Inhibited Plant Growth Research Articles

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.

Genome-Wide Identification and Functional Characterization of SKP1-like Gene Family Reveal Its Involvement in Response to Stress in Cotton.

SKP1 constitutes the Skp1-Cullin-F-box ubiquitin E3 ligase (SCF), which plays a role in plant growth and development and biotic and abiotic stress in ubiquitination. However, the response of the SKP1-like gene family to abiotic and biotic stresses in cotton has not been well characterized. In this study, a total of 72 SKP1-like genes with the conserved domain of SKP1 were identified in four Gossypium species. Synteny and collinearity analyses revealed that segmental duplication played a major role in the expansion of the cotton SKP1-like gene family. All SKP1-like proteins were classified into three different subfamilies via phylogenetic analysis. Furthermore, we focused on a comprehensive analysis of SKP1-like genes in G. hirsutum. The cis-acting elements in the promoter site of the GhSKP1-like genes predict their involvement in multiple hormonal and defense stress responses. The expression patterns results indicated that 16 GhSKP1-like genes were expressed in response to biotic or abiotic stresses. To further validate the role of the GhSKP1-like genes in salt stress, four GhSKP1-like genes were randomly selected for gene silencing via VIGS. The results showed that the silencing of GhSKP1-like_7A resulted in the inhibition of plant growth under salt stress, suggesting that GhSKP1-like_7A was involved in the response to salt stress. In addition, yeast two-hybrid results revealed that GhSKP1-like proteins have different abilities to interact with F-box proteins. These results provide valuable information for elucidating the evolutionary relationships of the SKP1-like gene family and aiding further studies on the function of SKP1-like genes in cotton.

Remediation of a diesel contaminated soil by means of anionic and non-ionic surfactants: Effect on soil phosphorus availability and Vicia Faba L. growth.

In the present study, the effectiveness of two surfactants (Polysorbate 80 - Tween 80 and Sodium Dodecyl Benzensulphonate - SDBS) was investigated for the remediation of a hydrocarbon-contaminated soil. Moreover, it was elucidated the impact of surfactants on soil phosphorus (P) availability and phytotoxic effect on the growth of Vicia Faba L. An experimental laboratory-scale apparatus (bench and pilot scale) was set up for the simulation of a soil flushing intervention. Different surfactant concentrations and flushing flow rates were investigated. Hydrocarbon extraction efficiency was evaluated after treatment and phytotoxicity tests were performed by means of germination index (GI). The treated soil with the pilot scale apparatus was then used for Vicia Faba (faba beans) cultivation in pots. The growth of Vicia Faba plants was monitored and, at the end of the growth period, the plants were uprooted and subjected to biometric and chemical analyses. Results highlighted that the use of surfactants significantly increased the efficiency of hydrocarbons extraction compared to flushing test with water (19.6%, 53.9%, and 65.6% for water, 0.1% by weight of Tween 80 and SDBS, respectively, at pilot scale). Referring to Vicia Faba L., the plants grown in the blank control and in the soil treated with Tween 80 reached the same average height thus suggesting that this surfactant does not inhibit plant growth. In contrast, the lowest plant growth occurred in the soils treated with SDBS; this suggests a negative impact on plant growth. Due to the reduced plant growth, total P uptake was the lowest in plants grown in SDBS-treated soils, although such soils experienced a 20% increase of soil available P. This increase could be ascribed to P supplied by the surfactant or high P availability as a consequence of soil pH decrease.

Boron controls apical dominance in Pea (Pisum sativum) via promoting polar auxin transport

AbstractPlant architecture and subsequent productivity are determined by the shoot apical dominance, which is disturbed by the deficiency of boron, one of the essential trace elements for plant growth and reproduction. However, the mechanism by which B controls shoot apical dominance or axillary bud outgrows under B deficiency is still unclear. This work aimed to investigate the mechanistic basis of this process, with focus on the interaction between B and polar auxin transport. Adopting an all‐buds phenotyping methodology and employing several complementary approaches, we found that boron deficiency inhibited plant growth and changed the shoot architecture, resulting in the outgrowth of axillary buds at nodes 1–3. This was related to the auxin accumulation in shoot apical parts buds under B deficiency. Applying N‐1‐naphthylphthalamic acid to inhibit auxin transport from the shoot apex promoted the outgrowth of axillary buds in boron‐sufficient (+B) plants. In decapitated plants, the application of exogenous auxin to the shoot apex only inhibited the outgrowth of axillary buds in +B plants. At higher auxin doses, the toxic effect of IAA was observed in the lower part of the shoot, which was more severe in +B plants than in B‐deprived (‐B) plants. Furthermore, the expression of PsPIN3 was significantly downregulated under ‐B conditions. These results indicate that B deficiency inhibits PAT from the apical bud through the main stem to the lower parts, leading to an increase of auxin level in the apical bud, which inhibits the growth of apical buds while stimulating the outgrowth of axillary buds.

