Wheat Root Growth Research Articles

Effect of endophytic bacteria from Algerian prickly pear roots on wheat under drought stress

Cactus are among the most drought tolerant plants. As Opuntia is able to grow under the stress of drought, this study aims to check if endophytic bacteria isolated from cactus roots have beneficial potential for crops such as wheat during drought. Two endophytic bacterial isolates were isolated from the roots of the cactus and screened for their plant growth promoting characteristics, such as N-free growth and auxin production. These bacteria have demonstrated their potential to promote the growth of durum wheat under in-vitro conditions and have been identified as Pseudomonas putida and P.brassicacearum, following the sequencing of the 16S rRNA gene and phylogenetic analysis, and significantly improved growth parameters such as seeding length compared to the unobstructed control. After 05 days of contact of the two bacteria, P.putida and P.brassicacearum, with sprouted wheat seeds, a root growth rate of (39.88% and 62.14%, respectively) was recorded. The same effect on the growth of wheat roots is caused by the volatile substances of these bacteria deposited separately, with a rate of (53.30% and 24.18%) respectively. Symptoms of drought stress were visibly reduced on seedlings inoculated with P.putida and P.brassicacearum bacteria, a result supported by a growth rate of root parameters in length (260.83% and 179.60%), surface (21.98% and 60.17%) and scope (59.46% and 62.67%), respectively. This work opens up many perspectives for the characterization and selection of endophyte bacteria of under-used drought-tolerant species such as cacti for the improvement of the growth of field crops. These results promote the deployment of Pseudomonas sp as an effective biofertilizer in wheat.

Effects of arbuscular mycorrhizal fungi on accumulation and translocation of selenium in winter wheat.

Selenium (Se) is an essential micronutrient for humans and animals, but not for plants. Generally, cereals including wheat and rice are the main source of dietary Se for humans. Although arbuscular mycorrhizal fungi (AMF) are ubiquitous soil microbes and commonly develop symbionts with winter wheat (Triticum aestivum L.), the influence of AMF on accumulation and translocation of Se during developmental cycle of winter wheat is still unclear. Based on a pot trial, the present results indicated that the effects of AMF on grain Se concentration in winter wheat depend on the Se species spiked in the soil and that Rhizophagus intraradices (Ri) significantly enhanced grain Se concentration under selenite treatment. Moreover, inoculation of AMF significantly increased grain Se content under selenite and selenate treatments. The enhanced grain Se content of mycorrhizal wheat could be attributed to (i) apparently increased root growth of mycorrhizal wheat at jointing could absorb more Se for translocating to aerial tissues and consequently result in significantly higher stalk Se content and (ii) enhancing Se translocation from vegetative tissues to grains. The present study showed that AMF significantly (P < 0.05) increased pre-anthesis Se uptake under selenate treatment and post-anthesis Se uptake under selenite treatment. The present study indicated the feasibility of inoculation of AMF for increasing grain Se concentration under selenite treatment and enhancing the efficiency of biofortification of Se under selenate treatments. © 2022 Society of Chemical Industry.

Simulating Root Growth as a Function of Soil Strength and Yield With a Field-Scale Crop Model Coupled With a 3D Architectural Root Model.

