Total Root Surface Area Research Articles

Morphological and physiological response of rice roots to the application of calcium polyamino acid under saline-alkali soil conditions

ABSTRACT Although application of calcium polyamino acid (Ca-polyAA) is one of the effective ways to improve saline-alkali soil and promote plant growth, the clear mechanisms are unknown. A two-year field experiment with four Ca-polyAA application treatments (added at rates of 0, 7.5, 15.0, and 22.5 × 103 kg ha−1) was conducted on saline-alkali soil in Songnen Plain of China. In the first year (2016), Ca-polyAA increased soil porosity and decreased pH, electrical conductivity (EC1:5) and exchangeable sodium percentage (ESP). Root Na+/K+ and Na+/Ca2+ ratio were reduced whereas hydraulic conductivity was increased. The hormone concentration and enzyme activity in the root were enhanced at tillering stage. Root structure development at the root tip was promoted after the application of Ca-polyAA. The total root length, surface area, volume and biomass were increased by increasing Ca-polyAA added rate. Similar results were obtained in the second year (2017). Path analysis demonstrate that Ca-polyAA can promote the accumulation of root biomass mainly by decreasing Na+/ K+ ratio, increasing root hydraulic conductivity and the activity of carbon metabolism enzymes, and the development of the root cortex. These results revealed that Ca-polyAA, as an efficient ameliorator, is capable to enhance agronomical and morphophysiological traits of rice in saline-alkali soil.

The Comprehensive Effects of Rhizophagus intraradices and P on Root System Architecture and P Transportation in Citrus limon L.

Both arbuscular mycorrhizal fungi (AMF) and phosphorus (P) collectively influence the root system architecture (RSA), but whether the combination of the two affects RSA, particularly lateral root formation, is unknown. In the present study, a pot experiment was conducted to evaluate the effects of an arbuscular mycorrhizal fungus (Rhizophagus intraradices) on the RSA of lemon (Citrus limon L.) seedlings under 0 (P0) and 50 mg/kg (P50) P levels. Moreover, P and carbohydrate content; acid phosphatase activity; and the expression of P transporter genes (PTs), phosphatase genes (PAPs), and lateral-root-related genes; were determined. Our results show that root mycorrhizal colonization and mycorrhizal dependency of lemon plants are significantly higher under P0 than under P50 conditions. AMF significantly promoted the plant growth performance of lemon, irrespective of substrate P levels. The RSA parameters of AMF plants, including total root length, projected area, surface area, average diameter, volume, and second- and third-order lateral root numbers, were distinctly increased under the two P levels compared to those of non-AMF plants. Mycorrhizal treatment also induced higher carbohydrate (sucrose, glucose, and fructose) and P contents, along with a higher activity of root acid phosphatase. The expression of P-related genes, including ClPAP1, ClPT1, ClPT3, ClPT5, and ClPT7, as well as the expression of lateral-root-related genes (ClKRP6, ClPSK6, and ClRSI-1), was dramatically upregulated by AMF inoculation, irrespective of substrate P levels. Principal component analysis showed that root P and carbohydrate contents, as well as the expression of ClKRP6 and ClPSK6, were positively correlated with RSA traits and lateral root development. Our study demonstrates that mycorrhizas accelerate the P acquisition and carbohydrate accumulation of lemon plants by upregulating the expression of lateral-root-related genes, thereby positively improving the RSA. Furthermore, AMF had a greater impact on the RSA of lemon than substrate P levels.

Complex effects of different types of acid rain on root growth of Quercus acutissima and Cunninghamia lanceolata saplings

