Lateral Root Branching Research Articles

A nitrogen-responsive cytokinin oxidase/dehydrogenase regulates root response to high ammonium in rice.

Plant root system is significantly influenced by high soil levels of ammonium nitrogen, leading to reduced root elongation and enhanced lateral root branching. In Arabidopsis, these processes have been reported to be mediated by phytohormones and their downstream signaling pathways, while the controlling mechanisms remain elusive in crops. Through a transcriptome analysis of roots subjected to high/low ammonium treatments, we identified a cytokinin oxidase/dehydrogenase encoding gene, CKX3, whose expression is induced by high ammonium. Knocking out CKX3 and its homologue CKX8 results in shorter seminal roots, fewer lateral roots, and reduced sensitivity to high ammonium. Endogenous cytokinin levels are elevated by high ammonium or in ckx3 mutants. Cytokinin application results in shorter seminal roots and fewer lateral roots in wild-type, mimicking the root responses of ckx3 mutants to high ammonium. Furthermore, CKX3 is transcriptionally activated by type-B RR25 and RR26, and ckx3 mutants have reduced auxin content and signaling in roots under low ammonium. This study identified RR25/26-CKX3-cytokinin as a signal module that mediates root responses to external ammonium by modulating of auxin signaling in the root meristem and lateral root primordium. This highlights the critical role of cytokinin metabolism in regulating rice root development in response to ammonium.

USING BLACK WALNUT ROOTSTOCK FOR CREATING HIGH-YIELDING WALNUT PLANTATIONS

The comparative analysis of seed germination and growth of walnut and black walnut seedlings in the conditions of the Right-Bank Forest-Steppe of Ukraine was carried out. It was found that in rows with a sowing depth of 10 cm and 13 cm, the germination rate of walnut had the highest rates and amounted to 70% and 63%, respectively, and black walnut - 80% and 84%. The lowest germination rate was observed at a sowing depth of 17 cm for walnut and 6 cm for black walnut, 46% and 39%, respectively. The influence of the position of the walnut seeds on their germination was determined. In particular, when sown by the "top up" and "on the edge" methods, the germination rate was 70% and 72%, which is 24-26% higher than the "top down" and "side by side" methods. The germination energy of black walnut seedlings was found to be higher than that of walnut seedlings. The first signs of germination of black walnut were observed 7 days earlier than in field crops of walnut. It was found that the main growth of seedlings in height began from the end of the first decade of June and lasted until the first decade of August. The average height of black walnut seedlings was 50 cm, while the average height of walnut seedlings was 19 cm lower and amounted to 31 cm. The yield of standard black walnut seedlings was recorded at 69% of the total number of seedlings, while in walnut this figure was only 12%. The compatibility of the varieties 'Webu-6', 'Chandler' and 'Kazaku' with black walnut and walnut during the cultivation of grafted seedlings was studied. It was found that the selected experimental varieties of walnut, which were grafted onto black walnut seedlings, showed approximately the same formation of callus tissues, except for the variety 'Vebu-6'. This once again confirms the information that not all walnut varieties can participate in interspecific combinations. It was found that the length of the central root of the black walnut at the end of the first year of cultivation is 15 cm longer than the length of the central root of the walnut and averages 43 cm. The main branching of lateral roots in walnut occurs at a depth of 10 to 20 cm. The number of main skeletal roots is generally 3-4 units. At the end of the first year of cultivation, the seedlings had a significantly smaller root system compared to black walnut. The root system of standard black walnut seedlings is on average 60% larger than that of walnut. The main branching of lateral roots is on average at a root length of 7 to 30 cm. Similar to the walnut, the root system of black walnut has 2-3 tiers. The number of skeletal roots averages 8-10 pieces, and the length of the main skeletal roots ranges from 15 to 30 cm. According to the research results, it can be concluded that walnut seedlings grafted on black walnut seedlings have prospects for further introduction into production as they can bear fruit faster, have relatively restrained growth, allow for the formation of a crown at the 3rd year of life and have a more powerful root system.

