Increased Root Dry Weight Research Articles

Growth-Promoting Effects of Grass Root-Derived Fungi Cadophora fastigiata, Paraphoma fimeti and Plectosphaerella cucumerina on Spring Barley (Hordeum vulgare) and Italian Ryegrass (Lolium multiflorum).

Many endophytic fungi are approved as plant growth stimulants, and several commercial biostimulants have already been introduced in agricultural practice. However, there are still many species of fungi whose plant growth-promoting properties have been understudied or not studied at all. We examined the growth-promoting effect in spring barley (Hordeum vulgare) and Italian ryegrass (Lolium multiflorum) induced by three endophytic fungi previously obtained from the roots of Festuca/Lolium grasses. Surface-sterilized seeds were inoculated with a spore suspension of Cadophora fastigiata (isolate BSG003), Paraphoma fimeti (BSG010), Plectosphaerella cucumerina (BSG006), and their spore mixture. Before harvesting, the inoculated plants were grown in a greenhouse, with the barley being in multi-cavity trays for 30 days and ryegrass being placed in an original cylindric element system for 63 days. All three newly tested fungi had a positive effect on the growth of the barley and ryegrass plants, with the most pronounced impact observed in their root size. The fungal inoculations increased the dry shoot biomass between 11% and 26% in Italian ryegrass, but no such impact was observed in barley. The highest root increment was observed in barley. Herein, P. cucumerina and C. fastigiata inoculations were superior to other treatments, showing an increase in root dry weight of 50% compared to 20%, respectively. All fungal inoculations significantly promoted root growth in Italian ryegrass, resulting in a 20-30% increase in dry weight compared to non-inoculated plants. Moreover, a strong stimulatory effect of the fungi-emitted VOCs on the root development was observed in plate-in-plate arrays. In the presence of C. fastigiata and P. cucumerina cultures, the number of roots and root hairs in barley seedlings doubled compared to control plants. Thus, in our study, we demonstrated the potential of the grass root-derived endophytes C. fastigiata, P. fimeti, and P. cucumerina as growth promoters for spring barley and Italian ryegrass. These studies can be extended to other major crops and grasses by evaluating different fungal isolates.

Bacillus siamensis orchestrates plant gene reprogramming and rhizosphere microbiome reshaping to bolster maize crop performance

AbstractPlant growth‐promoting rhizobacteria (e.g., Bacillus) confer health benefits to the host. Bacillus siamensis has been used to control plant disease in fruits and vegetables, but its potential effects on crop performance remain unclear. This study investigated changes in the growth, root transcriptomic profile, and rhizosp here microbiome of maize plants (Zea may L.) following inoculation with B. siamensis 33. All inoculated plants grew better than non‐inoculated controls in pots, as exemplified by 24.0% and 6.8% increase in plant height and stem diameter, respectively (p < 0.01). Shoot dry weight also increased by 20.6% upon inoculation, accompanied by 46.9% increase in root dry weight (p < 0.01). Transcriptomic analysis revealed that inoculation induced (2.16‐ to 5.53‐fold) upregulated expression of genes related to auxin signal transduction in maize. The expression of genes involved in phenylpropanoid biosynthesis, glutathione metabolism, and plant defense‐related signal (e.g., jasmonic acid and salicylic acid) transduction was (2.06‐ to 11.30‐fold) upregulated in inoculated plants. Upon inoculation, bacterial α‐diversity trended higher and potentially beneficial taxa (e.g., Sphingobium, Flavihumibacter, and Parasegetibacter) were enriched in the rhizosphere, likely a result of enhanced root exudation of specific metabolites (e.g., flavonoids) and subsequent recruitment of beneficial microbial taxa. Potential microbial functions associated with nitrogen cycling and pollutant degradation were stimulated by inoculation. These findings indicate that B. siamensis 33 mediates the reprogramming of plant gene expression and reshaping of rhizosphere microbiome structure to bolster maize crop performance.

Rice plants treated with biochar derived from Spirulina (Arthrospira platensis) optimize resource allocation towards seed production.

