Root Growth Inhibition Research Articles

Lung seven transmembrane receptors are involved in Arabidopsis root growth mediated by Danger-associated peptide Pep1.

Lung seven transmembrane receptor family is a small part of Arabidopsis gene family. So far, the function of some members of the this family is unknown. Plant elicitor peptide1 (Pep1) is one of damage-associated molecular patterns (DAMPs), which could trigger root growth inhibition and plant immunity responses. Here, we identified members of the Lung seven transmembrane family, and proved they are important for Pep1-induced root growth and development. We found that the expression levels of 7TM2 and 7TM6 were elevated in wild-type treated with Pep1. Phenotypic analysis showed that the growth phenotypes of 7tm2 and 7tm6 were similar to the wild-type under Pep1 treatment, but the 7tm2 7tm6 had a Pep1 hypersensitivity phenotype compared to wild-type. Furthermore, the complementation lines were able to restore the Pep1 phenotype of 7tm2 7tm6 to that similar to wild-type. These results suggest that 7TM2 and 7TM6 are involved in the regulation of root growth by Pep1. This study revealed the new functions of the Lung seven transmembrane receptor family and provided new ideas for further revealing the molecular mechanism of Pep1-regulated root growth and development.

The actin cytoskeleton regulates danger-associated molecular pattern signaling and PEP1 RECEPTOR1 internalization.

In plants, cytoskeletal proteins assemble into dynamic polymers that play numerous roles in diverse fundamental cellular processes, including endocytosis, vesicle trafficking, and the spatial distribution of organelles and protein complexes. Plant elicitor peptides (Peps) are damage/danger-associated molecular patterns (DAMPs) that are perceived by the receptor-like kinases PEP RECEPTOR 1 (PEPR1) and PEPR2 to enhance innate immunity and inhibit root growth in Arabidopsis (Arabidopsis thaliana). To date, however, there is little evidence that the actin cytoskeleton of the host cell participates in DAMP-induced innate immunity. Here, we demonstrated that the actin cytoskeleton alters the Pep1-triggered immune response. In addition, dual-color total internal reflection fluorescence-structured illumination microscopy (TIRF-SIM) showed that PEPR1 diffusion on the plasma membrane is closely related to the actin cytoskeleton. We performed single-particle tracking to quantify individual protein particles and found that the actin cytoskeleton notably regulates PEPR1 mobility and cluster size. More importantly, we demonstrated that actin filament reconfiguration is sufficient to inhibit Pep1-induced internalization, which alters the immune response. Taken together, these findings suggest that the actin cytoskeleton functions as an integration node for Pep1 signaling and PEPR1 endocytosis.

Cyto-Genotoxic Assessment of Sulfoxaflor in Allium cepa Root Cells and DNA Docking Studies.

Sulfoxaflor (SFX) is an insecticide that is commonly used for the control of sap-feeding insects. Since SFX is extensively applied globally, it has been implicated in the substantial induction of environmental toxicity. Therefore, in this study, Allium cepa roots have been employed to elucidate the potential cytogenotoxic effects of SFX in non-target cells by examination of mitotic index (MI), chromosomal aberrations (CAs), and DNA damage. Physiological effects of SFX were evaluated by A. cepa root growth inhibition assay, while cytogenotoxic effects were assessed by A. cepa ana-telophase and comet assay. Moreover, DNA binding affinity and binding mode of SFX were examined using molecular docking simulations to shed light on the genotoxic mechanism of action. The half maximal effective concentration (EC50) on the growth of A. cepa cells calculated for SFX was found as 500 mg/L. Moreover, dose- and time-dependent decrease in MI, increase in CAs (disturbed ana-telophase, chromosomal laggards, stickiness, and anaphase chromosome bridge) and DNA damage were observed by the exposure of A. cepa root tips to SFX after 24-, 48-, 72-, and 96-h treatment periods. A 6-bp double-stranded DNA structure containing two intercalation sites (PDB ID: 1Z3F) was used for docking studies. According to DNA docking results, SFX exhibited an energetically more favorable binding affinity with DNA (ΔG = -5.05 kcal/mol) compared with the experimental mutagen methyl methanesulfonate (MMS) (ΔG = -2.94 kcal/mol), and preferentially snugly fits into the minor groove of DNA possessing an intercalation gap, thus, providing valuable mechanistic data into the formation of chromosome aberrations and DNA fragmentation induced by this pesticide in A. cepa.

