Involvement of the ABA-and H_(2)O_(2)-Mediated Ascorbate-Glutathione Cycle in the Drought Stress Responses of Wheat Roots

Abscisic acid(ABA),hydrogen peroxide(H_(2)O_(2)) and ascorbate(AsA)–glutathione(GSH)cycle are widely known for their participation in various stresses.However,the relationship between ABA and H_(2)O_(2) levels and the AsA–GSH cycle under drought stress in wheat has not been studied.In this study,a hydroponic experiment was conducted in wheat seedlings subjected to 15%polyethylene glycol(PEG)6000–induced dehydration.Drought stress caused the rapid accumulation of endogenous ABA and H_(2)O_(2) and significantly decreased the number of root tips compared with the control.The application of ABA significantly increased the number of root tips,whereas the application of H_(2)O_(2) markedly reduced the number of root tips,compared with that under 15%PEG-6000.In addition,drought stress markedly increased the DHA,GSH and GSSG levels,but decreased the AsA levels,AsA/DHA and GSH/GSSG ratios compared with those in the control.The activities of the four enzymes in the AsA–GSH cycle were also markedly increased under drought stress,including glutathione reductase(GR),ascorbate peroxidase(APX),monodehydroascorbate reductase(MDHAR)and dehydroascorbate reductase(DHAR),compared with those in the control.However,the application of an ABA inhibitor significantly inhibited GR,DHAR and APX activities,whereas the application of an H_(2)O_(2) inhibitor significantly inhibited DHAR and MDHAR activities.Furthermore,the application of ABA inhibitor significantly promoted the increases of H_(2)O_(2) and the application of H_(2)O_(2) inhibitor significantly blocked the increases of ABA,compared with those under 15% PEG-6000.Taken together,the results indicated that ABA and H_(2)O_(2) probably interact under drought stress in wheat;and both of them can mediate drought stress by modulating the enzymes in AsA–GSH cycle,where ABA acts as the main regulator of GR,DHAR,and APX activities,and H_(2)O_(2) acts as the main regulator of DHAR and MDHAR activities.

Broad Hormonal Responses Induced by Aluminum in Roots of Dwarf Transgenics of Solanum lycopersicum L. cv “Micro-Tom”

The spatial pattern distribution of plant hormones in response to aluminum (Al) toxicity in roots remains to be shown. This study was performed to assess the root hormonal accumulation and gene expression in response to Al toxicity in five transgenic miniature dwarf tomatoes cv. Micro-Tom (MT). MT and MT transgenics to acid indole acetic, cytokinin, gibberellin, abscisic acid and ethylene were cultivated in nutrient solutions containing different Al concentrations. Root growth elongation was measured and cellular damage was visualized by staining Evans’s blue. The GUS reporter gene staining technique was used to visualize hormonal changes in MT apex root tissues. Data indicated that the MT is sensitive to Al that induced significant growth inhibition and cellular damage. Al concentration of 27 μM was significantly toxic, inducing root apex darkening and inhibition of root development. The qualitative evaluation of GUS reporter gene expression showed intense crosstalk among all hormones studied, underscoring the complexity of signaling induced by Al in apex roots. Results point out to a major understanding of the hormonal signaling in response to Al toxicity, which may induce a change of root growth and architecture with growth inhibition and cell constraints modulated by all different hormones evaluated.

The osteoclastic activity in apical distal region of molar mesial roots affects orthodontic tooth movement and root resorption in rats

