Root Proliferation Research Articles

Adaptation of microclones of blackberries to in vivo conditions

The results of studying the effect of mineral fertilizing on rhizogenesis and the development of aboveground organs of regenerant plants of blackberry thornless adaptable to in vivo conditions in the laboratory of selection, vegetable growing and horticulture, cloning “UNITS” Agrotechnopark “of Belgorod State Agrarian University are presented. Regenerated plants of thornless blackberry cultivar Agavam were adapted to in vivo conditions in a peat-perlite mixture with the addition of microelements and growth regulator root 16 days earlier than in the control. An active growth of the aboveground part and roots of regenerated plants of thornless blackberry was noted on the 21st day, in the control - on the 42nd day after the start of adaptation. By the end of the rooting stage on the 24th day, the regenerant plants formed an aerial part of two pairs of leaves 22 mm high and a developed root system - 37 mm. The mineral and hormonal composition of nutrient media for the cultivation of thornless blackberries has been optimized, an effective combination of physical and chemical factors at different stages of micropropagation has been determined, which enhance the proliferation of shoots and roots, and the dependence of the efficiency of adaptation of regenerated plants to in vivo conditions has been established. Along with traditional breeding methods, new opportunities for solving the problem of thorn-free blackberry varieties are provided, along with traditional breeding methods, which make it possible to accelerate the process of obtaining valuable planting material to provide the population and the processing industry with valuable berry products.

Rhizobium rhizogenes-mediated root proliferation in Cd/Zn hyperaccumulator Sedum alfredii and its effects on plant growth promotion, root exudates and metal uptake efficiency

In this study, Rhizobium rhizogenes-mediated root proliferation system in Sedum alfredii has been established. Twenty strains of R. rhizogenes were screened for root proliferation. A significant difference (P < 0.01) was observed in plant morphological characters under influence of different bacterial strains. The highest root fresh weight (3.236 g/plant) was observed with strain AS12556. Furthermore, significant difference (P < 0.05) was observed in the chemical composition of organic acids, Tartaric acid (TA), Succinic acid (SA), Malic acid (MA), Citric acid (CA) and Oxalic acid (OA), pH, Total Nitrogen (TN), Total Organic Carbon (TOC) and soluble sugars in root exudates with different R. rhizogenes mediated roots. Furthermore, a series of hydroponics experiments were conducted with varying concentrations of Cd (25, 50 and 75 µM) and Zn (100, 200 and 500 µM) to assess the phytoextraction efficiency of proliferated roots with Rhizobium. Several plants with proliferated roots showed enhanced growth and improved metal extraction efficiency. Five strains (LBA 9402, K599, AS12556, MSU440 and C58C1) were identified as potential strains for root proliferation in Sedum alfredii. R. rhizogenes strain AS12556 improved Cd/Zn phytoextraction by exogenous production of phytochemicals to promote root proliferation, improved shoot biomass, lowered oxidative damage and enhanced phytoextraction efficiency in S. alfredii. Therefore, it has been selected as a potential microbial partner of S. alfredii to develop extensive rooting system for better growth and enhanced phytoremediation potential. Results suggest that R. rhizogenes mediated root proliferation system can be used for optimizing metal extraction from contaminated soils.

Salt Stress Promotes Abscisic Acid Accumulation to Affect Cell Proliferation and Expansion of Primary Roots in Rice.

The primary root is the basic component of the root system and plays a key role in early seedling growth in rice. Its growth is easily affected by environmental cues, such as salt stress. Abscisic acid (ABA) plays an essential role in root development, but the molecular mechanism underlying ABA-regulated root growth in response to salt stress remains poorly understood. In this study, we report that salt stress inhibits primary root elongation and promotes primary root swelling. Moreover, salt stress induces the expression of ABA-responsive genes and ABA accumulation in the primary root, revealing that ABA plays an essential role in salt-modulated root growth. Transgenic lines of OsSAPK10-OE and OsABIL2-OE, which constitutively express OsSAPK10 or OsABIL2, with enhanced or attenuated ABA signaling, show increased and decreased sensitivity to salt, correspondingly. Microscopic analysis indicates that salt and ABA inhibits cell proliferation and promotes cell expansion in the root apical meristem. Transcriptome analysis showed that ABA induces the expression of EXPANSIN genes. Further investigations indicate that ABA exerts these effects largely through ABA signaling. Thus, our findings deepen our understanding of the role of ABA in controlling primary root growth in response to salt stress, and this knowledge can be used by breeders to cultivate rice varieties suitable for saline–alkali land.

