Plant and Soil

Wang, Shuqiong; van Dijk, Jerry; Wassen, Martin J.

doi: 10.1007/s11104-021-05230-2pmid: N/A

AimsPlant investment in sexual reproduction is affected by nitrogen (N): phosphorus (P) stoichiometry. It has been suggested that an important adaptation to strong P limitation is reduced investment in sexual reproduction. We aim to investigate the specific influence of N:P on sexual reproduction performance within and between grassland species.MethodsEleven grassland species were selected in ten plots covering N limitation, co-limitation and P limitation. Nutrients in soil and above-ground biomass were determined, plus soil pH and soil moisture. A range of sexual reproduction traits were measured as a proxy for investment in sexual reproduction.ResultsAt the intraspecific level: compared with N-limited plots, in P-limited/co-limited plots, flowering time was later, flowering period in individuals was shorter, and number of flowers (inflorescences) per individual was smaller. At the interspecific level, in P-limited/co-limited plots, species had a significantly earlier flowering time and a longer seed stalk and seed panicle, than those in N-limited plots. However, flowering period was shorter and number of flowers (inflorescences) per individual was smaller under P limitation/co-limitation. Moreover, significant correlations between soil pH and soil moisture, and sexual reproduction performance of the selected grassland species were also found.ConclusionsP limitation/co-limitation restrict the sexual reproduction of grassland species, which may hamper their dispersal capacity. We recommend future studies further analyze the relationship between soil pH and N:P stoichiometry and the influence of soil pH, as well as soil moisture on sexual reproduction performance of grassland species in addition to analyzing N:P stoichiometry.

Zhang, Lu; Wang, Xiangtao; Wang, Jie; Liao, Lirong; Lei, Shilong; Liu, Guobin; Zhang, Chao

doi: 10.1007/s11104-021-05287-zpmid: N/A

AimsBiological nitrogen fixation (BNF), a function performed by diazotrophic microbes, plays an essential role in nitrogen (N) bioavailability in terrestrial ecosystems. However, little is known about the effects of meadow degradation on soil BNF and diazotrophic communities in alpine meadows.MethodsWe investigated changes in soil BNF and their potential drivers in alpine meadows along a degradation gradient on the Tibetan Plateau (non-degraded, lightly degraded, moderately degraded, and severely degraded meadows) using real-time quantitative PCR and amplicon sequencing.ResultsSoil BNF rates decreased significantly along the meadow degradation gradient with a range of 17.34–79.84 nmol C2H4 g−1 dry soil d−1 across all sites. The highest BNF rate in the non-degraded meadow was 1.5–4.6-fold higher than that in the degraded meadows. The abundance and diversity of diazotrophs measured by nifH abundance and Shannon diversity was also decreased in the degraded meadows, accompanied by decreases in plant biomass, soil moisture, and nutrient content (C, N). Soil BNF rate was correlated with plant biomass, soil nutrient content, and diazotrophic abundance (including Nostoc, Scytonema, Rhodopseudomonas, and unidentified genera within the Rhizobiales and Proteobacteria). The community composition of diazotrophs differed markedly among sites with different levels of degradation, with both autotrophic (Cyanobacteria) and heterotrophic (Proteobacteria) diazotrophs contributing significantly to BNF. The plant functional groups, particularly the sedge family, were the primary drivers of soil BNF rates via mediating soil moisture, nutrient content (dissolved organic C and N), nifH gene abundance, and diazotrophic community composition.ConclusionsOur results reveal the main drivers of decreased BNF during alpine meadow degradation and emphasize the importance of plant functional groups in shaping the diazotrophic community and regulating the BNF rate. This information can be applied to the restoration of degraded meadow ecosystems.