ZnONPs alleviate cadmium toxicity in pepper by reducing oxidative damage.

Cadmium (Cd) is a genotoxic heavy metal causing severe toxicity symptoms in plants, which has been a major threat to worldwide crop production. Recently, nanoparticles (NPs) have been employed as a novel strategy to facilitate the Cd stress and act as nano-fertilizers directly. Therefore, this study aims to explore the effects of zinc oxide nanoparticles (ZnONPs; 15mg/L) on plant growth, photosynthetic activity, antioxidant activity and root morphology in Capsicum chinense Jacq. under Cd (CdCl2; 50μM/L) stress. The pepper plants were treated with Cd stress for 14 days, and the treatment was given directly into the hydroponic solution, while ZnONPs were applied as foliar spray two times a day (9 a.m. - 3 p.m.). The results revealed that Cd stress inhibited plant growth and biomass by impairing photosynthesis in photosystem function, gas exchange parameters, root activity, and morphology. In contrast, ZnONPs application notably reinforced the plant growth traits, increased photosynthesis efficiency in terms of chlorophyll content, SPAD index, gas exchange parameters and PSII maximum efficiency (Fv/Fm) and decreased Cd accumulation in leaf and root by 30% and 75%. Furthermore, ZnONPs efficiently restricted the hydrogen peroxide, superoxide ion (H2O2, O2•-). They restored cellular integrity (less MDA production) by triggering the antioxidant enzyme activities such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), protein content, sugar level and proline content. Besides, ZnONPs treatment enhanced secondary metabolites (phenols and flavonoids) contents and these metabolites potentially restricted excess H2O2 accumulation. In conclusion, our findings deciphered the potential functions of ZnONPs in alleviating Cd-induced phytotoxicity in pepper plants by boosting biomass production, photosynthesis, secondary metabolism and reducing oxidative stress.

Hydrothermal biochar enhances the photosynthetic efficiency and yield of alfalfa by optimizing soil chemical properties and stimulating the activity of microbial communities

Hydrothermal biochar has demonstrated potential in enhancing crop growth by improving soil properties and microbial activity; however, its effectiveness varies with application rate, with excessive amounts potentially inhibiting plant growth. This study employed a pot experiment approach to compare varying application rates of hydrothermal biochar (ranging from 0 to 50 t/ha) and to analyze its effects on alfalfa biomass, photosynthetic efficiency, soil nutrient content, and microbial community composition. Biochar application increased alfalfa dry weight by 12.22-21.20% in leaves, 31.60-55.60% in stalks, and 5.62-38.05% in roots. It also enhanced the light utilization efficiency of photosystem II. However, excessive biochar (50 t/ha) reduced biomass and photosynthesis. The addition of biochar amendments enhances soil nutrient availability, particularly increasing the accessibility of carbon, nitrogen, and phosphorus, while also lowering soil pH and enriching microbial interactions within bacterial communities. However, the effects on fungal communities are not pronounced. In conclusion, a moderate application of biochar (10-20t/ha) is recommended to maximize the growth of alfalfa and improve soil health, offering a practical approach for the sustainable cultivation of alfalfa.

The Transcription Factor VvbHLH053 Regulates the Expression of Copper Homeostasis-Associated Genes VvCTr5/6 and VvFRO4 and Confers Root Development in Grapevine