BackgroundSoil acidification caused by acid rain (AR) can damage plant roots, which in turn negatively impacts plant health. In response to changing AR types, research efforts to elucidate their specific impacts on plants have become intense.MethodsFor this study, we investigated the effects of simulated sulfuric, nitric, and mixed AR on the root systems of Quercus acutissima Carr. and Cunninghamia lanceolata (Lamb.) Hook. under different acidity levels.ResultsAs the AR S/N ratio and pH decreased, the height growth rate (HGR), basal diameter growth rate (DGR), total root length (TRL) and total root surface area (TRS) of C. lanceolata decreased, whereas the TRL and TRS of Q. acutissima remained the same. When the NO3− concentration in AR was increased, the root activity, superoxide dismutase (SOD) and catalase (CAT) activities of C. lanceolata roots revealed a downward trend; however, the root activity of Q. acutissima and the peroxidase (POD) activity of C. lanceolata roots revealed an upward trend. Further, redundant analysis and structural equation models indicated that AR pH had a greater impact on the HGR of Q. acutissima than that of C. lanceolata, while the impact of the AR S/N ratio on C. lanceolata growth rates was greater than that of Q. acutissima.ConclusionsOur results suggested that the root systems of different tree species had variable responses to AR, and the AR S/N ratio was an important factor affecting plant root growth. This might facilitate new strategies for the cultivation and protection of plantations in the future.

The Effects of Fertilizers on Rabbiteye Blueberry (Vaccinium ashei Reade.) Root Distribution and Fruit Yield

The root system plays an important role in the growth and development of blueberry. The aim of this study was to assess the impacts of different fertilizers on the root growth and root–yield relationship of blueberry to provide insight into the regulation of root growth and fruit yield by fertilizing from the perspective of the root system. Rabbiteye blueberry variety ‘Britewell’ as the test material, and six fertilizers, including BF, OR, CF, SF, HF, and RT were used in single-factor fertilization experiments to analyze the effects of different fertilizer treatments on the root morphology, root distribution, and fruit yield of blueberry. Fertilization overall increased the root length density and root surface area in most soil layers, and the RT treatment significantly increased the total root length density and total root surface area 98.6% and 98.5%, respectively, compared with a control lacking fertilizer. In addition, the effect of fertilization on the blueberry root system was mainly observed in the 0–20 cm layer. Fruit yield was positively correlated with total root length density and total root surface area, and negatively correlated with average root diameter. In summary, the SF and RT treatments increased the morphological indexes of the root system, particularly in the shallow soil layers, leading to an increase in blueberry fruit yield.

Root Phenotyping of Peptide-Treated Glycine max

Plant elicitor peptides (Peps) – endogenous chains of amino acids involved in natural plant defense – have been shown to decrease damage from herbivores and pathogens by inducing an immune response, increasing the emission of volatile organic compounds (VOCS), transcripts, and metabolites. Exogenous treatment of soybean seeds with plant elicitor peptide GmPep3 has been shown to induce these broad-spectrum defenses and offers a new method for increasing crop yield. However, the effects of GmPep3 on indicators of soybean health – root characteristics, growth stages, etc. – have not been fully realized. Using the root-phenotyping platform RhizoVision Explorer, several root traits of soybean plants treated with GmPep3 were analyzed to determine whether there was a statistically significant difference between the roots of plants treated with peptide and without peptide. These root traits included total number of root tips, total root length (mm), and surface area (mm2). Results indicate that there did not appear to be a statistically significant difference in the number of root tips between plants treated with GmPep3 and those not treated with GmPep3. There were, however, observed differences in total root length and surface area between treated and untreated seeds during one repetition of the experiment. However, these differences were no longer statistically significant by the end of the experimental period, indicating that although plant growth was initially impacted by the addition of the peptide treatment, these effects were no longer present by the end of the growing period.

Relative contribution of different members of OsDREB gene family to osmotic stress tolerance in indica and japonica ecotypes of rice.

Drought/osmotic stress is the single largest production constraint in rain-fed rice cultivation. Different members of the DREB gene family are known to contribute to osmotic stress tolerance. In this study, an attempt was made to understand their relative contribution towards osmotic stress tolerance in indica and japonica ecotypes of rice. Two genotypes (one tolerant and one susceptible) from each ecotype were grown hydroponically, and 21-day-old seedlings were subjected to polyethylene glycol-induced osmotic stress (15% PEG-6000, equivalent to -3.0 bars osmotic potential). The tolerant genotypes CR143 and Moroberekan were found to have superior root traits (total root length, surface area and volume), better plant water status and increased total dry biomass as compared to their susceptible counterparts after 10 days of osmotic stress. Different members of the DREB gene family were differentially induced in response to osmotic shock (1 h after stress) and osmotic stress (24 h after stress), which also differed between the two rice ecotypes. From the gene expression profiles of 10 DREB genes (both DREB1 and DREB2 families), in indica two DREB genes, DREB1B and DREB1G, were significantly correlated with stress tolerance indices, whereas in japonica significant correlations with five DREB genes (DREB1A, DREB1B, DREB1D, DREB1E and DREB2B) were observed. We found that only one member, i.e. DREB1B, showed a significant correlation with drought tolerance indices in both indica and japonica ecotypes. This study provides an overview of the relative contribution of different members of the DREB gene family and their association with drought/osmotic stress tolerance in rice.

