Average Root Diameter Research Articles

Technological Properties of Radish

Introduction. When cultivating root crops, harvesting is one of the most important operations. In industrial production, the technique for harvesting beets, carrots, black radishes, chicory, etc. is widely known, except for radishes, which differ significantly in the sowing scheme, maturation periods, and in physical and mechanical properties of the plants. In the study dealing with the development of small-scale mechanization for harvesting radishes, the authors made a determination of basic physical and mechanical properties of this plant. Materials and Methods. The study was conducted for the two radish varieties (Celeste and Belokrayka), typical for the Southern and North Caucasus federal districts of Russia. In doing so, the known methods were used to determine the size, mass and frictional characteristics of radishes. Results. It was established that the Celeste radishe was 1.2–2.1 times larger than the Belokrayka radish and 1.8–2.8 times heavier. The weight of the radish roots (10...28 g.) in the total mass of the plant was 52–90 %, and the weight was 0.5–0.6 %. The average diameter of the radish roots was 26.7–34 mm, with a coefficient of variation (V) about 13–14 %, radish root height was 29–45 mm (at V ≈ 18–20 %). A direct correlation between all the dimensions considered was found. The coefficient of the static friction of radish roots with unpainted steel was 0.63–0.66, the movement was 0.44–0.58. Frictional characteristics of the stems of the radish leaves were 1.25 times higher on the average. The diameter of the bundle of stems at the proposed cut end was 9–12 mm. Discussion and Conclusion. In general, the physical and mechanical characteristics of radishes depend significantly on their variety, maturity, freshness and other factors, so the results of the study vary significantly. Nevertheless, they can be used as primary information for designing radish harvesting machines.

Rooting and Related Physiological Characteristics Responses to Stolon Cuttings Pre-treatment by Cold Plasma in Centipedegrass (Eremochloa ophiuroides (Munro.) Hack.)

Cold plasma is a new agricultural technology demonstrating wide potential application in plants. Previous studies have elucidated that the cold plasma pre-treatment of seeds improves seed germination and early growth. However, the effects of cold plasma treatment on vegetative propagation, including rooting, remains unclear. In this study, effects of cold plasma treatment on rooting percentage, physiochemical properties in stolon cuttings and physiological characteristics in the rooting process of centipedegrass (Eremochloa ophiuroides (Munro.) Hack.) stolon cuttings were investigated. The centipedegrass stolon cuttings were pre-treated with 0, 150, 300 and 450 W of cold plasma for 15 s. Cold plasma treatments positively stimulated rooting of stolon cuttings, and the 300 W treatment yielded the best effect. Rooting percentage, numbers of adventitious roots, total root length, total root surface area, total root volume, average root diameter, and dry weights of roots were significantly improved by cold plasma treatments. The conductivity and water uptake increased by cold plasma treatments; the auxin (IAA) content and activities of polyphenol oxidase and peroxidase activities improved, and the IAA-oxidase activity decreased; the soluble sugar and protein contents increased after cold plasma treatment. The results of this study not only showed that cold plasma pre-treatment may improve rooting of vegetations but also provided inspiration and support for the application of cold plasma in vegetative propagation of plant.

Genome-wide association mapping of root system architecture traits in common wheat (Triticum aestivum L.)

Uncovering the genetic basis and optimization of root system architecture (RSA) traits are crucial for modern wheat breeding. Genome-wide association mapping has become a powerful approach to dissect the genetic architecture of complex quantitative traits. In the present study, RSA traits, viz. total root length (TRL), total root area, average root diameter and number of root tips in a diverse panel of 165 elite wheat cultivars from the Yellow and Huai River Valley Facultative Wheat Region of China were evaluated as seedlings in hydroponic culture and in the field to identify loci significantly associated with those traits. The diverse panel was genotyped using the wheat 90 K and 660 K SNP arrays, and a genome-wide association study using a mixed linear model identified 28 and 4 loci significantly associated with RSA traits in hydroponic culture and in the field, explaining 8.8–15.6% and 8.9–12.6% of phenotypic variances, respectively. Seven loci for RSA traits co-located with known genes or quantitative trait loci (QTL), whereas the other 22 were potentially new. Linear regression between favorable alleles and RSA traits suggested that QTL pyramiding should be effective in optimizing root systems. Two candidate genes for RSA traits were identified, including genes encoding calcium dependent protein kinase and E3-Ubiquitin protein ligase. This study provides novel insights into the genetic architecture of RSA traits.