The utilization of optimal orthodontic force is crucial to prevent undesirable side effects and ensure efficient tooth movement during orthodontic treatment.However,the sensitivity of existing detection techniques is not sufficient,and the criteria for evaluating optimal force have not been yet established.Here,by employing 3D finite element analysis methodology,we found that the apical distal region(A-D region)of mesial roots is particularly sensitive to orthodontic force in rats.Tartrate-resistant acidic phosphatase(TRAP)-positive osteoclasts began accumulating in the A-D region under the force of 40 grams(g),leading to alveolar bone resorption and tooth movement.When the force reached 80 g,TRAP-positive osteoclasts started appearing on the root surface in the A-D region.Additionally,micro-computed tomography revealed a significant root resorption at 80 g.Notably,the A-D region was identified as a major contributor to whole root resorption.It was determined that 40 g is the minimum effective force for tooth movement with minimal side effects according to the analysis of tooth movement,inclination,and hyalinization.These findings suggest that the A-D region with its changes on the root surface is an important consideration and sensitive indicator when evaluating orthodontic forces for a rat model.Collectively,our investigations into this region would aid in offering valuable implications for preventing and minimizing root resorption during patients’orthodontic treatment.

Fast,simple,efficient Agrobacterium rhizogenes-mediated transformation system to non-heading Chinese cabbage with transgenic roots

Non-heading Chinese cabbage, a variety of Brassica campestris, is an important vegetable crop in the Yangtze River Basin of China. However,the immaturity of its stable transformation system and its low transformation efficiency limit gene function research on non-heading Chinese cabbage. Agrobacterium rhizogenes-mediated(ARM) transgenic technology is a rapid and effective transformation method that has not yet been established for non-heading Chinese cabbage plants. Here, we optimized conventional ARM approaches(one-step and two-step transformation methods) suitable for living non-heading Chinese cabbage plants in nonsterile environments. Transgenic roots in composite non-heading Chinese cabbage plants were identified using phenotypic detection, fluorescence observation, and PCR analysis. The transformation efficiency of a two-step method on four five-day-old non-heading Chinese cabbage seedlings(Suzhouqing, Huangmeigui, Wuyueman, and Sijiu Caixin) was 43.33%-51.09%, whereas using the stout hypocotyl resulted in a transformation efficiency of 54.88% for the 30-day-old Sijiu Caixin.The one-step method outperformed the two-step method;the transformation efficiency of different varieties was above 60%, and both methods can be used to obtain transgenic roots for functional studies within one month. Finally, optimized ARM transformation methods can easily,quickly, and effectively produce composite non-heading Chinese cabbage plants with transgenic roots, providing a reliable foundation for gene function research and non-heading Chinese cabbage genetic improvement breeding.

Biomechanical behavior of grass roots at different gauge lengths

Gauge length influences the biomechanical properties of herbaceous roots such as tensile resistance,tensile strength and Young’s modulus.However,the extent to which and how these biomechanical properties of herbaceous roots are influenced remain unknown.To better understand the behavior of roots in tension under different conditions and to illustrate these behaviors,uniaxial tensile tests were conducted on the Poa araratica roots as the gauge length increased from 20 mm to 80 mm.Subsequently,ANOVA was used to test the impact of the significant influences of gauge length on the biomechanical properties,nonlinear regression was applied to establish the variation in the biomechanical properties with gauge length to answer the question of the extent to which the biomechanical properties are influenced,and Weibull models were subsequently introduced to illustrate how the biomechanical properties are influenced by gauge length.The results reveal that(1)the variation in biomechanical properties with root diameter depends on both the gauge length and the properties themselves;(2)the gauge length significantly impacts most of the biomechanical properties;(3)the tensile resistance,tensile strength,and tensile strain at cracks decrease as the gauge length increases,with values decreasing by 20%-300%,while Young’s modulus exhibits the opposite trend,with a corresponding increase of 30%;and(4)the Weibull distribution is suitable for describing the probability distribution of these biomechanical properties;the Weibull modulus for both tensile resistance and tensile strain at cracks linearly decrease with gauge length,whereas those for tensile strength and Young’s modulus exhibit the opposite trend.The tensile resistance,tensile strength,and tensile strain at the cracks linearly decrease with increasing gauge length,while the tensile strength and Young’s modulus linearly increase with increasing gauge length.

