uptake more in both layers. Root uptake recovered fast (within 6 h) after short-term waterlogging, whereas recovery of long-term waterlogged roots took more than 24 h, suggesting production of new root biomass. Despite affecting physical properties, medium compaction did not affect root uptake. Aboveground biomass was affected by waterlogging by increasing the dry matter percentage, decreasing nitrogen (N) percentage and increasing starch content.

Conclusions

The results confirmed that root uptake in different layers of small pots could be distinguished by the ¹⁵N technique, which was applicable under potentially denitrifying conditions. The results demonstrated that during short-term stress in part of the root system plants increased uptake from the non-affected parts of the root system, probably as compensation for suboptimal conditions.     

Acid phosphatase gene <Emphasis Type="Italic">GmHAD1</Emphasis> linked to low phosphorus tolerance in soybean,through fine mapping

Key message

Map-based cloning identified GmHAD1, a gene which encodes a HAD-like acid phosphatase, associated with soybean tolerance to low phosphorus stress.

Abstract

Phosphorus (P) deficiency in soils is a major limiting factor for crop growth worldwide. Plants may adapt to low phosphorus (LP) conditions via changes to root morphology, including the number, length, orientation, and branching of the principal root classes. To elucidate the genetic mechanisms for LP tolerance in soybean, quantitative trait loci (QTL) related to root morphology responses to LP were identified via hydroponic experiments. In total, we identified 14 major loci associated with these traits in a RIL population. The log-likelihood scores ranged from 2.81 to 7.43, explaining 4.23–13.98% of phenotypic variance. A major locus on chromosome 08, named qP8-2, was co-localized with an important P efficiency QTL (qPE8), containing phosphatase genes GmACP1 and GmACP2. Another major locus on chromosome 10 named qP10-2 explained 4.80–13.98% of the total phenotypic variance in root morphology. The qP10-2 contains GmHAD1, a gene which encodes an acid phosphatase. In the transgenic soybean hairy roots, GmHAD1 overexpression increased P efficiency by 8.4–16.5% relative to the control. Transgenic Arabidopsis plants had higher biomass than wild-type plants across both short- and long-term P reduction. These results suggest that GmHAD1, an acid phosphatase gene, improved the utilization of organic phosphate by soybean and Arabidopsis plants.

     

Microdistribution of major to trace elements between roots of Halimione portulacoides and host sediments (Tagus estuary marsh,Portugal)

Aim

This study presents a micrometre-scale map of the elemental distribution within roots and surrounding sediment of Halimione portulacoides of a contaminated salt marsh in the Tagus estuary.

Methods

Microprobe particle induced X-ray emission analysis was performed in sediment slices containing roots with tubular rhizoconcretions attached to host sediments.

Results

Strong concentration gradients were found particularly in the inner part of rhizoconcretions adjacent to the root wall. Local enrichment was observed in sediment interstices with Fe precipitates and other associated elements. A maximum of 55 % of Fe was measured near the concretion–root interface, with a decrease to <5 % in the host sediment. Maximum concentrations of P (3 %), As (1,200 μg g^?1) and Zn (3,000 μg g^?1) were registered in concretions, one order of magnitude above the values of the host sediment. The elemental concentration profiles across roots showed that the epidermis was an efficient selective barrier to the entrance of elements. Fe and As were retained in the epidermis. The highest Cu and Zn concentrations were also observed in the epidermis. However, the concentrations of Mn, Cu and Zn increased in the inner root.

Conclusions

As and Fe were mostly retained in the concretion, whereas P, Mn, Cu and Zn were mobilised by the root.