Variation in morphological and physiological root traits and organic acid exudation of three sweet potato (Ipomoea batatas) cultivars under seven phosphorus levels

Plants invest their carbon resource in various strategies to enhance phosphorus (P) uptake and use when growing in low P soils. Sweet potato has evolved and persisted in P-impoverished soils, but exhibits highly variable growth and yield. Variation among sweet potato cultivars in ability to access and use P may affect growth and yield: the influence of root system traits in this regard has been little researched. In this study we explored the root traits and rhizosphere chemistry of three sweet potato cultivars under P deficient and sufficient conditions.Three sweet potato cultivars, two native to Papua New Guinea (Tambul Mai and Whagi Besta) and one internationally grown commercial cultivar (Beauregard), were grown with seven levels of P (0–360 mg P kg−1 soil added as KH2 PO4) for 84 days in a glasshouse in low P soil. Dry mass yield, tissue P concentration, root exudation of organic acids, colonisation by arbuscular mycorrhizal fungi (AMF) and root morphological and physiological traits were measured.All cultivars maintained a constant tissue P concentration below 1.0 mg P g −1 DM when P supply was low. There were few distinct differences among the cultivars in the response to P addition for growth, total root length, specific root length, root tissue density, average root diameter, root mass fraction and colonisation by AMF. Four organic acids were exuded by roots. Malate and fumarate were abundant only in cultivars from Papua New Guinea, while citrate and oxalate were common across all cultivars.Under P deficiency, all sweet potato cultivars used internal P efficiently, preferentially allocating carbon to shoots and to supporting AMF and organic acid release, rather than to increasing the root mass or forming specialised root structures. Among the root factors studied, the type of organic acid exuded was noteworthy, with citrate and malate being reported for the first time.

Toxicity of cadmium to wheat seedling roots in the presence of graphene oxide

The effects of cadmium (Cd) on wheat seedlings in the presence of graphene oxide (GO) were investigated. Parameters evaluated include root morphology, microtubule protein content, cytochrome P450 activity, and the microcellular structure of wheat seedlings. Compared with treatments with Cd or GO in isolation, treatments combining GO and Cd inhibited the total root length, total root surface area, average root diameter, and number of root hairs. GO combined with Cd also increased cytochrome P450 activity and reduced tubulin content. Cotransport of GO-loading Cd entered root tissues and was then transported to the mesophyll cells; this, in turn, triggered damage to cellular structures, including the cell membranes and chloroplast, leading to root blockage and reduced respiratory efficiency, decreased effectiveness of water and nutrient absorption, and ultimate inhibition of wheat growth and development. These effects of GO exposure were also concentration-dependent. The results indicated that GO amplified the phytotoxicity of Cd in wheat seedling roots. Given the worldwide exposure of the environment to Cd contamination, careful consideration should be given to the effects of GO in combination with Cd in agricultural management.

Root morphology and seedling growth of three tree species in southern China in response to homogeneous and heterogeneous phosphorus supplies

Trees adjust their root morphological characteristics to respond heterogeneous phosphorus conditions, and root length and root-to-shoot ratio will increase to improve phosphorus nutrient absorption in heterogeneous phosphorus soils. This study examined the responses of root morphology and seedling growth to homogeneous and heterogeneous phosphorus (P) supplies in three major tree species (Cunninghamia lanceolata, Pinus massoniana, and Phoebe zhennan) in southern China. Pot experiments including two homo-P and five hetero-P supplies with different P dosage levels were conducted across three species. Root length, root average diameter, root biomass, aboveground biomass, root-to-shoot ratio, P accumulation, P-efficiency ratio, and increments in height and diameter of seedlings were quantified. Roots of the three species showed symmetric and asymmetric growth in response to homo-P and hetero-P supplies, respectively. The root biomass and average diameter were greater in the P-rich patch than in the P-poor patch, and roots in the P-poor patch were thinner and longer than their opposite counterparts. The root length and biomass were higher in hetero-P treatments than in homo-P treatments at an equivalent P dosage. The heterogeneity magnitude was negatively correlated with the aboveground biomass and positively correlated with the root biomass and root-to-shoot ratio. The P-efficiency ratio was negatively correlated with the dose of added P. The growth responses include a comprehensive adjustment in the root morphology and root-to-shoot ratio. The root growth pattern can change to adapt to lower P availability in soil, and the root-to-shoot ratio will increase to optimize nutrient partitioning and improve P-nutrient absorption in hetero-P soils.