The use of biofertilizers is becoming an economical and environmentally friendly alternative to promote sustainable agriculture. Biochar from microalgae/cyanobacteria can be applied to enhance the productivity of food crops through soil improvement, slow nutrient absorption and release, increased water uptake, and long-term mitigation of greenhouse gas sequestration. Therefore, the aim of this study was to evaluate the stimulatory effects of biochar produced from Spirulina (Arthrospira platensis) biomass on the development and seed production of rice plants. Biochar was produced by slow pyrolysis at 300°C, and characterization was performed through microscopy, chemical, and structural composition analyses. Molecular and physiological analyses were performed in rice plants submitted to different biochar concentrations (0.02, 0.1, and 0.5 mg mL-1) to assess growth and productivity parameters. Morphological and physicochemical characterization revealed a heterogeneous morphology and the presence of several minerals (Na, K, P, Mg, Ca, S, Fe, and Si) in the biochar composition. Chemical modification of compounds post-pyrolysis and a highly porous structure with micropores were observed. Rice plants submitted to 0.5 mg mL-1 of biochar presented a decrease in root length, followed by an increase in root dry weight. The same concentration influenced seed production, with an increase of 44% in the number of seeds per plant, 17% in the percentage of full seeds per plant, 12% in the weight of 1,000 full seeds, 53% in the seed weight per plant, and 12% in grain area. Differential proteomic analyses in shoots and roots of rice plants submitted to 0.5 mg mL-1 of biochar for 20 days revealed a fine-tuning of resource allocation towards seed production. These results suggest that biochar derived from Arthrospira platensis biomass can stimulate rice seed production.

Xylooligosaccharides Enhance Lettuce Root Morphogenesis and Growth Dynamics.

Enhancing root development is pivotal for boosting crop yield and augmenting stress resilience. In this study, we explored the regulatory effects of xylooligosaccharides (XOSs) on lettuce root growth, comparing their impact with that of indole-3-butyric acid potassium salt (IBAP). Treatment with XOS led to a substantial increase in root dry weight (30.77%), total root length (29.40%), volume (21.58%), and surface area (25.44%) compared to the water-treated control. These enhancements were on par with those induced by IBAP. Comprehensive phytohormone profiling disclosed marked increases in indole-3-acetic acid (IAA), zeatin riboside (ZR), methyl jasmonate (JA-ME), and brassinosteroids (BRs) following XOS application. Through RNA sequencing, we identified 3807 differentially expressed genes (DEGs) in the roots of XOS-treated plants, which were significantly enriched in pathways associated with manganese ion homeostasis, microtubule motor activity, and carbohydrate metabolism. Intriguingly, approximately 62.7% of the DEGs responsive to XOS also responded to IBAP, underscoring common regulatory mechanisms. However, XOS uniquely influenced genes related to cutin, suberine, and wax biosynthesis, as well as plant hormone signal transduction, hinting at novel mechanisms of stress tolerance. Prominent up-regulation of genes encoding beta-glucosidase and beta-fructofuranosidase highlights enhanced carbohydrate metabolism as a key driver of XOS-induced root enhancement. Collectively, these results position XOS as a promising, sustainable option for agricultural biostimulation.

Effects of water and exogenous glucose on apple seedling growth and soil enzyme activity in semiarid area.

Soil water and organic carbon (C) are key factors affecting the growth and development of apple seedlings. The objective of the study was to investigate the effects of different soil moisture and glucose supplies on apple seedling growth and soil enzyme activities. We hypothesized that the growth of apple seedlings was affected by soil water and C content through their effects on root structure, plant physiological properties and soil enzymatic activities. A pot experiment consisting of nine treatments was set up, including three water treatments with soil moisture contents at 75-85% (normal irrigation, CK), 65-75% (light water stress, LS), and 55-65% (mild water stress, MS) of the soil field capacity, in combination with three glucose treatments with carbon/nitrogen (C/N) ratio of 7.5 (C1, no adding glucose), 10 (C2) and 15 (C3), respectively. Results showed that the LSC2 treatment significantly increased plant height by 7%, stem diameter by 5% and leaf area by 17%, as compared with LSC1. Also, LSC2 significantly increased root dry weight, root vitality and soil enzyme activities. Moreover, results of leaf photosynthetic, malondialdehyde (MDA), peroxidase (POD), superoxide dismutase (SOD) and proline contents also proved that adding glucose improved the drought resistance of plants. LSC2 treatment is more conducive to the growth of apple seedlings, and application of carbon has a good alleviation effect on plant water stress. The study demonstrated that addition of exogenous glucose alleviated light water deficiency, significantly affected root vitality, and promoted apple seedling growth. © 2024 Society of Chemical Industry.

