Plant and Soil最新文献

Aims and Background

Cellulosic, hemicellulosic and pectinaceous mucilages produced by certain angiosperms as adaptation in myxodiaspory are investigated in the past to understand their role in seed dispersal. The present understanding of zoochory and telechory are based on mucilage amount, state of hydration and to a limited extent, role of mucilage microstructure studied using adhesion and friction. However, in the case of cellulosic mucilages, the role played by the cellulosic fibrils in seed dispersal is not clear, especially since they have a negative correlation with endozoochory.

Methods

Using fresh cellulosic seed mucilages from sweet basil (Ocimum basilicum) and chia (Salvia hispanica) we investigate the role of microstructure of the mucilage in two key behaviours: anchoring and adhesion properties of the seeds through Large Amplitude Oscillatory Shear (LAOS) rheological experiments carried out on seed mucilages along with wet tack strength studies.

Results

We report a special large deformation mechanism operational in these cellulosic mucilages triggered through ‘strain stiffening’. In comparison to pectin gels which also exhibit strain stiffening at lower strains, these mucilages show strain stiffening under large deformations along with higher wet adhesion strength. From the LAOS rheological studies and microstructure, we have shown that cellulosic components have a significant role towards the observed behaviour.

Conclusions

The unique strain stiffening behaviour and strong wet adhesion characteristics observed in basil and chia seed mucilage strongly point to the plausible role of cellulosic components in supporting the antitelechory found commonly in plants of arid habitats.

Background and aims

Pulses- grain legumes are vulnerable to waterlogging (WL) in South Asia. This study examined the effects of WL on two pulses at germination and reproductive stages and tested hypotheses: Mungbean (Vigna radiata L.) and blackgram (Vigna mungo L.) differ in WL tolerance; and the differences are due to phenotypic and growth traits.

Methods

Three mungbean and one blackgram cultivar were grown in pot-soil system. The treatments were at germination stage, 0 (drained control), 3, 5 and 7 d WL, while at the reproductive stage 0 (drained control), 3, 6 and 9 d WL and then drained to allow recovery (RE).

Results

Seed emergence decreased with longer WL duration. Blackgram cultivar showed 38% emergence, while mungbean cultivars had 14–18% after 7 d of WL. At the reproductive stage, WL reduced shoot and root growth compared to drained control. After 30 d of recovery, the chlorophyll concentration of first trifoliate leaves increased by 15% in blackgram cultivar, while it decreased in mungbean cultivars compared to their drained controls. Blackgram had higher relative growth rate (RGR) than mungbean at 9 d WL. After 9 d of WL, blackgram seed yield was reduced by 40% and mungbean cultivars by 52–60% compared to drained controls.

Conclusions

This study has provided evidence of a difference in WL tolerance between two summer pulses at both stages for the particular soil used here. Seedling emergence, RGR and yield attributed the variation. These new findings will allow growers to select suitable crops for different cropping systems.

Aims

Variabilities of vegetation and soil cause uncertainty to the factor of safety (FoS) of unsaturated vegetated slopes, yet the significance of these variabilities on the uncertainty of FoS is unclear. This study aims to quantify the effect of the uncertainties of root reinforcement and soil hydromechanical properties to the uncertainty of the FoS.

Methods

The variance‐based global sensitivity analysis was adopted to evaluate how the variance of FoS of vegetated slopes can be apportioned by the variabilities of soil and root parameters. A copula theory was applied to model the correlation amongst the parameters.

Results

For slip depths shallower than 0.30 m, the major source of the variance of the FoS included the parameters that define root reinforcement, followed by the parameters of soil shear strength. The variation of transpiration‐induced soil suction had limited effect on the FoS variance under heavy rainfall. Taking into account the correlations amongst the parameters had minor influence on their contribution to the variance of the FoS.

Conclusions

We observed threshold slip depths, where the relative contribution of uncertainties in root and soil parameters on the FoS uncertainty underwent a transition. Root reinforcement for slips as deep as 0.60 m can provide reliable slope stabilisation effects.

Background and aims

Attapulgite has been widely used to reclaim saline soils because it can affect the processes of nitrogen (N) transport and transformation through adsorption. However, the impact of attapulgite on crop uptake of N and the underlying mechanisms remain poorly understood.