Chlormequat chloride (CCC) has been demonstrated to inhibit plant growth and strengthen seedlings. The present study demonstrated that the root growth of Thompson seedless grapevine seedlings was significantly enhanced by the application of CCC treatment. Nevertheless, the precise mechanism by which CCC regulates plant root growth remains to be elucidated. Consequently, an RNA-sequencing (RNA-Seq) analysis was conducted on grapevine roots subjected to CCC treatment and those undergoing natural growth. A total of 819 differentially expressed genes were identified. Subsequently, Gene Ontology (GO) functional enrichment and weighted gene co-expression network analysis (WGCNA) identified the Copper (Cu) homeostasis-associated genes, VvCTr4/5/6/8 and VvFRO4, which play a pivotal role in mediating the effect of CCC. To further elucidate the transcription factor regulating these Cu homeostasis-associated genes, the key transcription factor VvbHLH053 was identified based on the PlantTFDB database, WGCNA results, and expression patterns under CCC treatment. Furthermore, multiple bHLH binding sites were identified on the promoters of VvCTr4/5/6 and VvFRO4. The GUS activity analysis and dual-luciferase assay demonstrated that VvbHLH053 can directly regulate the expression of VvCTr5/6 and VvFRO4. These findings reveal the feedback mechanism of grapevine root growth mediated by CCC and establish a direct functional relationship between CCC, VvbHLH053, and Cu homeostasis-associated genes that regulate root growth.

Effect of Selenium, Copper and Manganese Nanocomposites in Arabinogalactan Matrix on Potato Colonization by Phytopathogens Clavibacter sepedonicus and Pectobacterium carotovorum.

The effect of chemically synthesized nanocomposites (NCs) of selenium (Se/AG NC), copper oxide (Cu/AG NC) and manganese hydroxide (Mn/AG NC), based on the natural polymer arabinogalactan (AG), on the processes of growth, development and colonization of potato plants in vitro was studied upon infection with the causative agent of potato blackleg-the Gram-negative bacterium Pectobacterium carotovorum-and the causative agent of ring rot-the Gram-positive bacterium Clavibacter sepedonicus (Cms). It was shown that the infection of potatoes with P. carotovorum reduced the root formation of plants and the concentration of pigments in leaf tissues. The treatment of plants with Cu/AG NC before infection with P. carotovorum stimulated leaf formation and increased the concentration of pigments in them. A similar effect was observed when potatoes were exposed to Mn/AG NC, and an increase in growth and root formation was also observed. The infection of plants with Cms inhibited plant growth. Treatment with each of the NCs mitigated this negative effect of the phytopathogen. At the same time, Se/AG and Mn/AG NCs promoted leaf formation. The Se/AG NC increased the biomass of Cms-infected plants. The treatment of plants with NCs before infection showed a decrease in the intensity of the colonization of plants by bacteria. The Se/AG NC had the maximum effect, which is probably due to its high antioxidant capacity. Thus, the NCs are able to mitigate the negative effects of bacterial phytopathogens on vegetation and the intensity of colonization by these bacteria during the infection of cultivated plants.

Assemblies of leaf and root mycobiomes in a temperate grassland: Dispersal limitation overpowers selection

Abstract The emergence of β‐diversity of plant‐associated fungi across diverse coexisting host plant species in natural habitats is intricately linked to specific community assembly processes. Despite this, the relative contributions of various assembly processes to the observed β‐diversity patterns, as well as the influence of plant traits on these contributions, are still poorly understood. Here, we investigated the leaf/root‐associated fungal communities across nine coexisting dominant herbaceous perennials in a temperate grassland that had undergone a 17‐year mowing treatment. We elucidated the β‐diversity components and community assembly processes of these fungal communities. Furthermore, we explored relationships between leaf/root functional trait variations and fungal community assemblies. We tested the following hypotheses: (1) both species turnover and nestedness are important components of the fungal β‐diversity, with selection predominating in the fungal community assemblies; (2) mowing enhances the contributions of nestedness/selection; (3) plant trait variations significantly affect the fungal community assembly processes. Unexpectedly, our findings demonstrated a predominance of leaf/root fungal species turnover among coexisting plant hosts, contrasting with nestedness. Moreover, dispersal limitation emerged as the primary factor shaping fungal community assemblies, rather than selection processes. Although mowing significantly inhibited plant growth, its effects on the overall patterns of fungal assemblages were limited. We further observed that higher degrees of plant trait variations were primarily linked to stronger dispersal limitation, with a relatively weaker influence on heterogeneous selection. Additionally, the impact of plant traits on the selection process of root‐associated fungi was more pronounced compared to that of leaf‐associated fungi. Synthesis. Our study reveals that the β‐diversity of fungi associated with coexisting plants in natural grasslands is primarily attributed to fungal species replacement rather than gain‐and‐loss dynamics among these plants. Concurrently, this observed pattern is largely governed by dispersal limitation as opposed to selection. We propose that the primary mechanism through which plant hosts and their traits influence the structures of associated fungal communities is by limiting fungal dispersal, while niche differentiation among fungal taxa plays a secondary role. These findings offer a mechanistic insight into the assemblies of plant mycobiomes and further elucidate the plant‐mycobiome relationships within complex plant communities.