H2 supplied via ammonia borane stimulates lateral root branching via phytomelatonin signaling.

A reliable and stable hydrogen gas (H2) supply will benefit agricultural laboratory and field trials. Here, we assessed ammonia borane (AB), an efficient hydrogen storage material used in the energy industry, and determined its effect on plant physiology and the corresponding mechanism. Through hydroponics and pot experiments, we discovered that AB increases tomato (Solanum lycopersicum) lateral root (LR) branching and this function depended on the increased endogenous H2 level caused by the sustainable H2 supply. In particular, AB might trigger LR primordia initiation. Transgenic tomato and Arabidopsis (Arabidopsis thaliana) expressing hydrogenase1 (CrHYD1) from Chlamydomonas reinhardtii not only accumulated higher endogenous H2 and phytomelatonin levels but also displayed pronounced LR branching. These endogenous H2 responses achieved by AB or genetic manipulation were sensitive to the pharmacological removal of phytomelatonin, indicating the downstream role of phytomelatonin in endogenous H2 control of LR formation. Consistently, extra H2 supply failed to influence the LR defective phenotypes in phytomelatonin synthetic mutants. Molecular evidence showed that the phytomelatonin-regulated auxin signaling network and cell-cycle regulation were associated with the AB/H2 control of LR branching. Also, AB and melatonin had little effect on LR branching in the presence of auxin synthetic inhibitors. Collectively, our integrated approaches show that supplying H2 via AB increases LR branching via phytomelatonin signaling. This finding might open the way for applying hydrogen storage materials to horticultural production.

A Root Structure Architecture (Rsa) Study On Eggplant (Solanum melongena L.) Inoculated With Arbuscular Mycorrhizal Fungi (AMF) Biofertilizer

Solanum melongena L. is among the most economically valued horticultural crops globally. In the Philippines, the annual production of this staple crop increases continually. However, several biotic and abiotic factors deteriorate its overall growth and productivity. Recently, the use of sustainable biofertilizers such as arbuscular mycorrhizal fungi (AMF) is gaining interest because of their beneficial impacts on overall plant productivity. One way of examining plant productivity is through root structure architecture (RSA) assessment. Hence, this study aimed to investigate the effects of AMF on the RSA of eggplants to supplement valuable data on its beneficial effects as a biofertilizer. Seedlings were inoculated with four treatment conditions AMF + vermicompost (AMF + V), AMF alone (AMF), NPK fertilizer (NPK), and native soil (C) followed by RSA assessment Results showed that treatments AMF + V and AMF alone significantly promoted lateral root branching. Furthermore, the total diameter and surface area showed a significant increase under treatment AMF + V. Overall, the mycorrhizal-root association presented enhancement towards eggplant RSA which strongly establishes the efficacy of AMF as a promising solution in promoting sustainable agriculture.

Link between the aboveground and belowground biomass allocation with growing of Tamarix sp. seedlings in the hinterland of Taklimakan Desert, China.

The morphological characteristics and biomass allocation can reflect plant adaptive strategies to the environment. Tamarix sp. is an excellent shrub species used for windbreaks and fixing sand in the desert of northwest China. The successful establishment of Tamarix sp. seedlings and their growth into mature individuals require their adaptation to various environmental conditions, which is the key to naturally regenerating the Tamarix population. To clarify the root morphological characteristics, leaf structural characters, and biomass allocation of Tamarix sp. seedlings in response to drought conditions, we took the Tamarix sp. seedlings at the Daryaboyi oasis in the hinterland of Taklimakan Desert as the object of study, analyzed rooting depth, root dry weight (RDW), specific root length (SRL), root surface area (RA), specific root area (SRA), leaf area (LA), specific leaf area (SLA) and root: shoot ratio (R:S ratio). The gravimetric soil water content varied from 5.80% to 25.84% in this study area. The taproots of Tamarix sp seedlings with small basal stem diameters were shallower and had few lateral root branches and Tamarix sp. seedlings with large basal stem diameters had more obvious taproots and lateral roots. With the growth of Tamarix sp. seedlings, the taproot deepened, and the values ranged from 4.5 cm to 108.0 cm; the SRL, SRA, and SLA decreased, and the ranges of the values were 28.92-478.79 cm·g-1, 1.07-458.50 cm2·g-1, and 24.48-50.7 cm2·g-1; the RDW, RA, and LA increased, the ranges of the values were 0.16-21.34 g, 3.42-328.04 cm2, and 2.41-694.45 cm2; the more biomass was allocated to the aboveground parts, and the mean R: S ratio was 0.76. In better soil water conditions, the root growth rate decreased as Tamarix sp. seedlings grew, and more biomass was allocated to the aboveground. This further showed that stable surface water is highly significant to the biomass allocation strategy of Tamarix sp. seedlings.