The response of roots and the rhizosphere environment to integrative cultivation practices in paddy rice

Integrative cultivation practices(ICPs)are essential for enhancing cereal yield and resource use efficiency.However,the effects of ICP on the rhizosphere environment and roots of paddy rice are still poorly understood.In this study,four rice varieties were produced in the field.Each variety was treated with six different cultivation techniques,including zero nitrogen application(0 N),local farmers’practice(LFP),nitrogen reduction(NR),and three progressive ICP techniques comprised of enhanced fertilizer N practice and increased plant density(ICP1),a treatment similar to ICP1 but with alternate wetting and moderate drying instead of continuous flooding(ICP2),and the same practices as ICP2 with the application of organic fertilizer(ICP3).The ICPs had greater grain production and nitrogen use efficiency than the other three methods.Root length,dry weight,root diameter,activity of root oxidation,root bleeding rate,zeatin and zeatin riboside compositions,and total organic acids in root exudates were elevated with the introduction of the successive cultivation practices.ICPs enhanced nitrate nitrogen,the activities of urease and invertase,and the diversity of microbes(bacteria)in rhizosphere and non-rhizosphere soil,while reducing the ammonium nitrogen content.The nutrient contents(ammonium nitrogen,total nitrogen,total potassium,total phosphorus,nitrate,and available phosphorus)and urease activity in rhizosphere soil were reduced in all treatments in comparison with the non-rhizosphere soil,but the invertase activity and bacterial diversity were greater.The main root morphology and physiology,and the ammonium nitrogen contents in rhizosphere soil at the primary stages were closely correlated with grain yield and internal nitrogen use efficiency.These findings suggest that the coordinated enhancement of the root system and the environment of the rhizosphere under integrative cultivation approaches may lead to higher rice production.

THE ROOTS AND FRUITS OF CHINESE SPRING FESTIVAL

Traditional festivals forge a nation’s cultural identity and solidarity.Through opulent customs and celebratory activities,they convey the collective psyche,emotions,and aspirations of a nation.As a key part of Chinese culture,traditional Chinese festivals reinforce the bond among Chinese people and preserve our cultural roots.Of all Chinese festivals,the Spring Festival is the most important,both culturally and historically.

Optimization of Enzymatic Extraction Process of Polysaccharides from Pseudostellaria heterophylla Fibrous Roots by Response Surface Methodology and Its Pilot Application

[Objectives]To study and optimize the process conditions of enzymatic hydrolysis technology for extracting polysaccharides from Pseudostellaria heterophylla fibrous roots and its application in workshop pilot tests.[Methods]P.heterophylla fibrous roots were taken as the matrix material,and Box Behnken design was used to analyze the extraction time,composite enzyme addition amount,and liquid-solid ratio for response surface optimization experiments,and then applied to the pilot extraction of P.heterophylla fibrous roots.[Results]Response surface analysis showed that all factors had a significant impact on the experimental indicators.The optimal extraction process conditions for polysaccharides from P.heterophylla fibrous roots were extraction time of 2.7 h,compound enzyme addition of 2.5%,and liquid-solid ratio of 32.The yield of polysaccharides from P.heterophylla fibrous roots was 4.83%.The water extraction process of P.heterophylla fibrous roots extraction pilot was used as the control group for response surface optimization of the pilot experiment.The optimization results showed that the extraction time was 3 h,the amount of composite enzyme added was 2.5%,and the liquid-solid ratio was 28.The polysaccharide yield was 4.75%,an increase of 4.63%compared to the control group.[Conclusions]This paper could provide feasibility for the innovation of enzy-matic hydrolysis technology for P.heterophylla fibrous roots and its workshop pilot practice application,as well as a reference for the industrial application of its medicinal resources.

