Restricted Root Growth Research Articles

Cold mediates maize root hair developmental plasticity via epidermis-specific transcriptomic responses.

Cold stress during early development limits maize (Zea mays L.) production in temperate zones. Low temperatures restrict root growth and reprogram gene expression. Here, we provide a systematic transcriptomic landscape of maize primary roots, their tissues, and cell types in response to cold stress. The epidermis exhibited a unique transcriptomic cold response, and genes involved in root hair formation were dynamically regulated in this cell type by cold. Consequently, activation of genes involved in root hair tip growth contributed to root hair recovery under moderate cold conditions. The maize root hair defective mutants roothair defective 5 (rth5) and roothair defective 6 (rth6) displayed enhanced cold tolerance with respect to primary root elongation. Furthermore, dehydration response element-binding protein 2.1 (dreb2.1) was the only member of the dreb subfamily of AP2/EREB transcription factor genes upregulated in primary root tissues and cell types but exclusively downregulated in root hairs upon cold stress. Plants overexpressing dreb2.1 significantly suppressed root hair elongation after moderate cold stress. Finally, the expression of rth3 was regulated by dreb2.1 under cold conditions, while rth6 transcription was regulated by dreb2.1 irrespective of the temperature regime. We demonstrated that dreb2.1 negatively regulates root hair plasticity at low temperatures by coordinating the expression of root hair defective genes in maize.

Comparative Long Non-Coding Transcriptome Analysis of Three Contrasting Barley Varieties in Response to Aluminum Stress.

Aluminum toxicity is a major abiotic stress on acidic soils, leading to restricted root growth and reduced plant yield. Long non-coding RNAs are crucial signaling molecules regulating the expression of downstream genes, particularly under abiotic stress conditions. However, the extent to which lncRNAs participate in the response to aluminum (Al) stress in barley remains largely unknown. Here, we conducted RNA sequencing of root samples under aluminum stress and compared the lncRNA transcriptomes of two Tibetan wild barley genotypes, XZ16 (Al-tolerant) and XZ61 (Al-sensitive), as well as the aluminum-tolerant cultivar Dayton. In total, 268 lncRNAs were identified as aluminum-responsive genes on the basis of their differential expression profiles under aluminum treatment. Through target gene prediction analysis, we identified 938 candidate lncRNA-messenger RNA (mRNA) pairs that function in a cis-acting manner. Subsequently, enrichment analysis showed that the genes targeted by aluminum-responsive lncRNAs were involved in diterpenoid biosynthesis, peroxisome function, and starch/sucrose metabolism. Further analysis of genotype differences in the transcriptome led to the identification of 15 aluminum-responsive lncRNAs specifically altered by aluminum stress in XZ16. The RNA sequencing data were further validated by RT-qPCR. The functional roles of lncRNA-mRNA interactions demonstrated that these lncRNAs are involved in the signal transduction of secondary messengers, and a disease resistance protein, such as RPP13-like protein 4, is probably involved in aluminum tolerance in XZ16. The current findings significantly contribute to our understanding of the regulatory roles of lncRNAs in aluminum tolerance and extend our knowledge of their importance in plant responses to aluminum stress.

Evaluation of Different Container Types on Root Structure and Performance of Nursery-grown Citrus Plants

Health and quality of the root system are imperative to ensure the successful establishment of a citrus tree after transplant from the nursery into the field. Containerized citrus production in enclosed nurseries restricts root growth and can result in root circling and intertwining. This may hinder root expansion and result in root girdling after transplant, negatively affecting tree establishment and growth. The root structure of a transplanted citrus tree can also be affected by the container type used in the nursery. Containers with root-pruning properties like chemical pruning or air pruning reduce root circling and may produce superior root systems compared with regular, nonpruning containers. The aim of this study was to evaluate the effects of different nursery containers on root physiological and morphological traits and plant performance over 15 months of growth in the nursery. Three container types, chemical pruning containers, air-pruning containers, and standard nursery containers, were compared. The chemical pruning containers were standard citrus nursery containers with a mixture of copy hydroxide [Cu(OH)2] and copper carbonate (CuCO3) [10% copper (Cu)] applied to the inner wall. Pruning occurs upon contact of the roots with the Cu on the wall of the containers. The air-pruning containers were custom-sized Air-Pots in which pruning occurs on holes in the wall of the containers upon contact of the roots with the air. Two rootstocks, US-812 and US-942 (Citrus reticulata × Poncirus trifoliata), were included for comparison in the nongrafted stage and 12 months after grafting with ‘Valencia’ orange (Citrus sinensis). Chemical root pruning positively influenced tree height, shoot mass, leaf area, rootstock trunk diameter, and the nonfibrous root biomass. No differences among container types were observed for the fibrous root biomass, but chemical pruning produced more roots that were finer with a higher specific root length and a higher respiration rate. In contrast, air pruning produced more roots that were thicker compared with the other containers. Most of the leaf nutrients were lower in trees grown in the chemical pruning containers compared with the standard containers, except for Cu and zinc (Zn), which were highest in the former. Trees growing in air-pruning containers were not significantly different in growth from trees growing in standard containers.