Effects of Claroideoglomus etunicatum Fungus on the Growth Parameters of Maize (Zea mays L.) Plants under Boron Toxicity and Salt Stress

Soil salinity is an emerging phenomenon threatening arid and semiarid areas due to changing climatic events. Salinity, in combination with other elemental contaminants, can often harm crop performance and productivity. This experiment was conducted to evaluate the mitigating effect of Claroideoglomus etunicatum, an arbuscular mycorrhizal fungus (AMF), on combined boron (B) toxicity and salt stress symptoms in maize plants. After the stress and AMF treatments, plants were subjected to a wide range of analyses, such as AMF colonization rates, ion leakage, plant biomass, and concentration of B, phosphorus, sodium, potassium, iron, zinc, copper, and manganese in root and shoot tissues. The results showed that the combined stress did not affect the AMF colonization rate. AMF inoculation significantly increased plant biomass, the K+/Na+ ratio, and shoot B, sodium, and copper concentrations, but reduced root B concentrations and ion leakage. AMF inoculation slightly increased root dry weight and the sodium, potassium, zinc, copper and Mn contents in shoots under combined B and salinity stress, while AMF reduced the electrolyte leakage in leaves. It is inferred that AMF can ameliorate B toxicity in maize by improving biomass and reducing B concentration in plant tissues. Our research implies that C. etunicatum could be a valuable candidate for assisting in the remediation of boron-contaminated and saline soils.

Trichoderma harzianum enhances root biomass production and promotes lateral root growth of soybean and common bean under drought stress

AbstractDrought stress (DS) is one of the main environmental stresses that determines crop productivity. It has been estimated that DS depresses over 40%–60% of soybean (Glycine max (L.) Merr.) and common bean (Phaseolus vulgaris L.) production worldwide, respectively. Although different agronomic strategies are sometimes implemented, the current goal in sustainable agriculture could involve the inoculation with native microorganisms to mitigate DS effects. A potential fungal candidate is Trichoderma, which is recognized as a ubiquitous soil inhabitant with growth‐promoting and biocontrol potentiality. However, its potential for mitigating the stress for water deficit is less well‐documented. Our objective was to evaluate the effect of inoculation with native Trichoderma harzianum strains on soybean and common bean growth under contrasting conditions of water availability. Seeds were independently inoculated (or not) with IB‐J15 and IB‐363 strains, and plants were submitted to DS or were kept under optimal irrigation (well‐watered, WW). In both legumes, the most evident effect after being inoculated was the modification of plant root architecture, the increase in root area and the development of lateral roots in plants under WW and DS conditions. In soybean, both Trichoderma strains had a positive inoculation response, both fresh and dry root biomass increased under WW, and remarkably under DS conditions. The main effect was an increase of about 110% in root dry weight under WW and, about 330% in DS in plants inoculated with IB‐J15 strain, meanwhile, plants inoculated with IB‐363 increased root dry weight 60% in WW and 177% in DS conditions. Notably in soybean, the inoculation with both Trichoderma strains increased the root area more than 70% in both WW and DS conditions. Common beans inoculated with IB‐363 under WW conditions, reached a positive inoculation responsiveness of around 247% in shoot dry weight biomass, and under WW both strains increased the root area more than 50%. Further, IB‐363 increased leaf area by 25% in WW and 72% in DS. Additionally, the in vitro co‐culture between both Trichoderma strains and nodulating Rhizobium etli and Bradyrhizobium japonicum E109 showed compatibility between microorganisms, since no inhibition of their growth was observed. We emphasize that plants inoculated with Trichoderma showed better resistance to water deficit, as seen by redistribution of photosynthates, prioritizing mainly, the development of the root system. © 2024 Association of Applied Biologists.

Effects of arbuscular mycorrhizal fungi on uptake, partitioning and use efficiency of nitrogen in wheat