iRoot SP单尖法根管充填对牙体牙髓病患者的疗效及对疼痛、炎症反应的影响

目的 探讨iRoot SP单尖法根管充填对牙体牙髓病患者的疗效及对疼痛、炎症反应的影响。方法 选取106例牙体牙髓病患者,随机均分为常规组和观察组。常规组采用AHplus根充糊剂填充治疗,观察组采用iRoot SP单尖法根管充填治疗,两组均治疗3个月。比较两组患者根管填充时间、恢复时间、临床疗效、疼痛、炎症反应白细胞介素-6(IL-6)、高敏C反应蛋白(hs-CRP)水平、并发症发生率。结果 观察组患者根管填充时间、恢复时间短于常规组(P<0.05)。观察组总有效率高于常规组(P<0.05)。术后,两组患者IL-6与hs-CRP水平较术前均上升,且观察组低于常规组(P<0.05),观察组疼痛感低于常规组(P<0.05)。观察组并发症发生率低于常规组(P<0.05)。结论 iRoot SP单尖法根管充填治疗牙体牙髓病,能够缩短患者填充时间、恢复时间,提高疗效,降低炎症反应,缓解患者的疼痛感,降低并发症发生率,具有一定的推广价值。

The SmMYB36-SmERF6/SmERF115 module regulates the biosynthesis of tanshinones and phenolic acids in salvia miltiorrhiza hairy roots

Tanshinone and phenolic acids are the most important active substances of Salvia miltiorrhiza,and the insight into their transcriptional regulatory mechanisms is an essential process to increase their content in vivo.SmMYB36 has been found to have important regulatory functions in the synthesis of tanshinone and phenolic acid;paradoxically,its mechanism of action in S.miltiorrhiza is not clear.Here,we demonstrated that SmMYB36 functions as a promoter of tanshinones accumulation and a suppressor of phenolic acids through the generation of SmMYB36 overexpressed and chimeric SmMYB36-SRDX(EAR repressive domain)repressor hairy roots in combination with transcriptomic-metabolomic analysis.SmMYB36 directly down-regulate the key enzyme gene of primary metabolism,SmGAPC,up-regulate the tanshinones biosynthesis branch genes SmDXS2,SmGGPPS1,SmCPS1 and down-regulate the phenolic acids biosynthesis branch enzyme gene,SmRAS.Meanwhile,SmERF6,a positive regulator of tanshinone synthesis activating SmCPS1,was up-regulated and SmERF115,a positive regulator of phenolic acid biosynthesis activating SmRAS,was down-regulated.Furthermore,the seven acidic amino acids at the C-terminus of SmMYB36 are required for both self-activating domain and activation of target gene expression.As a consequence,this study contributes to reveal the potential relevance of transcription factors synergistically regulating the biosynthesis of tanshinone and phenolic acid.

Regulation of the growth of sprouting roots of black locust seedlings using root barrier panels

How can we regulate an invasive alien species of high commercial value?Black locust(Robinia pseudoacacia L.)has a unique capacity for seed dispersal and high germination.Field surveys indicate that black locust increases its growing area with sprouting roots and the elongation of horizontal roots at a soil depth of 10 cm.Therefore,a method to regulate the development of horizontal roots could be eff ective in slowing the invasiveness of black locust.In this study,root barrier panels were tested to inhibit the growth of horizontal roots.Since it is labor intensive to observe the growth of roots in the fi eld,it was investigated in a nursery setting.The decrease in secondary fl ush,an increase in yellowed leafl ets,and the height in the seedlings were measured.Installing root barrier panels to a depth of 30 cm eff ectively inhibit the growth of horizontal roots of young black locust.

The SmNPR4-SmTGA5 module regulates SA-mediated phenolic acid biosynthesis in Salvia miltiorrhiza hairy roots

Phenolic acids are the main bioactive compounds in Salvia miltiorrhiza,which can be increased by salicylic acid(SA)elicitation.However,the specific molecular mechanism remains unclear.The nonexpresser of PR genes 1(NPR1)and its family members are essential components of the SA signaling pathway.Here,we report an NPR protein,SmNPR4,that showed strong expression in hairy root after SA treatment,acting as a negative moderator of SA-induced phenolic acid biosynthesis in S.miltiorrhiza(S.miltiorrhiza).Moreover,a basic leucine zipper family transcription factor SmTGA5 was identified and was found to interact with SmNPR4.SmTGA5 activates the expression of phenolic acid biosynthesis gene SmTAT1 through binding to the as-1 element.Finally,a series of biochemical assays and dual gene overexpression analysis demonstrated that the SmNPR4 significantly inhibited the function of SmTGA5,and SA can alleviate the inhibitory effect of SmNPR4 on SmTGA5.Overall,our results reveal the molecular mechanism of salicylic acid regulating phenolic acid biosynthesis in S.miltiorrhiza and provide new insights for SA signaling to regulate secondary metabolic biosynthesis.