Accurate prediction of root growth and related resource uptake is crucial to accurately simulate crop growth especially under unfavorable environmental conditions. We coupled a 1D field-scale crop-soil model running in the SIMPLACE modeling framework with the 3D architectural root model CRootbox on a daily time step and implemented a stress function to simulate root elongation as a function of soil bulk density and matric potential. The model was tested with field data collected during two growing seasons of spring barley and winter wheat on Haplic Luvisol. In that experiment, mechanical strip-wise subsoil loosening (30–60 cm) (DL treatment) was tested, and effects on root and shoot growth at the melioration strip as well as in a control treatment were evaluated. At most soil depths, strip-wise deep loosening significantly enhanced observed root length densities (RLDs) of both crops as compared to the control. However, the enhanced root growth had a beneficial effect on crop productivity only in the very dry season in 2018 for spring barley where the observed grain yield at the strip was 18% higher as compared to the control. To understand the underlying processes that led to these yield effects, we simulated spring barley and winter wheat root and shoot growth using the described field data and the model. For comparison, we simulated the scenarios with the simpler 1D conceptual root model. The coupled model showed the ability to simulate the main effects of strip-wise subsoil loosening on root and shoot growth. It was able to simulate the adaptive plasticity of roots to local soil conditions (more and thinner roots in case of dry and loose soil). Additional scenario runs with varying weather conditions were simulated to evaluate the impact of deep loosening on yield under different conditions. The scenarios revealed that higher spring barley yields in DL than in the control occurred in about 50% of the growing seasons. This effect was more pronounced for spring barley than for winter wheat. Different virtual root phenotypes were tested to assess the potential of the coupled model to simulate the effect of varying root traits under different conditions.

Effect of Irrigation with Activated Water on Root Morphology of Hydroponic Rice and Wheat Seedlings

Raising yields and agricultural production efficiency is the primary goal of realizing modern agriculture. As a low-cost and environmentally friendly technology, activated water has the potential to increase crop yields and improve water and fertilizer use efficiency, but much research is still needed to make this technology widely available in the field. Hydroponic experiments were conducted to investigate the effects of magnetized water, aerated water, and magnetized aerated water on rice and wheat seedling and root growth. The results showed that aerated water irrigation significantly increased plant height by 5.1–9.6%, leaf area by 21.1%, and aboveground biomass by 14.8–16.3%, respectively. Aerated water irrigation also significantly promoted rice root biomass, maximum root length, total root length, total root surface area, and especially the proportion of roots less than 0.5 mm in diameter, indicating that aerated water enhances the growth of rice seedlings mainly by promoting root growth, especially fine root (D ≤ 0.5 mm) growth. The maximum root length and total root volume of wheat roots under magnetized water irrigation treatment were increased by 7.7–8.6% and 17.2%, respectively, resulting in a significant increase in aboveground dry biomass by 13.6%. Magnetized water and magnetized aerated water irrigation also promoted the growth of rice seedlings and roots. In contrast, aerated water and magnetized aerated water irrigation exhibited an inhibitory effect on the growth of wheat seedlings and roots. Therefore, activated water has different effects on different crops in hydroponics, and more research is needed in the future to determine the conditions for the application of activated water in agriculture.

Chemical Priming with β-aminobutyric acid (BABA) for Seedling Vigor in Wheat (Triticum aestivum L.)

To achieve efficiency in seedling development, the seed must germinate quickly and homogeneously. Pre-sowing applications such as priming are practiced to eliminate or reduce the negative effects of environmental factors through germination and seedling development. This allows to reach a higher germination rate, yield, and desired plant density, especially by protecting against biotic and abiotic stresses. This study was carried out to examine the effects of pre-sowing seed applications on seedling growth and vigor of bread wheat (Triticum aestivum L.). Three different doses of β-amino-n-butyric acid (BABA) were used as seed priming agents and Dimethyl sulfoxide (DMSO) as control groups. The study was carried out according to the completely randomized factorial design with three replications and ten plants per replication. As a result of priming applications, significantly higher values in the number of roots, longest root length, total root length, average root length and shoot fresh weight were obtained compared to control. Our results, for the first time, showed that seed priming with BABA had a promoting effect on many aspects of early seedling growth in bread wheat. This is a preliminary study to understand the mechanism of seed priming and its effects on germination and root growth in wheat. Further studies may shed light on the molecular mechanisms of BABA or other compounds as seed priming agents, benefits for abiotic and biotic stress tolerance, and good stand establishment at the seedling or later stages.

