Phosphorus (P) availability severely limits plant growth due to its immobility and inaccessibility in soils. Yet, visualization and measurements of P uptake from different root types or regions in ...soil are methodologically challenging. Here, we explored the potential of phosphor imaging combined with local injection of radioactive 33 P to quantitatively visualize P uptake and translocation along roots of maize grown in soils. Rhizoboxes (20 × 40 × 1 cm) were filled with sandy field soil or quartz sand, with one maize plant per box. Soil compartments were created using a gravel layer to restrict P transfer. After 2 weeks, a compartment with the tip region of a seminal root was labeled with a NaH 2 33 PO4 solution containing 12 MBq of 33 P. Phosphor imaging captured root P distribution at 45 min, 90 min, 135 min, 180 min, and 24 h post-labeling. After harvest, 33 P levels in roots and shoots were quantified. 33 P uptake exhibited a 50% increase in quartz sand compared to sandy soil, likely attributed to higher P adsorption to the sandy soil matrix than to quartz sand. Notably, only 60% of the absorbed 33 P was translocated to the shoot, with the remaining 40% directed to growing root tips of lateral or seminal roots. Phosphor imaging unveiled a continuous rise in 33 P signal in the labeled seminal root from immediate post-labeling until 24 h after labeling. The highest 33 P activities were concentrated just above the labeled compartment, diminishing in locations farther away. Emerging laterals from the labeled root served as strong sinks for 33 P, while a portion was also transported to other seminal roots. Our study quantitatively visualized 33 P uptake and translocation dynamics, facilitating future investigations into diverse root regions/types and varying plant growth conditions. This improves our understanding of the significance of different P sources for plant nutrition and potentially enhances models of plant P uptake.
Abstract
Background
Managed grasslands are global sources of atmospheric methanol, which is one of the most abundant volatile organic compounds in the atmosphere and promotes oxidative capacity for ...tropospheric and stratospheric ozone depletion. The phyllosphere is a favoured habitat of plant-colonizing methanol-utilizing bacteria. These bacteria also occur in the rhizosphere, but their relevance for methanol consumption and ecosystem fluxes is unclear. Methanol utilizers of the plant-associated microbiota are key for the mitigation of methanol emission through consumption. However, information about grassland plant microbiota members, their biodiversity and metabolic traits, and thus key actors in the global methanol budget is largely lacking.
Results
We investigated the methanol utilization and consumption potentials of two common plant species (
Festuca arundinacea
and
Taraxacum officinale
) in a temperate grassland. The selected grassland exhibited methanol formation. The detection of
13
C derived from
13
C-methanol in 16S rRNA of the plant microbiota by stable isotope probing (SIP) revealed distinct methanol utilizer communities in the phyllosphere, roots and rhizosphere but not between plant host species. The phyllosphere was colonized by members of
Gamma
- and
Betaproteobacteria
. In the rhizosphere,
13
C-labelled Bacteria were affiliated with
Deltaproteobacteria
,
Gemmatimonadates,
and
Verrucomicrobiae.
Less-abundant
13
C-labelled Bacteria were affiliated with well-known methylotrophs of
Alpha
-,
Gamma
-, and
Betaproteobacteria
. Additional metagenome analyses of both plants were consistent with the SIP results and revealed Bacteria with methanol dehydrogenases (e.g.,
MxaF1
and
XoxF1-5
) of known but also unusual genera (i.e.,
Methylomirabilis
,
Methylooceanibacter
,
Gemmatimonas
,
Verminephrobacter
).
14
C-methanol tracing of alive plant material revealed divergent potential methanol consumption rates in both plant species but similarly high rates in the rhizosphere and phyllosphere.
Conclusions
Our study revealed the rhizosphere as an overlooked hotspot for methanol consumption in temperate grasslands. We further identified unusual new but potentially relevant methanol utilizers besides well-known methylotrophs in the phyllosphere and rhizosphere. We did not observe a plant host-specific methanol utilizer community. Our results suggest that our approach using quantitative SIP and metagenomics may be useful in future field studies to link gross methanol consumption rates with the rhizosphere and phyllosphere microbiome.
