Root Activity Research Articles

Regulatory mechanism of bamboo biochar dosage on cadmium accumulation in Salix psammophila: insights from rhizosphere microbial communities, assembly processes, and interactions

Soil amendments play a pivotal role in regulating rhizosphere microbial communities, which is essential for maintaining robust plant growth under adverse environmental conditions. However, the microbial mechanisms that underlie the impact of biochar on phytoremediation performance remain incompletely understood in the context of different application rates. Here, we compared the phytoremediation performance, rhizosphere microbial community characteristics, and microbial interactions in Salix psammophila across different biochar application rates (1%, 3%, 5%, and 7%) in Cd-contaminated soil. Applying 5% biochar increased plant biomass by 10.02%, root activity by 183.82%, and Cd accumulation by 13.65%. Lower biochar rates (1% and 3%) decreased Cd accumulation in plants by 21.89% and 42.05%, respectively, compared to the control. Rhizosphere soil properties and Cd content, except for nitrogen, showed a gradient change with increasing biochar application rates. This was accompanied by an elevation in the Chao1 index for the bacterial community, although the fungal community remained unaffected in terms of diversity and structure. Null-model analyses indicated that fungal community assembly was mainly driven by ecological drift, explaining its unresponsiveness to biochar application. Applying 1% biochar enhanced microbial network stability while reducing bacterial network complexity. Conversely, 3% biochar application resulted in the lowest microbial network stability. Biochar application, except 3%, reduced the proportion of bacteria-fungi associations, suggesting increased independence between two microbial kingdoms. Random forest and piecewise structural equation models revealed that phytoremediation performance is influenced by microbial network stability, complexity, and bacteria-fungi associations. Fungal complexity and stability, along with bacterial stability, were identified as key predictors of phytoremediation performance. Our findings reveal potential mechanisms by which biochar influences phytoremediation through altering microbial interactions. For long-term microbial stability and cost-effectiveness, a 1% biochar application is recommended for phytoremediation. Conversely, for rapid Cd accumulation in plants, a 5% biochar application is optimal.Graphical

Anti-dengue viral activity of Glycyrrhiza glabra roots in Vero cells

Despite being a global public health problem, there are no antiviral agents for dengue. Plants are the sources of most approved drugs and many phytochemicals have exhibited in vitro antiviral activity. We explored the antiviral potential of the aqueous extract of Glycyrrhiza glabra roots (GGaq) on dengue viruses. Plaque reduction antiviral assay for half maximal inhibitory concentrations (IC50) was done in Vero cells infected with dengue serotypes 1–4 and exposed to varying concentrations of GGaq. Half-maximal cytotoxic concentration (CC50) of the GGaq was 651.9 µg/mL. The IC50 of the four dengue serotypes (10–50 µg/mL) indicated moderate inhibition by GGaq. 98–100% inhibition of all dengue serotypes was seen with GGaq at the maximum nontoxic dose. Preparative thin layer chromatography of GGaq, isolated sub fractions E and F which had low to moderate antiviral activity (IC50 12.65–85.95 and IC50 13.14–69.27 respectively). They exhibited good therapeutic potential only for dengue serotype-4. Virus adsorption to cells was significantly inhibited by GG (50%) and sub fraction E (24.9%). Chloroquine diphosphate was used as the positive control in all assays. The aqueous extract of GG was non-toxic and had better antiviral activity than sub fractions E and F.

Exogenous hydrogen sulfide increased Nicotiana tabacum L. resistance against drought by the improved photosynthesis and antioxidant system

Drought stress is an abiotic stressor that impacts photosynthesis, plant growth, and development, leading to decreased crop yields. Sodium hydrosulfide (NaHS), an exogenous additive, has demonstrated potential regulatory effects on plant responses to polyethylene glycol-induced drought stress in tobacco seedlings. Compared to the control, drought stress induced by 15 g/L PEG-6000 significantly reduced several parameters in tobacco seedlings: shoot dry weight (22.83%), net photosynthesis (37.55%), stomatal conductance (33.56%), maximum quantum yield of PSII (Fv/Fm) (11.31%), photochemical quantum yield of PSII (ΦPSII) (25.51%), and photochemical quenching (qP) (18.17%). However, applying NaHS, an H2S donor, mitigated these effects, ultimately enhancing photosynthetic performance in tobacco seedlings. Furthermore, optimal NaHS concentration (0.4 mM) effectively increased leaf stomatal aperture, relative water content (RWC) and root activity, as well as facilitated the absorption of N, K, Mg and S. It also enhanced the accumulation of soluble sugar and proline content to maintain osmotic pressure balance under drought stress. Compared to drought alone, pretreatment with NaHS also bolstered the antioxidant defense system in leaves, leading to 22.93% decrease in hydrogen peroxide (H2O2) content, a 22.19% decrease in malondialdehyde (MDA) content and increased activities of ascorbate peroxidase (APX) by 28.13%, superoxide dismutase (SOD) by 17.07%, peroxidase (POD) by 46.99%, and catalase (CAT) by 65.27%. Consequently, NaHS protected chloroplast structure and attenuated chlorophyll degradation, thus mitigating severe oxidative damage. Moreover, NaHS elevated endogenous H2S levels, influencing abscisic acid (ABA) synthesis and the expression of receptor-related genes, collaboratively participating in the response to drought stress. Overall, our findings provide valuable insights into exogenous NaHS’s role in enhancing tobacco drought tolerance. These results lay the foundation for further research utilizing H2S-based treatments to improve crop resilience to water deficit conditions.