Effect of Low Light Stress on Distribution of Auxin (Indole-3-acetic Acid) between Shoot and Roots and Development of Lateral Roots in Barley Plants.

Depending on their habitat conditions, plants can greatly change the growth rate of their roots. However, the mechanisms of such responses remain insufficiently clear. The influence of a low level of illumination on the content of endogenous auxins, their localization in leaves and transport from shoots to roots were studied and related to the lateral root branching of barley plants. Following two days' reduction in illumination, a 10-fold reduction in the emergence of lateral roots was found. Auxin (IAA, indole-3-acetic acid) content decreased by 84% in roots and by 30% in shoots, and immunolocalization revealed lowered IAA levels in phloem cells of leaf sections. The reduced content of IAA found in the plants under low light suggests an inhibition of production of this hormone under these conditions. At the same time, two-fold downregulation of the LAX3 gene expression, facilitating IAA influx into the cells, was detected in the roots, as well as a decline in auxin diffusion from shoots through the phloem by about 60%. It was suggested that the reduced emergence of lateral roots in barley under a low level of illumination was due to a disturbance of auxin transport through the phloem and down-regulation of the genes responsible for auxin transport in plant roots. The results confirm the importance of the long distance transport of auxins for the control of the growth of roots under conditions of low light. Further study of the mechanisms that control the transport of auxins from shoots to roots in other plant species is required.

Genome-wide alternative polyadenylation dynamics underlying plant growth retardant-induced dwarfing of pomegranate.

Dwarfed stature is a desired agronomic trait for pomegranate (Punica granatum L.), with its advantages such as lower cost and increased yield. A comprehensive understanding of regulatory mechanisms underlying the growth repression would provide a genetic foundation to molecular-assisted dwarfing cultivation of pomegranate. Our previous study induced dwarfed pomegranate seedlings via exogenous application of plant growth retardants (PGRs) and highlighted the important roles of differential expression of plant growth-related genes in eliciting the dwarfed phenotype of pomegranate. Alternative polyadenylation (APA) is an important post-transcriptional mechanism and has been demonstrated to act as a key regulator in plant growth and development. However, no attention has been paid to the role of APA in PGR-induced dwarfing in pomegranate. In this study, we characterized and compared APA-mediated regulation events underlying PGR-induced treatments and normal growth condition. Genome-wide alterations in the usage of poly(A) sites were elicited by PGR treatments, and these changes were involved in modulating the growth and development of pomegranate seedlings. Importantly, ample specificities were observed in APA dynamics among the different PGR treatments, which mirrors their distinct nature. Despite the asynchrony between APA events and differential gene expression, APA was found to regulate transcriptome via influencing microRNA (miRNA)-mediated mRNA cleavage or translation inhibition. A global preference for lengthening of 3' untranslated regions (3' UTRs) was observed under PGR treatments, which was likely to host more miRNA target sites in 3' UTRs and thus suppress the expression of the corresponding genes, especially those associated with developmental growth, lateral root branching, and maintenance of shoot apical meristem. Together, these results highlighted the key role of APA-mediated regulations in fine-tuning the PGR-induced dwarfed stature of pomegranate, which provides new insights into the genetic basis underlying the growth and development of pomegranate.