In vitro Plant Regeneration in Banana (Musa sp.) cv. Grand Nain

This study was conducted at the tissue culture laboratory in Pakistan. Suckers obtained from the banana cv. Grand Nain to explore the effects of different concentrations of BAP and IAA. After inoculation with Murashige and Skoog (MS) medium supplemented with different concentrations of 6-Benzylaminopurine (BAP) and the Indole-3- acetic acid (IAA) the suckers first turn into the brown after 5-10 days then turned into a green mass-like structure after 30 days. From this mass-like structure shoots and roots were developed. Among the different concentrations, BAP 7.5 mg/l and IAA 0.5 mg/l showed the highest number of shoots 0.75, 2.75 and 6.25 per explant and shows the highest shoot lengths which 1.03 cm, 2.45 cm and 3.40 cm respectively. IAA is essential for only roots proliferation. The roots of different lengths were produced when the concentration of IAA 0.5 mg/l was used and 2.93 cm, 4.63 cm and 5.88 cm roots length produced at 15, 30 and 45 days after occultation respectively. Then these plants were transferred to the greenhouse for hardening acclimatization with the environment, the hardening process took place, and the established plantlets are ready for planting.

Localized nutrient supply can facilitate root proliferation and increase nitrogen-use efficiency in compacted soil

Soil compaction constrains root growth and crop yield. Previous studies have shown that localized nutrient supply can significantly improve maize plant growth in field conditions at the early growth stage. However, this promoting effect has not been tested in the compacted soil. We describe 2-year field experimentation on a fluvo-aquic soil in the North China Plain to investigate the effect of localized vs. broadcast ammonium and phosphorus supply on maize under three soil compaction treatments (NC: non-compacted, C: compacted and SC: severely compacted) during 2012 and 2013. Results showed that compared with broadcast ammonium and phosphorus (BNP), localized ammonium and phosphorus supply (LNP) resulted in significantly higher PFPN in the NC (by 31–37%), C (by 43–44%) and SC (by 45%) treatments at harvest. When soil was compacted (C and SC), the enhancement of nitrogen (N) utilization in the LNP treatment was attributed to the increased root growth, including greater specific root length (a greater proportion of fine roots), lower root tissue density and deeper rooting at the seedling stage, especially in the compacted treatment (C). The enhanced root penetration capacity contributed to the increased N and water uptake from the deep soil layers. Our study highlighted the importance of nutrient management for mitigating negative impacts of soil compaction on crops, and will underpin new soil compaction management practices by considering optimal fertilization to strengthen the root-soil interactions.

Getting to the root of the problem: improving measurements of mangrove belowground production and carbon sequestration.

This article is a Commentary on Arnaud et al. (2021), 232: 1591–1602.

Maize root responses to drought stress depend on root class and axial position

In this study we tested the hypotheses that root classes would exhibit distinctive anatomical and architectural responses to drought stress, and that those responses would vary along the root axes. The root systems of four maize (Zea mays L.) sweet corn genotypes designated SC1, SC2, SC3 and SC4 were phenotyped under well-watered and drought treatments in greenhouse mesocosms, permitting increasing stratification of moisture availability as the drought progressed. Anatomical and architectural responses to drought were evaluated for each root class. Lignin distribution was assessed by image processing of UV-illuminated root cross-sections acquired by laser ablation tomography. The two cultivars with less biomass reduction under drought, SC3 and SC4, substantially enhanced lateral root development along the apical segments of axial roots when plants were grown with drought stress. These segments grew into the deeper part of the mesocosm where more moisture was available. Apical segments of the axial and large lateral roots from drought-stressed plants were thicker and had greater theoretical axial water conductance than basal segments, especially in SC3 and SC4. Basal segments of crown roots of SC3 and SC4 showed increased lignification of the stele under drought. Root anatomical and architectural responses to drought are complex and vary among cultivars and root classes, and along root axes. Drought-induced proliferation of lateral roots on apical segments of axial roots would be expected to enhance deep water acquisition, while lignification of axial roots could help preserve axial water transport.