Interaction Effects of Nitrogen Rates and Forms Combined With and Without Zinc Supply on Plant Growth and Nutrient Uptake in Maize Seedlings.

Previous studies have shown that zinc (Zn) accumulation in shoot and grain increased as applied nitrogen (N) rate increased only when Zn supply was not limiting, suggesting a synergistic effect of N on plant Zn accumulation. However, little information is available about the effects of different mineral N sources combined with the presence or absence of Zn on the growth of both shoot and root and nutrient uptake. Maize plants were grown under sand-cultured conditions at three N forms as follows: NO3– nutrition alone, mixture of NO3–/NH4+ with molar ratio of 1:1 (recorded as mixed-N), and NH4+ nutrition alone including zero N supply as the control. These treatments were applied together without or with Zn supply. Results showed that N forms, Zn supply, and their interactions exerted a significant effect on the growth of maize seedlings. Under Zn-sufficient conditions, the dry weight (DW) of shoot, root, and whole plant tended to increase in the order of NH4+ < NO3– < mixed-N nutrition. Compared with NH4+ nutrition alone, mixed-N supply resulted in a 27.4 and 28.1% increase in leaf photosynthetic rate and stomatal conductance, which further resulted in 35.7 and 33.5% of increase in shoot carbon (C) accumulation and shoot DW, respectively. Furthermore, mixed-N supply resulted in a 19.7% of higher shoot C/N ratio vs. NH4+ nutrition alone, which means a higher shoot biomass accumulation, because of a significant positive correlation between shoot C/N ratio and shoot DW (R2 = 0.682***). Additionally, mixed-N supply promoted the greatest root DW, total root length, and total root surface area and synchronously improved the root absorption capacity of N, iron, copper, manganese, magnesium, and calcium. However, the above nutrient uptake and the growth of maize seedlings supplied with NH4+ were superior to either NO3– or mixed-N nutrition under Zn-deficient conditions. These results suggested that combined applications of mixed-N nutrition and Zn fertilizer can maximize plant growth. This information may be useful for enabling integrated N management of Zn-deficient and Zn-sufficient soils and increasing plant and grain production in the future.

The Optimal Concentration of KH2PO4 Enhances Nutrient Uptake and Flower Production in Rose Plants via Enhanced Root Growth

Monopotassium phosphate is a widely used phosphorus and potassium fertiliser for ornamental plants, but it is not known what concentration will result in optimal flower production, root growth and nutrient uptake of rose plants. We compared potted rose plants fertilised with six different concentrations (0.0 as a water-only control, 1.0, 2.0, 3.0, 4.0 and 5.0 g·L−1) of an aqueous monopotassium phosphate solution as a combination of foliar and soil applications over two consecutive flowering cycles. Rose growth, flower production and nutrient accumulation responded differently to fertilisation with different concentrations of monopotassium phosphate. During the first flowering cycle, shoot and root dry weight, leaf chlorophyll content, flower diameter, total root length and surface area, and total fine root length significantly increased in response to increased monopotassium phosphate concentrations from 0.0 to 3.0 g·L−1 but decreased in response to fertilisation with 4.0 or 5.0 g·L−1 monopotassium phosphate. Similar trends were observed in shoot dry weight, leaf chlorophyll content, flower diameter and number, phosphorus and potassium accumulation during the second flowering cycle. According to quadratic equations derived from both flowering cycles, the optimal concentration of monopotassium phosphate, based on flower diameter and dry weight, as well as total phosphorus and potassium accumulation, was 2.6–3.0 g·L−1. Furthermore, total root length was significantly correlated with flower diameter, flower dry weight, and total phosphorus and potassium accumulation (p &lt; 0.05). These results indicated that fertilisation with optimal concentrations of monopotassium phosphate can increase rose growth, flower productivity and nutrient uptake through enhanced root growth.