Large root cortical cells and reduced cortical cell files improve growth under suboptimal nitrogen in silico.

Suboptimal nitrogen availability is a primary constraint to plant growth. We used OpenSimRoot, a functional-structural plant/soil model, to test the hypothesis that larger root cortical cell size (CCS), reduced cortical cell file number (CCFN), and their interactions with root cortical aerenchyma (RCA) and lateral root branching density (LRBD) are useful adaptations to suboptimal soil nitrogen availability in maize (Zea mays). Reduced CCFN increased shoot dry weight over 80%. Reduced respiration, reduced nitrogen content, and reduced root diameter accounted for 23%, 20%, and 33% of increased shoot biomass, respectively. Large CCS increased shoot biomass by 24% compared with small CCS. When simulated independently, reduced respiration and reduced nutrient content increased the shoot biomass by 14% and 3%, respectively. However, increased root diameter resulting from large CCS decreased shoot biomass by 4% due to an increase in root metabolic cost. Under moderate N stress, integrated phenotypes with reduced CCFN, large CCS, and high RCA improved shoot biomass in silt loam and loamy sand soils. In contrast, integrated phenotypes composed of reduced CCFN, large CCS, and reduced LRBD had the greatest growth in silt loam, while phenotypes with reduced CCFN, large CCS, and high LRBD were the best performers in loamy sands. Our results support the hypothesis that larger CCS, reduced CCFN, and their interactions with RCA and LRBD could increase nitrogen acquisition by reducing root respiration and root nutrient demand. Phene synergisms may exist between CCS, CCFN, and LRBD. CCS and CCFN merit consideration for breeding cereal crops with improved nitrogen acquisition, which is critical for global food security.

Lateral root branching: evolutionary innovations and mechanistic divergence in land plants.

The root system architecture in plants is a result of multiple evolutionary innovations over time in response to changing environmental cues. Dichotomy and endogenous lateral branching in the roots evolved in lycophytes lineage but extant seed plants use lateral branching instead. This has led to the development of complex and adaptive root systems, with lateral roots playing a key role in this process exhibiting conserved and divergent features in different plant species. The study of lateral root branching in diverse plant species can shed light on the orderly yet distinct nature of postembryonic organogenesis in plants. This insight provides an overview of the diversity in lateral root (LR) development in various plant species during the evolution of root system in plants.

Specification and evolution of lateral roots

Plants have evolved a remarkable capacity to develop new organs post-embryonically throughout their lifespan. A prime example of this is root branching. Root branching occurs in two ways: dichotomous and lateral branching. The dichotomous branching is the result of the division of the root apical meristem into two daughter meristems, likely through symmetric cell divisions of the root apical cell, as has recently been illustrated in the extant lycophyte Selaginella moellendorffii (Figure 1). Lateral root branching relies on the de novo specification of a subset of founder cells (hereinafter referred to as lateral root stem cells) located in the internal tissues of an existing root. This step is followed by initiation, in which the specified cells re-enter the cell cycle, and subsequently by primordium formation and emergence. In this primer, we summarize recent advances describing the molecular bases underlying lateral root stem cell specification in angiosperms and highlight the important positional signals that fine tune this process. By delving into the evolutionary origins of root branching, we point out that positional control of lateral root stem cell specification has not been the prevailing mechanism among all plants and discuss the process in ferns (i.e., a sister group of seed plants), where it seems to be under the control of lineage-dependent mechanisms.