Management strategies differentially affect root functional trait expression in cocoa agroforestry systems

In tree-based agroecosystems, environmental heterogeneity can be high and resource acquisition strategies among individual plants can be expected to vary. This poses a challenge for appropriate nutrient prescriptions. We used a novel trait-based approach to measure in situ fine root phenotypic response of cocoa (Theobroma cacao) to fertilization. Two levels of NPK fertilizer were applied to cocoa in agroforestry, with shade trees Entandrophragma angolense or Terminalia ivorensis, or in monoculture. Four months following fertilization, cocoa fine roots were extracted from ingrowth cores and analyzed for a suite of traits positively associated with resource acquisition: fine root production, ratio of absorptive to transport roots, specific root length, specific root area, specific root tip abundance, and root nitrogen content, as well as traits positively associated with longer-lived root organs (resource conservative): root tissue density, average root diameter, and root carbon to nitrogen ratio. In surface soils (0 to 10 cm), fertilization largely stimulated roots to express resource conservative strategies compared to unfertilized cocoa roots (up to 70% mean percent difference among all root traits) but with limited measurable differences in root trait response between the two fertilization levels. In subsurface soils (10 to 20 cm), however, inconsistent cocoa root responses to fertilization and shade trees suggested increasing complexity in nutrient acquisition strategies with soil depth. At both depths, we detected coordination among cocoa root trait variation including a resource acquisition to conservation axis explaining ~ 45% of total trait variation, yet an individual cocoa plant’s position on these coordinated trait axes was predominately affected by the shade tree rather than fertilization level. This study provides some of the first insights into intraspecific root functional trait expression to fertilization in multispecies agriculture. We show that a trait-based approach can be used to improve diagnostics and prescriptions of nutrient amendments in agroforestry systems.

The evaluation of NaHCO3 stress mechanisms of grape hybrid rootstocks

Soil salinization is the main ecological problem in northwestern China, the widely used rootstock 1103 P is still can not meet production requirements in severely salinized soil. The aim of this study was to explore the NaHCO3 resistance mechanism indifferent grape rootstocks, the NaHCO3 resistant strains SN15 and SN17 (hybrids of ‘Zuoshan1’ and ‘SO4’) were used as materials, and the 1103 P strain was used as a reference. The root system configurations were scanned, the flow rate of Na+ and K+were examined by Non-invasive Micro-test Technology, NMT, the Na+ and K+ content, and the relative expression of Na+ and K+ transporter genes were measured under 50 mM NaHCO3 treatment. The total root length, root surface area and average root diameter of SN15 decreased the least after 48 h of NaHCO3 treatment, and the flow rate of the Na+ and K+ efflux in the SN15 and SN17 rootstocks was significantly lower than that in 1103 P. The Na+ content in the roots and leaves of SN15 increased the least, and K+ decreased less than that of the control after NaHCO3 treatment. The relative expression of the VvHKT genein SN15 and SN17 was higher after NaHCO3 treatment. The relative expression of VvNHXP in SN15 increased and peaked at 3.81 times that of the control. Expression of VvNHXP in SN17 peaked at 3.26 times that of the control. Expression of VvNHXP in1103 P was not significantly different. The roots of SN15 and SN17 were less affected by NaHCO3 stress, had an increased ability to excrete sodium and retain potassium, and showed decreased Na+ accumulation. The VvHKT and VvNHXP genes play important roles in mitigating NaHCO3 stress.

Influence of low-vacuum helium cold plasma pre-treatment on the rooting and root growth of zoysiagrass (Zoysia Willd.) stolon cuttings

The influence of low-vacuum helium cold plasma treatment on the rooting percentage, root growth and physiochemical properties of zoysiagrass stolon cuttings was studied. Zoysiagrass stolon cuttings were pre-treated with 0, 100, 200, 300 and 400 W of cold plasma for 15 s. The cold plasma positively stimulated rooting and improved the root growth of the zoysiagrass stolon cuttings, and the 300 W treatment produced the best effect. The rooting percentage and root growth parameters, including the root length, total root surface area, total root volume, average root diameter, and root dry weight, significantly improved in response to the cold plasma treatment. In addition, the water uptake and relative conductivity of the stolon cuttings increased significantly in response to the cold plasma treatment. The results revealed that cold plasma-stimulated rooting and root growth appear to be a consequence of the improvement in permeability and water absorbing capacity of zoysiagrass stolon cuttings. The results of the present study will provide inspiration and support for the application of cold plasma in the vegetative propagation of plants.