Arbuscular mycorrhizal fungi (AMF) can promote the growth and yield of crops by increasing the use of nutrients. However, the influence of AMF on the uptake, utilization and partitioning of nitrogen (N) from different sources remain uncertain. Therefore, we investigated AMF inoculation on plant biomass, N-uptake (from fertilizers and soil), -partitioning and N use-efficiency (NUE) in two wheat cultivars using 15N isotope labeling in a field and pot experiment. Results showed that AMF inoculation increased both plant biomass and N accumulation, and altered N partitioning in wheat. AMF inoculation significantly increased root N concentration and decreased grain N concentration (GNC) and leaf N concentration. The decrease in GNC by the AMF was mainly attributed to the variations in pre-anthesis accumulated N in vegetative organs and a reduction in the amount of N translocation. AMF significantly increased root dry weight by 13.5–18.2%, N uptake of the root by 25.4–37.2%. The N partitioning ratio in roots increased, but decreased in grains. Further, AMF significantly increased plant uptake of top-dressed 15N-labeled fertilizer by 15.0–17.8%. AMF promoted grain N absorbed from fertilizer (basal and topdressing fertilizer) but reduced its uptake from soil. Importantly, fertilizer N recovery efficiency (FNRE), N utilization efficiency (NUtE) and NUE were higher in AMF than in the control (CK), demonstrating the benefits of AMF inoculation on growth in wheat. Therefore, using AMF as biofertilizers in field conditions may be an effective agronomic practice in order to ensure sustainable production.

Beneficial Bacteria Associated With Silica Nanoparticles for Growth Promotion of Paspalum notatum

Plant growth–promoting bacteria (PGPB) can play an essential role as biofertilizers to increase pasture efficiency and reduce the application of agrochemicals. Plant growth can be potentialized when these bacteria are combined with silica nanoparticles (SiNPs). The present study aimed to evaluate the effect of PGPB associated with SiNPs on the growth of bahiagrass (Paspalum notatum) seedlings. The PGPB were isolated from rhizospheric soils and leaves of Paspalum spp. grown in the tropical high‐altitude region of Brazil and selected by their ability to fix nitrogen, solubilize phosphate, and synthesize indoleacetic acid (IAA). They were identified as Alcaligenes faecalis, Enterobacter asburiae, and Serratia marcescens by 16S rDNA sequencing. Spherical SiNPs (85 nm in diameter) were synthesized by the hydrolysis of the silicon precursor tetraethyl orthosilicate (TEOS), characterized by infrared spectroscopy and scanning electron microscopy (SEM) and applied at 5% (0.05 mg·mL−1) and 10% (0.1 mg·mL−1) concentrations. Disinfected P. notatum seeds were treated with PGPB, SiNPs, and PGPB + SiNPs and cultivated in magenta boxes containing peat, sand, and perlite. The seedlings were evaluated for their germination percentage, root length, shoot length, root dry weight, and shoot dry weight. Disinfected seeds subjected to the same treatments were also grown in Petri dishes containing 0.7% agarose. The roots of the seedlings in Petri dishes were stained with diaminobenzidine tetrahydrochloride (DAB) and visualized using a light microscope to confirm bacterial colonization. The three strains without SiNPs promoted the growth of P. notatum seedlings. S. marcescens treatment presented the greatest shoot length, and both concentrations of nanosilica with PGPB improved or maintained root lengths. Treatments of S. marcescens and E. asburiae with 10% SiNPs showed 100% seed germination. Seedlings inoculated with 10% SiNPs with S. marcescens and E. asburiae alone showed the highest shoot dry weight, and all treatments increased root dry weight compared to the control. The 10% SiNPs’ concentration inoculated with S. marcescens and A. faecalis positively affected P. notatum seedlings’ growth. This study suggests that nanosilica can be applied with PGPB to improve the development of bahiagrass and reduce the need for applications of agrochemicals.

PENINGKATAN PERTUMBUHAN DAN HASIL KEDELAI YANG DITANAM DALAM KONDISI JENUH AIR MELALUI PEMBERIAN P ANORGANIK DAN KOMPOS TANDAN KOSONG KELAPA SAWIT DI ULTISOL

[ENHANCING GROWTH AND YIELD OF SOYBEAN GROWN UNDER WATER-SATURATED CONDITIONS BY INORGANIC P AND EMPTY FRUIT BUNCH COMPOST AMENDMENTS IN ULTISOL]. The saturated soil culture practices with which to obtain high yield of soybean in Ultisol, characterized by high acidity, nutrient deficiencies and imbalances, should be developed. This study was conducted to evaluate the beneficial effects of empty fruit bunch (EFB) compost combined with inorganic P application on growth and yield of soybean under water-saturated culture in Ultisol. This research was carried out from September to December 2022 in the rice field located in Kemumu Village, Arma Jaya District, North Bengkulu Regency, Bengkulu Province at an altitude of ±541 m above sea level. The field experiment was performed in factorial scheme based on a randomized complete block design with three replications. The experimental treatments included EFB compost as first factor at four levels (0, 5, 10, and 15 t/ha) and application of SP36 as second factor at four rates (0, 75, 150, and 225 kg/ha). Results show that Ultisol amended with a combination of 15 t/ha EFB compost and 75 kg/ha P2O5 resulted in the highest number of seeds per plant (about 142.266 seeds). The number of productive branches, fresh shoot weight, root dry weight, and root nodule weight was the highest in soil solely ammended with EFB compost at 15 t/ha. The sole P application at 225 kg/ha significantly (p<0.05) increased root dry weight and root nodule weight. Thus, under saturated soil culture, application of EFB compost and inorganic P in sole or combination would be the recommended nutrient management practice for enhancing soybean agronomic prformances in this acid soil.