The OsEIL1-OsWOX11 transcription factor module controls rice crown root development in response to soil compaction.

Optimizing the root architecture of crops is an effective strategy for improving crop yields. Soil compaction is a serious global problem that limits crop productivity by restricting root growth, but the underlying molecular mechanisms are largely unclear. Here, we show that ethylene stimulates rice (Oryza sativa) crown root development in response to soil compaction. First, we demonstrate that compacted soil promotes ethylene production and the accumulation of ETHYLENE INSENSITIVE 3-LIKE 1 (OsEIL1) in rice roots, stimulating crown root primordia initiation and development, thereby increasing crown root number in lower stem nodes. Through transcriptome profiling and molecular analyses, we reveal that OsEIL1 directly activates the expression of WUSCHEL-RELATED HOMEOBOX 11 (OsWOX11), an activator of crown root emergence and growth, and that OsWOX11 mutations delay crown root development, thus impairing the plant's response to ethylene and soil compaction. Genetic analysis demonstrates that OsWOX11 functions downstream of OsEIL1. In summary, our results demonstrate that the OsEIL1-OsWOX11 module regulates ethylene action during crown root development in response to soil compaction, providing a strategy for the genetic modification of crop root architecture and grain agronomic traits.

Silicon improves root system and canopy physiology in wheat under drought stress

AimsRoot system is an important regulator for unevenly distributed below-ground resource acquisition. In a rainfed cropping environment, drought stress (DS) significantly restricts root growth and moisture uptake capacity. The fact that silicon (Si) alleviates DS in wheat is widely reported, but its effects on the wheat root system remain unclear.MethodsThe present study investigated the effect of pre-sowing Si treatment on two contrasting wheat cultivars (RAC875, drought-tolerant; Kukri, drought-susceptible) at early growth stages. The cultivars were grown in a glasshouse in a complete randomized design with four replications and two watering treatments. Various root traits and physiological data, including non-destructive infrared thermal imaging for water stress indices, were recorded.ResultsUnder DS and Si (DSSi), Kukri had a significant increase in primary root length (PRL,44%) and lateral root length (LRL,28.1%) compared with RAC875 having a substantial increase in PRL (35.2%), but non-significant in LRL. The Si-induced improvement in the root system positively impacted canopy physiology and significantly enhanced photosynthesis, stomatal conductance and transpiration in Kukri and RAC875 under DSSi. Canopy temperature was reduced significantly in Kukri (4.24%) and RAC875 (6.15%) under DSSi, while canopy temperature depression was enhanced significantly in both the cultivars (Kukri,78.6%; RAC875, 58.6%) under DSSi.ConclusionThese results showed that Si has the potential to influence below-ground traits, which regulate the moisture uptake ability of roots for cooler canopy and improved photosynthesis under DS. It also suggests a future direction to investigate the underlying mechanisms involved in wheat’s Si-induced root growth and moisture uptake ability.