Exploring the differences between organic and conventional breeding in early vigour traits of winter wheat

Abstract Breeding for organic systems may be done as pure line or population breeding. Early vigour, critical to organic systems, was compared for different winter wheat breeding origins in a hydroponic system, as well as in the field. Entries were: the F15 of composite cross populations (CCPs), based on high yielding (Y), high quality (Q) or Y*Q varietal intercrosses after 11 generations evolving under organic management; four organically bred; four conventionally bred baking quality varieties; a hybrid bread wheat and a high yielding variety. Hydroponic traits corresponded well with ground cover and plant height measured in the field. The organically evolved Q and YQ CCPs, organic varieties ‘Poesie’, ‘Butaro’ and ‘Tobias’ and the conventional ‘Capo’ were best suited for organic conditions. Compared to most modern varieties, CCPs had fewer seminal roots, their roots tended to be thicker and their root systems heavier, suggesting specific adaptation to penetration into deeper soil zones. Conventionally bred ‘Capo’ exhibits a diverse combination of root traits adaptive to a variable range of soil and environmental conditions, which may contribute to higher nutrient-use efficiency. Average root diameter of conventional E-varieties (0.28 mm) was significantly lower compared to organic varieties or the Q/YQ CCPs (both 0.30 mm). Specific root length of conventional E-varieties (17.5 cm mg−1) was significantly higher than for organic varieties (15.9 cm mg−1) and both differed from the Q and YQ CCPs (14.3 cm mg−1). Seminal root length and shoot length were identified as reasonable non-destructive predictors for direct selection within segregating materials and populations.

Effect of exogenous ammonium gluconate on growth, ion flux and antioxidant enzymes of maize (Zea Mays L.) seedlings under NaCl stress.

Ammonium gluconate (AG) provides both an organic carbon source and a nitrogen source, which can positively improve soil fertility and delay soil degradation. We investigated the underlying mechanisms of both NH4 + - and C6 H11 O7 - -mediated resistance to high salt concentrations in maize (Zea mays L.), and how they relate to antioxidant cellular machinery, root system architecture, root activity and lignin content in roots. Seedlings treated with AG maintained lower Na+ content, higher chlorophyll content, higher CAT and POD activity, compared with those without AG and ammonium carbonate (AC). The total size of the root system, primary root length and number of lateral roots detected on the primary root treated with AG decreased compared with those not treated with AG at the same NaCl concentration. However, average root diameter and root activity when treated with AG were significantly higher than roots without AG at the same NaCl concentration. Furthermore, total size of the root system, primary root length and number of lateral roots detected on primary rootsof seedlings treated with AG were higher than those treated with AC at the same NaCl concentration. These results suggested that AG may be a good organic fertiliser under salt stress by decreasing Na+ content and increasing chlorophyll content, activity of antioxidant enzymes, root diameter and root activity in maize seedlings.

Effects of competition and phosphorus fertilization on leaf and root traits of late-successional conifers Abies fabri and Picea brachytyla

Leaf and root systems are known to show a high degree of developmental plasticity in response to the local environment. However, few studies have investigated simultaneously the leaf and root traits as affected by competition and phosphorus (P) fertilization, especially in connection with the primary succession. We investigated morphological and physiological responses to different competition treatments (intra- vs. interspecific competition) and P regimes in seedlings of Abies fabri and Picea brachytyla, collected from the late succession stage Hailuogou glacier retreat area. A. fabri had a greater total chlorophyll content and specific leaf area (SLA), higher leaf nitrogen (N) and P concentrations, as well as a higher water use efficiency (assessed by the carbon isotope composition, δ13C) and N absorption relative to P. brachytyla under P fertilization conditions, and its total biomass responded more strongly to P fertilization, especially under interspecific competition. P fertilization decreased the specific root length (SRL) and ectomycorrhizal infection in both species and specific root tip density in P. brachytyla but it had no effect on the average root diameter. We concluded that similar changes in root characteristics, but the superior performance of above-ground traits in A. fabri in response to P availability, especially under competition, explain the greater competitive capacity of A. fabri at final stages of succession. These findings highlight the influence of soil nutrition availability and competition on the functional traits of plants and contribute to the understanding of the role of relative modifications in leaf and root traits during succession.