Root Growth and Architecture of Wheat and Brachypodium Vary in Response to Algal Fertilizer in Soil and Solution

Alternative, recycled sources for mined phosphorus (P) fertilizers are needed to sustain future crop growth. Quantification of phenotypic adaptations and performance of plants with a recycled nutrient source is required to identify breeding targets and agronomy practices for new fertilization strategies. In this study, we tested the phenotypic responses of wheat (Triticum aestivum) and its genetic model, Brachypodium (Brachypodium distachyon), to dried algal biomass (with algae or high or low mineral P) under three growing conditions (fabricated ecosystems (EcoFABs), hydroponics, and sand). For both species, algal-grown plants had similar shoot biomass to mineral-grown plants, taking up more P than the low mineral P plants. Root phenotypes however were strongly influenced by nutrient form, especially in soilless conditions. Algae promoted the development of shorter and thicker roots, notably first and second order lateral roots. Root hairs were 21% shorter in Brachypodium, but 24% longer in wheat with algae compared to mineral high P. Our results are encouraging to new recycled fertilization strategies, showing algae is a nutrient source to wheat and Brachypodium. Variation in root phenotypes showed algal biomass is sensed by roots and is taken up at a higher amount per root length than mineral P. These phenotypes can be selected and further adapted in phenotype-based breeding for future renewal agriculture systems.

TaNRT2.1-6B is a dual-affinity nitrate transporter contributing to nitrogen uptake in bread wheat under both nitrogen deficiency and sufficiency

Multiple nitrate transporter (NRT) genes exist in the genome of bread wheat, and it is of great importance to identify the elite NRT genes for N-efficient wheat cultivar breeding. A candidate gene association study (CGAS) of six N use efficiency (NUE) related traits (grain N concentration (GNC), straw N concentration (SNC), grain yield (GY), grain N accumulation (GNA), shoot total N accumulation (STN) and N harvest index (NHI)) was performed based on SNPs in 46 NRT2 genes using a panel composed of 286 wheat cultivars. CGAS identified TaNRT2.1-6B as an elite NRT gene that is significantly associated with four (NHI, SNC, GNA and GY) of the six NUE-related traits simultaneously. TaNRT2.1-6B is located on the plasma membrane and acts as a dual-affinity NRT. The overexpression of TaNRT2.1-6B increased the N influx and root growth of wheat, whereas gene silence lines resulted in the opposite effects. The overexpression of TaNRT2.1-6B also improved GY and N accumulation of wheat under either limited or sufficient N conditions. The data provide the TaNRT2.1-6B gene and the two associated SNP markers as promising powerful tools for breeding wheat cultivars with high N uptake ability and NUE.

ПЕРСПЕКТИВЫ ИСПОЛЬЗОВАНИЯ БАКТЕРИИ PSEUDOMONAS ZHAODONGENSIS ДЛЯ СМЯГЧЕНИЯ ГЕРБИЦИДНОГО СТРЕССА У ПШЕНИЦЫ

The proliferation of herbicide-resistant forms of weeds provokes herbicide application in higher doses. It may have a negative impact on agricultural crops, causing oxidative stress, inhibiting the growth of plants, reducing yield potential. An important task is to find methods to mitigate herbicidal stress in crops. One approach may be to treat crops with microorganisms that favorably affect the growth of plants. Under the conditions of the light site, two-week wheat plants were sprayed with herbicides Octapon estra (0.1 µl/plant) based on 2,4-D and Nanomet (1.3 µg/plant) based on metsulfuron-methyl and a culture of bacteria 12N1 (107 CFU/plant). Herbicide-resistant strain 12N1, previously isolated from soil from the territory of a chemical industry enterprise (Republic of Bashkortostan, Russia), showed nitrogenase activity of 10.1 nmol C2H4•h-1•ml-1.The use of bacteria stimulated the growth of wheat roots both in the variants of the experiment with and without herbicides. Treatment with bacterial culture reduced the proline content in wheat leaves by 1.9 times against the background of the herbicide Octapon extra and by 6.6 times against the background of Nanomet, as well as the return of the total chlorophyll content to the control values. On the basis of the obtained data, the bacterial strain 12N1 was recognized as a potential antidote for mitigating herbicidal stress in wheat and was identified as member of the species Pseudomonas zhaodongensis based on the cultural, morphological, physiological, biochemical features and the sequence of the 16S RNA gene.