Effect of liquid organic fertilizer on lemon transplants exposed to water stress

This experiment was carried out in a canopy belonging to the Department of Horticulture and Landscape Engineering / College of Agricultural Engineering Sciences / University of Baghdad in 2019. A two-factor factorial experiment was designed according to randomized complete block design (RCBD). The first factor included irrigation for two periods (3 days and 6 days), and the second factor included organic fertilizer (Fulviegrow) with three concentrations (0, 2.5, 5 ml.L-1). Intending to know the effect of adding organic fertilizer on the endurance of these transplants exposed to water stress, It includes 6 treatments, three replications, and two transplants for each experimental unit. The number of transplants is 36. The results showed that the irrigation periods had a significant effect, as it gave (the irrigation period every 3 days) a significant increase in shoot and root dry weight, percentage of vegetative mass dry weight to root system dry weight, leaves area (cm2), leaves calcium content, As for the organic fertilizer, it was significantly superior in most of the mentioned characteristics compared to control treatment. Keywords: Water Stress, Irrigation Period, Organic Fertilizer, Citrus Lemon.

Potential Mechanism of Optimal Tillage Layer Structure for Improving Maize Yield and Enhancing Root Growth in Northeast China

A field experiment was conducted to evaluate the effect of different tillage structures on soil physical properties, soil chemical properties, maize root morphological and physiological characteristics, and yield. Four tillage structures were designed. Soil tillage plays a prominent role in agricultural sustainability. The different tillage layer structures affected soil physical properties. An enhancement in the optimal tillage layer structure improved soil structure. The MJ tillage layer structure created an improved soil structure by regulating the soil physical properties so that the soil compaction and soil bulk density would be beneficial for crop growth, increase soil water content, and adjust the soil phrase R value and GSSI. Soil nutrients are significantly affected by soil depth, with the exception of available potassium. However, soil nutrients are influenced by different tillage layer structures with soil depth. Soil nutrient responses with depth are different for MJ layer treatment compared with other tillage layer structures. Soil organic matter (SOM) is affected with an increase in depth and is significantly influenced by different tillage layer structures, except at 20–30 cm soil depth. MJ treatment increased by 10–20% compared with other tillage layer structures. In addition, QS treatment enhanced the increased pH value in soil profile compared to others. The root morphology characteristics, including root length, root ProjArea, root SurfArea, root AvgDiam, and root volume, were affected by years, depth, and the tillage layer structures. The MJ tillage layer structure enhanced root growth by improving tillage soil structure and increasing soil air and water compared with other tillage layer treatments. Specifically, the MJ layer structure significantly increased root length and root volume via deep tillage. However, the differences in root physiological properties were not significant among treatments. The root dry weight decreased with an increase in soil depth. Most of the roots were mainly distributed in a 0–40 cm soil layer. The MJ treatment enhanced the increase in root dry weight compared with others by breaking the tillage pan layer. Among the different tillage layer structures, the difference in root dry weight was smaller with an increase in soil depth. Moreover, the MJ treatment significantly improved maize yield compared with others. The yield was increased by 14.2% compared to others under MJ treatment via improvements in the soil environment. In addition, the correlation relationship was different among yield and root morphology traits, root physiology traits, soil nutrients, and soil physical traits. So, our results showed that the MJ tillage layer structure is the best tillage structure for increasing maize yield by enhancing soil nutrients, improving the soil environment and root qualities.

Efficiency of Complex Biopreparation Use on Winter Wheat Crops in Mordovia

Under field conditions in the Republic of Mordovia, we studied the effect of treatment of seeds and plants of winter wheat varieties Mironovskaya 808 and Skipetr with a complex biological preparation based on jointly cultivated strains PGPB Pseudomonas chlororaphis subsp. aureofaciens and PGPF Saccharomyces cerevisiae on plant growth and productivity. We used seed treatment with the biological preparation diluted with water at a ratio of 1 : 100, and plant treatment during vegetation at a dilution of 1 : 200. The complex biological preparation stimulated an increase in net productivity of photosynthesis and leaf surface, an increase in root dry weight and volume, but not plant height, and an increase in grain productivity by 25–36% compared with control. The stimulating effect of the biopreparation was variety-specific.