Effects of Intercropping and Mowing Frequency on Biological Nitrogen Fixation Capacity, Nutritive Value, and Yield in Alfalfa (Medicago sativa L. cv. Vernal).

Intercropping with legume forages is recognized as an effective strategy for enhancing nitrogen levels in agroforestry, while mowing may influence nitrogen fixation capacity and yield. This study investigated the rooting, nitrogen fixation, nutritive value, and yield of alfalfa (Medicago sativa L.) under intercropping and varying mowing frequencies (CK, 2, and 3) from 2021 to 2023, using walnut (Juglans regia L.) and alfalfa as experimental subjects. The results indicated that intercropping suppressed root growth, whereas increased mowing frequency stimulated root development in the topsoil (0-20 cm). Specifically, the average root length density, root surface area, and root volume from the twice- and thrice-mowed treatments increased by 18.26, 17.45, and 4.15%, respectively, in comparison to the control. The δ15N values of the intercropped alfalfa were significantly lower than those of the monocropped alfalfa (p < 0.05), with the δ15N values of the mowing-thrice treatment increasing by an average of 38.61% compared to the control. Intercropping suppressed alfalfa yield but did not affect the total nitrogen content in the leaves or the nutritive value, and all mowing treatments resulted in land equivalent ratios (LERs) greater than 1. Furthermore, increased mowing frequency enhanced both the nutritive value and yield of alfalfa. Our study suggests that intercropping with walnut can improve biological nitrogen fixation in alfalfa, and that adopting a mowing-thrice regime can optimize yield and nutritive value.

The Impact of Recycled Polyethylene Terephthalate as Aggregate Replacement on Mechanical and Ecotoxicological Properties of Mortar

The purpose of the study was to determine the mechanical and ecotoxicological properties of mortars with differently shaped recycled PET plastics as a partial natural aggregate replacement and assess its environmental impact. Different methods were used for determining mechanical properties, while ecotoxicity tests with two types of plants were performed for the assessment of the ecotoxicological potential of mortars. Results of strength tests revealed that PET in mortars increased 28-day compressive strength by up to 3% and decreased flexural strength by up to 14% compared to conventional mortar. Ultrasonic pulse velocity and dynamic modulus of elasticity were lower in PET mortars, while XRD and SEM-EDS showed fewer hydration products in PET mortars. Duckweed ecotoxicity test results revealed that frond growth inhibition values in PETS and conventional mortar leachate (100 g L−1) were around 50%, while root growth inhibition values did not exceed 40%. Mustard seed germination test results revealed root growth inhibition values in both mortar leachates were lower than 20%. Ecotoxicity tests showed that conventional and PET mortar were non-toxic to duckweed in aquatic environments and non-toxic to mustard seeds in terrestrial environments. Characterization of mortar leachates showed a significant increase in chloride, Ca, Si, and Ba content as potential causes for growth inhibition of both plants. Plastic waste reduction due to the potential use of PET in mortars confirmed that plastic waste could be completely eliminated and the global consumption of primary natural resources for concrete production reduced up to 4%. Such an approach could increase mortar sustainability.

Salt stress-accelerated proteasomal degradation of LBD11 suppresses ROS-mediated meristem development and root growth in Arabidopsis.