Seed Priming with Dynamically Transformed Selenium Nanoparticles to Enhance Salt Tolerance in Rice.

Seed priming with nanomaterials is an emerging approach for improving plant stress tolerance. Here, we demonstrated a mechanism for enhancing salt tolerance in rice under salt stress via priming with nonstimulatory nanoparticles such as selenium nanoparticles (SeNPs), distinct from stimulatory nanomaterials. Due to the dynamic transformation ability of SeNPs, SeNP priming could enhance rice salt tolerance by mediating the glutathione cycle to eliminate excess reactive oxygen species (ROS). During priming, SeNPs penetrated rice seeds and transitioned into a soluble form (99.9%) within the embryo endosperm. Subsequently, the soluble selenium (Se) was transported to rice roots and metabolized into various Se-related derivatives, including selenomethionine (SeMet), Na2SeO3 (Se IV), selenocysteine (SeCys2), and methylselenocysteine (MeSeCys). These derivatives significantly enhanced the root activities of key enzymes such as glutathione peroxidase (GSH-PX), glutathione reductase (GR), catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) by 24.97%, 47.98%, 16.23%, 16.81%, and 14.82%, respectively, thus reinforcing the glutathione cycle and ROS scavenging pathways. Moreover, these alterations induced transcriptional changes in rice seedlings, with genes involved in signal transduction, transcription factors (TFs), ROS scavenging, and protein folding being upregulated, activating signal perception and self-repair mechanisms. These findings offer valuable insights for the agricultural application of nanomaterials.

Tissue-Specific Regulation of Vesicular Trafficking Mediated by Rab-GEF Complex MON1/CCZ1 From Solanum chilense Increases Salt Stress Tolerance in Arabidopsis thaliana.

Salt stress constrains the development and growth of plants. To tolerate it, mechanisms of endocytosis and vacuolar compartmentalization of Na+ are induced. In this work, the genes that encode a putative activator of vesicular trafficking called MON1/CCZ1 from Solanum chilense, SchMON1 and SchCCZ1, were co-expressed in roots of Arabidopsis thaliana to determine whether the increase in prevacuolar vesicular trafficking also increases the Na+ compartmentalization capacity and tolerance. Initially, we demonstrated that both SchMON1 and SchCCZ1 genes rescued the dwarf phenotype of both A. thaliana mon1-1 and ccz1a/b mutants associated with the loss of function, and both proteins colocalized with their functional targets, RabF and RabG, in endosomes. Transgenic A. thaliana plants co-expressing these genes improved salt stress tolerance compared to wild type plants, with SchMON1 contributing the most. At the sub-cellular level, co-expression of SchMON1/SchCCZ1 reduced ROS levels and increased endocytic activity, and number of acidic structures associated with autophagosomes. Notably, greater Na+ accumulation in vacuoles of cortex and endodermis was evidenced in the SchMON1 genotype. Molecular analysis of gene expression in each genotype supported these results. Altogether, our analysis shows that root activation of prevacuolar vesicular trafficking mediated by MON1/CCZ1 emerges as a promising physiological molecular mechanism to increase tolerance to salt stress in crops of economic interest.

