Plant and Soil最新文献

Background and aims

Belowground carbon (C), nitrogen (N) and phosphorus (P) inputs by plants via roots and rhizodeposition are key drivers of these elements cycling in soils. Tracing and quantification of rhizodeposition using isotope enrichment techniques is based on assumptions that have not simultaneously been tested for C, N and P. Our objectives were: (i) to compare the elemental and isotopic composition (IC) of roots and soluble rhizodeposits for C, N and P; and (ii) to compare the IC of root segments of different ages to assess the homogeneity of root system labeling.

Methods

The legume Canavalia brasiliensis was grown in sand and labeled with ¹³C, ¹⁵N and ³³P by using a novel tri-isotope method in two different experiments lasting two (percolate collection) and three weeks (root observation) after labeling.

Results

Soluble rhizodeposits were less isotope enriched than roots at each time point, and each element showed a different course over time. The ¹³C:¹⁵N and ¹³C:³³P ratios of rhizodeposits were higher shortly after labeling than at later samplings, highlighting faster transfer of ¹³C than ¹⁵N and ³³P into rhizodeposits. Phosphorus fertilizer increased the difference between IC of P in roots and rhizodeposits. Youngest root segments were more isotopically enriched than older segments, again with element specific time course, showing that root segments of different ages differ in IC.

Conclusion

Assumptions underlying the quantification of rhizodeposition are not met. Temporal and spatial differences in IC of roots and soluble rhizodeposits are element specific, which needs to be considered in stoichiometric studies.

Aims

The formation of soil organic carbon (SOC) is a complex phenomenon mainly originating from plant- and microbial-derived C. Conservation tillage involving no-till and residue return (RR) has been widely practiced to enhance SOC, but the relative contributions of plant- and microbial-derived C to SOC under these practices are still unknown.

Methods

A global meta-analysis of 500-paired observations was used to identify the effects of no-till and RR on plant- and microbial-derived C and their drivers.

Results

The results showed that no-till increased microbial necromass C by 18.3%, and the contribution of microbial necromass C to SOC by 5.0%, whereas plant necromass C and its contribution to SOC remained unchanged under no-till. No-till increased the ratio of fungal to bacterial necromass C by 12.3%, indicating fungal necromass C contributes more to SOC. The microbial necromass C under no-till was increased the most at MAP < 550 mm, humidity index < 85, medium-textured soil, acid soil, and initial C/N ratio ≥ 10 (P < 0.05). Dissolved organic and microbial biomass carbon contributed to the formation of microbial necromass C and benefited the SOC accumulation. RR increased plant and microbial necromass C by 83.8% and 13.0%, respectively, and enhanced the contribution of plant necromass C to SOC by 64.1%. Greater plant-derived C was observed when the experiment duration was over 3 years.

Conclusions

Our global meta-analysis highlighted that no-till can improve soil carbon stability (microbial-derived C) while RR can increase soil carbon quantity (plant-derived C). Conservation tillage (no-till and RR) is sustainable strategies through collaborative improvement of SOC capacity and quality.

Aims

Arsenic (As) is a highly toxic metalloid that can accumulate in wheat, posing significant human health risks. However, the genetic basis underlying As accumulation in wheat grains remains largely unexplored.

Methods

This study utilized a recombinant inbred line (RIL) population derived from an endemic tetraploid wheat variety and a wild emmer accession. Phenotypic data were collected from three field environments and a pot experiment with three As levels.