Influence of nitrogen addition on the functional diversity and biomass of fine roots in warm-temperate and subtropical forests

Functional diversity strengthens species diversity and ecosystem function relationships; however, in the case of mixed forests, the relationship between fine root biomass and functional diversity is not completely understood. In this study, we compared fine root biomass and functional diversity of vegetation in response to canopy and understory nitrogen (N) addition rates of 0, 25, and 50 kg N ha−1 yr−1 in subtropical and warm-temperate forests. Canopy and understory N addition decreased the fine root biomass of the subtropical but increased the biomass of the warm-temperate forest during the growing season. The biomass and functional diversity of fine roots are more affected by N addition pattern than by rate. The functional richness index of fine roots was negatively correlated with fine root biomass at community level in the subtropical forest during the growing season, and NO3-N in the soil had the highest explanatory power for fine root biomass variation. Functional richness was positively correlated with fine root biomass at community level in the warm-temperate forest and had the highest explanatory power. In the warm-temperate forest, the synergistic increase in functional richness and fine root biomass promoted increases in nutrient uptake, whereas in the subtropical forest, either N restricted fine root growth or functional richness compensated for the reduction in fine root biomass. These findings indicate that the fine root biomass and functional diversity of subtropical and warm-temperate forests respond differentially to the addition of N.

Root exudation of organic acid anions and recruitment of beneficial actinobacteria facilitate phosphorus uptake by maize in compacted silt loam soil

Soil compaction restricts root growth and plant nutrient uptake, but the effects on the abundance and diversity of soil microbiome are poorly understood. A field study with maize (Zea mays L.) was conducted with two soil-compaction treatments (NC: non-compacted; C: compacted) to investigate the interactions of root exudates and microorganisms and the effect on P uptake at two growth stages (seedling and flowering). At the seedling stage, shoot P concentration was decreased by 13.7% in the C treatment compared with the NC. Root growth and arbuscular mycorrhizal fungi colonization were reduced probably due to the decreased soil porosity after compaction. However, root organic acid anions (OAAs) levels were increased by 170%. Several genera of actinobacteria were specifically enriched in the rhizosphere and their abundance was significantly correlated with the concentration of OAAs. However, the positive correlations of concentration of OAAs and abundance of microorganisms or plant P uptake were not observed at flowering stage. Our results indicated that besides the well-known function of exuded organic acid anions on soil P mobilization, maize might also select for microorganisms associated with the facilitation of P acquisition, and mitigating P deficiency at the early growth stage of the plant in compacted soil.

Responses of mangrove (Kandelia obovata) growth, photosynthesis, and rhizosphere soil properties to microplastic pollution

In this study, we used Kandelia obovata to explore the toxicities of three typical MPs in mangroves: polyethylene, polypropylene, and polyvinylchloride. MPs were mixed into soils at 5 % (w/w) for cultivation in mangrove tide-tank system. Plant growth and soil characteristics were determined after 12 months. The results showed that MPs multiply restricted root growth, leaf ionome, chlorophyll concentration, and photosynthetic efficiency, changed leaf photochemical efficiency and excited energy distribution. Polyethylene and polypropylene MPs with 150 μm sizes significantly reduced leaf and root biomass. As for soil properties, all MPs mainly reduced bulk density but improved porosity, with 600 μm polyethylene resulting in 1.4 g cm−3 bulk density and 55.1 % porosity. This study represent the first paper highlighting that MPs negatively affect mangrove plants by affecting plant growth, leaf ionome, and photosynthesis, which may be related with the changed soil properties, especially reduced bulk density and improved porosity.

Impact of Tillage on Growth, Productivity and Economics of Soybean Grown in Vertisols of Western Madhya Pradesh, India

The investigation entitled, “Impact of Tillage on Growth, Productivity and Economics of Soybean Grown in Vertisols of Western Madhya Pradesh, India’’ was conducted during the kharif season of the year 2019-20 in the Department of Soil Science and Agricultural Chemistry, R.V.S.K.V.V., College of Agriculture, Indore. The objective of the experiment was to study the effect of tillage practices on the growth and productivity of soybean and to evaluate the effect of tillage on the economics and energy use efficiency of soybean. The experiment conducted in randomized block design and replicated five times. There were four treatments T1-Sub Soiling (SS) + Sowing by precision seed drill, T2- Tillage by Cultivator twice (CT), T3- Deep Tillage by M.B. plough (DT) and T4- Reduced Tillage + Crop Residues (RT+CR 30 % of previous crop). The results indicated that T1-Sub Soiling (SS) treatment was recorded maximum value of growth parameters, yield attributes ,seed yield, test weight, seed weight plant-1, Nodules Weight per plant, net returns and B:C which was statistically at par with treatment T2 Cultivator twice (CT). The overall conclusion drawn from the study is that due to continuous mechanization and use of heavy machinery a compact layer was observed in Vertisols at 20-30 cm soil depth which restricts root growth, reduces infiltration rate, thereby, causes water logging during rainy season. The poor soil aeration results in reduction in soybean productivity in Madhya Pradesh.