Root Trait Variation in Lentil (Lens culinaris Medikus) Germplasm under Drought Stress.

Drought is the most critical environmental factor across the continents affecting food security. Roots are the prime organs for water and nutrient uptake. Fine tuning between water uptake, efficient use and loss determines the genotypic response to water limitations. Targeted breeding for root system architecture needs to be explored to improve water use efficiency in legumes. Hence, the present study was designed to explore root system architecture in lentil germplasm in response to drought. A set of 119 lentil (Lens culinaris Medik.) genotypes was screened in controlled conditions to assess the variability in root traits in relation to drought tolerance at seedling stage. We reported significant variation for different root traits in lentil germplasm. Total root length, surface area, root volume and root diameter were correlated to the survival and growth under drought. Among the studied genotypes, the stress tolerance index varied 0.19–1.0 for survival and 0.09–0.90 for biomass. Based on seedling survival and biomass under control and drought conditions, 11 drought tolerant genotypes were identified, which may be investigated further at a physiological and molecular level for the identification of the genes involved in drought tolerance. Identified lines may also be utilised in a lentil breeding program.

Deciphering the change in root system architectural traits under limiting and non-limiting phosphorus in Indian bread wheat germplasm.

The root system architectures (RSAs) largely decide the phosphorus use efficiency (PUE) of plants by influencing the phosphorus uptake. Very limited information is available on wheat's RSAs and their deciding factors affecting phosphorus uptake efficiency (PupE) due to difficulties in adopting scoring values used for evaluating root traits. Based on our earlier research experience on nitrogen uptake efficiency screening under, hydroponics and soil-filled pot conditions, a comprehensive study on 182 Indian bread wheat genotypes was carried out under hydroponics with limited P (LP) and non-limiting P (NLP) conditions. The findings revealed a significant genetic variation, root traits correlation, and moderate to high heritability for RSAs traits namely primary root length (PRL), total root length (TRL), total root surface area (TSA), root average diameter (RAD), total root volume (TRV), total root tips (TRT) and total root forks (TRF). In LP, the expressions of TRL, TRV, TSA, TRT and TRF were enhanced while PRL and RAD were diminished. An almost similar pattern of correlations among the RSAs was also observed in both conditions except for RAD. RAD exhibited significant negative correlations with PRL, TRL, TSA, TRT and TRF under LP (r = -0.45, r = -0.35, r = -0.16, r = -0.30, and r = -0.28 respectively). The subclass of TRL, TSA, TRV and TRT representing the 0-0.5 mm diameter had a higher root distribution percentage in LP than NLP. Comparatively wide range of H' value i.e. 0.43 to 0.97 in LP than NLP indicates that expression pattern of these traits are highly influenced by the level of P. In which, RAD (0.43) expression was reduced in LP, and expressions of TRF (0.91) and TSA (0.97) were significantly enhanced. The principal component analysis for grouping of traits and genotypes over LP and NLP revealed a high PC1 score indicating the presence of non-crossover interactions. Based on the comprehensive P response index value (CPRI value), the top five highly P efficient wheat genotypes namely BW 181, BW 103, BW 104, BW 143 and BW 66, were identified. Considering the future need for developing resource-efficient wheat varieties, these genotypes would serve as valuable genetic sources for improving P efficiency in wheat cultivars. This set of genotypes would also help in understanding the genetic architecture of a complex trait like P use efficiency.

Effects of different interstocks on the growth, yield, and fruit quality of Hanfu apple

A field experiment was conducted using Hanfu apple grafted on 10 dwarfing interstocks to evaluate plant growth, yield, and fruit quality of different apple-interstock combinations in Hulu-dao, Liaoning Province, in order to select the most suitable apple-interstock combinations in the study area. The results showed that tree vigor, yield, and fruit quality were largely affected by the interstocks. Among the interstocks evaluated here, plant height, branch numbers, leaf fresh weight, branch fresh weight, root fresh weight, total root volume, average root diameter and total root tip numbers were the largest on GM256, while the highest trunk diameter, branch length, total root length and total root surface area were observed on CX5, the highest fruit firmness, soluble solids and soluble sugar contents were observed on M26, and the highest fruit vertical diameter, transverse diameter and single fruit weight were observed on GM256. The fuzzy evaluation results showed that the comprehensive character scores decreased in order of GM256, CX5, B9, JM7, CG80, Liaozhen 2, M26, Qingzhen 3, SH38 and MD001. Our results indicated that interstock GM256 and CX5 was better for the cold climate region.