Results

Seven quantitative trait loci (QTL) associated with grain As concentration (GrAsc) were identified. Among these, two major QTL—QGrAsc.sau-AM-1A and QGrAsc.sau-AM-4A— were located on chromosomes 1A and 4A, respectively, and were detected in over four environments. These loci, which explained 7.96% to 12.51% and 10.20% to 21.45% of phenotypic variance, respectively, and were successfully validated using Kompetitive Allele-Specific PCR (KASP) markers in a natural population. Additionally, four wheat varieties with low As concentrations were screened using KASP markers. Comparisons with previous studies suggest that these two major QTL are likely novel. Furthermore, the effects of QGrAsc.sau-AM-1A and QGrAsc.sau-AM-4A on GrAsc were analyzed. Candidate genes related to As uptake and transport were predicted to be associated with these loci. Correlation analysis between GrAsc and nine agronomic traits revealed a significant negative correlation with thousand kernel weight (TKW). Additionally, QGrAsc.sau-AM-1A was found to significantly increase spikelet number per spike, while QGrAsc.sau-AM-4A was associated with increased spike density. Overall, these results suggest that QGrAsc.sau-AM-1A and QGrAsc.sau-AM-4A are promising loci for further fine mapping and molecular breeding aimed at reducing As accumulation in wheat.

Conclusions

Two novel, major QTL—QGrAsc.sau-AM-1A and QGrAsc.sau-AM-4A— were identified for grain arsenic concentration. Their effects were validated in a natural wheat population, offering the potential for marker-assisted selection (MAS) and molecular breeding.

Background

The rhizosphere plays a critical role in forest soil organic carbon (SOC) dynamics. However, the patterns and drivers of SOC and its components within rhizosphere and bulk soils, as well as rhizosphere effects, remain unclear throughout stand development.

Methods

We examined SOC, particulate organic carbon (POC), and mineral-associated organic carbon (MAOC) contents in both rhizosphere and bulk soils, alongside fine root traits and associated soil and microbial parameters, across a 9- to 55-year chronosequence of Cryptomeria japonica plantations in subtropical China.

Results

SOC, POC, and MAOC contents increased from young (9-year-old) to mature (35-year-old) plantations in both rhizosphere and bulk soils. In over-mature stands (55 years old), MAOC content in rhizosphere and bulk soils decreased compared to maturity, while SOC and POC contents remained consistent. SOC and POC contents in the rhizosphere were 83.0% and 232.2% greater than those in bulk soil, respectively. The rhizosphere effect on SOC decreased with stand age, primarily driven by its impact on MAOC. This was associated with decreased rhizosphere effects on soil nutrient availability, microbial properties, and root traits. The rhizosphere effect on soil nutrient availability accounted for a larger proportion of the variance in the rhizosphere effect on SOC than root traits and microbial properties.

Conclusion

Extending plantation age can promote SOC sequestration but may compromise SOC stability. This study provides direct evidence of the crucial role that rhizosphere processes play in soil carbon dynamics and contributes valuable insights to the sustainable management of plantations and the mitigation of global climate change.

Aims

NaHCO₃ causes stress in plants, significantly affecting agricultural production. While microorganisms have been shown to mitigate such stress, the underlying microbiome-mediated mechanisms remain unclear.

Methods

In this study, a NaHCO₃-tolerant strain NYJ was inoculated into cucumber-planted soil contaminated with NaHCO₃. Its effects on the rhizospheric microbiome, antioxidant enzymes and soil enzymes were analyzed.

Results

Under NaHCO₃ stress, 16 genera were depleted and one genus was enriched, all of which were enriched after NYJ application. Consistently, NYJ application changed microbial interaction networks and shifted the symbiont-related, osmotic stress-responsive and sodium ion-responsive functions of soil microbial communities under NaHCO₃ stress. As a result, NYJ application under NaHCO₃ stress significantly improved plant growth, affected Na⁺ concentrations in cucumber and decreased hydrogen peroxide levels in seedlings. Additionally, the NYJ application enhanced the activities of seven antioxidant enzymes in leaves, induced catalase in soil and enriched genes responding to reactive oxygen species in GO:0052550 and GO:0052567 of soil microbial communities in a NaHCO₃ environment, thereby reducing NaHCO₃-induced oxidative stress. In the meantime, NYJ application significantly induced soil enzymes including ureases, phosphatases and sucrases and increased the abundances of chitinase genes in K01183 of microbial communities in NaHCO₃-contaminated soil, facilitating the promotion of plant growth.