Effect of Aerated Irrigation on the Growth and Rhizosphere Soil Fungal Community Structure of Greenhouse Grape Seedlings

Conventional irrigation methods decrease greenhouse soil aeration, which leads to restricted root growth and reduced soil fungal abundance in greenhouse grapes. In this study, aerated irrigation equipment was used to investigate the effects of aerated irrigation on the biomass accumulation, root growth, and soil fungal community structure of grape seedlings. The results show that aerated irrigation significantly increased the root length, root surface area, root volume, and number of root tips by 38.5%, 32.1%, 62.1%, and 23.4%, respectively, at a soil depth of 20–40 cm (p ≤ 0.05). The chao1 index and ACE index of fungi at different soil depths under aerated irrigation were higher than those without aerated treatment; aerated irrigation changed the relative abundance of dominant fungi in rhizosphere soil. At a soil depth of 20–40 cm, aerated irrigation increased the abundance of Fusarium by 42.2%. Aerated irrigation also contributed to the abundance of the beneficial fungal genera Mortierella, Cladosporium, and Glomus. At a soil depth of 0–20 cm, the abundance of Mortierella in the soil that received aerated treatment was 180.6% higher than in the control treatment. These findings suggest that aerated irrigation is a promising strategy for the promotion of grape root growth and biomass accumulation, and it can also increase the abundance of some beneficial fungi.

The persistently breaking trade-offs of three-decade plastic film mulching: Microplastic pollution, soil degradation and reduced cotton yield

Plastic mulching has been extensively used for near 40 years in China because of the commonly recognized trade-offs between economic profit and adverse impacts. Whether the trade-offs is well kept after decades of mulching usage is poorly understood. In this study, microplastic (MP) pollution, soil physical properties, as well as the root traits and yields of cotton under plastic mulching for different years (up to 32 years) in northwest China were investigated. The results showed that average abundance of MPs in soil ranged from 28.00 to 1426.67 items kg−1 and increased with time whereas size of MPs decreased with time. With respect to soil physical properties, bulk density and penetration resistance significantly increased with mulching time while saturated hydraulic conductivity and mean weight diameter of water-stable aggregates in cotton fields decreased over time, indicating that long-term plastic mulching has irreversible adverse impact on soil function. The significantly increased soil penetration resistance and decreased hydraulic conductivity substantially restricted root growth and this finally led to remarkable reduction of seed cotton yield. It is urgent for the agricultural departments to take appropriate measures to mitigate the constantly increased negative trade-offs of plastic mulching in the arid areas.

Quantifying the impact of induced topsoil and historical subsoil compaction as well as the persistence of subsoiling

Mechanical soil compaction increasingly occurs in arable land but the state and effects of historical compaction from regular operations are still poorly documented. Therefore, a typical field was selected and the effects of both newly formed topsoil compaction and historical developed subsoil compaction (below 30 cm) on soil physical and hydraulic properties, soil water movement, soil mineral nitrogen leaching potential and crop parameters were evaluated on a Luvisol under a winter rye (Secale cereale L.) and summer maize (Zea mays L.) rotation system. Three subsoil compaction levels were included, i.e., a i) highly compacted headland zone, and a moderately compacted in-field zone ii) without and iii) with deep tillage by subsoiling in the winter of 2016. Topsoil compaction on the other hand was induced by one machine pass with a rotary cultivator in addition to the regular machine passes during field preparation for the summer maize season of 2017, and compared with a control without extra compaction. For subsoil compaction treatments, both visual evaluation and lab or field based measurements indicated that soil physical and hydraulic properties were deteriorated in the headland compared with in-field zones. As a result, both winter and summer crop above-ground biomass were decreased in the highly compacted headland zone because of the restricted root growth, which further increased the risk of soil mineral nitrogen leaching. The alleviation effect of deep tillage remained after ∼ 2 years, which significantly increased maize height in the extremely dry and hot summer of 2018. For topsoil compaction, one traffic pass with a rotary cultivator increased topsoil penetration resistance and water content but summer maize above-ground biomass was not affected. Overall, prevention and alleviation of subsoil compaction are essential in increasing the resistance and resilience to the continuing deteriorating climatic conditions.