Root ABA Accumulation Delays Lateral Root Emergence in Osmotically Stressed Barley Plants by Decreasing Root Primordial IAA Accumulation

Increased auxin levels in root primordia are important in controlling root branching, while their interaction with abscisic acid (ABA) likely regulates lateral root development in water-deficient plants. The role of ABA accumulation in regulating root branching was investigated using immunolocalization to detect auxin (indoleacetic acid, IAA) and ABA (abscisic acid) in root primordia of the ABA-deficient barley mutant Az34 and its parental genotype (cv. Steptoe) barley plants. Osmotic stress strongly inhibited lateral root branching in Steptoe plants, but hardly affected Az34. Root primordial cells of Steptoe plants had increased immunostaining for ABA but diminished staining for IAA. ABA did not accumulate in root primordia of the Az34, and IAA levels and distribution were unaltered. Treating Az34 plants with exogenous ABA decreased root IAA concentration, while increasing root primordial ABA accumulation and decreasing root primordial IAA concentration. Although ABA treatment of Az34 plants increased the root primordial number, it decreased the number of visible emerged lateral roots. These effects were qualitatively similar to that of osmotic stress on the number of lateral root primordia and emerged lateral roots in Steptoe. Thus ABA accumulation (and its crosstalk with auxin) in root primordia seems important in regulating lateral root branching in response to water stress.

Maize Breeding for Low Nitrogen Inputs in Agriculture: Mechanisms Underlying the Tolerance to the Abiotic Stress

Nitrogen (N) is essential for sustaining life on Earth and plays a vital role in plant growth and thus agricultural production. The excessive use of N fertilizers not only harms the economy, but also the environment. In the context of the environmental impacts caused by agriculture, global maize improvement programs aim to develop cultivars with high N-use efficiency (NUE) to reduce the use of N fertilizers. Since N is highly mobile in plants, NUE is related to numerous little-known morphophysiological and molecular mechanisms. In this review paper we present an overview of the morpho-physiological adaptations of shoot and root, molecular mechanisms involved in plant response to low nitrogen environment, and the genetic effects involved in the control of key traits for NUE. Some studies show that the efficiency of cultivars growing under low N is related to deep root architecture, more lateral roots (LR), and sparser branching of LR, resulting in lower metabolic costs. The NUE cultivars also exhibit more efficient photosynthesis, which affects plant growth under suboptimal nitrogen conditions. In this sense, obtaining superior genotypes for NUE can be achieved with the exploitation of heterosis, as non-additive effects are more important in the expression of traits associated with NUE.

Responses of rubber tree seedlings (Hevea brasiliensis) to phosphorus deficient soils

ABSTRACT While the adaptation and responses of model plants to phosphorus (P) deficiency are well documented, those of the rubber tree remain unclear. Here, we investigated above‐ and below‐ground responses of rubber tree seedlings over the development of the first to third extension unit in a mesocosm system. Rubber tree seedlings were grown in high and low phosphorus soil for 7 months. Tissue nutrient contents, morphological, and physiological traits were quantified. We found that low P significantly reduced leaf P content, photosynthetic capabilities, and induced the accumulation of phenolic and flavonoid compounds, particularly in old leaves. Root traits were significantly affected by P stress early in their development. Root surface area and volume were increased through reduced lateral root branching and increased lateral root length. The alteration of root architectural traits took place prior to the reduction of P content in roots and leaves. Our findings provide new insights into rubber tree physiology and the effective fertilization management of rubber plantation in low P soils.

Characteristics of the Forest Clove Plant Organ (Syzygium obtusifolium L) Endemic Maluku, Indonesia

Forest clove (Syzygium obtusifolium L.) has not been widely known for its properties and characteristics. To recognize them properly, deeply, and thoroughly, efforts are required to characterize the morphological characteristics of the main organs. The research aims to reveal the morphological characteristics of the main organ (cormus) of the forest clove plant, which include roots, stems, and leaves. The research was conducted on the island of Ambon, Maluku, Eastern Indonesia, for five months from May-September 2020. This research is survey research, data collection using a questionnaire arranged according to IPGRI criteria. The list of questions was filled indirectly to the field. The results showed that the root system of the forest clove plant was a taproot consisting of primary roots followed by lateral roots (primary root branches), secondary, tertiary, and quartet-like roots which were then overgrown with root hairs. Lateral root branches are large, and in subsequent root branches, the size is smaller but in increasing numbers. The trunk is round, with a diameter ranging from 12.5-25.5 cm, the surface of the trunk is rough brown and grayish, accompanied by black spots. The branching pattern is intensive with the main branching angles included in the medium category, meaning that the angles formed with the main rods range from 45-90o. The leaves of the forest clove plant are oblong with a length ranging from 15-25.5 cm and a width of 5.5-9.5 cm. The correction factor to determine leaf area is 0.65, therefore the leaf area ranges from 53.63 to 157.46 cm2. The shape of the base of the leaf is tapered, the angle of the petiole is sharp (<45o). The nature of the tips of the leaves is rather hard, the texture of the leaves is strong, the edges are flat, and the color of the leaves is dark green (green 139 A).