Complete root specimen of plants grown in soil-filled root box: sampling, measuring, and staining method

BackgroundDetailed datasets containing root system and its architecture in soil are required to improve understanding of resource capture by roots. However, most of the root study methods have paid little attention to make and preserve whole root specimens. This study introduces root system sampling equipment that makes the entire root specimen with minimum impairment and without displacement of the spatial arrangement of the root system in root boxes. The objectives are to assess: whether the equipment can rapidly sample the entire root system; whether root surface area is measurable from a scanned digital image of the root specimen; and whether staining of the entire root specimens would provide multidimensional visual information on the interaction between soil and physiological function of root system architecture (RSA). For validation, we examined the root response of two soybean cultivars to arbuscular mycorrhizal (AM) inoculation and the effect of waterlogging stress on the physiological activity of buckwheat RSA.ResultsThe root boxes allowed soybean and buckwheat plants to grow uniformly across the replications. Both species showed significant differences between cultivars and/or among treatments in shoot and root traits. The equipment enabled to sample the whole-root specimens of soybean and buckwheat, where the tips of the fine roots were alive (diameter < 0.2 mm). Also, the whole root specimens of soybean were made in about 7 min. The root surface area calculated from the scanned soybean specimens showed a significant correlation with that calculated from the roots spread out in water (a common method). Staining of the soybean root specimens enabled us to observe the localized root proliferation induced by AM colonization. Moreover, staining of the buckwheat root specimens made it possible to examine the respiratory activity of each root at different depths.ConclusionsThe present method realized: fast and accurate production of the whole root specimen and precise calculation of the specimens’ root surface area. Moreover, staining of the root specimens enabled analyzing the interaction between soil and physiological function of RSA. The evaluation of root traits, using our methods, will contribute to developing agronomic management and breeding program for sustainable food production.

Soil-Applied Boron Combined with Boron-Tolerant Bacteria (Bacillus sp. MN54) Improve Root Proliferation and Nodulation, Yield and Agronomic Grain Biofortification of Chickpea (Cicer arietinum L.)

Chickpea is widely cultivated on calcareous sandy soils in arid and semi-arid regions of Pakistan; however, widespread boron (B) deficiencies in these soils significantly decreases its productivity. Soil application of B could improve chickpea yield and grain-B concentration. However, optimizing suitable B level is necessary due to a narrow deficiency and toxicity range of B. Nonetheless, the co-application of B-tolerant bacteria (BTB) and synthetic B fertilizer could be helpful in obtaining higher chickpea yields and grain-B concentration. Therefore, this study optimized the level of soil applied B along with BTB, (i.e., Bacillus sp. MN54) to improve growth, yield and grain-B concentrations of chickpea. The B concentrations included in the study were 0.00 (control), 0.25, 0.50, 0.75 and 1.00 mg B kg−1 soil combined with or without Bacillus sp. MN54 inoculation. Soil application of B significantly improved root system, nodulation, yield and grain-B concentration, and Bacillus sp. MN54 inoculation further improved these traits. Moreover, B application at a lower dose (0.25 mg B kg−1 soil) with BTB inoculation recorded the highest improvements in root system (longer roots with more roots’ proliferation), growth, nodulation and grain yield. However, the highest grain-B concentration was recorded under a higher B level (0.75 mg B kg−1 soil) included in the study. Soil application of 0.25 mg B kg−1 with Bacillus sp. MN54 inoculation improved growth and yield-related traits, especially nodule population (81%), number of pods plant−1 (38%), number of grains plant−1 (65%) and grain yield (47%) compared with control treatment. However, the grain-B concentration was higher under the highest B level (1.00 mg kg−1 soil) with Bacillus sp. MN54 inoculation. In conclusion, soil application of 0.25 mg B kg−1 with Bacillus sp. MN54 inoculation is a pragmatic option to improve the root system, nodule population, seedling growth, yield and agronomic grain-B biofortification of chickpea.