Influence of sonic activation of epoxy-resin and calcium silicate sealer on postoperative pain: a patient-blinded, parallel group, randomized clinical trial

BackgroundThis clinical study aims to compare postoperative pain after single-visit root canal treatment of teeth with asymptomatic apical periodontitis using epoxy-resin-based AH Plus and calcium silicate-based Endosequence BC sealers with or without sonic activation.MethodsThis study included 72 individuals with one first or second mandibular premolar tooth with asymptomatic apical periodontitis. They were randomly divided into four groups according to the root canal sealer (AH Plus or Endosequence BC) and activation protocol (sonic activation or non-activation) (n = 18). The participants were ask to rate their postoperative pain intensity on a NRS scale as none, minimal, moderate, or severe after 24 h, 48 h, 72 h, and 7 days following treatment. Patients were also asked to record the number of prescribed analgesic medication tablets (400 mg of ibuprofen) taken. Statistical analysis were performed using the Mann-Whitney U test, the Friedman test, the Spearman’s correlation test, the Chi-square test. Significance level was established at 0.05.ResultsThere was no statistically significant difference in postoperative pain scores or analgesic intake between AH Plus and Endosequence BC sealers regardless of the activation protocol (p > 0.05). There was no statistically significant difference in postoperative pain scores between the sonic activation and non-activation groups (p > 0.05). A weak positive correlation was detected between Endoactivator sonic activation and sealer extrusion (r = 0.36).ConclusionsAH Plus and EndoSequence BC root canal sealers showed similar results in terms of prevalance and intensity of postoperative pain. Sonic activation and non-activation groups had similar postoperative pain scores.Clinical trial registrationThe study was retrospectively registered with ClinicalTrials.gov (NCT06403293). Date of Registration: 07/05/24.

Exopolysaccharide-Producing Bacteria Regulate Soil Aggregates and Bacterial Communities to Inhibit the Uptake of Cadmium and Lead by Lettuce

The accumulation of heavy metals in the soil not only causes serious damage to the soil ecosystem, but also threatens human health through the food chain. Exopolysaccharides have the functions of adsorbing and chelating heavy metals and reducing their bioavailability in the soil. In our study, exopolysaccharide-producing bacteria with a high efficiency in adsorbing cadmium (Cd) and lead (Pb) were screened from heavy metal-contaminated farmland. Through pot experiments, the influence of functional strains on the size distribution, heavy metal content, and bacterial community structure of soil aggregates in lettuce was studied using high-throughput sequencing technology. The results show that 11 strains secreting exopolysaccharides were initially screened from heavy metal-contaminated soil. Among them, strain Z23 had a removal rate of 88.6% for Cd and 93.2% for Pb. The rate at which Cd was removed by strain Z39 was 92.3%, and the rate at which Pb was removed was 94.4%. Both strains belong to Bacillus sp. Strains Z23 and Z39 induced the formation of Fe2Pb(PO4)2, Cd2(PO4)2, and Pb2O3 in the solution. The pot experiments showed that strains Z23 and Z39 increased (19.1~23.9%) the dry weight and antioxidant enzyme activity of lettuce roots and leaves, while reducing (40.1~61.7%) the content of Cd and Pb. Strains Z23 and Z39 increased the proportion of microaggregates (<0.25 mm) and the content of exopolysaccharides in rhizosphere soil and reduced (38.4–59.7%) the contents of available Cd and Pb in microaggregates, thus inhibiting the absorption of heavy metals by lettuce. In addition, the exopolysaccharide content and the bacterial community associated with heavy metal resistance and nitrogen (N) cycling (Patescibacteria, Saccharimonadales, Microvirga, and Pseudomonas) in microaggregates were key factors affecting the available heavy metal content in soil. These results show that the exopolysaccharide-producing bacteria Z23 and Z39 reduced the absorption of Cd and Pb by lettuce tissues, thus providing strain resources for the safe utilization of soils that exceed heavy metal standards for farmland and for reducing the heavy metal content in vegetables.

Peanut-Colonized Piriformospora indica Enhanced Drought Tolerance by Modulating the Enzymes and Expression of Drought-Related Genes.

Peanut (Arachis hypogaea L.) is an important cash and oil seed crop, mostly distributed in arid and semi-arid areas. In recent years, due to the influence of atmospheric circulation anomalies and other factors, drought has become frequent and increasingly serious in China. This has posed serious challenges to peanut production. The objective of this study was to investigate the potential of the endophytic fungus Piriformospora indica to form a symbiotic relationship with peanut plants and to evaluate the drought tolerance of P. indica-colonized peanut plants subjected to a simulated drought stress treatment using 20% polyethylene glycol 6000 (PEG6000). The endophytic fungus P. indica affected the physiological characteristics of the host plant by colonizing the plant roots, thereby conferring greater resistance to drought stress. This fungus strongly colonized the roots of peanuts and was found to enhance root activity after 24 h of P. indica colonization under PEG6000. Catalase (CAT) and peroxidase (POD) activities were increased at 24 h in peanut leaves colonized with P. indica. Expression of drought-related genes, such as AhNCED1, AhP5CS, and DREB2A was upregulated at 24 h of P. indica colonization. In addition, after PEG6000 treatment, proline, soluble protein, and abscisic acid (ABA) concentrations in plants were increased, while the accumulation of malondialdehyde (MDA), and hydrogen peroxide (H2O2) was decreased in P. indica colonized peanut. In conclusion, P. indica mediated peanut plant protection against the detrimental effects of drought resulted from enhanced antioxidant enzyme activities, and the upregulated expression of drought-related genes for lower membrane damage.