Hydraulic flux-responsive hormone redistribution determines root branching.

Plant roots exhibit plasticity in their branching patterns to forage efficiently for heterogeneously distributed resources, such as soil water. The xerobranching response represses lateral root formation when roots lose contact with water. Here, we show that xerobranching is regulated by radial movement of the phloem-derived hormone abscisic acid, which disrupts intercellular communication between inner and outer cell layers through plasmodesmata. Closure of these intercellular pores disrupts the inward movement of the hormone signal auxin, blocking lateral root branching. Once root tips regain contact with moisture, the abscisic acid response rapidly attenuates. Our study reveals how roots adapt their branching pattern to heterogeneous soil water conditions by linking changes in hydraulic flux with dynamic hormone redistribution.

In silico evidence for the utility of parsimonious root phenotypes for improved vegetative growth and carbon sequestration under drought.

Drought is a primary constraint to crop yields and climate change is expected to increase the frequency and severity of drought stress in the future. It has been hypothesized that crops can be made more resistant to drought and better able to sequester atmospheric carbon in the soil by selecting appropriate root phenotypes. We introduce OpenSimRoot_v2, an upgraded version of the functional-structural plant/soil model OpenSimRoot, and use it to test the utility of a maize root phenotype with fewer and steeper axial roots, reduced lateral root branching density, and more aerenchyma formation (i.e. the 'Steep, Cheap, and Deep' (SCD) ideotype) and different combinations of underlying SCD root phene states under rainfed and drought conditions in three distinct maize growing pedoclimatic environments in the USA, Nigeria, and Mexico. In all environments where plants are subjected to drought stress the SCD ideotype as well as several intermediate phenotypes lead to greater shoot biomass after 42 days. As an additional advantage, the amount of carbon deposited below 50cm in the soil is twice as great for the SCD phenotype as for the reference phenotype in 5 out of 6 simulated environments. We conclude that crop growth and deep soil carbon deposition can be improved by breeding maize plants with fewer axial roots, reduced lateral root branching density, and more aerenchyma formation.

Особенности формирования корневой системы Crambe tataria Sebeόk в Западном Казахстане

The morphology of root systems is paramount for a scientifically sound strategy for the conservation of rare and endangered plants. The morphology of the root system of Crambe tataria Sebeók, a rare and endangered plant listed in the Red Book of Kazakhstan, growing on the chalk hills of the Poduralsky Plateau in the valley of the Uilriver, was studied. Root systems were studied by the method of I.O. Baitulin separately for each age condition. At the first stages of its development, the root system develops ahead of time. In the immature state, a long rod-like low-branched root is formed, reaching 40 cm deep. In the virginal state, the roots reach a depth of 100–150 cm, have a diameter at the base of the socket 2–2.5(3) cm. According to the classification of root systems in adults, the root system is ombrophytic, it does not reach the groundwater level. The depth of penetration into the ground is average (up to 4 m). The spread of lateral roots is drooping or semi-drooping — the roots are directed downward at an angle of 45°. According to the density of branching of lateral roots (the ratio of the number of lateral roots of the first order to the length of the main root (pcs/cm) is rare (0.1–0.5 pcs/cm) or weak 0.2–1.0 pcs/cm), the root system is rare and weakly branching.

Cellular and gene expression patterns associated with root bifurcation in Selaginella.