Methods

We conducted a pot experiment over two seasons involving a rotation of barley (Hordeum vulgare) and maize (Zea mays) in which distinct ¹⁵N-labellled fertilizers (low N [LN], 180 kg N ha⁻¹; high N [HN], 240 kg N ha⁻¹) and attapulgite (no attapulgite; 5% attapulgite) were utilized. The effects of attapulgite on the utilization of N fertilizer and its residues were analysed along with the utilization of residual N fertilizers by subsequent crops.

Results

Barley utilized 42.91–46.79% ¹⁵N fertilizer. Notably, the LN treatment involving attapulgite reduced ¹⁵N fertilizer utilization by barley by 3.33%, whereas it increased it by 4.62% in the HN treatment. A total of 14.26–20.55% of the ¹⁵N fertilizer remained in the soil, and attapulgite had no significant effect on the ¹⁵N fertilizer residual levels or its utilization by maize. The addition of attapulgite significantly reduced the abundance of genes involved in nitrification and denitrification, thereby decreasing the risk of N loss by denitrification.

Conclusion

Attapulgite offers significant benefits in terms of N fertilizer absorption and crop N utilization efficiency and mitigates the loss of N when high levels of fertilizers are applied.

Background

Water insufficiency is a major abiotic stressor that significantly reduces crop yields, posing a serious threat to global food security. Soybean, a key legume and one the the top five global crops, serves as a primary source of protein, minerals, and oil. Water deficit has profound impacts on soybean's growth, physiology, and ultimately its yield.

Scope

Improving soybean productivity under drought stress is crucial to addressing food security challenges. Advanced breeding tools that leverage soybean physiological responses to water scarcity are essential for identifying and transferring drought-tolerance genes. Further research into the physiological, biochemical, and molecular responses of soybean to drought stress will enable breeders to enhance drought resilience effectively.

Conclusion

This review comprehensively details the morphological and physiological responses of soybean to drought stress and outlines various agronomical, molecular, and cutting-edge technological approaches to enhance drought tolerance. By synthesizing current research, this work identifies key strategies and tools that breeders can use to develop drought-resilient soybean cultivars, contributing to improved productivity under water-limited conditions.

Background and aims

Organic matter additions in coastal wetlands contribute to blue carbon sequestration and adjustment to sea-level rise through vertical substrate growth, with accurate modelling of these dynamics requiring information of root mass and volume additions across tidal gradients. This study aims to characterise the influence of vegetation zonation and tidal position on root mass and volume dynamics within substrates.

Methods

The root ingrowth technique was coupled with sediment cores to quantify below-ground root mass and volume production, standing stocks and turnover across two years to 90 cm depth at Kooweerup, Victoria, Australia.

Results

We indicate a complex non-linear relationship between fine root mass production and tidal position, influenced by variable vegetation structures across mangrove (442–3427 g m⁻² yr⁻¹), saltmarsh (540–860 g m⁻² yr⁻¹) and supratidal forest (599 g m⁻² yr⁻¹) zones. Fine root volume additions ranged from 274 to 4055 cm³ m⁻² yr⁻¹ across sampling locations. Root production was greatest for older mangroves and tidally defined optimal zones of production were evident for mangrove and saltmarsh. Live roots extended deeper than typically studied, reaching depths of 1.0 m in forested zones.

Conclusion

This information of root mass and volume additions across wetland live rooting zones can be used to improve highly parameterised models accounting for carbon sequestration and substrate vertical adjustment along intertidal gradients. We recommend that future studies measure root production across the entire active rooting zone or to 1 m depth to align with standard carbon accounting measurement depths.

Aim

Patchy degradation of alpine meadow is a common phenomenon in the natural ecosystem of the QTP, and the advent of bare patches (BPs) in degraded meadow impairs its ecosystem functions. Soil microbial diversity is an important biomarker essential to maintain the health of the meadow ecosystem. At present, there is a lack of understanding about how soil microbial communities change during the natural recovery of patchily degraded BPs in alpine meadows on the QTP.

Method

We analyzed soil archaea/bacteria and fungi at different recovery stages from BP, and their relationship with carbon fluxes during peak growth. The patches at different recovery stages were monitored to determine the changing patterns of soil microbial diversity and to establish the relationship between microbial communities and ecosystem carbon functions during the recovery process of BP.

Results

We found that the recovery of BP to healthy alpine meadow caused significant structural changes in the soil archaeal/bacterial and fungal communities, as evidenced by a significant decrease in their alpha-diversity. The recovery of bare patches leads to changes in soil nitrate nitrogen, pH, available phosphorus, microbial biomass carbon, and soil water content. All of them either directly or indirectly affected microbial community composition and alpha-diversity. Soil microbial alpha-diversity was negatively correlated with carbon sequestration and the respiratory rate of carbon flux components.