Greater morphological and primary metabolic adaptations in roots contribute to phosphate-deficiency tolerance in the bread wheat cultivar Kenong199

BackgroundPhosphate (Pi) deficiency severely affects crop growth and productivity, including wheat, therefore it is necessary to develop cultivars with enhanced Pi-deficiency tolerance. However, the underlying mechanism of Pi-deficiency tolerance in wheat is still elusive. Two contrasting wheat cultivars, low-Pi tolerant Kenong199 (KN199) and low-Pi sensitive Chinese Spring (CS) were used to reveal adaptations in response to Pi deficiency at the morphological, physiological, metabolic, and molecular levels.ResultsKN199 was more tolerant to Pi deficiency than CS with significantly increased root biomass and R/S ratio. Root traits, the total root length, total root surface area, and total root volume, were remarkably enhanced by Pi deficiency in KN199. The shoot total P and soluble Pi concentrations of KN199 were significantly higher than those of CS, but not in roots. In KN199, high Pi level in shoots is a higher priority than that in roots under Pi deficiency. It was probably due to differentially regulation in the miR399-mediated signaling network between the shoots of the two cultivars. The Pi deficiency-induced root architecture adaptation in KN199 was attributed to the regulation of the hormone-mediated signaling (ethylene, gibberellin, and jasmonates). The expression of genes associated with root development and Pi uptake was enhanced in KN199. Some primary metabolites (amino acids and organic acids) were significantly accumulated in roots of KN199 under Pi deficiency.ConclusionsThe low-Pi tolerant wheat cultivar KN199 possessed greater morphological and primary metabolic adaptations in roots than CS under Pi deficiency. The adaption and the underlying molecular mechanisms in wheat provide a better understanding of the Pi-deficiency tolerance and the strategies for improving Pi efficiency in wheat.

Functional root trait‐based classification of cover crops to improve soil physical properties

AbstractCover crop use is a well‐established soil conservation technique and has been proven effective for erosion control and soil remediation in many arable systems. Whereas the obvious protection mechanism of cover crops occurs through the canopy, plant roots perform multiple functions. It is important to consider the soil functions delivered by different root systems in order to increase the uptake of cover crops for sustainable soil and water management. A classification of cover crop root systems up to 0.6 m deep based on functional traits will allow us to better study their potential role in soil bio‐engineering, soil structural improvements for hydrological services and soil resource protection. This was a glasshouse experiment, using large 1‐m3 containers filled with loam soil, loose topsoil and compacted subsoil, in which seven cover crop species (oat, rye, buckwheat, vetch, radish, mustard, phacelia) were grown for 90 days. Root cores were taken at the end of the experiment, washed and imaged to determine root traits (total root length density, average root diameter, root specific length and root surface area) for both the topsoil and subsoil layers. Root identity was determined from a distinctive combination of single root traits and related to three soil functional variables, representing soil structural improvement, runoff mitigation and erosion control. The results showed that total root length and root surface area correlate well with aggregate stability and soil macroporosity. Buckwheat, mustard and rye had significantly greater aggregate stability, as well as 10, 8 and 7% greater microporosity, respectively, at the interface with the compacted layer when compared to the control bare soil. Furthermore, average root diameter negatively correlated with soil macroporosity, indicating that cover crops with a fine root system are more beneficial for creating pore‐space than those with thicker taproots. Selecting cover crop species with the right root traits is therefore crucial to improve soil health.Highlights Roots of cover crops are a largely unexplored frontier for bio‐engineering of agricultural soils. Combinations of root traits were identified that most improve soil characteristics. Cover crops with finer root systems were better at enhancing porosity. Root length and surface area were most important for enhancing soil structure.