The roots of lycophytes branch through dichotomy or bifurcation, during which the root apex splits into two daughter roots. This is morphologically distinct from lateral root (LR) branching in the extant euphyllophytes, with LRs developing along the root axis at different distances from the apex. Although the process of root bifurcation is poorly understood, such knowledge can be important, because it may represent an evolutionarily ancient strategy that roots recruited to form new stem cells or meristems. In this study, we examined root bifurcation in the lycophyte Selaginella moellendorffii. We characterized an in vitro developmental time frame based on repetitive apex bifurcations, allowing us to sample different stages of dichotomous root branching and analyze the root meristem and root branching in S. moellendorffii at the microscopic and transcriptomic level. Our results showed that, in contrast to previous assumptions, initial cells (ICs) in the root meristem are mostly not tetrahedral but rather show an irregular shape. Tracking down the early stages of root branching argues for the occurrence of a symmetric division of the single IC, resulting in two apical stem cells that initiate root meristem bifurcation. Moreover, we generated a S. moellendorffii root branching transcriptome that resulted in the delineation of a subset of core meristem genes. The occurrence of multiple putative orthologs of meristem genes in this dataset suggests the presence of conserved pathways in the control of meristem and root stem cell establishment or maintenance.

Effects of strontium on the morphological and photosynthetic physiological characteristics of Vicia faba seedlings

The adaptation of plants to strontium (Sr) stress requires a more systematic understanding. In the present study, the morphological and photosynthetic physiological characteristics of Vicia faba seedlings under Sr stress (88Sr, 0–1,000 mg·L−1) were analyzed in solution culture. The results showed that Sr treatment decreased the biomass and root activity of V. faba seedlings significantly, but fortunately, there was almost no root necrosis. In plant morphology, the taproot length, lateral root number, plant height, branching number and internodes number of V. faba were significantly inhibited, thus the apical dominance of taproot and terminal bud was more obvious. The accumulation of Sr resulted in the decrease of leaf area, dry weight, stomatal density and stomatal aperture, while the guard cell length increased, and the specific leaf weight (SLW) increased first and then decreased. These changes in stomatal morphology may be a positive regulation to reduce water loss. In addition, V. faba increased the non-photochemical quenching (NPQ) and the activities of peroxidase (POD) and ascorbate peroxidase (APX) to protect the photosynthetic structure. Low concentration of Sr (250 mg·L−1) promoted the photochemical efficiency and electron transfer of PSII (e.g., increased F v/F m, Φ PSII, qP and ETR). However, Sr (250–1,000 mg·L−1) inhibited the net photosynthetic rate (P n), transpiration rate (T r) and stomatal conductance (G s) in leaves. In general, the P n was affected by both stomatal and non-stomatal factors. Since Sr did not cause significant damage to the PSII function, the non-stomatal factor may be the dark reaction in photosynthesis affected, but this needs to be proved by further studies.

Maize varieties and their root trait variation mediate the development of rhizosphere arthropod diversity

While ecological roles of rhizosphere arthropods are well documented, little is known about the relationship between the development of plant roots and soil arthropod communities in agroecosystems. In this study, we investigated the effects of maize varieties and their root traits on the diversity and community composition of soil arthropods over time. Soil arthropods and root traits were evaluated before planting and at 30 and 60 days after planting in four maize varieties with different root growth angles and lateral root branching. Arthropod diversity declined from day 0 to 30 but recovered by day 60 with the development of maize roots. Two maize varieties (Nei 542018 and Nei 542022) exhibited lower brace and crown root angles, and arthropod taxon richness was greater in these two varieties than in others. The highest abundance of detritivores and predators was found in one of the maize varieties (Nei 542018) which, in addition to lower root angle, attained greater root diameter and lateral root branching and length. Redundancy analysis indicated that soil arthropod composition was correlated with crown root angle. Our findings highlight the importance of root traits, especially the angle of the roots, to enhance arthropod biodiversity in the rhizosphere ecosystem.