Cerium oxide nanoparticles alleviates stress in wheat grown on Cd contaminated alkaline soil

The cadmium contamination of soil is an alarming issue worldwide and among various mitigation strategies, nanotechnology mediated management of Cd contamination has become a well-accepted approach. The Cerium Oxide Nanoparticles (CeO2-NPs) are widely being explored for their novel works in Agro-Industry and Environment, including stress mitigation in crops. Very little work is reported regarding role of CeO2-NPs in management of Cd contamination in cereal crops like wheat. Present work was planned to check efficacy of CeO2-NPs in Cd stress mitigation of wheat under alkaline calcareous soil conditions. In this experiment, 4 sets of Cd contamination (Uncontaminated control-UCC, 10, 20, and 30 mg Cd per kg soil) and 5 sets of CeO2-NPs NPs (0, 200, 400, 600, and 1000 mg NP per kg soil) were applied in pots following completely randomized design (CRD) and wheat crop was grown. The growth, physiology, yield and Cd and Ce accumulation by wheat root, shoot and grain was monitored. The maximum Cd spiking level (30 mg kg−1) was found to be most toxic for plant growth. The results showed that the nanoparticles were overall beneficial for wheat growth and maximum level (1000 mg kg−1) being the most significant one under all Cd spiking sets. In Cd-30 sets, 1000 mg kg−1 NPs application resulted in decreased soil bioavailable Cd concentration (49.63% decrease compared to 30 mg kg−1 Cd spiked sets termed as Cd-30 Control), decreased Cd accumulation in all three tissues: root (58.36% decrease), shoot (52.30% decrease) and grain (55.56% decrease) while increased root dry weight (62.14%), shoot dry weight (89.32%), total grain yield (80.08%) and improved plant physiology with respect to Cd-30 control. Nanoparticles application substantially increased wheat root, shoot and grain Ce concentrations as well. The further prospects of these nanoparticles in relation to various biotic and abiotic stresses are advised to be explored.

Exogenous application of low and high molecular weight organic acids differentially affected the uptake of cadmium in wheat-rice cropping system in alkaline calcareous soil

Anthropogenic cadmium (Cd) in arable soils is becoming a global concern due to its harmful effects on crop yield and quality. The current study examined the role of exogenously applied low molecular weight organic acids (LMWOAs) including oxalic acid (OxA), tartaric acid (TA) and high molecular weight organic acids (HMWOAs) like citric acid (CA) and humic acid (HA) for the bioavailability of Cd in wheat-rice cropping system. Maximum increase in root dry-weight, shoot dry-weight, and grain/paddy yields was recorded with HA for both crops. The HA significantly decreased AB-DTPA Cd in contaminated soils which remained 41% for wheat and 48% for rice compared with their respective controls. The minimum concentration of Cd in roots, shoots and grain/paddy was observed in HA treatment in both crops. The organic acids significantly increased the growth parameters, photosynthetic activity, and relative leaf moisture contents for both wheat and rice crops compared to that with the contaminated control. Application of OxA and TA increased the bioavailability of Cd in soils and plant tissues while CA and HA decreased the bioavailability of Cd in soils and plants. The highest decrease in Cd uptake, bioaccumulation, translocation factor, immobilization, translocation, harvest, and health risk indices were observed with HA while maximum increase was recorded with OxA for both wheat and rice. The results concluded that use of HMWOAs is effective in soil Cd immobilization being maximum with HA. While LMWOAs can be used for the phytoextraction of Cd in contaminated soils having maximum potential with OxA.

Relationship between pepper (Capsicum annuum L.) root morphology, inter-root soil bacterial community structure and diversity under water-air intercropping conditions.