Roots absorb water and nutrients from the soil, support the plant's aboveground organs, and detect environmental changes, making them crucial targets for improving crop productivity. Roots are particularly sensitive to soil salinity, a major abiotic stress that poses a serious threat to global agriculture. In response to salt stress, plants suppress root meristem size, thus reducing root growth; however, the mechanisms underlying this growth restriction remain unclear. Here, we explore the role of reactive oxygen species (ROS) in this process, reveal that LATERAL ORGAN BOUNDARIES DOMAIN 11 (LBD11) plays a central role in the ROS-mediated regulation of meristem size and the salt stress-induced inhibition of root growth. Under normal conditions, LBD11 governs the expression of key ROS metabolic genes, maintaining ROS homeostasis within root developmental zones to control meristem size and overall root growth. Upon sensing salt stress, LBD11 undergoes rapid proteasome-mediated degradation, leading to decreased O2•- distribution, which in turn curtails the meristem size and limits root length. Our findings shed light on an unexplored plant adaptation strategy, where the growth-promoting LBD11/ROS pathway is downregulated to finely regulate root growth under challenging conditions, and suggest a principle for developing crops with heightened resilience and increased yields in salt-affected environments.

Argonaute 2 regulates nuclear DNA damage, repair, and phenotypes in Arabidopsis under genotoxic stress.

Argonaute (AGO) proteins are involved in gene expression and genome integrity during biotic and abiotic stress responses. AGO2 mediates double-strand break (DSB) repair in DNA damage response (DDR) induced by genotoxic stress. However, beyond DSB repair, the involvement of AGO proteins in DDR remains unknown. To investigate the potential roles and functions of AGO2 in DDR, we exposed three different ago2 mutants, each harboring a T-DNA insertion in the promoter, the N-terminal domain of exon 2, or the P-element-induced wimpy testis (PIWI) domain of exon 3, to genotoxic stress, and examined their DDR phenotypes. DDR phenotypes, such as root cell death and growth inhibition following γ-irradiation and zeocin treatment, were significantly suppressed by defects in the promoter or N-terminal domain of AGO2 but not by defects in the PIWI domain, which is responsible for RNA silencing. The weak DDR phenotypes were rescued by AGO2 overexpression and were attributed to reduced nuclear DNA damage despite impaired DNA repair, including DSB repair, as shown in comet and γH2AX assays. These results suggest that AGO2 regulates overall nuclear DNA damage and DDR phenotypes beyond DSB repair through the N-terminal domain rather than the PIWI domain. The potential role of AGO2 in the DDR implies that DNA repair may not be the primary factor for determining susceptibility to genotoxic stress.

Linoleic acid alleviates aluminum toxicity by modulating fatty acid composition and redox homeostasis in wheat (Triticum aestivum) seedlings.

Lipids, as key components of biological membranes, play vital roles in sensing and initiating plant responses to various abiotic stresses. Here, the alteration of membrane fatty acids in wheat roots under Al stress was investigated using two genotypes differing in Al tolerance, and the role of linoleic acid in Al tolerance was comprehensively explored. Significant differences in the fatty acid profiles were observed, with increased linoleic acid accumulation in the Al-tolerant genotype. Supplementation with linoleic acid enhanced fatty acid synthesis, reduced membrane lipid saturation, improved membrane fluidity, and alleviated root growth inhibition. Wheat seedlings treated with linoleic acid exhibited a reduction in lipid peroxidation, as evidenced by decreased levels of malondialdehyde and lipid hydroperoxides. Furthermore, the application of linoleic acid increased the total contents and reduced forms of ascorbic acid (AsA) and glutathione (GSH), thereby restoring the cellular redox balance in wheat roots under Al stress. The elevated levels of AsA and GSH maintained by linoleic acid, can be attributed to the high efficiency of the AsA-GSH cycle, as linoleic acid enhanced the activities of the antioxidant enzymes involved. These results suggest that linoleic acid enhances wheat Al tolerance by maintaining both fatty acid synthesis and the levels of unsaturated fatty acids, as well as protecting membrane lipids from peroxidation by reactive oxygen species through the regulation of the AsA-GSH cycle.

The Effects of Polystyrene Microplastics and Copper Ion Co-Contamination on the Growth of Rice Seedlings.