Integrated stress responses in okra plants (cv. ‘’Meya’]: unravelling the mechanisms underlying drought and nematode co-occurrence

BackgroundClimate change threatens sub-Saharan Africa’s agricultural production, causing abiotic and biotic stressors. The study of plant responses to joint stressors is crucial for understanding molecular processes and identifying resilient crops for global food security. This study aimed to explore the shared and tailored responses of okra plants (cv. ‘’Meya’), at the biochemical and molecular levels, subjected to combined stresses of drought and Meloidogyne incognita infection.DesignThe study involved 240 okra plants in a completely randomized design, with six treatments replicated 20 times. Okra plants were adequately irrigated at the end of every 10-days water deficit that lasted for 66 days (D). Also, the plants were infected with M. incognita for 66 days and irrigated at 2-days intervals (R). The stresses were done independently, in sequential combination (D before R and R before D) and concurrently (R and D). All biochemical and antioxidant enzyme assays were carried out following standard procedures.ResultsSignificant reductions in leaf relative water content were recorded in all stressed plants, especially in leaves of plants under individual drought stress (D) (41.6%) and plants stressed with root-knot nematode infection before drought stress (RBD) (41.4%). Malondialdehyde contents in leaf tissues from plants in D, nematode-only stress (RKN), drought stress before root-knot nematode infection (DBR), RBD, and concurrent drought-nematode stress (RAD) significantly increased by 320.2%, 152.9%, 186.5%, 283.7%, and 109.6%, respectively. Plants in D exhibited the highest superoxide dismutase activities in leaf (147.1% increase) and root (105.8% increase) tissues. Catalase (CAT) activities were significantly increased only in leaves of plants in D (90.8%) and RBD (88.9%), while only roots of plants in D exhibited a substantially higher CAT activity (139.3% increase) in comparison to controlled plants. Okra plants over-expressed NCED3 and under-expressed Me3 genes in leaf tissues. The NCED3 gene was overexpressed in roots from all treatments, while CYP707A3 was under-expressed only in roots of plants in RBD and RKN. CYP707A3 and NCED3 were grouped as closely related genes, while members of the Me3 genes were clustered into a separate group.ConclusionThe biochemical and molecular responses observed in okra plants (cv. ‘’Meya’) subjected to combined stresses of drought and Meloidogyne incognita infection provide valuable insights into enhancing crop resilience under multifaceted stress conditions, particularly relevant for agricultural practices in sub-Saharan Africa facing increasing climatic challenges.

The roles of nanoparticle-enriched biochars in improving soil enzyme activities and nutrient uptake by basil plants under arsenic toxicity

Enriched biochar with improved properties and functionality can play a significant role in providing sustainable solutions for mitigating heavy metal contamination in soil. In this experiment, the effects of solid and enriched biochars (potassium-enriched biochar (BC-K), magnesium-enriched biochar (BC-Mg), both individually and combined) were examined on soil microbial and enzyme activities, as well as nutrient uptake by basil plants cultivated in a soil with three levels of arsenic (nontoxic, 50 mg As kg−1 soil, and 100 mg As kg−1 soil). Biochar-related treatments, increased soil organic matter (65–76%), while decreased availability of arsenic (6–55%) in the soil. The microbial biomass carbon (by about 123%) and soil basal respiration (by about 256%), and soil enzymatic activities (β-glucosidase, urease, alkaline phosphatase, and dehydrogenase) were enhanced by enriched biochars under arsenic toxicity. The solid and particularly enriched biochars decreased arsenic content and improved nitrogen and phosphorus contents of roots and shoots, root length, root activity, and root and shoot biomass in basil plants. Therefore, it is conceivable to suggest that enriched biochars are superior treatments for improving nutrient absorption rates and basil growth under arsenic toxicity through decreasing arsenic mobility and increasing soil microbial activities.