Foliar application of gibberellin inhibits the cadmium uptake and xylem transport in lettuce (Lactuca sativa L.)

Gibberellin (GA) has been shown to exert numerous beneficial physiological functions in the resistance of plant to various abiotic stresses, however, the mechanism of GA for the mitigation of Cd stress in vegetables has not been well established. This study was carried out to investigate the effect of GA on the growth and Cd uptake in lettuce plants. Result showed that 10 µmol/L GA treatment restored part of the root morphology and vigor of lettuce under Cd stress by increasing the total root length, surface area and total root tip number, which directly showed an increased biomass of lettuce. On the other hand, GA reduced Cd uptake by roots and Cd root-to-shoot translocation by down-regulated expression of IRT1, Nramp1, HMA2 and HMA4, which finally alleviated the toxic effects of Cd on lettuce leaves, as confirmed by Non-invasive micro-test Technique (NMT) results. Overall, these findings provide new insights into the mechanism of cadmium toxicity mitigation in vegetables by GA and provide a theoretical basis for the development of physiological blockers with gibberellin components.

On the Importance of Soybean Seed P for Shoot P Uptake before Anthesis

Phosphorus (P) is an important macronutrient required for crop growth but a finite resource in agriculture. The objective of this study was to examine the effects of soybean seed size and seed P content on growth and P accumulation up to anthesis (30–40 DAP). Pot experiments were carried out in a greenhouse with 15 soybean genotypes of different seed size (TKW 146–304 g) and with two substrates differing in plant available P, i.e., low P (LP) at 6.17 mg kg−1 vs. high P (HP) at 68.12 mg kg−1 CAL-P. The observations included measurements of seed and shoot dry matter and P concentrations as well as root characteristics. In the case of LP, shoot P accumulation relied, to a large degree, on seed P reserves during the vegetative growth period. In the case of HP, however, the role of seed P is negligible with regard to absolute P uptake. Yet, a very close linear relationship between seed P and shoot P uptake was also confirmed at HP. Some genotypes reacted more positively than others on HP in biomass production and P uptake, but none of the selected genotypes showed an outstanding biomass production or P uptake under LP. Total root length or root surface area of soybean did not explain differences in P uptake between genotypes at either P supply level. Overall, no substantial genotypic differences were observed in P use efficiency under P deficiency apart from the effect of seed P reserves. We conclude that seed size can be considered an important trait when screening genotypes for fast early P accumulation and growth.

Petunia Performance Under Application of Animal-Based Protein Hydrolysates: Effects on Visual Quality, Biomass, Nutrient Content, Root Morphology, and Gas Exchange.

Sustainable plant production practices have been implemented to reduce the use of synthetic fertilizers and other agrochemicals. One way to reduce fertilizer use without negatively impacting plant nutrition is to enhance crop uptake of nutrients with biostimulants. As the effectiveness of a biostimulant can depend on the origin, species, dose, and application method, the aim of this research was to evaluate the effect of a commercial animal-based protein hydrolysate (PH) biostimulant on the visual quality, biomass, macronutrient content, root morphology, and leaf gas exchange of a petunia (Petunia × hybrida Hort. “red”) under preharvest conditions. Two treatments were compared: (a) three doses of an animal-based PH biostimulant: 0 (D0 = control), 0.1 (D0.1 = normal), and 0.2 g L–1 (D0.2 = high); (b) two biostimulant application methods: foliar spray and root drenching. The dose × method interaction effect of PH biostimulant on the plants was significant in terms of quality grade and fresh and dry biomass. The high dose applied as foliar spray produced petunias with extra-grade visual quality (number of flowers per plant 161, number of leaves per plant 450, and leaf area per plant 1,487 cm2) and a total aboveground dry weight of 35 g, shoots (+91%), flowers (+230%), and leaf fresh weight (+71%). P and K contents were higher than in untreated petunias, when plants were grown with D0.2 and foliar spray. With foliar spray at the two doses, SPAD showed a linear increase (+21.6 and +41.0%) with respect to untreated plants. The dose × method interaction effect of biostimulant application was significant for root length, projected and total root surface area, and number of root tips, forks, and crossings. Concerning leaf gas exchange parameters, applying the biostimulant at both doses as foliar spray resulted in a significant improvement in net photosynthesis (D0.1: 22.9 μmol CO2 m–2 s–1 and D0.2: 22.4 μmol CO2 m–2 s–1) and stomatal conductance (D0.1: 0.42 mmol H2O m–2 s–1 and D0.2: 0.39 mmol H2O m–2 s–1) compared to control. These results indicate that application of PH biostimulant at 0.2 g L–1 as foliar spray helped to achieve extra-grade plants and that this practice can be exploited in sustainable greenhouse conditions for commercial production of petunia.