Aristolochic Acids and Aristoloxazines Are Widespread in the Soil of Aristolochiaceae Herb Cultivation Fields.

The cancer risk associated with aristolochic acid (AA) exposure through the consumption of AA-containing herbal medicine has received tremendous attention in the past decades. However, environmental exposure routes from the associated medicinal herb cultivation fields have received little attention. We reveal through liquid chromatography-tandem mass spectrometry analysis of over 400 soil samples collected from three different Aristolochiaceae herb cultivation fields that AAs, which are nephrotoxic and carcinogenic, and aristoloxazines (AXs), a family of recently identified neurotoxic and genotoxic AA analogues, are widespread pollutants in these areas. In particular, aristoloxazine C was detected for the first time in the environment and was found in 318 out of 320 soil samples, at concentrations as high as 2.8 mg/kg, from an Asarum heterotropoides cultivation field. We show that in fact AXs are ecotoxic, inhibiting plant growth and significantly reducing the soil microorganism population. With the extensive cultivation of Aristolochiaceae herbs in order to meet their market demand, we believe our study points to an important environmental hazard that may place food crops and non-AA/AX-producing medicinal herbs at risk of AA/AX contamination. While previous research focused primarily on the health risks associated with exposure to AAs, this study uncovers environmental exposure as a new human exposure pathway that warrants the attention of both the general public and regulatory agencies.

Bioremediation of polyaromatic hydrocarbon polluted sewage sludge soil employing a bacterial consortium and phytotoxicity evaluation.

A consortium of five distinct bacterial strains was evaluated for their ability to biodegrade multiple polyaromatic hydrocarbons (PAHs) in sewage sludge under microcosm studies. The presence of PAHs was determined from the sludge samples collected during pre- and post-monsoon seasons from three different wastewater treatment plants (WWTPs). Among the sixteen PAHs found, the lowest concentration detected was 1.75 ng g-1 of benz(k)fluoranthene, and the highest concentration of 5.41 mg g-1 indeno(1,2,3-cd) pyrene was found in both dry and wet samples, perhaps owing to its multiple origin of contamination. A bacterial consortium comprising of well characterized bacteria Stenotrophomonas maltophilia IITR87, Ochrobactrum anthropi IITR07, Microbacterium esteraromaticum IITR47, Pseudomonas aeruginosa IITR48 and Pseudomonas mendocina IITR46 employed for PAHs bioremediation in a microcosm study. In 20 days, 65-70% of PAHs were remediated, and low molecular weight PAHs such as naphthalene, phenanthrene, and pyrene showed enhanced degradation. Bioremediated samples showed a significant reduction in phytotoxicity using plant germination of wheat (Triticum aestivum), black chickpea (Cicer arietinum), and mustard (Brassica juncea), whereas the contaminated soil showed severe inhibition of plant growth. The results comprehensively suggest a possible remediation option for PAHs occurring in complex sewage sludge, preventing further contamination into other environmental compartments.

Integrated transcriptomic and metabolomic analyses uncover the key pathways of Limonium bicolor in response to salt stress.

Salinity significantly inhibits plant growth and development. While the recretohalophyte Limonium bicolor can reduce its ion content by secreting salt, the metabolic pathways it employs to adapt to high salt stress remain unclear. This study aims to unravel this enigma through integrated transcriptomic and metabolomic analyses of L. bicolor under salt stress conditions. The results showed that compared to the control (S0), low salt treatment (S1) led to a significant increase in plant growth, photosynthesis efficiency and antioxidant enzyme activity but caused no significant changes in organic soluble substance and ROS contents. However, high salt treatments (S3 and S4) led to a significant decrease in plant growth, photosynthesis efficiency and antioxidant enzyme activity, accompanied by a significant increase in organic soluble substance and ROS contents. A significant increase in phenolic compounds, such as caffeoyl shikimic acid and coniferin, upon the treatments of S1, S3 and S4, and a decrease and increase in flavonoids upon the treatments of S1 and S3 were also observed, respectively. This study also demonstrated that the expression patterns of key genes responsible for the biosynthesis of these metabolites are consistent with the observed trends in their accumulation levels. These results suggest that under low salt stress conditions, the halophyte L. bicolor experiences minimal osmotic and oxidative stress. However, under high salt stress conditions, it suffers severe osmotic and oxidative stress, and the increase in organic soluble substances and flavonoids serves as a key response to these stresses and also represents a good strategy for the alleviation of them.