Subirrigation Effects on Larch Seedling Growth, Root Morphology, and Media Chemistry

Subirrigation (SI), where water is provided to container seedlings from below and rises through the growing media via capillary action, is regarded as an environmentally-responsible method of delivering water and fertilizer to nursery-grown plants, resulting in more uniform crops and improved production efficiency. While a concern around adopting this method is that a potential higher salt concentration in the upper layers of growing media under SI may inhibit root growth and result in decreased plant quality, few studies have focused on how root morphology is altered by SI. Therefore, a balanced two-factor factorial design with three rates of fertilization (50, 100, and 150 mg N seedling−1) and two irrigation methods (SI or overhead irrigation (OI)) was used to examine the growth response of Prince Rupprecht’s larch (Larix principis-rupprechtii Mayr) seedlings for one nursery season. Associated changes between rhizosphere electrical conductivity (EC) and root morphology of different root size classes were analyzed. Results show that (1) height, root-collar diameter, and root volume were similar between seedlings grown under SI and OI. However, (2) compared to seedlings receiving OI, SI-seedlings had less root mass, length, and surface area but greater average root diameter (ARD). (3) Morphological differences were evident primarily in root diameter size classes I–III (D ≤ 1.0 mm). (4) Fertilizer rate influenced root length and surface area up to 130 days after sowing but affected ARD throughout the growing season such that seedlings treated with 50 mg N had smaller ARD than seedlings treated with 100 mg N. (5) As the growing season progressed, SI-media had significantly higher EC compared to OI-media and EC increased with increasing fertilizer rate under SI but not under OI. These results indicate that SI can produce larch seedlings of similar height and root collar diameter (RCD) compared to OI, but root systems are smaller overall with fewer small-diameter roots, which may be related to high EC levels in SI-media, which is exacerbated by the use of high rates of fertilizer. Therefore, the EC in the media should be monitored and adjusted by reducing fertilizer rates under SI.

Variation in root morphology and P acquisition efficiency among Trifolium subterraneum genotypes

Trifolium subterraneum L. is widely grown in the phosphorus (P) deficient soils of southern Australia. However, this pasture legume has a high critical external P requirement and requires frequent applications of P fertiliser to achieve high productivity. Twenty-six genotypes of T. subterraneum were grown to determine: (i) differences in shoot growth and P acquisition under low-P supply; (ii) the root morphological traits important for P acquisition; and (iii) the feasibility of selection among genotypes for these root morphological traits. Micro-swards of each genotype were grown with a topsoil layer that was either moderately P-deficient or had P supplied in excess of the critical requirement for maximum yield; the subsoil layer was P-deficient. Yield and P content of shoots and roots were determined after 5 weeks’ growth, and root samples were assessed for diameter, length and root hair length. All genotypes were equally highly productive when excess P was supplied. However, relative shoot yield in the moderately P-deficient soil ranged from 38–71%. Total root length ranged from 63–129 m pot–1, and was correlated with total plant P uptake (R2 = 0.78, P < 0.001). Variation was also observed in average root diameter (0.29–0.36 mm) and root hair length (0.19–0.33 mm). These traits were combined with root length to calculate the total surface area of the root hair cylinder, which was also correlated with total plant P uptake (R2 = 0.69, P < 0.001). The results demonstrated that there was significant variation in P acquisition efficiency and shoot yield among genotypes of T. subterraneum when grown in P-deficient soil, and that root length was important for improved P uptake. The results indicate potential to identify superior genotypes that achieve improved P acquisition and higher shoot yields in low-P soil.