Physiological and biochemical responses in a cadmium accumulator of traditional Chinese medicine Ligusticum sinense cv. Chuanxiong under cadmium condition

Ligusticum sinense cv. Chuanxiong (L. Chuanxiong), one of the widely used traditional Chinese medicines (TCM), is currently facing the problem of excessive cadmium (Cd) content. This problem has significantly affected the quality and safety of L. Chuanxiong and become a vital factor restricting its clinical application and international trade development. Currently, to solve the problem of excessive Cd, it is essential to research the response mechanisms of L. Chuanxiong to Cd stress. However, there are few reports on its physiological and biochemical responses under Cd stress. In this study, we conducted the hydroponic experiment under 25 μM Cd stress, based on the Cd content of the genuine producing areas soil. The results showed that 25 μM Cd stress not only had no significant inhibitory effect on the growth of L. Chuanxiong seedlings but also significantly increased the chlorophyll a content (11.79%) and root activity (51.82%) compared with that of the control, which might be a hormesis effect. Further results showed that the absorption and assimilation of NH4+ increased in seedlings under 25 μM Cd stress, which was associated with high photosynthetic pigments. Here, we initially hypothesized and confirmed that Cd exceedance in the root system of L. Chuanxiong was due to the thickening of the root cell wall, changes in the content of the cell wall components, and chelation of Cd by GSH. There was an increase in cell wall thickness (57.64 %) and a significant increase in cellulose (25.48%) content of roots under 25 μM Cd stress. In addition, L. Chuanxiong reduced oxidative stress caused by 25 μM Cd stress mainly through the GSH/GSSG cycle. Among them, GSH-Px (48.26%) and GR (42.64%) activities were significantly increased, thereby maintaining a high GSH/GSSG ratio. This study preliminarily reveals the response of L. Chuanxiong to Cd stress and the mechanism of Cd enrichment. It provides a theoretical basis for solving the problem of Cd excessive in L. Chuanxiong.Graphical Physiological and biochemical mechanisms of L. Chuanxiong seedlings under Cd stress.

Effect of Paenibacillus favisporus CHP14 inoculation on selenium accumulation and tolerance of Pakchoi (Brassica chinensis L.) under exogenous selenite treatments

The effects of Paenibacillus favisporus CHP14 inoculation on selenium (Se) accumulation and Se tolerance of Pakchoi were studied by a pot experiment conducted in greenhouse. The results revealed that the growth traits such as plant height, root length, and biomass were significantly elevated during CHP14 treatment at 0 ∼ 8.0 mg·kg−1 Se(IV) levels. CHP14-inoculated plants accumulated more Se in root and shoot, which were 24.1%∼57.3% and 7.5%∼50.9% higher than those of non-inoculated plants. The contents of leaf nitrogen (N), phosphorus (P), magnesium (Mg), and iron (Fe), as well as the ratio of indoleacetic acid and abscisic acid contents (IAA/ABA) were increased by CHP14 inoculation, and positively associated with photosynthetic pigment contents (p < 0.05). At ≥ 4.0 mg·kg−1 Se(IV) levels, superoxide dismutase, peroxidase, and glutathione peroxidase activities of Pakchoi roots were increased with CHP14 inoculation, by 9.9%∼17.1%, 28.4%∼40.7%, and 7.4%∼15.3%, respectively. Moreover, CHP14 inoculation enhanced ascorbate-glutathione (AsA-GSH) metabolism in roots by upregulating the related enzymes activities and antioxidant contents under excess Se(IV) stress. These findings suggest that CHP14 is beneficial to improve plant growth and enhance Se(IV) resistance of Pakchoi, and can be exploited as potential inoculants for phytoremediation process in Se contaminated soil.

Facilitating effects of plant extracts on soil health and replanted Panax ginseng growth in recession soil.