Subsoil compaction effect on spatio-temporal root growth, reuse of biopores and crop yield of spring barley

Subsoil compaction in arable farming caused by increasingly heavy machinery results in increased subsoil strength and reduced aeration and water flow. This can restrict root growth and reduce crop yield. To mitigate these effects of subsoil compaction, we included a deep-rooted catch crop of fodder radish (Raphanus sativus var. oleifera) in a rotation of spring barley (Hordeum vulgare). The objective was to determine the effect of subsoil compaction on root growth and grain yield of barley, and to investigate the creation and use of biopores for subsequent root growth. Studies were carried out in 2013–2016 in a soil compaction experiment established in 2010 on a sandy loam. The soil had for four consecutive years (2010–2013) been compacted with multi-passes in an 8 Mg wheel load treatment (M8) or had not been compacted (Control). Spring barley was grown every year and fodder radish was grown as a catch crop from harvest to winter in 2013–2016. Penetration resistance to 90 cm depth was measured in 2015 at a soil water content near field capacity. Root growth and biopore reuse were investigated using horizontal minirhizotrons installed at 30, 50 and 70 cm depth from 2013–2016. Spring barley grain yield was recorded annually. We found that M8 caused critical subsoil compaction with penetration resistance peaking at 3.5 MPa in the upper subsoil (30−40 cm depth). Subsoil compaction reduced root growth by c. 50 % at 30 cm depth and barley yields by 6–8 % compared to the Control in three years after cessation of the compaction treatment. The number of biopores that were reused were higher for fodder radish than for spring barley, 4.1 % and 3.1 %, respectively, but did not differ between compaction treatments. Our study displayed a marked, negative residual effect of soil compaction on above- and belowground crop growth. There was no tendency towards a recovery within the years studied (1–3 years after compaction). Severe subsoil compaction is a widespread problem and therefore we call for more studies on the spatio-temporal dynamics of the creation and subsequent use of biopores for root growth as these are essential for the recovery of compacted subsoils.

Genotypic variation among chickpea and wild Cicer spp. in nutrient uptake with increasing concentration of solution Al at low pH

In many acidic soils, high concentrations of toxic Al3+ hamper plant growth by restricting root growth which in turn restricts water and nutrient absorption. Previous research showed variation among chickpea (Cicer arietinum L.) and wild Cicer species in root elongation at 15 μM Al or more, but effects on nutrient absorption have not been examined. The variation in nutrient uptake of two chickpea varieties (PBA HatTrick and PBA Striker) and two wild Cicer species (C. echinospermum (C. echi) and C. reticulatum (C. reti)) was determined in low pH (4.2) nutrient solution with increasing Al concentrations (0, 7.5, 15, 30 μM Al). While C. echi, PBA HatTrick and PBA Striker had thicker roots and more lateral roots compared to C. reti, C. reti had greater aluminium tolerance index (AlTI) at 15 and 30 μM Al. The C. echi had higher uptake of root and shoot Al (7.5, 15 and 30 μM Al), P and S (15 and 30 μM Al) while its uptake was marginally lower for Mg, Ca (all Al treatments) and K (15 and 30 μM Al). By contrast, C. reti contained higher shoot Ca concentration at 15 and 30 μM Al and it had lower root Al uptake. Manganese uptake by C. reti roots and shoots were high enough to induce moderate Mn toxicity at 0 and 7.5 μM Al. Therefore, in response to Al toxicity, C. reti maintained greater AlTI and restricted Al uptake while increasing Ca uptake.