Evaluating Soybean Cultivars for Low- and High-Temperature Tolerance During the Seedling Growth Stage

Soybean (Glycine max L.) seedlings may be exposed to low or high temperatures under early or conventional soybean production systems practiced in the US Midsouth. However, a wide range of soybean cultivars commonly grown in the region may inherit diverse tolerance to degrees of temperatures. Therefore, a study was conducted in a controlled-environment facility to quantify 64 soybean cultivars from Maturity Group III to V, to low (LT; 20/12 °C), optimum (OT; 30/22 °C), and high (HT; 40/32 °C) temperature treatments during the seedling growth stage. Several shoot, root, and physiological parameters were assessed at 20 days after sowing. The study found a significant decline in the measured root, shoot, and physiological parameters at both low and high temperatures, except for root average diameter (RAD) and lateral root numbers under LT effects. Under HT, shoot growth was significantly increased, however, root growth showed a significant reduction. Maturity group (MG) III had significantly lower values for the measured root, shoot, and physiological traits across temperature treatments when compared with MG IV and V. Cultivar variability existed and reflected considerably through positive or negative responses in growth to LT and HT. Cumulative stress response indices and principal component analysis were used to identify cultivar-specific tolerance to temperatures. Based on the analysis, cultivars CZ 5225 LL and GS47R216 were identified as most sensitive and tolerant to LT, while, cultivars 45A-46 and 5115LL identified as most tolerant and sensitive to HT, respectively. The information on cultivar-specific tolerance to low or high temperatures obtained in this study would help in cultivar selection to minimize stand loss in present production areas.

Relationship between volatile organic compounds released and growth of Cunninghamia lanceolata roots under low-phosphorus conditions

To understand whether Chinese fir (Cunninghamia lanceolata) can conserve energy by reducing root volatiles to maintain growth under low phosphorus (P) conditions, we cultivated two half-sib families of Chinese fir that display high and low P use efficiency under conditions of normal P supply and total P deficiency. Gas chromatography-mass spectrometry analysis was used to determine the content of root volatiles, and the relationships among root volatiles and root growth index, P content, and distribution were analyzed. There were significantly fewer volatile organic compounds (VOCs) in the rhizosphere of these two fir families, No. 25 and No. 32, under P deficiency. Low P supply significantly promoted root growth in No. 25, increasing both average diameter and volume. A negative correlation was found between the volatiles and the increment of root average diameter and surface area. The belowground P distribution and the root to shoot P concentration (Pr/Ps) were higher in No. 25 than in No. 32. The total amount of VOCs, as well as the amount of 18 individual volatiles were positively correlated with P accumulation, aboveground P distribution, and belowground P distribution, but the opposite pattern was seen in Pr/Ps for family No. 25 seedlings. We conclude that the content and types of VOCs differ among the Chinese fir genotypes. Under low-P stress, the roots of Chinese fir reduce the release of VOCs to maintain seedling growth.

Growth of Ormosia henryi seedlings and photosynthetic and physiological characteristics with rhizobia inoculation.

To screen the growth-promoting strains of rhizobia for Ormosia henryi and to establish a good symbiotic nitrogen-fixing system, root nodules of O. henryi collected from Guizhou, Zhejiang, Anhui, Fujian, and Jiangxi Provinces were isolated and identified. Using randomized block design, 20 strains of rhizobia that passed reinoculation and 16SrDNA sequence analysis were inoculated into one-year-old aseptic potted O. henryi seedlings followed by measurement of the photosynthetic rate, transpiration rate, chlorophyll fluorescence parameters, growth indexes, and nodulation indexes. Results showed that the nodulation rates of the 20 strains were above 90.0%, the nodule number and nodule weight of strain No. 7 was the highest. Compared to the control which was not been inoculated, inoculation rhizobium significantly (P < 0.05) increased photosynthetic rate, transpiration rate and chlorophyll fluorescence parameters of O. henryi seedlings. Rhizobium also promoted the growth of above ground and underground parts as well as accumulation of total biomass. Seedlings with different rhizobium strains increased the photosynthetic rate (41.6%-197.4%), transpiration rate (3.2%-512.9%), actual photosynthetic quantum yield (4.8%-95.2%), total root surface area (3.4%-866.1%), average root diameter (6.7%-193.3%), root number (0.5%-92.1%), seedling height growth (6.3%-273.8%), diameter growth (10.7%-185.7%), and biomass (37.9%-310.3%). The comprehensive evaluation showed that the best five strains for promoting growth of O. henryi seedlings were No. 15, 16, 7, 18, and 17, and these could be used as excellent strains for inoculation of O. henryi seedlings.

Temporal and spatial distributions of fine roots of different varieties of Camellia oleifera.