Plant extracts have been shown to be effective agricultural strategies for improving soil fertility and quality, and promoting plant growth in soil degradation remediation. The application of plant extracts improves the material cycle of soil microecology, such as the decomposition of nitrogen, phosphorus, and potassium, while increasing plant resistance. However, there is currently no experiment to demonstrate whether plant extracts have a promoting effect on the growth of ginseng and the mechanism of action. Pot experiments were carried out to investigate the effects of extracts, namely Rubia cordifolia (RC), Schisandra chinensis (SC), and Euphorbia humifusa (EH) on soil properties, enzyme activities, and plant physiological characteristics were evaluated. Results showed that compared with CK, plant extract-related treatments increased soil Organic carbon (OC), Available nitrogen (AN), Available phosphorus (AP) contents, and Soil urease activity. (S-UE), Soil sucrase activity (Soil sucrase), Soil acid phosphatase activity. (S-ACP). Meanwhile, plant extract-related treatments significantly increased plant physiological properties and TP (Total protein) content, and decreased the content of MDA (malondialdehyde) by 15.70% -36.59% and PRO (proline) by 30.13% -148.44%. Furthermore, plant extract-related treatments also significantly promote plant growth and reduce plant incidence, the fresh weight of ginseng increased by 27.80% -52.08%, ginseng root activity increased by 45.13% -90.07%, and ginseng incidence rate decreased by 20.00% -46.67%. Through correlation analysis between fresh weight of ginseng and root parameters and soil index, fresh weight is significantly positively correlated with root diameter, fiber root number, root activity, total protein (TP), catalytic activity (CAT) and superoxide dismutase activity (SOD), H, soil urea activity (S-UE), soil sucrose activity (S-SC), soil acid phosphate activity (S-ACP), and soil laccase activity (SL); The fresh weight was significantly negatively correlated with incidence rate, disease severity index, and malondialdehyde content (MDA). In summary, plant extract-related treatments improve soil quality and promote ginseng growth, further enhancing soil health and plant disease resistance. These findings provide new insights into ginseng cultivation and soil health management and highlight a new approach that can be applied to a wider range of agricultural practices and environmental sustainability.

The balance between alleviating copper damage and maintaining root function during root pruning with excessive copper.

Coating high concentrations of copper (Cu) on the inner wall of containers can efficiently inhibit root entanglement of container-grown seedlings. However, how the protective and defensive responses of roots maintain root structure and function during Cu-root pruning is still unclear. Here, Duranta erecta seedlings were planted in the containers coated with 40 (T1), 80 (T2), 100 (T3), 120 (T4), 140 (T5), and 160 (T6) g L-1 Cu(OH)2 with containers without Cu(OH)2 as the control. Although T5 and T6 produced the best inhibitory effect on root entanglement, root anatomy structure was damaged. T1 and T2 not only failed to completely control root circling, but also led to decreased root activity and stunted growth. Cu(OH)2 treatments significantly increased lignin concentration of roots with the highest values at T3 and T4. Compared with T3, seedlings at T4 had higher height, biomass, and root activity and no significant root entanglement. Excessive Cu accumulation in Cu(OH)2 treatments changed the absorption of other mineral nutrients and their allocation in the roots, stems, and leaves. Overall, Ca was decreased while Mg, Mn, Fe, and K were increased, especially K and Mn at T4 which is related to defense capacity. The results indicate that there is a Cu threshold to balance root entanglement control, defense capacity, and nutrient uptake function under excessive Cu for container-grown D. erecta seedlings.

Integrated deep banding and fertigation of phosphorus improves cotton yield by regulating root spatial distribution and growth

Context or problemTraditionally, 100 % phosphorus (P) fertilizer application as a band at various depths before sowing significantly influenced crop root growth and yield by reducing P fixation and optimizing its spatial distribution. However, with the advent of drip fertigation in Xinjiang, China, P fertilization practices have shifted from 100 % basal to a combination of basal and fertigation for enhanced P nutrition in cotton. Despite this, the impact of pre-sowing P band application on cotton growth under drip fertigation remains unclear. Objective or research questionThis study aimed to determine the optimal P fertilizer banding depth for cotton under a drip fertigation system. MethodsField trials were conducted comparing different basal P fertilizer application depths (5 cm, 15 cm, and 25 cm, denoted as D5, D15, and D25, respectively) with 50 % of the P rate and the remaining 50 % applied as topdressing via drip fertilization. A control (CK) involving 50 % broadcasted P fertilizer and 50 % topdressed P was included. The study focused on the effects of P application depth on soil P availability, root growth patterns, P utilization, and cotton yield. ResultsAt the boll opening stage, the D15 treatment exhibited a significant 18.69 %-49.76 % increase in available phosphorus in the 10–40 cm soil layer compared to the CK. During the peak boll to boll opening stage, the D15 treatment significantly outperformed the CK in terms of total root biomass density (11.62 %-17.54 %), total root length (16.75 %-24.81 %), total root surface area (23.07 %-37.59 %), and total root volume (20.69 %-26.23 %). Moreover, root activity and growth parameters were notably higher in the D15 treatment within the 10–40 cm soil layer. ConclusionsApplying 50 % of the P fertilizer as a band at a 15 cm depth before planting drip-irrigated cotton is optimal. This practice enhances soil P availability, stimulates root growth and distribution, and ultimately improves P utilization and cotton yield. Implications or significanceBanding P fertilizer at a 15 cm depth in combination with drip fertigation demonstrates superior yield benefits. This technology offers a novel approach to fertilizer application, enhancing nutrient use efficiency and crop productivity in drip-irrigated systems.