Effect of Coconut (&lt;em&gt;Cocos nucifera&lt;/em&gt;) Water Extract on the Development of Adventitious Roots in &lt;em&gt;Polyscias fillicifolia&lt;/em&gt; Stem Cuttings

Purpose Vegetative propagation continues to be a popular method to propagate ornamental plant species. Coconut water (CW) can be considered as an abundant source of hormones and other plant growth regulators (PGRs). In this study, vegetative propagation of Polyscias fillicifolia was attempted using PGRs isolated from CW. Research method Stem cuttings were treated with varying concentrations (5, 10, 25, 50,100 μg mL-1) of PGR isolated from CW. The results were compared with a control set (treated with distilled water) and with those treated with solutions of pure synthetic indole acetic acid (IAA). Findings P. fillicifolia canes treated with a 25 μg mL-1 concentration of IAA, isolated from CW, showed the highest levels of root induction and development. Root development was more rapid (5 weeks) in the samples treated with PGRs isolated from CW compared to the canes propagated in the field by placing the canes on coir beds in plant nurseries. (6 weeks). Originality This is the first study to use PGRs isolated from CW extracts to improve lateral root proliferation, induce shoot development and leaf emergence in P. fillicifolia.

Application of calcium nitrate with phosphorus promotes rhizosphere alkalization in acid subsoil

AbstractCombatting subsoil acidity is a challenge as the incorporation of lime in subsurface layers may not be economically feasible. The use of nitrate to facilitate plant excess anion uptake has shown the potential to increase soil pH. A column experiment was carried out to demonstrate this root‐induced alkalization in various depths in an acid soil with pH 4.28 (0.01 M CaCl2). It consisted of two types of nitrogen (N) fertilizers (urea and Ca(NO3)2, both at 5 atom% 15N enrichment) banded at a depth of 0–10 cm, 10–20 cm or 20–30 cm, with phosphorus (P) fertilizer (NaH2PO4) at 150 mg P per column either applied to the N layers (N+P) or evenly mixed into the remaining layers without N addition (N‐P). Aluminium‐tolerant wheat (ET8) was used as test plants, receiving an initial N dose of 60 mg kg−1 soil at sowing and an additional dose of 30 mg kg−1 every 10 days from 40 days after sowing. Plants had a total N supply of 90 mg N kg−1 at 50 days and 180 mg N kg−1 at 80 days after sowing. The N+P treatments increased plant N uptake and increased rhizosphere and bulk soil pH. Nitrate placement increased pH of treated layers by up to 0.4 and 0.2 units in the rhizosphere and bulk soils, respectively, compared with the control at Day 80. Rhizosphere alkalization was greater with deeper N+P treatments as these encouraged the proliferation of deeper roots in the treated layer. The form of N and the application method of P fertilizer had no effect on shoot biomass over 80 days of growth. The N+P treatments had 7% higher 15N recovery of fertilizer in plants than the N‐P treatments. The current study also showed that P fertilizer enhanced rhizosphere alkalization induced by calcium nitrate. The results suggest that the use of nitrate fertilizer with P treatments can facilitate alkalization of acid subsoils.Highlights Phosphorus facilitates amelioration of subsurface soil acidity with nitrate fertilizer Placement of nitrate induces alkalization of acid soil at various depths Combined addition of nitrate and P at depth enhances nitrate uptake by wheat Balanced nutrient supply enhances excess anion uptake and rhizosphere alkalization

Tomato root senses horizontal/vertical mechanical impedance and correspondingly modulates root/shoot metabolome

Plant root encounters coarse environs right after emergence from the seed. Little is known about the metabolic changes enabling the root to overcome the soil impedance. It is also not known whether roots respond differently to soil hardness when grown in the horizontal and vertical orientation.We grew tomato (Solanum lycopersicum) seedlings vertically or horizontally on agarose with increasing hardness (0.2 % → 1.2 %). We examined the morphology of roots and shoots of the seedling and also profiled phytohormones, primary metabolite levels, and transcript levels of related genes from the respective organs.Tomato seedlings grown vertically or horizontally, on agarose with increasing hardness, exhibited lateral roots proliferation, shorter hypocotyl, and primary root. In primary root tip, hardness increase elicited loss of amyloplast staining; induced reactive oxygen species, and nitric oxide accumulation. The level of indole butyric acid, zeatin, jasmonates, and salicylic acid markedly differed in root and shoot exposed to increasing hardness. Increasing hardness lowered indole acetic acid and elevated abscisic acid level, while increased ethylene emission was confined to the horizontally-impeded seedling. The trajectories of metabolomic shift distinctly differed between vertically/horizontally-impeded root/shoot. In the horizontal root, amino acids were the major affected group, while in the vertical root, sugars were the major group. Commonly affected metabolites in root and shoot, trehalose, dopamine, caffeoylquinic acid, and suberic acid, hallmarked the signature for hardness. Increasing hardness lowered Snf1-related protein kinase1a (SnRK1a) expression in root/shoot implying regulation of metabolic homeostasis by the SnRK1 signalling module. The lower E2Fa expression may lead to growth inhibition by reduced meristematic activity.Our study highlights the importance of metabolic homeostasis in facilitating root ramification in the soil. Though hardness is a common denominator, root distinguishes the horizontal/vertical orientation and correspondingly modulates metabolites level. Altogether, the data uncovers ABA, E2Fa, and SnRK1 as key regulators of hardness-induced growth inhibition of tomato seedlings.