Wheat (Triticum spp) roots influenced by crop residue and phosphorus under maize (Zea mays)-wheat system

A field experiment was initiated with maize (Zea mays L.)-wheat (Triricum spp.) cropping system in the year 2013to assess the impact of crop-residue retention (CCR) and phosphorus fertilization on root growth, growth parameters and nutrient content of wheat at ICAR-Indian Agricultural Research Institute Research Farm, New Delhi. Treatments of main-plot were of different CRR and that of subplot were of different P fertilizer management accounting for 20 treatments combinations. For the present study, collected samples were analyzed during 2014–15 and 2015–16 using appropriate methods. Results indicated that mean root-weight densityof wheat at 40 and 75 days after sowing (DAS) was significantly increased from 0.64 (control) to 0.84 mg/cm3 and 2.19 (control) to 2.82 mg/cm3 with 50% cropresidue retention (CRR), respectively. Similarly, the root-growth rate of wheat was also affected significantly due to CRR under different treatments over control. The treatment 50% RDP + PSB amd AM significantly enhanced dry root weight density (0.91 mg/cm3 at 40 and 2.82 mg/cm3 at 75 DAS of wheat with root-growth rate of 48.5 μg/cm3/day). Moreover, significant highest root-growth rate was noticed (49.2μg/cm3/day) under 150% RDP treatment which was statistically similar to 50% RDP + PSB and AM treatment. Significant highest P content in wheat at different stages as well as in grain was recorded with 50% CRR along with 50% RDP + PSB and AM treatment combination. Application of 50% RDP+PSB and AM in combination with 50% CR was found most beneficial in terms of improving root-growth rate, root-weight density, growth attributes and P content in wheat at different stages as well as in grain.

Root and shoot growth of spring wheat (Triticum aestivum L.) are differently affected by increasing subsoil biopore density when grown under different subsoil moisture

A column experiment with five different pore densities (0, 1, 2, 3, and 4 pores column−1) and two varying moisture regimes (comparatively dry and comparatively moist regime) in the subsoil part of the columns was established. In each pore, Lumbricus terrestris was introduced for 28 days before sowing wheat plants. After 40 days of plant growth, watering was stopped to induce progressive topsoil drying. Parameters describing the shoot hydration, mineral uptake, and aboveground biomass were quantified. Root biomass and root length densities (RLD) were measured separately for six soil layers. Under dry subsoil conditions, plants grown under increasing biopore density showed an increase of the RLD and an improved shoot hydration but the aboveground biomass was unaffected. Since RLD but not root biomass was enhanced, it is assumed that roots were able to explore a larger volume of soil with the same amount of root biomass. Thereby, subsoil water likely was used more efficiently leading to an improved hydration. Under moist subsoil conditions, plants grown with increasing biopore density revealed enhanced shoot biomasses and nutrient uptake while the belowground biomass was unaffected. The improved nutrient uptake can be ascribed to, first, the higher subsoil water availability favoring mass flow driven nutrient uptake, and second, to direct and indirect effects of earthworms on the availability of soil nutrients. It is concluded that high biopore abundancies have the potential to improve not only the belowground but also the aboveground biomass. This, however, largely depends on subsoil moisture.

The relationship between characteristics of root morphology and grain filling in wheat under drought stress.