Cadmium absorption and translocation in rice plants are influenced by lower air temperatures during grain filling stage

The increasing frequency and severity of low temperatures, and soil cadmium (Cd) pollution threaten food security. However, the interactive effects of Cd exposure and low temperatures on rice yield and quality, as well as the mechanisms of Cd absorption and translocation, remain unclear. In this study, two rice varieties were cultivated in soils with two Cd contamination levels (Cdhigh and Cdlow) and exposed to control (CT25) or lower temperatures of 20 °C (LT20) and 17 °C (LT17) during grain-filling stage. Results showed significant decreases in seed setting rate and grain weight, reduced head rice yield, and increased chalkiness due to low temperatures, particularly in Cdhigh soils. Compared to CT25, LT17 and LT20 increased Cd concentration by 37.6 % and accumulation by 14.8 % in grains grown in Cdhigh soils. Enhanced root activity and upregulation of OsNramp1 and OsNramp5 under both low-temperatures increased Cd levels in roots. Lower temperatures also decreased phytochelatins (PCs) and increased expression of OsHMA2 and OsCAL1, facilitating Cd transport and raising Cd levels in stems. Furthermore, upregulated OsHMA2, OsLCT1, and OsZIP7 in stems under low-temperatures promoted Cd transport to panicles. Overall, low temperatures during grain filling increased Cd uptake and translocation into rice grains, especially in high Cd contaminated soils, raising health risks. The study highlights the need to address climate change's impact on cadmium hazards in rice.

Involvement of plasma membrane H+-ATPase in the nitrate-nutrition uptake and utilization in indica rice

Utilization of nitrogen by crops is essential for sustainable agriculture. The transport of nitrate (NO3−) across the plasma membrane is a critical gateway for N uptake and subsequent utilization. This process requires proton (H+) coupled cotransport, which is driven by proton motive force, provided by plasma membrane (PM) H+-ATPase. In this report, two indica rice varieties [Meixiangzhan 2 (MXZ) and Jifengyou 1002 (JFY)] in South China were selected and cultivated in hydroponic solution with 0.5 mM or 2.0 mM NO3− as the N source. The JFY exhibited stronger growth with higher biomass than MXZ under both 0.5 mM and 2.0 mM NO3−. PM H+-ATPase activity of JFY roots was significantly higher than that of MXZ. The higher PM H+-ATPase activity in JFY was consistent with a higher abundance of PM H+-ATPase protein and higher transcription levels of OSAs, such as OSA2, OSA7 and OSA8 in roots, OSA3, OSA7 and OSA8 in leaves. The expression of nitrate transporters (OsNRT1;1b, OsNRT2.1, OsNRT2.2, and OsNAR2.1) were also higher in roots or shoots of JFY than those in MXZ. Under 0.5 mM and 2.0 mM NO3−, the NO3− absorption and translocation rate, nitrate content, as well as nitrate reductase (NR) activity were all significantly higher in JFY, as compared to those in MXZ. Taken together, in JFY and MXZ, a higher level of PM H+-ATPase protein and higher activity coupled with greater efficiency in nitrate uptake, translocation and assimilation, suggesting the existence of a close correlation between PM H+-ATPase and nitrate utilization in indica rice. PM H+-ATPase may one of the elite genes that can contribute to nitrate use efficiency in rice.

Effects of Steel Slag Used as Substrate on the Growth of Hydrangea macrophylla Cuttings

Steel slag is an industrial solid waste produced during the steelmaking process. To explore the application of steel slag in the agricultural field, the present experiment was carried out to study the effect of substrates with different contents of steel slag on the growth of Hydrangea macrophylla cuttings. The conventional substrate (perlite: vermiculite: peat = 1:1:1) was used as the control (CK), and the treatments were designed as T1 (steel slag: perlite: vermiculite: peat = 1:3:3:3, v/v/v/v), T2 (steel slag: perlite: vermiculite: peat = 1:2:2:2, v/v/v/v), T3 (steel slag: perlite: vermiculite: peat = 1:1:1:1, v/v/v/v), and T4 (steel slag: perlite: vermiculite: peat = 1:0:0:0, v/v/v/v). The results showed that the addition of steel slag significantly increased the substrate’s bulk density, EC, and pH and improved its water retention capacity to a certain extent. There were significant differences among different treatments in morphological indicators, root growth and development, and physiological and biochemical characteristics of cutting seedlings. All traits, including plant height, fresh weight, dry weight, root length, root surface area, root volume, the number of root tips, root activity, and soluble protein content of seedlings grown in T3 were significantly higher than those in other substrates. The results indicated that the appropriate addition of steel slag is helpful to hydrangea cuttings’ growth, and the optimal mixing ratio is steel slag: perlite: vermiculite: peat = 1:1:1:1 (v/v/v/v). This is a significant innovation in applying steel slag in agricultural production.