Sileshi, Frehiwot; Nebiyu, Amsalu; Van Geel, Maarten; Abeele, Samuel Vanden; Du Laing, Gijs; Boeckx, Pascal

doi: 10.1007/s11104-021-05289-xpmid: N/A

AimsThis study has been carried out to determine the spatial variability of faba bean seed Fe, Zn and Se content across agro-ecological zones in central and southwestern Ethiopia, where it is an important source of protein in the diet. The study assessed whether soil properties, arbuscular mycorrhizal fungi (AMF), faba bean characteristics and genetic diversity and agro-ecological zone as random factor affect seed Fe, Zn and Se content.MethodologyMulti-location fields were sampled in three important faba bean growing agro-ecologies during the 2018–2019 cropping season.ResultsSeed Fe content varied from 45.7–61.9, 41.6–102 and 31.1–77.0 mg kg−1 in Cheliya, Dedo and Dendi, respectively. Likewise, Zn content ranged from 38.3–56.3, 44.6–73.6 and 21.6–49.9 mg kg−1. Selenium content varied from 10.1–45.1, 12.1–160 and 16.2–167 μg kg−1. Significant differences were observed for Zn and Se content across agro-ecologies. Consumption of 100 g faba beans per day can provide an overall average of 64 and 28% of the recommended daily allowance (RDA) for Fe, 45 and 62% for Zn and only 8% for Se for male and female adults, respectively. Soil properties explained seed Fe, Zn and Se content variation. However, for Zn and Se content the largest share of the difference was explained by agro-ecological mediated environmental variations. As a consequence, differences in dietary intake of micro-nutrients via faba beans are determined by living area.ConclusionSoil properties and especially agro-ecological mediated environmental conditions explained seed Zn and Se content of faba bean and hence potential dietary intake.

Taye, Zelalem M.; Noble, Kalli; Siciliano, Steven D.; Helgason, Bobbi L.; Lamb, Eric G.

doi: 10.1007/s11104-022-05296-6pmid: N/A

BackgroundThe plant root-rhizosphere microbial community interactions play important roles in crop production as those interactions can be beneficial, detrimental, or neutral for the plant. In Brassica napus, our current understanding of root growth dynamics and dominance of bacterial taxa and their dynamics across growth stages is insufficient. In addition, the association of root traits with dominant and potential growth promoting bacteria across growth stages under field conditions has not been well studied.Methods:Here, we use temporally intensive weekly sampling of B. napus over a ten-week period to characterize root growth dynamics, dominant rhizosphere bacterial taxa, and association between the two. We characterized the rhizosphere bacteria using high throughput sequencing of the 16S rRNA genes.Results:B. napus root length showed distinct growth stage patterns with an increase in root length at early stages followed by s and/or gradual increase at flowering followed by reduction at maturity. Fine root length at the two-three leaf stage and seed yield were significantly positively correlated. The dominant microbial community composition was positively correlated with root traits and environmental variables, with the strongest correlation at the vegetative stage. Positive and significant correlations between individual bacterial genera and root traits were observed during vegetative stage, suggesting possible causal linkage between the two.ConclusionsThe observed significant positive correlations between the bacterial genera and root traits and between root length and seed yield under field conditions suggest the potential for designing root development and beneficial microbial interaction-based canola breeding and management strategies.

Jia, Lijuan; Wang, Zhen; Ji, Lei; De Neve, Stefaan; Struik, Paul C.; Yao, Yuqing; Lv, Junjie; Zhou, Tao; Jin, Ke