Mechanism of S-allyl-L-cysteine Alleviating Cadmium Stress in Seedling Roots and Buds of Rice Seedlings

Cd has toxic effects on rice seed germination and plant growth, which may eventually lead to decreased yield and excessive Cd content in rice grains. The potential mechanism of S-allyl-L-cysteine (SAC), a natural sulfur compound derived from garlic extract, in alleviating Cd2+ stress in young roots and buds of rice seedlings was studied by a seed germination experiment. "Zhong zao 35", one of the main rice varieties in Southern China, was selected as the test material. Firstly, the alleviating effect of SAC on Cd2+ stress in rice seedling roots and buds was studied. Following this, the physiological mechanism of Cd2+ stress alleviation by SAC was examined based on the expression of the Cd transporter coding gene using real-time fluorescent quantitative PCR. The results showed that when the Cd2+ stress concentration reached 50 μmol·L-1, the young roots and buds of rice seedlings were significantly inhibited, and when the SAC concentration reached 200 μmol·L-1, Cd2+ stress was significantly alleviated. Compared to a Cd2+ stress treatment group, the total root length, surface area, and volume of young roots was increased by 173.5%, 65.52%, and 37.04%, respectively; CAT and SOD activity in young roots and buds was increased by 212.42% and 110.76%, and 31.41% and 47.31%, respectively; MDA and GSH content was decreased by 43.09% and 34.12%, and 33.97% and 35.74%, respectively; and Cd content was decreased by 35.91% and 28.86%, respectively. The results of quantitative real-time PCR showed that the relative expression levels of OsNramp5 and OsHMA2 were significantly reduced by 33.38% and 34.99% compared with the Cd2+ stress group, respectively. However, the relative expression level of OsHMA3 was significantly increased by 33.96%. From the above experimental results, the main mechanism by which SAC reduces Cd2+ stress in the young roots and buds of rice is via the regulation of Cd transporter-encoding genes, reducing Cd2+ transport to young roots and buds, and increasing transport to vacuoles.

Immobilization of cadmium in soil and improved iron concentration and grain yields of maize (Zea mays L.) by chelated iron amendments.

With the development of industrial and agricultural production, the cadmium (Cd) pollution in farmland soil is increasing which threatens the quality and safety of agricultural products in China. The purpose of this research is to explore the potential of chelated iron amendments for reducing the bioavailability of Cd to maize plants. The experiment of maize cultivation was carried out in pots. Maize was cultivated in brown soil collected from a northeast region in China and then artificially contaminated with Cd with an average concentration of 10 mg/kg. The potential of ethylenediamine tetra acetic acid ferric-sodium (EDTANa2Fe) and ethylenediamine-N, N'-bis(2-hydroxyphenylacetic acid) ferric-sodium (EDDHAFe) as amendments for Cd immobilization in soils were tested. Effects of different concentrations (0.013, 0.026, 0.053, and 0.08 g/kg) of EDTANa2Fe and EDDHAFe (calculated by iron) on the growth of maize and the Cd and Fe uptake in maize were evaluated. Principle component analysis (PCA) was performed to further analyze the overall effects of iron amendments on Cd accumulation in plants. The results showed that EDTANa2Fe and EDDHAFe at dose of 53 mg/kg reduced available Cd in soil to the value of 5.19 and 4.59 mg/kg, respectively. EDTANa2Fe of 80 mg/kg and EDDHAFe of 26, 53, and 80 mg/kg increased Fe concentration in grains by 34.86%, 36.88%, 41.46%, and 44.05%, respectively, while reduced the Cd content in grains by 39.82%, 42.67%, 48.41%, and 35.08%, respectively. Fe concentration in grains showed a significant negative correlation with the concentration of Cd (P < 0.05). EDTANa2Fe of 53 mg/kg treatment increased the maize yield by 30.45% which was higher than in all other treatments. EDDHAFe treatments of 26 and 53 mg/kg increased the total root length by 39.72% and 48.68%, respectively, and increased the total root surface area by 19.95% and 22.98%, respectively. In general, the application of EDTANa2Fe and EDDHAFe at dose of 53 mg/kg can effectively immobilize Cd in soil and reduce Cd accumulation in maize and improve Fe uptake in grains.