Drought is a common yield limiting factor in wheat production and has become a significant threat to global food security. Root system is the organ responsible for water uptake from soil and root growth is closely associated with yield and quality of wheat. However, the relationship between morphological and structural characteristics of root growth and caryopsis enrichment in wheat under drought stress is unclear. In this study, two wheat cultivars (YM13 and YN19) were treated with drought from flowering to caryopsis maturity stage. The changes in morphological structure of roots and characteristics of endosperm enrichment were investigated. Drought stress significantly reduced the root length, plant height, root dry weight and aboveground parts dry weight, whereas the root-shoot ratio of YM13 and YN19 increased by 17.65% and 8.33% under drought stress, respectively. The spike length, spike weight, grains number per spike and 1,000-grains weight of mature wheat also significantly declined under drought stress. Meanwhile, the cross section structure of roots was changed with the enlargement of vascular cylinder and dense distribution of xylem vessels under drought stress. Additionally, drought stress affected the substance enrichment in wheat caryopses, decreasing starch accumulation and increasing protein accumulation of endosperm. Correlation analysis suggested that the root length was closely correlated with the relative areas of amyloplast (0.51) and protein body (0.70), and drought stress increased the correlation coefficient (0.79 and 0.78, respectively). While the root dry weight had a significantly positive correlation with the plant height and aboveground parts dry weight. The results can provide theoretical basis for root architecture optimization, water-saving and high-yield cultivation and quality improvement in wheat.

Blended controlled-release nitrogen fertilizer with straw returning improved soil nitrogen availability, soil microbial community, and root morphology of wheat

Microbial activities and nitrogen (N) availability in soil directly affect root morphology and consequently crop yield. These relationships are even more critical at the filling stage of wheat due to the grain formation. The objective of this study was to compare effects of blended controlled-release N fertilizer (CRFS) and conventional urea (BBFS) on soil microflora, soil N content, and root growth of wheat at the filling stage in a field with straw return for seven years. The method of 16 s rRNA and ITS high-throughput sequencing was used to probe soil microbial status, and the in-situ root scanner was used for in-situ observation and monitoring of wheat root morphology during two growing seasons. The results showed that CRFS increased the relative abundance of Penicillium and Aspergillus fungal genera and reduced the operational taxonomic unit of nitrifying bacteria of the genus Nitrospira compared to BBFS treatment. Nitrate, ammonium, total N, and organic matter in soils treated CRFS were 15.8 %, 10 %, 7.5 %, and 11.6 % higher than these in soils treated with BBFS, respectively, while the total root length, root surface area, and root volume from CRFS treatment were 57.6%, 48.8 %, and 54.1 % higher than these from BBFS, respectively. Above-ground growth of wheat showed that CRFS increased plant height by 5.8–12.6 %, net photosynthetic rate by 13.5–22.2 %, N content of stems and spikes by 10.0 % and 64.1 %, respectively compared to BBFS. Wheat yield and economic efficiency were increased by 9.9–46.8 %, 11.6–41.7 %, respectively with CRFS treatments than these with BBFS treatments. Wheat received reduced application rate (2/3) of CRFS had similar availability of N and plant growth as the full rate of BBFS. Therefore, using blended controlled-release N fertilizer is a practically and environmentally feasible approach for wheat production in the straw retuning wheat-corn rotation system.

Role of miR164 in the growth of wheat new adventitious roots exposed to phenanthrene

Polycyclic aromatic hydrocarbons (PAHs), ubiquitous organic pollutants in the environment, can accumulate in humans via the food chain and then harm human health. MiRNAs (microRNAs), a kind of non-coding small RNAs with a length of 18–30 nucleotides, regulate plant growth and development and respond to environmental stress. In this study, it is demonstrated that miR164 can regulate root growth and adventitious root generation of wheat under phenanthrene exposure by targeting NAC (NAM/ATAF/CUC) transcription factor. We observed that phenanthrene treatment accelerated the senescence and death of wheat roots, and stimulated the occurrence of new roots. However, it is difficult to compensate for the loss caused by old root senescence and death, due to the slower growth of new roots under phenanthrene exposure. Phenanthrene accumulation in wheat roots caused to generate a lot of reactive oxygen species, and enhanced lipoxygenase activity and malonaldehyde concentration, meaning that lipid peroxidation is the main reason for root damage. MiR164 was up-regulated by phenanthrene, enhancing the silence of NAC1, weakening the association with auxin signal, and inhibiting the occurrence of adventitious roots. Phenanthrene also affected the expression of CDK (the coding gene of cyclin-dependent kinase) and CDC2 (a gene regulating cell division cycle), the key genes in the cell cycle of pericycle cells, thereby affecting the occurrence and growth of lateral roots. In addition, NAM (a gene regulating no apical meristem) and NAC23 may also be related to the root growth and development in wheat exposed to phenanthrene. These results provide not only theoretical basis for understanding the molecular mechanism of crop response to PAHs accumulation, but also knowledge support for improving phytoremediation of soil or water contaminated by PAHs.