Conclusion

These findings suggest that NYJ application modifies the soil microbiome and enhances its resilience against NaHCO₃ stress, offering a promising strategy for improving crop tolerance in alkaline soils. This study provides novel insights into the microbiome-mediated mitigation of NaHCO₃ stress through the application of NYJ.

Technosols from the heap of the abandoned Italian Cu deposit Caporciano contain important amounts of potentially toxic elements (Cr_tot., Co, Ni, Cu, Zn, As, Cd and Pb). Copper contents exceed the Italian law limits for industrial/commercial sites. The studied metals in Pinus sylvestris and Quercus petraea (Matt.) Liebl. show strategy of excluders (bioconcentration factor < 1.0) except Ni and Pb (calculated for branches and leaves in Pinus sylvestris) while the translocation factor indicates preferential metal accumulation to leaves/needles (translocation factor > 1.0) in both plant speciments.At the heap the contents of the chlorophyll in leaves in the photosynthetic tissues of Quercus petraea (Matt.) Liebl. (8.56 CCI—chlorophyll content index) are significantly lower as those measured at reference area (17.71 CCI). The goal of the study is to use a modified methodology for the fractional analysis of soils for the determination of the potential bioavailability of potentially toxic elements in six steps. The innovative steps of sequential analysis are adapted with respect to the release of PTEs from the clay mineral surfaces. (fraction I: 1 M ammonium acetate at pH 7; fraction II: ammonium acetate at pH 5; fraction III: H₂O₂ in ammonium acetate buffer solution; fraction IV: acidic 0.2 M ammonium oxalate (pH 3.2); fraction V: 0.2 M ammonium oxalate and 0.1 M ascorbic acid mixture; fraction VI: 0.5 M ammonium acetate; pH 6). The best bioavailable metals are Cd, Cu, Zn and Pb. The obtained results enable international comparison with similar Cu-deposits.

Background

Climate change and human activities are shifting plant species distributions, relocating plant litter to new environments. The home-field advantage (HFA) is a phenomenon where litter decomposes more rapidly in its original habitat due to long-term co-adaptation between decomposer communities and litter quality. Despite its importance in carbon and nutrient cycling, it remains unclear how various litter types demonstrate differences in HFA beyond just surface leaf litter.

Methods

Here we conducted a comprehensive 35-month transplant decomposition experiment on the Tibetan Plateau, using 630 litter bags across three typical ecosystems (Mesic meadow, Wet meadow, and Fen) to assess the HFA effects on the decomposition of surface and standing leaf litter.

Results

Compared to surface leaf litter, the decomposition of standing leaf litter was slower, but it exhibited a stronger HFA effect across three ecosystems. Additionally, the HFA effect on litter decomposition varied across different ecosystems. In mesic and wet meadow ecosystems, standing leaf litter decomposition displayed a more pronounced positive HFA effect compared to surface leaf litter. Contrastingly, in fen ecosystems, surface leaf litter exhibited a positive HFA effect, while standing leaf litter demonstrated a negative HFA effect. The differing HFA effects between surface and standing leaf litter were primarily driven by variations in litter quality and the hydrological conditions of the respective ecosystems.

Conclusions

These findings suggest that the HFA in decomposition differed between surface and standing leaf litter and highlight future studies should consider different litter types when predicting the carbon cycle of ecosystems.

Aims

This study aimed to explore the effects of increasing image texture features and removing soil background on the alfalfa salt stress diagnosis accuracy.

Methods

This study extracted spectral reflectance to construct 15 vegetation indexes, and used gray level co-occurrence matrix to calculate eight image texture features. The Canny edge detection algorithm was used to remove the soil background, and set T1 (vegetation index non-removed soil background), T2 (vegetation index + image texture features non-removed soil background), T3 (vegetation index removed soil background), T4 (vegetation index + image texture features removed soil background), as independent variables to construct salt stress diagnosis model based on the support vector regression algorithm, and determined the best salt stress diagnosis model.