Effects of Melatonin on Ginseng Leaf Phenotypic and Photosynthetic Properties Following Chilling and Freezing Stress

Spring frost damage is a significant natural disaster, which can lead to large-scale ginseng (Panax ginseng C. A. Mey) yield reduction. To determine chilling and freezing stress damage to ginseng, we designed an experiment using three-year-old potted ginseng plants. We simulated chilling (0±0.3 ℃) and freezing (-2.5±0.3 ℃, -5±0.3 ℃) in an artificial room, with 16±2 ℃ of the room temperature at night as the control, to evaluate their physiological effects on ginseng leaf spectral reflectance, photosynthetic characteristics, and chlorophyll fluorescence parameters. We also investigated the mitigating effects of exogenous melatonin on ginseng leaves exposed to chilling and freezing stress. All ginseng leaves died under -5 ℃ freezing stress and the mortality rate reached 25∼57% under -2.5 ℃ freezing stress, while no plants died under 0 ℃ chilling stress. After -2.5 ℃ and 0 ℃ stress, leaf spectral reflectance in the 750∼1000 nm band was significantly lower than the control; transpiration rate, net photosynthetic rate, intercellular CO2 concentration, and stomatal conductance decreased significantly compared with the control, and there was no significant change in recovery time. The Fv/Fm ratio and qp decreased after low-temperature stress, while NPQ increased. After one week of melatonin application, leaf spectral reflectance in the 600∼650 and 750∼1000 nm bands reflected significant differences between the effects of melatonin application and no application on ginseng leaf chlorophyll content and structure under freezing stress. Ginseng leaf net photosynthetic rate increased by 23.79% and 4.48%, while intercellular CO2 concentration increased by 33.49 and 11.83% under stress at -2.5°C and 0°C. The ginseng leaf chlorophyll fluorescence parameter (Fv/Fm) recovered to 0.8 and above in one week after melatonin application, and qp decreased under -2.5°C and 0°C stress after melatonin application. Additionally, the NPQ values were 11.44% and 4.6% lower in -2.5+MT and 0+MT, respectively, compared to the treatment without MT applied. A sudden drop in temperature to 0 ℃ or even below caused ginseng plant growth inhibition, but melatonin application at a concentration of 100 nmol L−1 had certain mitigating effects on ginseng growth, which provides a theoretical basis and technical support for ginseng production.

Okra WRKY Transcription Factor AeWRKY32 and AeWRKY70 Are Involved in Salt Stress Response.

Soil salinization is one of the abiotic stresses that inhibit plant growth and development, which seriously restricts global crop production. WRKY transcription factors play an important role in regulating plant responses to stress such as salt stress. In our previous study, two WRKY family genes from okra, AeWRKY32 and AeWRKY70, were significantly up-regulated and down-regulated, respectively, in response to salt stress. In this study, subcellular localization showed that they were localized to the nucleus. The down-regulation of AeWRKY32 and AeWRKY70 via whole plant virus-induced gene silencing (VIGS) increased and decreased plant sensitivity to salt stress, respectively. Ectopic expression of AeWRKY32 and AeWRKY70 led to promoted and reduced salt tolerance in transgenic Arabidopsis, respectively. There was no significant difference between transgenic plants and wild type (WT) without salt treatment. Salt stress significantly inhibited plant growth. The decrease of chlorophyll content and the increase of anthocyanin content in AeWRKY32-overexpressed transgenic plants were lower than those in the WT, while AeWRKY70-overexpressed plants had the opposite effect. Under salt stress, the AeWRKY70-overexpressed plants had the highest malondialdehyde (MDA) content, followed by the WT, and the lowest in AeWRKY32-overexpressed plants. The hydrogen peroxide (H2O2) content and superoxide anion (O2•-) generation rate were only slightly increased. Moreover, salt stress significantly increased plant proline content and antioxidant enzyme activities, which was highest in AeWRKY70-overexpressed plants except superoxide dismutase (SOD). Taken together, these results suggest that AeWRKY32 and AeWRKY70 play positive and negative roles in plant in response to salt stress, respectively.