Heterogeneous nutrient supply promotes maize growth and phosphorus acquisition: additive and compensatory effects of lateral roots and root hairs.

Root proliferation is a response to a heterogeneous nutrient distribution. However, the growth of root hairs in response to heterogeneous nutrients and the relationship between root hairs and lateral roots remain unclear. This study aims to understand the effects of heterogeneous nutrients on root hair growth and the trade-off between root hairs and lateral roots in phosphorus (P) acquisition. Near-isogenic maize lines, the B73 wild type (WT) and the rth3 root hairless mutant, were grown in rhizoboxes with uniform or localized supply of 40 (low) or 140 (high) mg P kg-1 soil. Both WT and rth3 had nearly two-fold greater shoot biomass and P content under local than uniform treatment at low P. Significant root proliferation was observed in both WT and rth3 in the nutrient patch, with the WT accompanied by an obvious increase (from 0.7 to 1.2 mm) in root hair length. The root response ratio of rth3 was greater than that of WT at low P, but could not completely compensate for the loss of root hairs. This suggests that plants enhanced P acquisition through complementarity between lateral roots and root hairs, and thus regulated nutrient foraging and shoot growth. The disappearance of WT and rth3 root response differences at high P indicated that the P application reduced the dependence of the plants on specific root traits to obtain nutrients. In addition to root proliferation, the root response to a nutrient-rich patch was also accompanied by root hair elongation. The genotypes without root hairs increased their investment in lateral roots in a nutrient-rich patch to compensate for the absence of root hairs, suggesting that plants enhanced nutrient acquisition by regulating the trade-off of complementary root traits.

Examining the Effects of the Nitrogen Environment on Growth and N2-Fixation of Endophytic Herbaspirillum seropedicae in Maize Seedlings by Applying 11C Radiotracing.

Herbaspirillum seropedicae, as an endophyte and prolific root colonizer of numerous cereal crops, occupies an important ecological niche in agriculture because of its ability to promote plant growth and potentially improve crop yield. More importantly, there exists the untapped potential to harness its ability, as a diazotroph, to fix atmospheric N2 as an alternative nitrogen resource to synthetic fertilizers. While mechanisms for plant growth promotion remain controversial, especially in cereal crops, one irrefutable fact is these microorganisms rely heavily on plant-borne carbon as their main energy source in support of their own growth and biological functions. Biological nitrogen fixation (BNF), a microbial function that is reliant on nitrogenase enzyme activity, is extremely sensitive to the localized nitrogen environment of the microorganism. However, whether internal root colonization can serve to shield the microorganisms and de-sensitize nitrogenase activity to changes in the soil nitrogen status remains unanswered. We used RAM10, a GFP-reporting strain of H. seropedicae, and administered radioactive 11CO2 tracer to intact 3-week-old maize leaves and followed 11C-photosynthates to sites within intact roots where actively fluorescing microbial colonies assimilated the tracer. We examined the influence of administering either 1 mM or 10 mM nitrate during plant growth on microbial demands for plant-borne 11C. Nitrogenase activity was also examined under the same growth conditions using the acetylene reduction assay. We found that plant growth under low nitrate resulted in higher nitrogenase activity as well as higher microbial demands for plant-borne carbon than plant growth under high nitrate. However, carbon availability was significantly diminished under low nitrate growth due to reduced host CO2 fixation and reduced allocation of carbon resources to the roots. This response of the host caused significant inhibition of microbial growth. In summary, internal root colonization did little to shield these endophytic microorganisms from the nitrogen environment.