Effects of entomopathogenic fungi on durum wheat nutrition and growth in the field

Entomopathogenic fungi (EF), which are widely used as biological insecticides, have been shown to colonize a wide range of plants influencing their performance. Also, recent studies under controlled conditions have revealed that EF can additionally act as plant growth promoters and nutritional enhancers. In this work, we examined the effects of the EF species Beauveria bassiana and Metarhizium brunneum on durum wheat (Triticum durum L.) plants grown on calcareous Vertisols in two field experiments spanning two consecutive seasons. The fungi were either directly applied to the soil (2015–2016) or used for seed dressing (2016–2017). With the soil application treatment, neither fungus was detected in soil 30 days after sowing (DAS) and only M. brunneum was present in plants (up to 16.6 % of them). With seed dressing, B. bassiana and M. brunneum colonized plant tissues in up to 16.6 and 4.1 %, respectively. Both fungi increased aerial dry matter in 5 of the 7 samplings conducted at early and mid-crop growth stages [viz., before Zadok’s stage 55 (heading)] in the two seasons, the increase being significant at the P < 0.10 level in 3 samplings and at P < 0.05 in 2 with B. bassiana. Direct application of B. bassiana to soil significantly increased total root length and root surface area at stem elongation stage, as well as root length and root surface area in the finest roots with both application methods. On the other hand, grain yield was significantly affected by neither treatment. Metarhizium brunneum increased P and Na grain nutrient concentrations, whereas B. bassiana applied by seed dressing decreased grain vitrosity. Overall, B. bassiana was more influential on wheat performance than M. brunneum. Our results encourage the use of EF for agriculture as they increased some wheat growth parameters in early and middle phenological stages.

Root architecture of main tree species and the effects on soil reinforcement in typical black soil region.

To explore root architecture and its effects on soil reinforcement of main tree species in typical black soil region, we measured root spatial distribution characteristics, root fractal characte-ristics, and geometric morphological characteristics of Amygdalus triloba, Caragana microphylla, Betula platyphylla, Acer negundo, Picea koraiensis, Pinus sylvestris var. mongolica, using whole root excavation method and WinRHIZO Pro LA2004 root analysis system. All the examined species are distributed widely in typical black soil region. The vertical uprooting force was determined by in-situ uprooting tests. The results showed that inclined roots were dominant in A. triloba, horizontal roots were dominant in C. microphylla, B. platyphylla, A. negundo and P. koraiensis, and the horizontal and vertical distribution of roots were commensurable in P. sylvestris var. mongolica. Except for the total root surface area of B. platyphylla and the total root length of P. koraiensis, the total root length and root surface area of shrub species were significantly greater than those of arbor species, while deciduous broad-leaved trees were significantly larger than coniferous evergreen trees. The total root volume of B. platyphylla was significantly larger than that of C. microphylla, A. negundo, P. koraiensis and P. sylvestris var. mongolica. The root fractal dimension and abundance of A. triloba, C. microphylla, B. platyphylla were significantly higher than those of P. koraiensis and P. sylvestris var. mongolica. The average maximum uprooting force of A. triloba, C. microphylla, and A. negundo was significantly higher than that of B. platyphylla, P. koraiensis, and P. sylvestris var. mongolica. Due to the role of total root length, total root surface area and the number of inclined roots, root system of A. triloba, C. microphylla and A. negundo showed strong soil reinforcement capacity. A. triloba, C. microphylla and A. negundo could be used as the option-preferred tree species when constructing soil and water conservation vegetation in typical black soil region.