Microplastics (MPs) are emerging pollutants of global concern, while heavy metals such as copper ions (Cu2+) are longstanding environmental contaminants with well-documented toxicity. This study investigates the independent and combined effects of polystyrene microplastics (PS-MPs) and Cu on the physiological and biochemical responses of rice seedlings (Oryza sativa L.), a key staple crop. Hydroponic experiments were conducted under four treatment conditions: control (CK), PS-MPs (50 mg·L-1), Cu (20 mg·L-1 Cu2+), and a combined PS-MPs + Cu treatment. The results showed that PS-MPs had a slight stimulatory effect on root elongation, while Cu exposure mildly inhibited root growth. However, the combined treatment (PS-MPs + Cu) demonstrated no significant synergistic or additive toxicity on growth parameters such as root, stem, and leaf lengths or biomass (fresh and dry weights). Both PS-MPs and Cu significantly reduced peroxidase (POD) activity in root, stem, and leaf, indicating oxidative stress and disrupted antioxidant defenses. Notably, in the combined treatment, PS-MPs mitigated Cu toxicity by adsorbing Cu2+ ions, reducing their bioavailability, and limiting Cu accumulation in rice tissues. These findings reveal a complex interaction between MPs and heavy metals in agricultural systems. While PS-MPs can alleviate Cu toxicity by reducing its bioavailability, they also compromise antioxidant activity, potentially affecting plant resilience to stress. This study provides a foundation for understanding the combined effects of MPs and heavy metals, emphasizing the need for further research into their long-term environmental and agronomic impacts.

Melatonin Enhances the Low-Calcium Stress Tolerance by Regulating Brassinosteroids and Auxin Signals in Wax Gourd.

In plants, calcium (Ca) serves as an essential nutrient and signaling molecule. Melatonin is a biologically active and multi-functional hormone that plays an important role in improving nutrient use efficiency. However, its involvement in plant responses to Ca deficiency remains largely unexplored. This study aimed to assess the effects of melatonin on Ca absorption, the antioxidant system, and root morphology under low-Ca (LCa) stress conditions, as well as to identify key regulatory factors and signaling pathways involved in these processes using transcriptome analysis. Under LCa conditions, wax gourd seedling exhibited significant decreases in Ca accumulation, showed inhibition of root growth, and demonstrated the occurrence of oxidative damage. However, melatonin application significantly enhanced Ca content in wax gourd seedlings, and it enhanced the absorption of Ca2+ in roots by upregulating Ca2+ channels and transport genes, including BhiCNGC17, BhiCNGC20, BhiECA1, BhiACA1, and BhiCAX1. Furthermore, the application of exogenous melatonin mitigated the root growth inhibition and oxidative damage caused by LCa stress. This was evidenced by increases in the root branch numbers, root tips, root surface area, and root volume, as well as enhanced root vitality and antioxidant enzyme activities, as well as decreases in the reactive oxygen species content in melatonin treated plants. Transcriptome results revealed that melatonin mainly modulated the brassinosteroids (BRs) and auxin signaling pathway, which play essential roles in root differentiation, elongation, and stress adaptation. Specifically, melatonin increased the active BR levels by upregulating BR6ox (a BR biosynthesis gene) and downregulating BAS1 (BR degradation genes), thereby affecting the BR signaling pathway. Additionally, melatonin reduced IAA levels but activated the auxin signaling pathway, indicating that melatonin could directly stimulate the auxin signaling pathway via an IAA-independent mechanism. This study provides new insights into the role of melatonin in nutrient stress adaptation, offering a promising and sustainable approach to improve nutrient use efficiency in wax gourd and other crops.