Host-specific influence on early growth and physiological attributes of sandal (Santalum album) grown in farmlands

Aim: The present study aimed to investigate the host- specific compatibility of sandal (Santalum album) for better root proliferation and boosting the growth of tree. Methodology: Sandal (Santalum album) was grown with 8 different leguminous and non-leguminous species at early stage to evaluate its biometric growth (height and basal diameter) and physiological (chlorophyll, photosynthesis rate and transpiration rate) performance under field conditions. Results: Sandal grown with Sesbania grandiflora recorded highest biometric observations, chlorophyll, photosynthesis and transpiration rate followed by Sandal + Albizia lebbeck and sandal + Casuarina junghuhniana. The sandal grown with leguminous host showed superior growth performance than sandal grown with non-leguminous host. Interpretation: The present study recommended that Sesbania grandiflora can be grown as transit host for boosting the growth of sandal.

Assessment of clonal fidelity and phytomedicinal potential in micropropagated plants of Bulbophyllum odoratissimum - An endangered medicinal orchid of Indo Burma megabiodiversity hotspot

Bulbophyllum odoratissimum (Sm.) Lindl. ex Wall. is widely used as traditional medicine for the treatment of tuberculosis, chronic inflammation and is listed as an endangered orchid due to over-exploitation and habitat destruction. The present study was carried out to establish a genetically stable in vitro regeneration protocol for mass multiplication using nodal segments and to determine phytochemical constituents, the antioxidant capacity of different parts (leaf, pseudobulb and root) of mother plants and acclimatized in vitro raised plants of B. odoratissimum. The synergistic effect of BA (4.0 mgl−1) and IBA (0.5 mgl−1) was found to be optimum for producing maximum shoot proliferation. IBA was found to be more effective for root proliferation than IAA, NAA and an average (3.08 roots/shoot) was obtained in 0.5 mgl−1 IBA. The well rooted plantlets were successfully acclimatized (more than 90% survival rate) in greenhouse, exhibiting normal development. The ISSR banding profiles confirmed high degree of genetic homogeneity among the clones. Extraction of all plant material from both mother plant and in vitro raised plant possess relevant TPC, TFC, radical scavenging activity (DPPH and ABTS) as well as total reducing power ability. HPLC chromatogram exhibited that phytochemical compounds detected in regenerated plants were similar to those present in mother plant and there was no remarkable difference. High regeneration frequency along with its genetic stability and secondary metabolite production validate the efficiency of this micropropagation protocol of B. odoratissimum for species recovery program as well as a potential source of commercial application.

Farmyard manure application and associated root proliferation improve the net greenhouse gas balance of Italian ryegrass – Maize double-cropping field in Nasu, Japan

In Japan, most cows are fed indoors, so cow manure must be carefully treated and used to manage soil fertility. The objective of this study was to compare the net greenhouse gas (GHG) balance (NGHGB) of Italian ryegrass – corn (maize) double-cropping fields receiving farmyard manure (FYM), slurry, or methane fermentation digestion liquid (MFDL). FYM, Slurry, MFDL, mineral fertilizer only (Fert.), and no-N control (Cont.) plots were set up in a randomized block design (n = 3). FYM, slurry, or MFDL was applied to meet the K requirement for forage production, and then mineral fertilizers were supplemented to meet the N and P requirements. From September 2017 to September 2020, C inputs as manure and crop residue, heterotrophic respiration (RH), and emissions of methane (CH4) and nitrous oxide (N2O) from soil were determined. The similarity of the total yields in FYM, Slurry, MFDL, and Fert. plots reflected judicious fertility management. However, the residue-C input of Italian ryegrass was 38% greater in FYM plots than in the other plots. Manure-C input decreased in the order of FYM > Slurry > MFDL plots. RH was greater in FYM and Slurry plots than in MFDL plots. Net ecosystem C balance (NECB) ([residue-C + manure-C] − [RH-C + CH4-C]) decreased in the order of FYM > Slurry > MFDL plots. N2O emission was greater in Slurry and MFDL plots than in FYM plots. Consequently, NGHGB ([CH4 and N2O emissions] − NECB) in terms of CO2 equivalent decreased in the order of MFDL > Slurry > FYM plots, so FYM application contributed most to GHG mitigation. Yield-scaled NGHGB was smallest in FYM plots owing to the synergy of the greatest residue-C and manure-C inputs, less N2O emission, and the achievement of a high enough yield, reflecting judicious fertility management based on manure and mineral fertilizer.