Comparison of piperine content, antimicrobial and antioxidant activity of Piper chaba root and stem

Piper chaba (locally known as “Choi Jhal”) is used traditionally as spices and folk medicine in different parts of Bangladesh. One of the most important bioactive compounds in this plant is piperine. In this study, the amount of piperine in P. chaba root and stem was investigated and the optimal solvent for piperine extraction at room temperature was also studied. High performance liquid chromatography (HPLC) was operated using a reverse phase column where methanol and water (70:30) were used as mobile phase. The detection was performed using photo diode array (PID) detector at a wavelength of 345 nm. The standard piperine showed linearity between 0.005 % and 0.04 % and the correlation co-efficient found for the linearity was 0.9933. The percentage of relative standard deviation (RSD) for both retention time and peak area were less than 2.0 %. The theoretical plate number (N) > 3000 and a tailing factor (T) < 1.5 were found in the acceptable range. The recovery percentage (%) of standard piperine was 99.16 %. Low value of co-efficient of variation and standard deviation are recognized for high precision of the method. The highest amount of piperine was found in root extracted with methanol (MR) amounting to 1.75 % in the root powder. The maximum amount of piperine in the stem was 1.59 % when extracted with methanol (MS). The piperine quantification in other extract like n-hexane root (HR), ethyl acetate root (ER), n-hexane stem (HS), ethyl acetate stem (ES) were 0.76 %, 1.69 %, 0.33 % and 1.46 % respectively. Methanol has given the highest yield of piperine compared to ethyl acetate and n-hexane for both root and stem. The developed method was simple, rapid, economic and validated in terms precision, accuracy and recovery. This selective method is found to be repeatable, accurate and successfully utilized for the Piper extract in marketed and pharmaceutical samples with well chromatographic conditions. The ethyl acetate extract of root and stem showed promising DPPH (1, 1-diphenyl-2-picrylhydrazyl) free radical scavenging activity with an IC50 value of 39.62 ± 0.95 μg/mL and 43.85 ± 1.50 μg/mL respectively. The study reports potential antibacterial activity and antifungal activity of P. chaba root and stem extracts. These outcomes revealed that different extracts of P. chaba may be used as natural preservatives.

The rhizosphere contributes disproportionately to free-living nitrogen fixation in subalpine forest soils

Root activity creates a unique microbial hotspot in the rhizosphere, profoundly regulating free-living nitrogen fixation (FLNF). However, empirical assessments of rhizosphere FLNF and its ecological consequences for nitrogen (N) budgets remain lacking, particularly for different root functional modules. Here, we separately collected rhizosphere soils attached to two root functional modules, absorptive roots and transport roots, and investigated the rates (15N2 incorporation) and regulators of rhizosphere FLNF in a N-limited subalpine coniferous forest. The measured rates were further extrapolated to annual fluxes based on the volume of the rhizosphere and the relationship between FLNF rate and temperature. We found that absorptive roots drove significantly higher rhizosphere FLNF rates than did transport roots (12.2 vs. 7.5 ng N g-1 d-1), with both rhizosphere compartments exhibiting rates well exceeding those in the bulk soil (0.9 ng N g-1 d-1). The FLNF rates were positively correlated with soil organic carbon content but showed no significant relationship with the abundance or composition of the diazotrophic community. Moreover, when extrapolated to the ecosystem level the FLNF fluxes were 2-fold greater in the rhizosphere of absorptive roots than in that of transport roots (0.13 vs. 0.04 kg N ha-1 yr-1). Taken together, despite representing only 6.0% of the soil volume, the two rhizosphere compartments contributed as much as 47.2% to the total soil FLNF fluxes. Overall, we provide empirical evidence that despite its limited volume, the rhizosphere contributes disproportionately to the FLNF in subalpine forest soils. Our findings also underscore the critical role of root functional differentiation in regulating rhizosphere FLNF, which is essential for integrating this process into the ecosystem-level N cycle.