Phenylmercury stress induces root tip swelling through auxin homeostasis disruption

We previously reported that in Arabidopsis, the phytochelatin-mediated metal-detoxification machinery is also essential for organomercurial phenylmercury (PheHg) tolerance. PheHg treatment causes severe root growth inhibition in cad1-3, an Arabidopsis phytochelatin-deficient mutant, frequently accompanied by abnormal root tip swelling. Here, we examine morphological and physiological characteristics of PheHg-induced abnormal root tip swelling in comparison to Hg(II) stress and demonstrate that auxin homeostasis disorder in the root is associated with the PheHg-induced root tip swelling. Both Hg(II) and PheHg treatments severely inhibited root growth in cad1-3 and simultaneously induced the disappearance of starch-containing plastid amyloplasts in columella cells. However, further confocal imaging of the root tip revealed distinct effects of Hg(II) and PheHg toxicity on root cell morphology. PheHg treatment suppressed most major genes involved in auxin homeostasis, whereas these expression levels were up-regulated after 24 h of Hg(II) treatment. PheHg-triggered suppression of auxin transporters PIN1, PIN2, and PIN3 as GFP-fusion proteins was observed in the root tip, accompanied by an auxin reporter DR5rev::GFP signal reduction. Supplementation of indole-3-acetic acid (IAA) drastically canceled the PheHg-induced root swelling, however, Hg(II) toxicity was not mitigated by IAA. The presented results show that the collapse of auxin homeostasis especially in root tips is a cause for the abnormal root tip swelling under PheHg stress conditions.

ZmSPL12 Enhances Root Penetration and Elongation in Maize Under Compacted Soil Conditions by Responding to Ethylene Signaling.

Soil compaction poses a significant challenge in modern agriculture, as it constrains root development and hinders crop growth. The increasing evidence indicated that various phytohormones collaborate in distinct root zones to regulate root growth in compacted soils. However, the study of root development in maize under such conditions has been relatively limited. Here, we identified that the ZmSPL12 gene, belonging to the SPL transcription factor family, plays a crucial and positive role in regulating root development in the compacted soil. Specifically, the overexpression of ZmSPL12 resulted in significantly less inhibition of root growth than the wild-type plants when subjected to soil compaction. Histological analysis revealed that the capacity for root growth in compacted soil is closely associated with the development of the root cap. Further exploration demonstrated that ZmSPL12 modulates root growth through regulating ethylene signaling. Our findings underscored that ZmSPL12 expression level is induced by soil compaction and then enhances root penetration by regulating root cap and development, thereby enabling roots to thrive better in the compacted soil environment.

Evaluation of morphological and cytotoxic effects of minoxidil on Phaseolus vulgaris L. as a plant model.

The increasing presence of drugs in the environment has triggered a pollution crisis on a global scale, generating concern about their ecotoxicological effects on ecosystems. In this context, minoxidil, a vasodilator drug widely used in the treatment of androgenic alopecia, has been scarcely investigated in plant systems. Therefore, this study evaluated the morphological and cytotoxic effects of minoxidil on Phaseolus vulgaris L as a bioindicator. P. vulgaris seeds were exposed to different concentrations of minoxidil (0.0, 0.25, 0.5, 1, 1.25, 2.5 and 5mg/L) and parameters such as germination, root growth, mitotic index and frequency of chromosomal abnormalities were assessed. The results showed a significant inhibition of germination (75-76%) and root growth (52.6-55.3%) at high concentrations of minoxidil (2.55mg/L-5mg/L). In addition, a decrease in the mitotic index (8.2) and an increase in the frequency of chromosomal abnormalities (10.2) were observed, suggesting a cytotoxic effect. These findings show that minoxidil, even at low concentrations, can have adverse effects on the morphology and cell division of P. vulgaris. This study demonstrates the potential of plants as tools to evaluate the phytotoxicity and cytotoxicity of drugs and highlights the need to implement measures to reduce the contamination of these drugs in the environment.

Mechanisms of Aluminum Toxicity Impacting Root Growth in Shatian Pomelo.