The combination of water and gas at an aeration rate of 15mg/L and irrigation amount of 0.8Ep significantly promoted the root morphology, inter-root soil bacterial community structure and diversity of pepper, enhanced the structure of molecular symbiotic network, and stimulated the potential ecosystem function. Poor aeration adversely affects the root morphology of pepper (Capsicum annuum L.) and bacterial community. It is critical to understand the effects of water-air interactions on root morphology and bacterial community structure and diversity. A randomized block experiment was conducted under the two aeration rates of dissolved oxygen mass concentrations, including A: 15mg/L, O: 40mg/L, and C: non-aeration as control treatment, and two irrigation rates of W1 and W2 (0.8Ep and 1.0Ep). The results showed that aerated irrigation had a significant effect on the root morphology of pepper. Compared with treatment CW1, treatment AW1 increased root dry weight, root length, root volume, and root surface area by 13.63%, 11.09%, 59.47%, and 61.67%, respectively (P < 0.05). Aerated irrigation significantly increased the relative abundance of Actinobacteria, Gemmatimonadetes, Alphaproteobacteria, Gemmatimonas, Sphingomonas, and KD4-96 aerobic beneficial bacteria. It decreased the relative abundance of Proteobacteria, Monomycetes, Bacteroidetes, Corynebacterium, Gammaproteobacteria, Anaerolineae, Subgroup_6, MND1, Haliangium, and Thiobacillus. The Pielou_e, Shannon and Simpson indexes of treatment AW1 were significantly higher than treatments OW1 and CW1. The results of the β-diversity of bacterial communities showed that the structure of soil bacterial communities differed significantly among treatments. Actinobacteria was a key phylum affecting root morphology, and AW1 treatment was highly correlated with Actinobacteria. Molecular ecological network analysis showed a relatively high number of bacterial network nodes and more complex relationships among species under the aeration of level 15mg/L and 0.8Ep, as well as the emergence of new phylum-level beneficial species: Dependentiae, BRC1, Cyanobacteria, Deinococcus-Thermus, Firmicutes, and Planctomycetes. Therefore, the aeration of 15mg/L and 0.8 times crop-evaporation coefficient can increase root morphology, inter-root soil bacterial community diversity and bacterial network structure, and enhance potential ecosystem functions in the rhizosphere.

Selenium and Nitrogen Fertilizer Management Improves Potato Root Function, Photosynthesis, Yield and Selenium Enrichment

The application of selenium (Se) can promote the growth of potatoes and increase the Se content of potato tubers. Nitrogen (N) can promote nutrient absorption and potato yield. However, the effects of Se and N on the yield and Se content of potato tubers have not been reported. Field experiments were conducted in 2019–2020 and 2020–2021. Three N levels, i.e., 0 kg N ha−1 (N0), 150 kg N ha−1 (N1) and 200 kg N ha−1 (N2), and three Se levels, i.e., 0 g Se ha−1 (Se0), 500 g Se ha−1 (Se1) and 1000 g Se ha−1 (Se2), were set up. Potato yield, root dry weight, root activity, leaf area index (LAI), net photosynthetic rate (Pn), malondialdehyde (MDA) content, antioxidant enzyme activity and Se content were investigated. N application increased root dry weight and activity, LAI, antioxidant enzymes activities, Se content and decreased MDA content. Pn, total potato yield and commercial potato yield first increased and then decreased with the increase in N application level. Se application increased root activity, Pn, antioxidant enzyme activities, total yield, commercial potato yield, commercial potato rate, Se content and decreased MDA content. In general, compared with the single application, the combination of N and Se fertilizers further promoted the growth of potatoes, increased the yield of potatoes and the Se content of potato pieces.

Effects of elevated CO2 on the response of glyphosate resistant and susceptible Palmer amaranth (Amaranthus palmeri S. Wats.) to varying rates of glyphosate

ABSTRACT Repeated application of herbicides has led to herbicide-resistant weed populations. Elevated CO2 often increases weed growth, exacerbating problems including impacts on crop yield and weed control. How rising CO2 affects herbicide-resistant weeds remains largely unknown. Palmer amaranth (Amaranthus palmeri) populations resistant to or susceptible to glyphosate were exposed to ambient or elevated (ambient +200 μmol mol−1) concentrations of CO2 in open-top chambers. Two weeks after CO2 exposure, each population was sprayed with glyphosate at 0, 0.5×, 1.0×, or 1.5× the label rate. Afterwards, CO2 exposure continued for an additional two weeks when visual herbicide injury and leaf gas exchange were assessed. Plants were harvested for determination of treatment effects on growth. Elevated CO2 had little effect on most variables except for decreasing stomatal conductance (~25.5%) and increasing water use efficiency (~49.2%). Glyphosate resistant plants showed decreased height (9.8%) and damage (~56.4%) and increased root dry weight (12.1%), photosynthesis (~41.2%), stomatal conductance (~63.3%), and water use efficiency (~32.0%). In general, increasing rates of glyphosate decreased growth and gas exchange variables, which was frequently only seen in the susceptible ecotype. Data suggest that rising atmospheric CO2 is unlikely to affect Palmer amaranth, including control of glyphosate-resistant populations.