doi: 10.1007/s11104-022-05297-5pmid: N/A

PurposeKeystone taxa play an important role in soil nutrient cycling and crop growth and can be influenced by soil tillage. We investigated the composition of keystone taxa and their relationships with soil properties under different long-term tillage practices.MethodsFour tillage treatments (i.e., CT, conventional tillage; NT, no tillage with mulch; RT, reduced tillage; and SS, subsoiling with mulch) were maintained for twenty-one years. Co-occurrence network (CoNet) was constructed to identify the keystone taxa, and redundancy analysis (RDA) was carried out to explore the relationships between keystone taxa and soil properties under the four tillage practices at two growth stages (elongation and grain filling stages) of winter wheat.ResultsCompared with CT, RT had no significant effect on the microbial community and the keystone microbiome, while NT and SS remarkably altered the microbial community structure and the keystone microbiome at both growth stages. Massilia was the keystone genus under CT and RT, while Sphingomonas, Asanoa and Hoeflea were the keystone genera under NT and SS. RDA results showed that keystone genera were significantly correlated with soil organic carbon (SOC), dissolved organic carbon (DOC) and microbial biomass nitrogen (MBN) at both stages, especially at the elongation stage. Our results further revealed that the effects of NT and SS on crop growth might be related to the changes in keystone microbiome.ConclusionOur study suggests that NT and SS may contribute to the development of sustainable agricultural production in the Chinese Loess Plateau.

Li, Qin; Liu, Shuang; Li, Yongbin; Hao, Tianyi; Chen, Sanfeng

doi: 10.1007/s11104-022-05307-6pmid: N/A

AimsTo study nitrogen contribution to cucumber derived from nitrogen fixation of Paenibacillus polymyxa WLY78.MethodsThe nif gene cluster deletion mutant (ΔnifB-V) of Paenibacillus polymyxa WLY78 was constructed by a homologous recombination method. The effects of plant-growth promotion were investigated by greenhouse experiments. The nitrogen fixation contribution was estimated by 15N isotope dilution method (also being called the 15N natural abundance technique).ResultsDeletion of nif gene cluster of P. polymyxa WLY78 resulted in complete loss of nitrogenase activity. Greenhouse experiments showed that inoculation with P. polymyxa WLY78 could significantly enhance the lengths and dry weights of cucumber roots and shoots, but inoculation with ΔnifB-V mutant could not. 15N isotope dilution experiments showed that cucumber plants derive 25.93% nitrogen from nitrogen fixation performed by P. polymyxa WLY78, but the ΔnifB-V mutant nearly could not provide nitrogen for plant growth.ConclusionsThis present study demonstrated that nitrogen fixation performed by P. polymyxa WLY78 contributes to plant growth.

Manh Tuong, Ho; Garcia Mendez, Sonia; Vandecasteele, Michiel; Willems, Anne; Luo, Dexian; Beirinckx, Stien; Goormachtig, Sofie

doi: 10.1007/s11104-022-05304-9pmid: N/A

AimsPlant Growth-Promoting Rhizobacteria (PGPR) support plant growth by alleviating plant stresses, among which those triggered by saline soils. We isolated Stenotrophomonas sp. SRS1 from salt-resistant Carex distans (distant sedge) roots to understand how this growth promotion was enabled and whether an active contribution of the bacteria and/or plant was required.MethodsVarious growth assays were used to analyze the effect of bacterial inoculation on Arabidopsis thaliana and Solanum lycopersicum (cherry tomato MicroTom) growth. Furthermore, droplet microfluidics, bacterial genome mining, and bacterial and plant gene expression analysis combined with plant mutant analysis were used for in-depth analysis.ResultsSRS1 application enhanced plant growth in both saline and nonsaline environments. The fresh weight of SRS1-inoculated plants was higher than that of noninoculated plants, whereas the fresh weight ratio between SRS1-inoculated and noninoculated plants differed whether the plants were grown on agar plates, white sand or in soil. We demonstrated that the strain grew well in high salt-containing media and that, besides plant-growth-promotion-related genes, the bacterium contained various active stress genes. Interestingly, inoculation with the strain increased the induction of plant genes related to abscisic acid and auxin signaling pathways under saline conditions.ConclusionsSRS1 inoculation promoted the growth of Arabidopsis and MicroTom tomato under saline and nonsaline conditions, also when the plants were grown in white sand and potting soil. Overall, genetic traits related to stress alleviation, derived from both the bacteria and the plants, play a crucial role in the impact of this novel PGPR strain on plant performance.