Aluminum (Al) toxicity in acidic soils poses significant challenges to crop growth and development. However, the response mechanism of Shatian pomelo (Citrus maxima 'Shatian Yu') roots to Al toxicity remains poorly understood. This study employed root phenotype analysis, physiological response index measurement, root transcriptome analysis, and quantitative PCR (qPCR) validation to investigate the effects of Al toxicity on Shatian pomelo roots. The findings revealed that Al toxicity inhibited root growth and development, resulting in reduced root biomass, total root length, total root surface area, root volume, average root diameter, and root tip count. Antioxidant enzyme activities (peroxidase, superoxide dismutase, ascorbate peroxidase, and catalase activity) and soluble protein content increased with rising Al toxicity, whereas malondialdehyde content initially increased and then declined. Additionally, Al toxicity stress increased Al (1439.25%) content and decreased boron (B, 50.64%), magnesium (Mg, 42.04%), calcium (Ca, 46.02%), manganese (Mn, 86.75%), and iron (Fe, 69.92%) levels in the roots. RNA sequencing (RNA-seq) analysis identified 3855 differentially expressed genes (DEGs) between 0 mmol/L Al (control) and 4 mmol/L Al (Al toxicity) concentrations, with 1457 genes up-regulated and 2398 down-regulated, indicating a complex molecular regulatory response. The qPCR results further validated these findings. This study elucidates the response mechanisms of Shatian pomelo roots to Al toxicity stress, providing insights into the regulatory pathways involved. The findings offer valuable reference points for breeding Al-resistant Shatian pomelo varieties. The results of this study provide important genetic tools and technical support for the screening and breeding of highly resistant varieties of Shatian pomelo. On the one hand, by detecting the key indexes (such as antioxidant enzyme activity and nutrient absorption capacity) of Shatian pomelo, varieties with excellent anti-Al toxicity characteristics can be selected. On the other hand, the Al-resistant genes identified in this study, such as TFM1 and ALERTFA0, can be used to develop molecular markers, assisted marker breeding, or transgenic breeding to accelerate the breeding process of Al-resistant strains.

Investigating the mechanism of auxin-mediated fulvic acid-regulated root growth in Oryza sativa through physiological and transcriptomic analyses.

As rice is one of the most crucial staple food sources worldwide, enhancing rice yield is paramount for ensuring global food security. Fulvic acid (FA), serving as a plant growth promoter and organic fertilizer, holds significant practical importance in studying its impact on rice root growth for improving rice yield and quality. This study investigated the effects of different concentrations of FA on the growth of rice seedlings. The results indicated that 0.05 g/L FA could promote the growth of rice seedlings, while 0.5 g/L FA inhibited root growth, reduced cell activity and enzyme activity in the root tips, and accumulated reactive oxygen species in root cells. To further elucidate the molecular mechanisms underlying these effects, we performed transcriptomic analysis and found that auxin (Aux) may be involved in the growth process mediated by FA. Furthermore, transcriptome heatmap analysis revealed a significant upregulation of the Aux/indoleacetic acid (Aux/IAA) gene family after FA treatment, suggesting that this gene family plays a crucial role in the impact of FA on root growth. Additionally, by detecting endogenous Aux content and adding exogenous Aux inhibitors, we confirmed the involvement of FA in rice seedling root growth as well as in the synthesis and transduction pathway of Aux.

Screening High-Biomass Grasses for Cadmium Phytoremediation.