Aims The influence of changing carbon (C) assimilation and relative C partitioning during plant development on the transfer of absolute C amounts (mg C per plant) into the subsurface should be ...analyzed and estimated. Moreover, an approach to determine the precision of the modeled C transfer values should be developed. Methods Several relative 14C partitioning coefficients were derived from pulse labeling experiments at different developmental stages using spring rye as a model plant. Subsequently, relative 14C allocation was dynamically linked with daily shoot C mass increments to obtain precise information about C partitioning at different plant developmental stages and during the entire growing season. Results The transfer of assimilated C into the subsurface during the plant development is a highly dynamic process, in which the maximum root growth preceded maximum shoot growth by approximately 17 days. The model simulations indicate that 18 ± 2 % of all assimilated C that was not respired by shoots was transferred into the subsurface during the entire growing season. This flow splits into 9 ± 0.8 % C for root growth, 6 ± 0.7 % C for belowground respiration, and 3 ± 0.3 % C for detectable rhizodeposition. Nearly half of the downward-transferred C flowed into the subsurface between elongation growth and the last boot stage. Moreover, highly correlated relationships between root growth, rhizodeposition, and belowground respiration were found. Conclusions Our study clearly shows that the dynamic linking of relative C partitioning with absolute C assimilation can provide detailed and precise information about the downward-transferred C during different developmental stages and the entire growing season.
Aims The influence of changing carbon (C) assimilation and relative C partitioning during plant development on the transfer of absolute C amounts (mg C per plant) into the subsurface should be ...analyzed and estimated. Moreover, an approach to determine the precision of the modeled C transfer values should be developed. Methods Several relative .sup.14C partitioning coefficients were derived from pulse labeling experiments at different developmental stages using spring rye as a model plant. Subsequently, relative .sup.14C allocation was dynamically linked with daily shoot C mass increments to obtain precise information about C partitioning at different plant developmental stages and during the entire growing season. Results The transfer of assimilated C into the subsurface during the plant development is a highly dynamic process, in which the maximum root growth preceded maximum shoot growth by approximately 17 days. The model simulations indicate that 18 ± 2 % of all assimilated C that was not respired by shoots was transferred into the subsurface during the entire growing season. This flow splits into 9 ± 0.8 % C for root growth, 6 ± 0.7 % C for belowground respiration, and 3 ± 0.3 % C for detectable rhizodeposition. Nearly half of the downward-transferred C flowed into the subsurface between elongation growth and the last boot stage. Moreover, highly correlated relationships between root growth, rhizodeposition, and belowground respiration were found. Conclusions Our study clearly shows that the dynamic linking of relative C partitioning with absolute C assimilation can provide detailed and precise information about the downward-transferred C during different developmental stages and the entire growing season.
Aims: The influence of changing carbon (C) assimilation and relative C partitioning during plant development on the transfer of absolute C amounts (mg C per plant) into the subsurface should be ...analyzed and estimated. Moreover, an approach to determine the precision of the modeled C transfer values should be developed. Methods: Several relative super(14)C partitioning coefficients were derived from pulse labeling experiments at different developmental stages using spring rye as a model plant. Subsequently, relative super(14)C allocation was dynamically linked with daily shoot C mass increments to obtain precise information about C partitioning at different plant developmental stages and during the entire growing season. Results: The transfer of assimilated C into the subsurface during the plant development is a highly dynamic process, in which the maximum root growth preceded maximum shoot growth by approximately 17 days. The model simulations indicate that 18 plus or minus 2 % of all assimilated C that was not respired by shoots was transferred into the subsurface during the entire growing season. This flow splits into 9 plus or minus 0.8 % C for root growth, 6 plus or minus 0.7 % C for belowground respiration, and 3 plus or minus 0.3 % C for detectable rhizodeposition. Nearly half of the downward-transferred C flowed into the subsurface between elongation growth and the last boot stage. Moreover, highly correlated relationships between root growth, rhizodeposition, and belowground respiration were found. Conclusions: Our study clearly shows that the dynamic linking of relative C partitioning with absolute C assimilation can provide detailed and precise information about the downward-transferred C during different developmental stages and the entire growing season.