Impact of Inulin Extracted, Purified from (Chicory and Globe Artichoke) Roots and the Combination with Maltodextrin as Prebiotic Dietary Fiber on the Functional Properties of Stirred Bio-Yogurt

Inulin is a prebiotic dietary fiber that plays an integral role in producing functional dairy products with improved health benefits. Therefore, the objectives of this study are as follows: extract and purify inulin from chicory roots and globe artichoke roots;evaluate the physicochemical, functional properties and functional groups of the purified inulin;determine the functional properties of chicory roots inulin-maltodextrin and globe artichoke roots inulin-maltodextrin and compare it with that of the commercial inulin;examine the impact of various inulin on physiochemical, microstructural, textural, sensory characteristics and as prebiotic dietary fiber on probiotic bacteria’s viability of stirred bio-yogurt. The characteristics of the microstructure were investigated by scanning electron microscopy and, Fourier transforms infrared spectroscopy to detect the functional group. The resulting inulin exhibited a high yield and purity along with enhanced functional properties. Stirred bio-yogurt fortified with chicory roots inulin or globe artichoke roots inulin showed enhanced physicochemical, microstructural, microbiological, and overall sensorial acceptability followed by chicory roots inulin-maltodextrin or globe artichoke roots inulin-maltodextrin and the commercial inulin as compared to the control. Stirred bio-yogurt samples can offer various health benefits and wide applications as supplement of prebiotic dietary fiber in dairy industry.

Chromosome-level genome assembly of Salvia miltiorrhiza with orange roots uncovers the role of Sm2OGD3 in catalyzing 15,16-dehydrogenation of tanshinones

Salvia miltiorrhiza is well known for its clinical practice in treating heart and cardiovascular diseases.Its roots,used for traditional Chinese medicine materials,are usually brick-red due to accumulation of red pigments,such as tanshinone IIA and tanshinone I.Here we report a S.miltiorrhiza line(shh)with orange roots.Compared with the red roots of normal S.miltiorrhiza plants,the contents of tanshinones with a single bond at C-15,16 were increased,whereas those with a double bond at C-15,16 were significantly decreased in shh.We assembled a high-quality chromosome-level genome of shh.Phylogenomic analysis showed that the relationship between two S.miltiorrhiza lines with red roots was closer than the relationship with shh.It indicates that shh could not be the mutant of an extant S.miltiorrhiza line with red roots.Comparative genomic and transcriptomic analyses showed that a 1.0 kb DNA fragment was deleted in shh Sm2OGD3m.Complementation assay showed that overexpression of intact Sm2OGD3 in shh hairy roots recovered furan D-ring tanshinone accumulation.Consistently,in vitro protein assay showed that Sm2OGD3 catalyzed the conversion of cyptotanshinone,15,16-dihydrotanshinone I and 1,2,15,16-tetrahydrotanshinone I into tanshinone IIA,tanshinone I and 1,2-dihydrotanshinone I,respectively.Thus,Sm2OGD3 functions as tanshinone 15,16-dehydrogenase and is a key enzyme in tanshinone biosynthesis.The results provide novel insights into the metabolic network of medicinally important tanshinone compounds.