MicroRNA-based markers as a tool to monitor the barley (Hordeum vulgare L.) response to soil compaction

Plants are often exposed to adverse environmental conditions that can significantly interfere with their genomic response. Soil compaction induced by heavy field machinery represents a major problem for crop production mainly due to restricted root growth and penetration into soil and therefore reduced water and nutrient uptake by the plants. Tested hypotheses were to declare whether the plant‘s genome responds to soil compaction and whether the microRNA-based markers are suitable to determine this response. A long term field scale experiment was established in 2009 where different levels of soil compaction are researched from the soil and crop point of view. The analyzed barley (Hordeum vulgare L.) plants were collected during the growing season in 2019. The effect of soil compaction was analysed by four different DNA-based markers corresponding to miRNA sequences of dehydratation stress-responsive barley miRNAs (hvu-miR156, and hvu-miR408) and nutrition-sensitive markers (hvu-miR399 and hvu-miR827), within the leaf, stem and root tissues of barley plants. Our preliminary data support hypotheses that plant genome response was tissue-specific due to significant induction of the biomarkers to dehydratation and nutrition stress. The most affected part of the plant by dehydration, were roots and lack of nutrient supply was most pronounced on leaves.

Root and shoot growth in safflower as affected by soil compaction

Soil compaction, induced by no-tillage practices, can negatively impact soil properties important for plant growth. Compacted soils can restrict root growth depth, resulting in reduced crop yield. Although safflower (Carthamus tinctorius) has a deep root system, yield may still be affected by soil compaction. Therefore, this study aimed to evaluate safflower root and shoot growth when submitted to soil compaction in an Oxisol soil under controlled (greenhouse) and field conditions. Five soil bulk density measures were performed in a greenhouse (1.1, 1.2, 1.3, 1.4 and 1.5 Mg m–3). Four compaction levels (established by the number of passes of a farm tractor: 0, 1, 3, and 5 passes consecutively) were performed to evaluate the effect of soil compaction in the field. Root and shoot growth were measured after harvesting the plants. Safflower root growth was reduced when soil compaction increased from 1.1 to 1.5 Mg m–3 under controlled (greenhouse) conditions. In field conditions, we observed a decrease in root length, and fresh and dry matter in roots and shoots of safflower as the soil compaction increased to 5P (1.28 Mg m–3). The results of our study suggest safflower root and shoot growth can be impacted by soil compaction which could affect crop yield.

Redefining the fragipan to improve field recognition and land use relevance

AbstractThe fragipan subsoil horizon can be a significant limitation to land use and management because of its ability to perch water, restrict root growth, and reduce available water storage. Recognition of the presence of a fragipan is used to describe some diagnostic horizons (mollic, umbric, cambic) and to identify the limits of the particle size control section when classifying a soil according to the U.S. soil taxonomic system. While soil scientists often disagree on whether fragipan diagnostic criteria are met, they will typically agree that the horizon has fragic soil properties. To potentially improve field identification agreement, we propose that the fragipan be redefined to meet criteria more like fragic soil properties. We also propose to include some current criteria for the fragipan denoting pedogenesis, slaking, and HCl reaction. In addition, we propose a new requirement be added for redoximorphic features above the fragipan as additional evidence of its restrictive nature. Changing the fragipan's definition will do little to alter soil land use interpretations given most interpretations are based indirectly off the effects of the fragipan. Analysis of existing series indicates that our proposal should not remove series now classified with a fragipan but would eliminate some ambiguities in field identification. Whether the fragipan's spatial extent would increase or decrease is dependent on regional mapping efforts.

Effects of subsoiling depth, period interval and combined tillage practice on soil properties and yield in the Huang-Huai-Hai Plain, China