Results

Compared with the T1, the modeling and validation accuracies of salt stress diagnosis model constructed based on the T2 increased by 13.39% and 13.36%, respectively, and those of salt stress diagnosis model constructed based on the T3 increased by 6.30% and 5.33%. The salt stress diagnosis accuracy constructed based on T4 was the highest, with the modeling set R², RMSE, and RPD of 0.675, 0.2143, and 1.7735, respectively, and the validation set R², RMSE, and RPD of 0.652, 0.2349, and 15,749, respectively. The modeling and validation accuracies of the salt stress diagnosis model constructed based on crop salt stress index (CSSI) reached more than 0.564 and 0.549, respectively, which can be used as a new indicator for diagnosing salt stress.

Conclusions

Both increasing image texture features and removing soil background can significantly improve the accuracy of alfalfa salt stress diagnosis.

Background and aims

A long-standing ecological assumption posits that insect herbivory increases in warmer, more stable climates at lower elevations. However, this paradigm has been called into question in recent decades. Some studies suggest that differences in tri-trophic interactions, particularly the diversity, abundance, and activity of herbivore natural enemies, may explain inconsistent patterns in herbivory. Additionally, plant ontogeny significantly influences herbivore susceptibility, with adult plants being more apparent and thus more susceptible to herbivore attacks than saplings. These ontogenetic differences in herbivory might, in turn, determine changes in herbivore predation across elevations. Unfortunately, most research addressing these ecological assumptions has focused on aboveground tri-trophic interactions.

Methods

Here, we investigated elevational differences in the activity of entomopathogenic nematodes (EPNs), known killers of soil-dwelling insects, and compared these patterns between young and adult oak (Quercus, Fagaceae) trees. We collected soil samples from rhizospheres of adult trees and saplings throughout the optimal elevational range (low, mid, and high) of 10 Mediterranean oak species in the Iberian Peninsula, estimating EPN activity through insect baiting with wax moth larvae.

Results

Our results showed higher larval mortality and EPN activity at lower elevations, with this effect being influenced by plant ontogeny; therefore, elevation-related variations were observed only in rhizospheres of mature trees. Additionally, we found that soil characteristics did not significantly affect these outcomes.

Conclusions

Our study provides evidence that plant ontogeny influences belowground tri-trophic interactions along elevational gradients in oak species, emphasizing the minimal impact of abiotic soil factors on these processes.

Aims

Global change threatens ecosystem functions, including those driven by soil fauna. In temperate forests, soil nutrients, litter quality, and microarthropods are essential players during litter decomposition. However, the impact of nutrient enrichment on the functional role of soil fauna remains poorly understood.

Methods

We used a full factorial experiment to test the effects of nitrogen (N), phosphorus (P), and potassium (K) addition on litter decomposition through changes in soil conditions and litter quality. We incubated senesced leaves from fertilized and unfertilized control plots in litter bags with two different mesh sizes that included (2 mm) or excluded (45 µm) microarthropods. We assessed the interactive effects of nutrient addition and litter quality on microarthropod-driven decomposition using linear mixed-effects models.

Results

Nutrient addition was a stronger predictor than litter quality for organic matter remaining in litter bags over time. While N addition strongly influenced litter quality, it did not affect microarthropod activity in decomposition. P addition suppressed decomposition when microarthropods were present but enhanced it when microarthropods were absent. K strongly influenced litter quality and regulated the effects of phosphorus on decomposition.

Conclusions

Microarthropods may promote decomposition under conditions of limited nutrient availability in both litter and soil, potentially enhancing microbial activity. The responses of fungi and microbes to nutrient enrichment may explain the relatively modest effect of microarthropods on decomposition. Our study shows that nutrient enrichment in temperate forests may limit microarthropod participation in decomposition by possibly altering microsite conditions or affecting the availability of alternative food resources, thereby influencing carbon fluxes.