PagERF16 of Populus Promotes Lateral Root Proliferation and Sensitizes to Salt Stress.

The aggravation of soil salinization limits the growth and development of plants. The AP2/ERF transcription factors (TFs) have been identified and play essential roles in plant development and stress response processes. In this study, the function of PagERF16 was detected using the overexpressing (OX) and RNAi transgenic poplar 84K hybrids. Plant growth, stomatal conductance, antioxidant enzymes activity, and PagERF16 co-expressed TFs were analyzed using morphological, physiological, and molecular methods. OX showed a more robust lateral root system with a bigger diameter and volume compared to the wild-type plants (WT). Physiological parameters indicated the bigger stomatal aperture and lower stomatal density of OX along with the lower Catalase (CAT) activity and higher malondialdehyde (MDA) content contributed to the salt sensitivity. The plant height and rooting rate of OX and RNAi were significantly worse compared to WT. Other than that, the morphology and physiology of RNAi plants were similar to WTs, suggesting that the function of PagERF16 may be redundant with other TFs. Our results indicate that when PagERF16 expression is either too high or too low, poplar growth and rooting is negatively affected. In addition, a downstream target TF, NAC45, involved in Auxin biosynthesis, was identified and PagERF16 could directly bind to its promoter to negatively regulate its expression. These results shed new light on the function of ERF TFs in plant root growth and salt stress tolerance.

A cellophane-supported Arabidopsis culture for seamless transfer between different media is useful for studying various nitrogen responses

ABSTRACT Transferring plants between different nutritional media is a common technique in plant nutrition research. Solidified sterile media are often used for plant culture and subsequent transfer experiments. Transplanting is generally performed one plant at a time using sterile tweezers. This method has several challenges: it is time-consuming, which makes analyzing short-term responses to nutritional changes difficult; plants can be mechanically damaged, which can confound results; transferring mature plants is accompanied by root wounding due to root penetration into the solidified medium; and root shapes are altered, which precludes a precise evaluation on nutritional responses of root system architecture. To solve these problems, this study tried to adopt a system for Arabidopsis culture using solidified media covered with cellophane disks for the transfer experiments to analyze nitrogen responses as a case study. The cellophane disk prevented the penetration of roots into the solidified medium and fixed the roots loosely; thereby, facilitating sterile, rapid and noninvasive transfer of young and mature Arabidopsis plants between media without changing root shape. The plants-on-cellophane grown on the solidified media were directly transferred onto hydroponics, where plants vegetate and propagate seeds under strict nutritional control. The root proliferation on the cellophane disk allowed direct observations of root architecture and green fluorescent protein (GFP) fluorescence in the roots. Collectively, we conclude that the introduction of a cellophane sheet to the existing culture system would accelerate experiments in plant nutritional research.

No neighbour-induced increase in root growth of soybean and sunflower in mesh-divider experiments after controlling for nutrient concentration and soil volume.

Root competition is a key factor determining plant performance, community structure and ecosystem productivity. To adequately estimate the extent of root proliferation of plants in response to neighbours independently of nutrient availability, one should use a set-up that can simultaneously control for both nutrient concentration and soil volume at plant individual level. With a mesh-divider design, which was suggested as a promising solution for this problem, we conducted two intraspecific root competition experiments: one with soybean (Glycine max) and the other with sunflower (Helianthus annuus). We found no response of root growth or biomass allocation to intraspecific neighbours, i.e. an ‘ideal free distribution’ (IFD) norm, in soybean; and even a reduced growth as a negative response in sunflower. These responses are all inconsistent with the hypothesis that plants should produce more roots even at the expense of reduced fitness in response to neighbours, i.e. root over-proliferation. Our results suggest that neighbour-induced root over-proliferation is not a ubiquitous feature in plants. By integrating the findings with results from other soybean studies, we conclude that for some species this response could be a genotype-dependent response as a result of natural or artificial selection, or a context-dependent response so that plants can switch from root over-proliferation to IFD depending on the environment of competition. We also critically discuss whether the mesh-divider design is an ideal solution for root competition experiments.