Investigating the ability of non-hyperaccumulator plants to grow in soils polluted by cadmium (Cd) and their potential for phytostabilization or phytoextraction is essential for assessing their use in phytomanagement efficiency. Therefore, we evaluated the tolerance of high-biomass grasses to Cd by measuring biomass production and element accumulation and valued them for their suitability for phytoextraction or phytostabilization purposes on moderately Cd-polluted land (total Cd concentration of 7.5 mg kg-1) by determining Cd accumulation in the plants and calculating the bioconcentration (Cd BCF) and translocation factors (Cd TF). Among the ten species under investigation, Panicum maximum cv. Massai and Pennisetum glaucum cv. Purpureum Schum showed lower root biomass due to Cd exposure. Cadmium exposure altered element accumulation in some grass species by reducing P, K, and Mg accumulation in P. glaucum cv. Purpureum Schum; K accumulation in P. maximum cv. Massai; Mg accumulation in P. maximum cv. Mombaça; Ca, Fe, and Zn accumulation in P. maximum cv. Aruana; and B accumulation in Brachiaria brizantha cv. Piatã. However, this was not correlated with lowered biomass production, except for K, which was associated with lowered root biomass allocation in P. maximum cv. Massai and P. glaucum cv. Purpureum Schum. Cadmium concentrations decreased from roots to shoots, indicating a clear limitation of upward Cd transport. Although some grasses exhibited a Cd BCF > 1, the Cd TF remained below 0.4 for all tested species. These results indicate that, under moderate Cd pollution, the evaluated grasses are more suitable for Cd phytostabilization than phytoextraction, except for P. maximum cv. Massai and P. glaucum cv. Purpureum Schum, which showed inhibited root growth and may not be efficient over time.

Response of Morphological Plasticity of Quercus variabilis Seedlings to Different Light Quality

This experiment explores the regulatory mechanisms of various light qualities on the phenotypic plasticity of Quercus variabilis seedlings during their growth. The light conditions included blue light (BL), red light (RL), far-red light (FrL), a blend of RL and FrL with a ratio of 1:1 (RFr1:1L), and a blend of RL and FrL with a ratio of 1:2 (RFr1:2L), alongside a broad-spectrum white light (WL) as the control. Each treatment was maintained at a consistent photosynthetic photon flux density of 400 µmol·m−2·s−1. Results indicate significant morphological variations in Q. variabilis seedlings under different light qualities. Compared to white light treatment, all light quality treatments enhance seedling height, with the FrL treatment exhibiting the most pronounced effect. Seedling ground diameter elongation is stimulated by all light quality treatments, except for the BL treatment. Although the BL treatment promotes leaf morphology in Q. variabilis seedlings, it inhibits root growth, leading to reduced biomass accumulation and a lower root-to-shoot ratio. FrL can mitigate the effects of RL. Under the FrL treatment, Q. variabilis seedlings exhibit a greater increase in plant height and a higher height-to-diameter ratio. While the leaf morphology of RFr1:1L treatment does not show significant advantages, it demonstrates substantial root growth, resulting in the highest biomass accumulation. Quercus variabilis displays the strongest morphological plasticity in its root system, showing greater sensitivity to variations in light quality compared to leaf morphology and biomass accumulation. Strategically optimizing light spectrum and wavelength can significantly boost economic yields and improve the quality of forestry products.

Phytotoxicity risk assessment of diuron residues in sands on wheat, chickpea, and canola.

While diuron residues are being detected more frequently in agricultural soils, there is limited information available regarding their potential phytotoxicity to non-target grain crops. This study aims to determine robust phytotoxicity thresholds for three common, but contrasting, crop species (canola, chickpea, and wheat) exposed to a range of diuron concentrations and to determine how loamy sand soil can change the toxicity thresholds relative to an inert sand. The log-logistic non-linear regression model proved most effective in determining toxicity thresholds by analysing crop responses to diuron. Canola was the most sensitive to diuron in sand followed by wheat and chickpea. Diuron exhibits higher phytotoxicity in sand compared to loamy sand, with ED50 values (which is the dose at which diuron causes a 50% decrease in plant growth) of 0.03 mg kg-1 and 0.07 mg kg-1 for canola shoot biomass inhibition and 0.01 mg kg-1 and 0.06 mg kg-1 for root dry weight reduction, respectively. The ED50 values for wheat shoot biomass (0.11 and 0.24 mg kg-1) in sand and loamy sand, respectively, and the ED50 values for root growth inhibition are 0.14 mg kg-1 in sand and 0.19 mg kg-1 in loamy sand. These values were lower than label concentrations and previously estimated average and maximum diuron residue loads (0.17 and 0.29 mg kg-1) in Western Australia paddocks. The larger ED50 values of diuron in the loamy sand can be attributed to higher soil organic matter and cation exchange capacity that decreased bio-available diuron levels. Average diuron residue loads in Western Australia crop fields exceed the ED50 value emphasizes the need for careful planning of crop rotations to avoid crop phytotoxicity from soil-borne diuron residues. Further study is needed to determine the effect of a wider range of soil properties such as pH, clay content, and soil organic matter on the phytotoxicity risk of diuron to rotational crops.