双波长激光联合生物陶瓷材料iRoot SP辅助磨牙根管治疗效果分析

目的:探讨双波长激光联合生物陶瓷材料iRoot SP辅助磨牙根管治疗的效果。方法:选择2020年1月—2023年6月收治的104例磨牙根管治疗患者,按照随机数字表法分为对照组与试验组,每组52例。对照组采用iRoot SP糊剂进行根管充填,试验组以双波长激光(Nd:YAG和Er:YAG)联合iRoot SP糊剂进行治疗。比较2组总有效率、疼痛程度及并发症,观察治疗前、治疗后6周及12周的血清白细胞介素6(IL-6)、白细胞介素17(IL-17)、肿瘤坏死因子α(TNF-α)、出血指数(bleeding index,BI)、牙周探诊深度(depth of periodontal probing,PD)和临床附着水平(clinical attachment level,CAL)。采用SPSS 22.0软件包对数据进行统计学分析。结果:试验组总有效率显著高于对照组,根管填充后疼痛程度显著低于对照组(P<0.05);试验组治疗后6、12周的IL-6、IL-17、TNF-α、BI、PD和CAL显著低于对照组(P<0.05)。结论:双波长激光联合生物陶瓷材料iRoot SP辅助磨牙根管治疗效果较为理想,有利于减轻牙周炎症和疼痛程度。

Single-cell transcriptome atlas reveals spatiotemporal developmental trajectories in the basal roots of moso bamboo (Phyllostachys edulis)

Roots are essential for plant growth and development.Bamboo is a large Poaceae perennial with 1642 species worldwide.However,little is known about the transcriptional atlas that underpins root cell-type differentiation.Here,we set up a modified protocol for protoplast preparation and report single-cell transcriptomes of 14279 filtered single cells derived from the basal root tips of moso bamboo.We identified four cell types and defined new cell-type-specific marker genes for the basal root.We reconstructed the developmental trajectories of the root cap,epidermis,and ground tissues and elucidated critical factors regulating cell fate determination.According to in situ hybridization and pseudotime trajectory analysis,the root cap and epidermis originated from a common initial cell lineage,revealing the particularity of bamboo basal root development.We further identified key regulatory factors for the differentiation of these cells and indicated divergent root developmental pathways between moso bamboo and rice.Additionally,PheWOX13a and PheWOX13b ectopically expressed in Arabidopsis inhibited primary root and lateral root growth and regulated the growth and development of the root cap,which was different from WOX13 orthologs in Arabidopsis.Taken together,our results offer an important resource for investigating the mechanism of root cell differentiation and root system architecture in perennial woody species of Bambusoideae.

牙体牙髓病根管治疗应用iRoot SP冷侧法的效果

目的探讨牙体牙髓病根管治疗应用iRoot SP冷侧法的效果。方法筛选2018-06至2020-06在解放军总医院京南医疗区就诊的牙体牙髓病患者100例,随机分为对照组和试验组,每组50例,均进行根管治疗,其中对照组充填根管采用热牙胶垂直加压法,试验组采用iRoot SP冷侧法。比较两组根管充填效果、临床总有效率、疼痛视觉模拟评分(VAS)及咀嚼功能。结果两组治疗后根管充填效果和临床总有效率比较,差异无统计学意义(P>0.05);试验组治疗后1周[(4.13±0.79)vs.(5.11±0.98)]及1个月[(2.45±0.37)vs.(3.11±0.67)]VAS评分低于对照组,治疗后咬合力[(131.25±11.21)lbs vs.(120.34±14.09)lbs]及咀嚼效率[(90.12±4.13)%vs.(78.98±7.45)%]均优于对照组,差异均有统计学意义(P<0.05)。结论根管治疗牙体牙髓病中应用iRoot SP冷侧法的充填效果和疗效与热牙胶垂直加压法基本相同,但iRoot SP冷侧法在减轻患者疼痛,改善咀嚼功能方面更具优势。