Previous and Current Crop Effects on Early-Season Root Growth and Growing Season’s Soil Moisture Under Dryland Agriculture in Temperate Climate

Understanding the root growth and changes in soil moisture content during the growing season for dryland agriculture crops can improve crop production. It was hypothesized that early-season root growth might be influenced by previous crop and current crops, and soil moisture content and depletion pattern during the growing season and residual soil moisture may be affected by the crop type. A study was conducted on the early-season root growth of canola (Brassica napus L.), wheat (Triticum aestivum L.), and flax (Linum usitatissimum L.) in 2015; and changes in soil water content during the 2013, 2014, and 2015 growing seasons under canola, flax, wheat, barley (Hordeum vulgare L.), and pea (Pisum sativum L.). Early-season root growth of the canola and flax crops was better on wheat than canola stubble, while for wheat it was similar on the stubbles of both wheat and canola. Soil moisture depletion started relatively earlier under the barley and wheat and later under the flax compared to the canola and pea crops. Flax continued to deplete soil moisture for a longer period than the other crops. With some exceptions, all crops could deplete soil moisture to a similar level (down to about 15% or somewhat lower) by the end of their growing seasons. Generally, almost equal amounts of residual soil moisture remained after the different crops.

Can precrops uplift subsoil nutrients to topsoil?

Precrops exhibit vigorous deep root growth, especially when grown perennially. However, their contribution to accumulate essential nutrients derived from deeper soil layers in the topsoil has not been quantified. We determined the vertical distribution of phosphorous (P) and potassium (K) affected by contrasting root systems of 3 precrops and their effects on subsequently grown spring wheat. Three precrops (lucerne, chicory and tall fescue) were grown for 1, 2 and 3 years prior to spring wheat cultivation. We measured plant available soil P and K from 0 to 30 cm to 75–105 cm of soil depth after precropping. Root growth and crop performance of spring wheat as affected by precropping were measured in two repeated trials. We observed maximum 22-fold higher root-length density (RLD; cm cm− 3) of taprooted chicory compared with fibrous-rooted tall fescue in the subsoil. There were significant increases in plant available K in the topsoil by 27 mg kg− 1 over the precrop duration between 1 and 3 years. Grain yield of subsequently grown spring wheat was significantly increased by 10 % and 14 % from 1 year to 3 year-treatments of lucerne and chicory, respectively. Similarly, significant increases in P uptake (7 % and 19 %) and K uptake (21 and 14 %) of spring wheat was noted for the same treatments. Our data suggest that there is potential for the yield of short-season cereals to be improved by increased soil nutrient bioavailability in the topsoil derived from deeper soil layers by the deep roots of perennial precrops.

Raised bed planting reduces waterlogging and increases yield in wheat following rice

Waterlogging stress is a major problem for wheat production in rice-wheat double cropping systems on the Yangtze River Plain in China and might become more frequent and intense due to global warming. To alleviate the profound impacts of waterlogging stress on wheat production, a raised bed planting (RBP) pattern was developed. The results showed that RBP significantly increased soil water drainage and reduced the soil water content. The reduced waterlogging stress promoted wheat seedling establishment and root growth, accelerated stem and tiller development, and delayed late-season root and leaf senescence, resulting in 11.3 % and 14.1 % higher grain yields in Fengtai and Guohe, respectively. Furthermore, RBP required fewer inputs and produced more outputs, generating 63.1 % and 59.6 % more net income in Fengtai and Guohe, respectively. Based on this study, RBP can be considered an effective, sustainable soil tillage practice to reduce waterlogging stress and thereby increase wheat productivity and profitability under future waterlogging conditions.