Comparative carcinogenic and non-carcinogenic health risks, and cytogenotoxicity of wastewaters from natural and artificial fishponds indiscriminately disposed in Nigeria.

As the demand for fish increases, the amount of wastewater generated from fishponds is also increasing with potential environmental and public health effects from their indiscriminate disposal. This study aimed at comparative analyses of the physicochemical and heavy metal constituents and potential DNA damage by wastewaters from natural and artificial fishponds using Allium cepa assay. A. cepa were grown on 3.13, 6.25, 12.5, 25.0, and 50.0% (v/v; wastewater/tap water) concentrations of each wastewater. At 48 and 72h, respectively, genotoxic and root growth inhibition analyses were carried out on the exposed onions. The onion root tips exposed to wastewaters showed a significant (P<0.05) inhibition of root growth and cell division in a concentration-dependent manner. Additionally, chromosomal abnormalities like spindle disturbances, sticky chromosomes, micronucleus, bridges, and binucleated cells were observed in the exposed onions and their induction was higher significantly relative to the negative control. Generally, wastewater from the natural fishpond caused higher chromosomal aberrations than the wastewater from artificial fishpond. It is our belief that the cytotoxicity and genotoxicity observed in the onions were primarily caused by heavy metals like Cr, Cd, Fe, Pb, Cu, and Zn found in the wastewaters. These metals also showed a significant carcinogenic and non-carcinogenic risks in children and adults with Cd as the highest contributor to these detrimental risks. Ingestion route was the major exposure route to the toxic metals in these wastewaters. Wastewater from the natural fishpond showed a higher health risk than the wastewater from the artificial fishpond. These findings suggest that the wastewaters from natural and artificial fishpond contain compounds that might induce cytogenotoxicity in exposed organisms.

Cell Cycle Arrest Via DNA Damage Response (DDR) Pathway Induced by Extracellular Self-DNA (esDNA) Application in Rice Root

Conspecific plant growth is inhibited by extracellular fragments in a concentration-dependent manner. Although several reports have addressed this self-DNA inhibition, the underlying mechanism remains unclear. In this investigation, we evaluated the progression of cell cycle of rice roots in responding to extracellular-self DNA (esDNA). We analyzed root growth, hydrogen peroxide (H2O2) production, Catalase (CAT) and Ascorbate Peroxidase (APX) enzyme activities, DNA Damage Response (DDR)-related gene expression, and cell cycle progression. Our results suggest that esDNA-induced root growth inhibition on days 7 and 10 and might associated with cell cycle arrest initiated several hours after esDNA treatment. The esDNA-induced cell cycle arrest is facilitatedthrough the DDR pathway, activated by DNA damage resulting from elevated reactive oxygen species (ROS) induced by esDNA. Specifically, esDNA upregulates DDR-related gene expression including OsATM (Oryza sativa ataxia telangiectasia mutated), OsATR (Oryza sativa ATM and Rad3-related), OsSOG1 (Oryza sativa SUPPRESSOR OF GAMMA RESPONSE 1), OsWEE1 (Oryza sativa WEE1-like kinase 1), and OsSMR4 (Oryza sativa SIAMESE-RELATED 4), leading to cell cycle arrest. Finally, we propose that cell cycle arrest might be a plausible explanation for the phenomenon of root growth inhibition by esDNA. This result highlights the significance of DDR signaling in the plant’s response to esDNA. This finding will be helpful as initial information for developing green herbicides to control monocot weeds in agriculture.