The worldwide allometric relationship in anatomical structures for plant roots

The cortex(i.e.,absorptive tissue)and stele(transportive vascular tissue)are fundamental to the function of plant roots.Unraveling how these anatomical structures are assembled in absorptive roots is essential for our understanding of plant ecology,physiology,and plant responses to global environmental changes.In this review,we first compile a large data set on anatomical traits in absorptive roots,including cortex thickness and stele radius,across 698 observations and 512 species.Using this data set,we reveal a common root allometry in absorptive root structures,i.e.,cortex thickness increases much faster than stele radius with increasing root diameter(hereafter,root allometry).Root allometry is further validated within and across plant growth forms(woody,grass,and liana species),mycorrhiza types(arbuscular mycorrhiza,ectomycorrhiza,and orchid mycorrhizas),phylogenetic gradients(from ferns to Orchidaceae),and environmental change scenarios(e.g.,elevation of atmospheric CO_(2)concentration and nitrogen fertilization).These findings indicate that root allometry is common in plants.Importantly,root allometry varies greatly across species.We then summarize recent research on the mechanisms of root allometry and potential issues regarding these mechanisms.We further discuss ecological and evolutionary implications of root allometry.Finally,we propose several important research directions that should be pursued regarding root allometry.

Identification of the HAK gene family reveals their critical response to potassium regulation during adventitious root formation in apple rootstock

Adventitious root formation is a bottleneck during vegetative proliferation.Potassium(K^(+))is an essential macronutrient for plants.K^(+)accumulation from the soil and its distribution to the different plant organs is mediated by K^(+)transporters named K^(+)transporter(KT),K^(+)uptake(KUP),or high-affinity K^(+)(HAK).This study aimed to identify members of the HAK gene family in apples and to characterize the effects of K^(+)supply on adventitious root formation and on the expression of HAK genes and the genes that putatively control auxin transport,signaling,and cell fate during adventitious root formation.In this study,34 HAK genes(MdHAKs)were identified in the apple(Malus×domestica‘Golden Delicious’)genome.A phylogenetic analysis divided MdHAKs into four clusters(Ⅰ,Ⅱ,Ⅲ,andⅣ),comprising 16,1,4,and 13 genes,respectively.The syntenic relationships revealed that 62.5%of the total MdHAK genes arise from genomic duplication events.Chromosome location,domain structure,motif analysis,and physico-chemical characteristics were subsequently investigated.Furthermore,the application of K^(+)indicated the emergence of adventitious roots at 8 d and produced more adventitious roots at 16 d than the K^(+)-free control(CK)treatment.In addition,various MdHAKs showed root-specific expression in B9 apple rootstock stem cuttings and enhanced expression during the initiation and emergence stages of adventitious root formation in response to K^(+)treatment.Additionally,K^(+)treatment enhanced the expression levels of MdPIN1,MdPIN2,and MdAUX1.Further data indicated that a higher expression of MdWOX11,MdLBD16,and MdLBD29 and of cell cycle-related genes contributed to the auxin-stimulated adventitious root formation in response to K^(+).

Exogenous melatonin improves cotton yield under drought stress by enhancing root development and reducing root damage

The exogenous application of melatonin by the root drenching method is an effective way to improve crop drought resistance.However,the optimal concentration of melatonin by root drenching and the physiological mechanisms underlying melatonin-induced drought tolerance in cotton(Gossypium hirsutum L.)roots remain elusive.This study determined the optimal concentration of melatonin by root drenching and explored the protective effects of melatonin on cotton roots.The results showed that 50μmol L-1 melatonin was optimal and significantly mitigated the inhibitory effect of drought on cotton seedling growth.Exogenous melatonin promoted root development in drought-stressed cotton plants by remarkably increasing the root length,projected area,surface area,volume,diameter,and biomass.Melatonin also mitigated the drought-weakened photosynthetic capacity of cotton and regulated the endogenous hormone contents by regulating the relative expression levels of hormone-synthesis genes under drought stress.Melatonin-treated cotton seedlings maintained optimal enzymatic and non-enzymatic antioxidant capacities,and produced relatively lower levels of reactive oxygen species and malondialdehyde,thus reducing the drought stress damage to cotton roots(such as mitochondrial damage).Moreover,melatonin alleviated the yield and fiber length declines caused by drought stress.Taken together,these findings show that root drenching with exogenous melatonin increases the cotton yield by enhancing root development and reducing the root damage induced by drought stress.In summary,these results provide a foundation for the application of melatonin in the field by the root drenching method.