Compaction layers are widely distributed in the Huang-Huai-Hai Plain, China, which restrict root growth and reduce yields. The adoption of subsoiling has been recommended to disrupt compacted soil layers and create a reasonable soil structure for crop development. In this paper, the effects of subsoiling depth (30, 35 and 40 cm), period interval (2 or 3 years) and combined pre-sowing tillage practice (rotary cultivation or ploughing) on soil condition improvement was studied on a tidal soil in the Huang-Huai-Hai Plain. Seven tillage patterns were designed by combining different subsoiling depths, period intervals and pre-sowing. The evaluation indicators for soil condition improvement were as follows: thickness of the plough layer and hard pan, soil bulk density, cone index, soil three-phase R values, alkali nitrogen content, crop yield, and economic benefits. The results showed that subsoiling can significantly improve the soil structure and physical properties. In all subsoiling treatments, the depth of 35 or 40 cm at a 2-year interval was the most significant. The thickness of the plough layer increased from 13.67 cm before the test to 21.54–23.45 cm in 2018. The thickness of the hard pan decreased from 17.68 cm before the test to 12.09–12.76 cm in 2018, a decrease of about 40.07%. However, the subsoiling combined pre-sowing tillage practice, that is, rotary cultivation or ploughing, was not significant for soil structure and physical properties. For all subsoiling treatments, the soil bulk density, cone index and soil three-phase R values of the 15–25 cm soil layer were significantly lower compared to single rotary cultivation. Subsoiling was observed to increase the soil alkaline nitrogen and water contents. The tillage patterns that had subsoiling at the depth of 35–40 cm at a 2-year interval combined with rotary cultivation had the highest alkali nitrogen and water contents, which increased by 31.08–34.23% compared with that of the single rotary cultivation. Subsoiling can significantly increase the yield both of wheat and corn, as well as the economic benefits. The treatment of subsoiling at the depth of 35 cm at an interval of 2 years combined with rotary cultivation had the highest annual yield and economic benefits. For this treatment, the annual yield and economic benefits increased by 14.55 and 62.87% in 2018, respectively. In conclusion, the tillage patterns that involved subsoiling at a depth of 35 cm at a 2-year interval along with rotary cultivation are suitable for the Huang-Huai-Hai Plain.

The APC/CTE E3 Ubiquitin Ligase Complex Mediates the Antagonistic Regulation of Root Growth and Tillering by ABA and GA.

The antagonistic regulation of seed germination by the phytohormones abscisic acid (ABA) and gibberellic acid (GA) has been well-established. However, how these phytohormones antagonistically regulate root growth and branching (tillering in rice, Oryza sativa) remains obscure. Rice TILLER ENHANCER (TE) encodes an activator of the APC/CTE E3 ubiquitin ligase complex that represses tillering but promotes seed germination. In this study, we identified a dual role of GA and APC/CTE in regulating root growth. High GA levels can activate APC/CTE to promote the degradation of rice SHORT-ROOT1 (OsSHR1, a key factor promoting root growth) in the root meristem (RM) or MONOCULM1 (MOC1, a key factor promoting tillering) in the axillary meristem (AM), leading to restricted root growth and tillering, while low GA levels can activate the role of APC/CTE in stimulating RM cell division to promote root growth. In addition, moderate enhancement of ABA signaling helps maintain the RM and AM size, sustaining root growth and tillering by antagonizing the GA-promoted degradation of OsSHR1 and MOC1 through the SnRK2-APC/CTE regulatory module. We conclude that APC/CTE plays a key role in regulating plant architecture by mediating the crosstalk between ABA and GA signaling pathways.

Penetration Resistance of Laacher See-tephra Andosols—Evaluating Rooting Conditions of Undisturbed and Excavated Forest Soils in SW-Germany

This study discusses penetration resistance (PR) of forested Pumice-Andosol sites. PR, a key soil property influencing root growth and elongation, exerts a substantial influence on ecological site quality and tree growth. Andosols were expected to show low PR because of their unique characteristics (low bulk density, loose soil matrix). Five sites, two undisturbed and three backfilled, were sampled. The latter result from pumice excavation and were examined to quantify potential PR alterations in the aftermath of backfilling and pumice removal. Penetrologger sampling on undisturbed sites showed mean PR not exceeding 3 MPa, a literature-based, critical threshold restricting root growth, in the upper 0.80 m, indicating conditions fostering tree rooting. Backfilled sites mostly exhibited increased (> 3 MPa) PR, leading to rooting restrictions even beginning at −0.21 m. Deviations from undisturbed soils range from −15.6 to +109.3% depending on depth and age of the backfilled site. Furthermore, GIS-based data interpolation helped to identify spatial PR patterns and allowed a direct comparison before/after backfilling at one site. Statistical analysis revealed significantly altered PR after backfilling, while a concluding ANOVA provided at least significant governing factors (depth, area, clay + silt content, soil organic matter), albeit with only small effect sizes.