Effects of phosphorus fertilizer on root characteristics, uptake and utilization of phosphorus and yield of dryland wheat with contrasting yearly rainfall pattern.

To understand the growth responses of dryland wheat to different application rates of phosphorus fertilizer in different rainfall years, we examined root characteristics, spike number, yield and phosphate utilization. Results would help improve phosphate fertilizer use in dryland wheat production. We carried out a field experiment at the research station of Shanxi Agricultural University from 2012 to 2016. We examined the effects of four application rates of phosphorus (0, 75, 150 and 225 kg·hm-2 on root growth, phosphate utilization and yield formation of dryland wheat in different years with contrasting rainfall pattern. Compared with the treatment without phosphorus fertilization, phosphate application increased root surface area at all growth stages and root weight density in the 0-80 cm soil layer at jointing, anthesis, and maturity stages. Phosphate application significantly increased soil water consumption from jointing to anthesis, and total soil water consumption in the growing season. Phosphate application enhanced the amount of pre-anthesis phosphate translocation and phosphate accumulation of grain. Spike number, yield and water use efficiency were increased with 75, 150 and 225 kg P·hm-2 by 9.2% to 22.5%, 11.8% to 30.0%, and 2.1% to 12.1%, respectively. In the dry years, the application rates of 150 and 225 kg P·hm-2 in comparison to 75 kg P·hm-2 significantly increased root weight density and root surface area at all stages, soil water consumption from sowing to jointing and from jointing to anthesis, and total water consumption in the growing season. In comparison to the rate of 75 kg P·hm-2, 150 and 225 kg P·hm-2 increased soil water consumption from sowing to jointing by 7.3-8.7 mm, soil water consumption from jointing to anthesis by 15.6-18.1 mm, and total water consumption by 15.6-18.1 mm. Significant increase in the pre-anthesis phosphate translocation and phosphate accumulation in grain was higher under 150 and 225 kg P·hm-2 than that under 75 kg P·hm-2 in dry years. Furthermore, the two rates (150 and 225 kg P·hm-2) in dry years increased spike number by 9.3%-10.7% and yield by 11.9%-14.6%. The application rate of 150 kg P·hm-2 significantly improved phosphorus use efficiency by 20%-82% in comparison to other rates. In normal years, the rates of 150 and 225 kg P·hm-2 increased root surface area, root weight density at both anthesis and maturity compared with 75 kg P·hm-2. Soil water consumption from anthesis to maturity and total soil water consumption in the growing season were also increased by 1.2-15.0 and 3.8-23.1 mm, respectively. In addition, phosphorus accumulation in post-anthesis and phosphate accumulation in grain were increased in both 150 and 225 kg P·hm-2, which increased spike number by 1.4%-9.6% and yield by 3.5%-10.4%. The effects of phosphate application at the rate of 150 kg P·hm-2 were significantly different from 75 and 225 kg P·hm-2. In conclusion, phosphorus fertilizer application enhanced uptake of water and phosphate in dryland wheat at early and middle growth stages in dry years and at the late growth stage in normal years. Phosphorus application increased wheat yield mainly due to the increases of spike number. The application of 150 kg P·hm-2 is the best choice for high water and phosphorus fertilizer use efficiency and high yield in both dry and normal years.