Conclusion

It is concluded that the diversity of soil microorganisms was significantly reduced as bare patches of the degraded meadow naturally recovered to become healthy meadow.

Background and aims

Understanding how inorganic N fertilizers applied to agroforestry systems impact N₂-fixation and development of legume trees is essential for optimizing management practices. This study hypothesized that inorganic N fertilization with urea (CH₄N₂O) could reduce the quantity of N derived from the atmosphere in the leaves, and decrease the overall development of the legume tree Mimosa caesalpiniifolia Benth. under an agroforestry system.

Methods

The trial was settled in a randomized complete block design with three repetitions, and evaluated four different rates of N fertilization (0, 100, 200, and 400 kg N ha⁻¹ year⁻¹), over a three-year trial. The agroforestry was composed of M. caesalpiniifolia double rows, grass pasture (Megathyrsus maximus Jacq. cv. Massai), and dispersed babassu palm trees (Attalea speciosa Mart. ex Spreng), located in the Amazon region of Brazil.

Results

This study proved that increasing rates of inorganic N fertilization using urea, up to 400 kg ha⁻¹ year⁻¹, did not affect the regular development of M. caesalpiniifolia trees under an agroforestry system; however, the level of N applied, especially the highest dosage (400 kg ha⁻¹ year⁻¹), was capable of reducing by approximately 45% the quantity of N derived from the atmosphere.

Conclusion

These findings indicate a negative impact of the inorganic N fertilization with urea on the symbiotic N₂-fixation of M. caesalpiniifolia trees. This study also evidenced that as the trees of M. caesalpiniifolia aged they tended to display a significant reduction of the content of N derived from the atmosphere in their leaves.

Aims

Environmental stresses can influence root mechanical strength, the impact of submersion of the water level fluctuation zone on the root mechanical strength of Cynodon dactylon was evaluated in this study.

Methods

Variations in the physicochemical properties (root weight density and root activity), mechanical strengths (tensile and pullout strength) and failure types of C. dactylon roots were investigated using a submersion experiment with 8 durations (0, 15, 30, 60, 90, 120, 150, 180 d), with a treatment without submersion serving as the control (CK). Additionally, corresponding variation in the microstructure of the roots was observed.

Results

The root weight density, root activity, root tensile strength and pullout strength of C. dactylon rapidly decreased, followed by a gradual decrease with increasing duration, and the reductions during the first 15 d of submersion accounted for 65.15%, 75.86%, 61.14% and 68.26% of the maximum reduction during the submersion process, respectively. Negative power function relationships were found between root mechanical strength and root diameter. Submersion increased the proportion of fracture failures during the pullout process. Moreover, the influence of submersion on root mechanical strength and failure type was regulated by a reduction in root activity.

Conclusions

Submersion deteriorates the mechanical properties of C. dactylon roots and alters their failure type.

Background and aims

Knotweeds are known to influence microbial processes. This study aimed to unravel the clonal control of microbial nitrogen cycle activities by established knotweed patches, as function of plant growth phases and ramet positions within the patch, all according to six different soils.

Methods

At six sites, we measured N-microbial activities (free-living nitrogen fixation, nitrification, and denitrification, substrate-induced respiration), soil N mineral forms, moisture and pH across five plant growth phases and at two ramet positions within the patch (centre and front). The sites were categorized as having High, Medium or Low soil functioning based on (a)biotic parameters (nitrification, denitrification, soil moisture, and pH).

Results

The influence of the patch centre on N-microbial activities varied with soil functioning during the plant growth phases. Nitrification and N fixation increased in Low functioning soils but decreased or remained unchanged in High functioning soils. Denitrification remained constant in Low functioning soils but decreased in High functioning soils. In Medium functioning soil, denitrification and N fixation were reduced, whereas nitrification remained unchanged. Significant differences in N cycle control were found between the patch centre and front, depending on the growth phase and soil functioning.

Conclusion

During the growth period (N demand), the patch centre influences N-microbial activities differently, depending on soil functioning, leading to improved N acquisition in soils with strong competition for mineral N (High and Medium functioning soils). Ramets at the patch centre and front control the N cycle differently, with the centre likely facilitating N acquisition and the front promoting colonization.