Allelopathic effects of leaf extracts of Eucalyptus camaldulensis Dehnh. on morphological, physiological, and yield traits of Ethiopian wheat (Triticum durum L.) cultivars

Allelochemicals released into the soil from the leaves of eucalyptus species affect the growth and physiology of various crops. This study aimed to evaluate the allelopathic effects of aqueous and methanolic leaf extracts from Eucalyptus camaldulensis on three Ethiopian wheat cultivars (Assasa, Mukiye and Ude) of Triticum durum L. It was conducted as a pot experiment, and it utilized four concentrations of the extracts (Control (0%), 10%, 15%, and 20%) in a completely randomized design with three replicates. Results indicated that both extracts inhibited plant growth, biomass, and yield, with the methanolic extract showing stronger inhibitory effects. For instance, a concentration of 20% methanolic leaf extracts decreased chlorophyll fluorescence in the Assasa, Ude, and Mukiye cultivars by 53.97%, 36.36%, and 36.51%, respectively. The growth of both shoots and roots in Assasa, Ude, and Mukiye was significantly reduced at higher concentrations. Increasing concentrations of the extracts led to greater reductions in seedling traits and overall crop yield, with significant impacts observed (p ≤ 0.05). The findings suggest that eucalyptus should not be planted on agricultural land due to its negative impact on crop productivity.

Response of potato tuber as an effect of the N-fertilizer and paclobutrazol application in medium altitude

Abstract Development of G0 potato seeds in medium altitude with high temperatures has been constrained high temperatures, which inhibited plant growth and development, especially for tuber formation. The production of G0 potato seeds in the high-temperature area can be increased by the application of nitrogen (N) fertilizer and paclobutrazol (PBZ). The study aimed to identify the effect of different doses of N-fertilizer and the frequency of PBZ application on the plant growth and yield of first-generation potato seeds (G0) in medium land. The Randomized Complete Block Design with two factors was used in this experiment. The first factor was the dose of N-fertilizer (n 1 = 60, n 2 = 120, and n 3 = 180 kg/ha) and the second factor was the frequency of PBZ application (p 1 = 1, p 2 = 2, and p 3 = 3 times), applied starting at 40 DAP and repeated every 10 days with a concentration of 100 ppm. The results showed that there was a significant interaction between the dose of N-fertilizer and the frequency of PBZ application on plant dry weight. The 120 kg/ha of N-fertilizer-treated plants exhibited the highest plant height and the number of stolons per plant, whereas three times PBZ application treated plant exhibited the higher tuber growth rate, the number, and weight of tuber per plant with the value of number and weight of tuber per plant of 9.26 and 83.97 g, respectively. It can be concluded that N-fertilizer increased plant growth, whereas PBZ increased G0 potato seeds in the medium land altitude with high temperature.

Light intensity moderates photosynthesis by optimizing photosystem mechanisms under high VPD stress

In recent decades, the global increase in vapor pressure deficit (VPD) has significantly inhibited plant growth and photosynthesis. Light intensity, a crucial environmental regulator, plays a vital role in stress response and photosynthetic adjustment. This study investigated whether increasing light intensity under high VPD conditions could optimise the photosystem and thereby enhance photosynthesis. We designed experiments using factorial combinations of two VPD levels (HVPD; high VPD, AVPD; appropriate VPD) and two irradiance gradients (L300; 300 μmol photons m−2 s−1, L600; 600 μmol photons m−2 s−1). Under high VPD, plants protect their photosystems by reducing light energy absorption and limiting photosynthetic electron flow, which results in reduced photosynthesis. However, when exposed to HVPD + L600, plants exhibited increased light energy absorption, as evidenced by elevated chlorophyll b and carotenoid levels, enhanced response to irradiance, and decreased NPQ and Y(NO). This regimen also enhanced photosynthetic electron transport by increasing the total driving force and plastoquinone pool, consequently improving the photochemical efficiency of the photosystem and ultimately boosting the net photosynthetic rate by 46.9%. This study confirmed that modulating light intensity under high VPD stress can improve photosynthesis by optimizing the photosystem. This novel approach can be utilized to enhance tomato production in arid regions.