Alleviatory effects of Silicon on the morphology, physiology, and antioxidative mechanisms of wheat (Triticum aestivum L.) roots under cadmium stress in acidic nutrient solutions

Silicon (Si), as a quasi-essential element, has a vital role in alleviating the damaging effects of various environmental stresses on plants. Cadmium (Cd) stress is severe abiotic stress, especially in acidic ecological conditions, and Si can demolish the toxicity induced by Cd as well as acidic pH on plants. Based on these hypotheses, we demonstrated 2-repeated experiments to unfold the effects of Si as silica gel on the root morphology and physiology of wheat seedling under Cd as well as acidic stresses. For this purpose, we used nine treatments with three levels of Si nanoparticles (0, 1, and 3 mmol L−1) derived from sodium silicate (Na2SiO3) against three concentrations of Cd (0, 50, and 200 µmol L−1) in the form of cadmium chloride (CdCl2) with three replications were arranged in a complete randomized design. The pH of the nutrient solution was adjusted at 5. The averages of three random replications showed that the mutual impacts of Si and Cd in acidic pH on wheat roots depend on the concentrations of Si and Cd. The collective or particular influence of low or high levels of Si (1 or 3 mM) and acidic pH (5) improved the development of wheat roots, and the collective influence was more significant than that of a single parallel treatment. The combined effects of low or high concentrations of Cd (50 or 200 µM) and acidic pH significantly reduced root growth and biomass while increased antioxidants, and reactive oxygen species (ROS) contents. The incorporation of Si (1 or 3 mmol L−1) in Cd-contaminated acidic nutrient solution promoted the wheat root growth, decreased ROS contents, and further increased the antioxidants in the wheat roots compared with Cd single treatments in acidic pH. The demolishing effects were better with a high level of Si (3 mM) than the low level of Si (1 Mm). In conclusion, we could suggest Si as an effective beneficial nutrient that could participate actively in several morphological and physiological activities of roots in wheat plants grown under Cd and acidic pH stresses.

Winter wheat root distribution with irrigation, planting methods, and nitrogen application

Soil water uptake is a function of root growth and distribution. Therefore, restrictions on root system growth may reduce water and nutrient uptake, which results in slower plant growth. The objective of this study was to determine the effects of different irrigation strategies, nitrogen application rates, and planting methods on the winter wheat root growth. The experimental factors included two irrigation strategies (variable alternate furrow irrigation defined as partial root-zone irrigation and ordinary furrow irrigation), two planting methods (in-furrow planting and on-ridge planting), and three nitrogen (N) application rates (0, 150, and 300 kg N ha−1) in 2015–2016 and 2016–2017 growing seasons. Results indicated that the in-furrow planting decreased mean root length density and root mass density (8% and 10%, respectively, in the fertilized treatments) compared to that obtained in the on-ridge planting. The partial root-zone irrigation reduced root length density by about 5% and 7% in the fertilized treatments compared to that obtained in full irrigation in the first and second year, respectively; however, these reductions were not statistically significant. Furthermore, the results implied that nitrogen fertilizer application increased root length density by 48% and 24% in the first and second year, respectively. Likely, root mass density increased by 32% and 5% in the first and second year, respectively. The exponential decaying relationship between root length density and soil depth indicated that the in-furrow planting with 300 kg N ha −1 produced the highest root density at the soil surface layer and reduced deep root penetration compared to the on-ridge planting and the other N treatments. Further analysis revealed that grain yield linearly correlated with root length density and root mass density in the first year. However, a polynomial (quadratic) relationship was obtained in the second year. Consequently, increasing the main root traits, including root length and root mass, enhanced winter wheat grain yield until it reached a threshold value. Higher values negatively affected grain yield, which might be due to allocating carbon to roots instead of grains.

Interrelation of physicochemical, spectral, and biological properties of self-organized multi-component aqueous systems based on N-(phosphonomethyl)glycine in the low concentration range

The relationship between non-monotonic concentration dependencies of the size of the dispersed phase (nanoassociates), physicochemical properties (specific electrical conductivity, pH), and fluorescence intensity (λex 225 nm, λem 340 nm) of a multi-component dispersed system based on herbicide N-(phosphonomethyl)glycine and its effect on the development of some hydrobionts and on the inhibition of Triticum vulgare wheat root growth in the range of calculated concentrations 1·10−19−1·10−3 g L−1 is established for the first time. The obtained results indicate that coherent changes in fluorescence intensity, physicochemical properties, and bioeffects are related to the rearrangement of nanoassociates which accompanies the dilution of the systems.