We examined fine root distribution dynamics at the depth of 0-40 cm soil profile for five varieties of Camellia oleifera, including "Ganwu 1", "Ganyong 5", "Changlin 4", "Changlin 40" and "Gan 447", in one year using minirhizotron technique. The temporal and spatial distribution characteristics of total root tip number (TRT), average root length density (ARLD) and average root diameter (ARD) were analyzed. The results showed that the TRT and ARLD changes of each variety were relatively stable in the second half of 2016, while there was a significant monthly fluctuation in the first half of 2017, especially for "Ganwu 1" and "Changlin 40". The TRT and ARLD of "Ganwu 1" peaked in May 2017, while the ARD of "Changlin 4" peaked in March 2017. The TRT and ARLD values of "Ganwu 1" and the ARD value of "Changlin 4" were significantly greater than those of other varieties during the whole observation period. The spatial distribution and monthly dynamics of fine roots varied significantly among different varieties of Camellia oleifera. The fine roots were mainly distributed at the soil layer of 0-20 cm for "Ganwu 1" and" Gan 447 ", but at 20-40 cm for " Changlin 4 "and " Changlin 40 ". The latter two varieties had relatively stable spatial distribution and monthly dynamics of fine roots when compared to others. In contrast, the root biomass of "Ganyong 5" was not significantly different between both soil layers despite a large spatial variation. The ARD of "Changlin 4" was significantly larger at the soil layer of 20-40 cm than that of 0-20 cm. There was no significant difference in ARD between both soil layers for other varieties. In conclusion, within the five varieties, "Ganwu 1" had the greatest biomass of fine roots, which were mainly distributed in the upper soil layer, while "Changlin 4" had the largest diameter of fine roots, which were mainly distributed in the lower soil layer.

Improvements in the Root Morphology, Physiology, and Anatomy of Platycladus orientalis Seedlings from Air-root Pruning

Air-root pruning (AP) has been identified as an effective technique for enhancing root growth and development. However, little information is available regarding the temporal changes in the root system of Platycladus orientalis (L.) Franco under AP. We performed integrated morphological, physiological, and anatomical analyses of the roots in P. orientalis seedlings that had been air-root pruned for 120, 150, and 190 days. Our results found that the whole root length, number of root tips, and root surface area of AP seedlings at 120, 150, and 190 days were higher than those of the non–root-pruned (NP) seedlings (P &lt; 0.05), but the average root diameter did not differ significantly between the treatments. Compared with NP treatment, AP increased the root length, surface area, number of tips, and specific root length of the ≤0.5 mm diameter roots in P. orientalis during the experimental periods (P &lt; 0.05), but those of 0.5- to 1-mm-diameter roots were only increased on day 190 (P &lt; 0.05). The AP plants also exhibited higher root vitality and proportion of live fine roots than the NP plants (P &lt; 0.05). Our anatomical evaluation of the ≤0.5 mm roots and taproots revealed features that could account for the morphological differences found between the AP and NP plants. In conclusion, our results indicate that air-root pruning induced changes in the roots that promote the root system development in P. orientalis compared with the NP treatment during the experimental period. These results thus provide experimental evidence to support the use of AP in P. orientalis seedlings.

Natural variation of ZmHKT1 affects root morphology in maize at the seedling stage.

Eight variants in ZmHKT1 promoter were significantly associated with root diameter, four haplotypes based on these significant variants were found, and Hap2 has the largest root diameter. Roots play an important role in uptake of water, nutrients and plant anchorage. Identification of gene and corresponding SNPs associated with root traits would enable develop maize lines with better root traits that might help to improve capacity for absorbing nutrients and water acquisition. The genomic sequences of a salt tolerance gene ZmHKT1 was resequenced in 349 maize inbred lines, and the association between nucleotide polymorphisms and seedling root traits was detected. A total of 269 variants in ZmHKT1 were identified, including 226 single nucleotide polymorphisms and 43 insertions and deletions. The gene displayed high level of nucleotide diversity, especially in non-genic regions. A total of 19 variations in untranslated region of ZmHKT1 were found to be associated with six seedling traits. Eight variants in promoter region were significantly associated with average root diameter (ARD), four haplotypes were found based on these significant variants, and Hap2 has the largest ARD. Two SNPs in high-linkage disequilibrium (SNP-415 and SNP 2169) with pleiotropic effects were significantly associated with plant height, root surface area, root volume, and shoot dry weight. This result revealed that ZmHKT1 was an important contributor to the phenotypic variations of seedling root traits in maize, these significant variants could use to develop functional markers to improve root traits.