Preliminary symbiotic performance of indigenous soybean (Glycine max)-nodulating rhizobia from agricultural soils of Tanzania

Globally, the increase in human population continues to threaten the sustainability of agricultural systems. Despite the fast-growing population in Sub-Saharan Africa (SSA) and the efforts in improving the productivity of crops, the increase in the yield of crops per unit area is still not promising. The productivity of crops is primarily constrained by inadequate levels of soil nutrients to support optimum crop growth and development. However, smallholder farmers occasionally use fertilizers, and the amount applied is usually small and does not meet plant requirements. This is due to the unaffordability of the cost of fertilizers, which is enough to suffice the crop requirement. Therefore, there is a need for alternative affordable and effective fertilization methods for sustainable intensification and improvement of the smallholder farming system's productivity. This study was designed to evaluate the symbiotic performance of indigenous soybean nodulating rhizobia in selected agricultural soils of Tanzania. In total, 217 rhizobia isolates were obtained from three agroecological zones, i.e., eastern, northern, and southern highlands. The isolates collected were screened for N2 fixing abilities under in vitro (nitrogen-free medium) and screen house conditions. The results showed varying capabilities of isolates in nitrogen-fixing both under in vitro and screen house conditions. Under in vitro experiment, 22% of soybean rhizobia isolates were identified to have a nitrogen-fixing capability on an N-free medium, with the highest N2-fixing diameter of 1.87 cm. In the screen house pot experiment, results showed that soybean rhizobia isolate significantly (P &amp;lt; 0.001) influenced different plant growth and yield components, where the average shoot dry weight ranged from 2.49 to 10.98 g, shoot length from 41 to 125.27 cm whilst the number of leaves per plant ranged from 20 to 66. Furthermore, rhizobia isolates significantly (P = 0.038) increased root dry weight from 0.574 to 2.17 g. In the case of symbiotic parameters per plant, the number of nodules was in the range of 0.33–22, nodules dry weight (0.001–0.137 g), shoot nitrogen (2.37–4.97%), total nitrogen (53.59–6.72 g), and fixed nitrogen (46.878–0.15 g) per plant. In addition, the results indicated that 51.39% of the tested bacterial isolates in this study were ranked as highly effective in symbiosis, suggesting that they are promising as potential alternative biofertilizers for soybean production in agricultural soils of Tanzania to increase productivity per unit area while reducing production cost.

Root Yield and Starch Synthase Type IV Gene Activity under Different Micro Nutrient Fertilizer and Harvest Ages on Cassava (Manihot esculenta Crantz)

Abstract The important part of cassava root is starch which is probably controlled by starch synthase type IV (SSIV) gene. The information of micro nutrient and harvest age related to the activity starch synthase type IV (SSIV) gene is still very rare. The objectives of this study were to evaluate root fresh weight of cassava, to compare yield of storage root, and to evaluate the activity of starch synthase type IV (SSIV) gene by real-time quantitative polymerase chain reaction (RT-PCR) applied by micro nutrient fertilizer. Treatments were arranged by factorial (3 × 3) in randomized complete block design (RCBD) with three replications used as block. The first factor was three different dosages of micro nutrient fertilizer as 0, 20, and 40 kg/ha. The second factor was harvest ages as 7, 8, and 10 months after planting (MAP). The micro nutrient fertilizer mainly contents of 5,888 ppm Fe and 1,368 ppm Zn. Variables were leaf number (LN), leaf fresh weight (LFW), leaf dry weight (LDW), stem fresh weight (SFW), stem dry weight (SDW), root fresh weight (RFW), root dry weight (RDW), skin root fresh weight (SRFW), skin root dry weight (SRDW), starch content, and activity of SSIV gene. The result showed that RDW of cassava applied by 40 kg micro nutrient/ha was significantly increased at 10 MAP. The increase in RDW was due to mainly high SSIV gene activity. Additionally, the SSIV gene activity caused by 20 kg micro nutrient/ha treatment showed almost as twice as those by 40 kg micro nutrient/ha. Keywords: Real-time PCR, Root dry weight, Root yield, Starch, Stem dry weight