Calcium Silicate Application as a Salt Stress Mitigation Strategy for Vegetables in the Salt-affected Soils of Sandy Plains of Kerala, India

Soil salinity inhibits plant growth due to osmotic stress and reduced plant and water uptake. In the Onattukara sandy plains of Kerala, saltwater intrusion is a major problem in several panchayaths near the coastal area. In uplands also, cultivation is not possible due to the salt stress from saltwater intrusion. One of the strategies for removing the inhibitory effect of salt stress on plant growth is the application of beneficial nutrients to the plants. Therefore, a study was carried out to understand the effect of calcium silicate application on mitigating salt stress in vegetables and using tomato as a test crop. A detailed germination study was conducted in laboratory conditions prior to pot culture experiment to find out the critical level of salinity for tomato and two salinity levels 30mM and 40 mM NaCl were selected for the pot culture experiment. For accessing the effect of the various levels of calcium silicate on reducing salt stress in tomato, a pot culture experiment was conducted in Onattukara region (AEU 3) in completely randomized design with ten treatments replicated thrice with varying levels of CaSiO3 from 100 kg ha-1 to 150 kg ha-1. The treatments had a significant effect on all the biometric characteristics and yield attributes of the crop. The highest fruit weight, fruit per plant, and fruit yield were observed in treatment with soil test-based NPK recommendation and 125 kg ha-1 of CaSiO3 applied. It was also observed that the relative water content was higher and the water saturation deficit was lower in this treatment. CaSiO3 application @125 kg ha-1 along with soil test-based recommendation of NPK can be recommended as a salt stress mitigation strategy for boosting vegetable production in the salt-affected soils of sandy plains of Kerala.

Revealing the size effect mechanisms of micro(nano)plastics on nitrogen removal performance of constructed wetland

Micro(nano)plastics (MPs) in aquatic environments can disrupt wastewater treatment, particularly nitrogen removal in constructed wetlands (CWs). However, their broader effects on microbial and plant nitrogen metabolism remain unclear. This study investigated the effects of different-sized MPs (4 mm, 100 µm, and 100 nm) on nitrogen transformation in CWs. Results revealed that 4 mm- and 100 µm-MPs did not significantly affect total nitrogen (TN) removal, although 100 µm-MPs significantly increased leaf antioxidant enzyme activities and reduced plant uptake of nitrogen by 12.95 % (p < 0.05). In contrast, 100 nm-MPs decreased the TN removal efficiency by 7.97 % via inhibiting both nitrification and denitrification, since 100 nm-MPs penetrated cell membranes, disrupted reactive oxygen species balance, and reduced bacterial viability, thus suppressing microbial nitrogen degradation by 8.07 % (p < 0.05). Additionally, 100 nm-MPs significantly inhibited plant growth and reduced plant nitrogen uptake by 16.05 % (p < 0.05). Furthermore, 100 µm-MPs increased the abundance of nitrifiers but reduced denitrifiers and functional genes, whereas 100 nm-MPs reduced the abundance of both nitrifiers and denitrifiers along with their functional genes (p < 0.05). These findings highlight the need to improve waste management to mitigate the adverse effects of MPs on nitrogen removal.

Saline-alkaline conditions altered Bolboschoenus planiculmis carbon and nitrogen allocation tradeoffs

Soil salinization is an important factor that limits global agricultural production, specifically limiting the effectiveness of nitrogen-carbon resources and inhibiting plant growth. However, previous observations have focused on resource allocation, and there is little information about the coordination of carbon-nitrogen acquisition, allocation, and regulatory processes. We performed glasshouse pot experiments under different saline-alkaline conditions, and we measured 66 above- and belowground functional traits of Bolboschoenus planiculmis, to examine carbon-nitrogen resource acquisition and allocation strategies and their driving processes. Saline-alkaline conditions shifted B. planiculmis root-leaf functional traits toward a more acquisitive phenotype. Under low saline-alkaline conditions, although the root-leaf economic strategy inhibited resource acquisition efficiency, the opportunistic carbon-nitrogen capture and allocation strategy contributed to the maintenance of normal growth. However, highly saline-alkaline conditions led to the early enrichment of carbon-nitrogen resources in the corm. Additionally, saline-alkaline conditions altered the importance of physiological and biochemical processes in the carbon and nitrogen allocation regulatory network. In summary, B. planiculmis uses an opportunistic resource acquisition strategy under saline-alkaline conditions and a salt-avoidance allocation strategy under highly saline-alkaline conditions. This approach enables the maintenance of growth dominance under saline-alkaline conditions via gradient resource utilization.