Aims The influence of changing carbon (C) assimilation and relative C partitioning during plant development on the transfer of absolute C amounts (mg C per plant) into the subsurface should be ...analyzed and estimated. Moreover, an approach to determine the precision of the modeled C transfer values should be developed. Methods Several relative ¹⁴C partitioning coefficients were derived from pulse labeling experiments at different developmental stages using spring rye as a model plant. Subsequently, relative ¹⁴C allocation was dynamically linked with daily shoot C mass increments to obtain precise information about C partitioning at different plant developmental stages and during the entire growing season. Results The transfer of assimilated C into the subsurface during the plant development is a highly dynamic process, in which the maximum root growth preceded maximum shoot growth by approximately 17 days. The model simulations indicate that 18 ± 2 % of all assimilated C that was not respired by shoots was transferred into the subsurface during the entire growing season. This flow splits into 9 ± 0.8 % C for root growth, 6 ± 0.7 % C for belowground respiration, and 3 ± 0.3 % C for detectable rhizodeposition. Nearly half of the downward-transferred C flowed into the subsurface between elongation growth and the last boot stage. Moreover, highly correlated relationships between root growth, rhizodeposition, and belowground respiration were found. Conclusions Our study clearly shows that the dynamic linking of relative C partitioning with absolute C assimilation can provide detailed and precise information about the downward-transferred C during different developmental stages and the entire growing season.
Purpose
The goal of this work was to contribute to a better understanding of the process of rhizodeposition in crops and to find helpful approaches for creating a simple model of rhizodeposition. For ...this purpose, we tested three hypotheses about the relationships and changes in the relative C partitioning coefficients and their ratios. In particular, we analyzed the relationships between root growth, belowground respiration, rhizodeposition and other traits during plant growth.
Methods
The ranges of variation in
14
C partitioning coefficients and various plant traits were determined after
14
C labeling of four winter oilseed rape genotypes in three developmental stages.
Result
For all genotypes, we found very strong and significant correlations between the percentages of freshly assimilated C used for rhizodeposition and root growth. In addition, we showed that the ratios of the relative
14
C fluxes in the root-soil-soil gas system changed significantly during plant development and that the relative and absolute C fluxes of rhizodeposition followed different trends. The root growth rate and the change in the ratio of the percentages of
14
C in rhizodeposition and root tissue over time were the key factors that determined the absolute amount of rhizodeposited C. We also found that the C partitioning in a taproot system leading to root growth and rhizodeposition was similar to that of an adventitious root system.
Conclusion
Based on our results, we conclude that using the identified key factors in combination with a root growth model, a simple model can be generated to describe rhizodeposition.
Erosion leads to a decline in carbon (C) stocks in arable soils and negatively impacts soil functions worldwide. For soil restoration, it is critical to identify the factors that link crop residue ...quality to effective C sequestration in the soil, primarily through the formation of mineral-associated organic matter (MAOM) and through incorporation into aggregates (oPOM). The widely accepted concept links effective C stabilization with input of high-quality substrates, but studies of C-deficient soils do not support this assumption. Therefore, we aimed to determine the potential of eroded arable soils to stabilize C from barley shoot and root residues, which represent high- and low-quality inputs, respectively. In a year-long laboratory experiment, we added the residues to two soil pairs (eroded and non-eroded) with different soil textures, observed the formation of oPOM and MAOM and identified microbial groups important for substrate transformation. We found that eroded soils retained added residues very efficiently (35–65% bound residue C), making them a high-priority target for C sequestration. Root residues caused more efficient MAOM formation than shoot residues, primarily by direct binding of depolymerized root-C to mineral surfaces without subsequent microbial transformation. This root C stabilization in MAOM was more pronounced in eroded (highly C-undersaturated) soils than in non-eroded soils and in fine-textured soils, which provided more space for microbial colonization and C sorption, than in coarse-textured soils. Shoot residues were decomposed and metabolized by a microbiome rich in efficient bacterial decomposers (Actinobacteria, Xanthomonadales). This led to inevitably higher C losses related to their growth and biomass turnover, and probably also to an intense priming effect on pre-existing MAOM that lowered the efficiency of MAOM formation. Our results argue for crops with robust root systems, or for the inclusion of deep-rooted plants in crop rotations, which could help rapidly restore the C stocks in arable soils.
Display omitted
•Intensively managed arable soils are strong sinks for stabilized C.•Fine-textured soils have a greater capacity to stabilize C than coarse-textured soils.•Mineral-associated organic matter (MAOM) is formed more efficiently from root than from shoot residues.•Eroded soils are more efficient at stabilizing root C than non-eroded soils.•Bacterial communities, in particular, accelerated substrate transformation and limited stabilization.
Aims
The goal of this work was to quantitatively describe the influence of soil erosion on the distribution of recently assimilated carbon (C) within the plant-soil system and different soil ...fractions.
Methods
Surface soil was manipulated in the field to simulate a strong erosion event, and maize plants were cultivated in a growth chamber using soil material from the manipulated (eroded) and non-eroded sites. The maize plants were pulse labeled with
14
C-labeled carbon dioxide (CO
2
) at the start of flowering, and C partitioning within the plants and the distribution of recently assimilated C into organo-mineral soil fractions of different particle size were assessed after 25 days.
Results
The distribution of C differed significantly between the particle size fractions separated from the soil material of the eroded and non-eroded sites. For example, a much higher percentage of
14
C was found in macro-aggregate-occluded organic particles of the eroded soil than in the same fraction of soil from the non-eroded site. Furthermore, a significantly higher absolute amount of recently assimilated C was found in the < 20-
μ
m mineral particles and aggregates of the eroded soil than in the same particle fraction of the non-eroded soil. We show that this C is most likely derived from rhizodeposition or metabolites originating from the microbial decomposition of rhizodeposits.
Conclusions
The findings provide experimental evidence of the concept of the “dynamic replacement” of organic C (OC) losses due to erosion by C derived from crops growing on eroded soils. The rapid and enhanced sorption of recently assimilated C on the surfaces of mineral particles and occlusion in aggregates < 20
μ
m confirms the role of erosion processes in creating an immediate terrestrial C sink with the potential to enhance long-term soil C storage.
That silicon is an important element in global
biogeochemical cycles is widely recognised. Recently, its relevance for
global crop production has gained increasing attention in light of possible
...deficits in plant-available Si in soil. Silicon is beneficial for plant
growth and is taken up in considerable amounts by crops like rice or wheat.
However, plants differ in the way they take up silicic acid from soil
solution, with some species rejecting silicic acid while others actively
incorporate it. Yet because the processes governing Si uptake and regulation
are not fully understood, these classifications are subject to intense
debate. To gain a new perspective on the processes involved, we investigated
the dependence of silicon stable isotope fractionation on silicon uptake
strategy, transpiration, water use, and Si transfer efficiency. Crop plants
with rejective (tomato, Solanum lycopersicum, and mustard, Sinapis alba) and active (spring wheat, Triticum aestivum) Si
uptake were hydroponically grown for 6 weeks. Using inductively coupled
plasma mass spectrometry, the silicon concentration and isotopic composition
of the nutrient solution, the roots, and the shoots were determined. We
found that measured Si uptake does not correlate with the amount of
transpired water and is thus distinct from Si incorporation expected for
unspecific passive uptake. We interpret this lack of correlation to indicate
a highly selective Si uptake mechanism. All three species preferentially
incorporated light 28Si, with a fractionation factor 1000×ln (α) of −0.33 ‰ (tomato), −0.55 ‰ (mustard), and −0.43 ‰ (wheat)
between growth medium and bulk plant. Thus, even though the rates of active
and passive Si root uptake differ, the physico-chemical processes governing
Si uptake and stable isotope fractionation do not. We suggest that isotope
fractionation during root uptake is governed by a diffusion process. In
contrast, the transport of silicic acid from the roots to the shoots depends
on the amount of silicon previously precipitated in the roots and the
presence of active transporters in the root endodermis, facilitating Si
transport into the shoots. Plants with significant biogenic silica
precipitation in roots (mustard and wheat) preferentially transport
silicon depleted in 28Si into their shoots. If biogenic silica is not
precipitated in the roots, Si transport is dominated by a diffusion process,
and hence light silicon 28Si is preferentially transported into the
tomato shoots. This stable Si isotope fingerprinting of the processes that
transfer biogenic silica between the roots and shoots has the potential to
track Si availability and recycling in soils and to provide a monitor for
efficient use of plant-available Si in agricultural production.
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