Morphological and Physiological Responses to Short-Term Micronutrient Deficiency in the Root of Two Citrus Rootstocks

Roots play essential roles in the acquisition of water and minerals from soils in higher plants. However, water or nutrient limitation can alter plant root morphology. To clarify the spatial distribution characteristics of essential nutrients in citrus roots and the influence mechanism of micronutrient deficiency on citrus root morphology and architecture, especially the effects on lateral root (LR) growth and development, two commonly used citrus rootstocks, trifoliate orange (Poncirus trifoliata L. Raf., Ptr) and red tangerine (Citrus reticulata Blanco, Cre), were employed here. The analysis of the mineral nutrient distribution characteristics in different root parts showed that, except for the P concentrations in Ptr, the last two LR levels (second and third LRs) had the highest macronutrient concentrations. All micronutrient concentrations in the second and third LRs of Ptr were higher than those of Cre, except for the Zn concentration in the second LR, which indicates that Ptr requires more micronutrients to maintain normal root system growth and development. Principal component analysis (PCA) showed that B and P were very close in terms of spatial distribution and that Mo, Mn, Cu, and Fe contributed significantly to PC1, while B, Cu, Mo, and Zn contributed significantly to PC2 in both rootstocks. These results suggest that micronutrients are major factors in citrus root growth and development. The analysis of root morphology under micronutrient deficiency showed that root growth was more significantly inhibited in Ptr and Cre under Fe deficiency (FeD) than under other micronutrient deficiencies, while Cre roots exhibited better performance than Ptr roots. From the perspective of micronutrient deficiency, FeD and B deficiency (BD) inhibited all root morphological traits in Ptr and Cre except the average root diameter, while Mn deficiency (MnD) and Zn deficiency (ZnD) had lesser impacts, as well as the morphology of the stem. The mineral nutrient concentrations in Ptr and Cre seedlings under micronutrient deficiency revealed that single micronutrient deficiencies affected both their own concentrations and the concentrations of other mineral nutrients, whether in the roots or in stems and leaves. Dynamic analysis of LR development revealed that there were no significant decreases in either the first or second LR number in Ptr seedlings under BD and ZnD stress. Moreover, the growth rates of first and second LRs in Ptr and Cre did not significantly decrease compared with the control under short-term (10 days) BD stress. Altogether, these results indicate that micronutrients play essential roles in citrus root growth and development. Moreover, citrus alters its root morphology and biological traits as a nutrient acquisition strategy to maintain maximal micronutrient acquisition and growth. The present work on the spatial distribution characteristics and micronutrient deficiency of citrus roots provides a theoretical basis for effective micronutrient fertilization and the diagnosis of micronutrient deficiency in citrus.

花生是较耐旱的经济和油料作物, 长期少雨或季节性干旱是限制花生产量提高的重要环境因子, 也是花生收获前黄曲霉素感染的重要因素。根系是植物吸水的主要器官, 不同土壤水分状况下植物的根系构型可能会表现出显著差异, 进而影响植物根系吸收养分和水分的能力。研究不同土壤水分状况下花生根系形态的发育特征与抗旱性的关系对进一步理解花生的水分吸收、运输、利用和散失机制以及培育抗旱性花生具有非常重要的作用。为明确不同抗旱性花生品种的根系形态发育特征, 探讨其根系形态发育特征对不同土壤水分状况的响应机制, 在防雨棚旱池内进行土柱栽培试验, 研究抗旱型花生品种"花育22号"和干旱敏感型花生品种"花育23号"生育中后期根系生长特征及其对干旱胁迫的响应。设置正常供水和中度干旱胁迫(分别控制土壤含水量为田间持水量的80%~85%和45%~50%)2个水分处理, 分别在花针期、结荚期和饱果期进行取样,根长、根表面积和体积扫描后通过WinRhizo Pro Vision 5.0a程序进行分析; 收获时测定产量和抗旱系数(干旱胁迫处理与正常供水处理下产量之比)。结果表明, "花育22号"具有较高的产量和抗旱系数, "花育23号"对干旱胁迫的适应性小于"花育22号"。抗旱型品种"花育22号"具有较大的根系生物量、总根长和根系表面积, 且深层土壤内根系表面积和体积大于"花育23号"。与正常供水处理相比, 干旱胁迫显著降低2个品种花针期的根系总根长、根系总表面积和总体积, 对结荚期和饱果期根系性状无显著影响; 干旱胁迫增加2个品种生育中后期40 cm以下土层内的根长密度分布比例、根系表面积和体积, 但"花育23号"各根系性状增加幅度小于"花育22号"。干旱胁迫处理下20~40 cm和40 cm以下土层内根系表面积和体积分别与总根长、总表面积和总体积呈显著或极显著正相关, 而正常供水处理下0~20 cm土层内根系表面积和体积与整体根系性状表现极显著正相关。总体而言, 具有较大根系和深层土壤内较多的根系分布是抗旱型花生的主要根系分布特征; 土壤水分亏缺条件下, 花生主要通过增加深层土壤内根长、根系表面积和体积等形态特性调节植株对水分的利用。

Phytohormones can be responsible for activating tolerance responses of drought stress (DS). The present study was done to evaluate the effects of an arbuscular mycorrhizal fungus (AMF), Funneliformis mosseae, on root morphology and root phytohormones levels in trifoliate orange (Poncirus trifoliata) seedlings exposed to well-watered (WW, 75% of maximum water holding capacity) and drought stress (55% of maximum water holding capacity). The six-week DS treatment strongly restricted root mycorrhizal colonization by 27.7%. The DS treatment caused the decrease of total plant biomass and root morphological traits, but the AMF inoculation significantly increased total plant biomass and root total length, projected area, surface area, average diameter, volume, and number of 1st, 2nd, and 3rd lateral root under WW and DS conditions. AMF plants exhibited significantly higher leaf water potential than non-AMF plants exposed to WW and DS. AMF colonization notably regulated the changes in root phytohormone levels: the increase of indole-3-acetic acid (IAA), abscisic acid (ABA), methyl jasmonate (MeJA), and zeatin riboside (ZR) levels under WW condition, and the increase of IAA, ABA, MeJA, ZR, and brassinosteroids (BRs) concentrations under DS conditions. These results concluded that AMF enhanced drought tolerance in trifoliate orange through modulation of root phytohormones and root morphology.

Root morphology is an important factor determining nitrogen (N) uptake by plants, which might be affected by the extent of N application. The processes associated with root morphogenesis of spring maize in response to N application rates remain poorly understood. In this study, both field and pot experiments were conducted to explore the effect of zero-N (N0), optimized-N (N180), and high-N (N360) on root morphology, anatomical structure, and N accumulation in spring maize. N application rates affected root length and surface area, and its endogenous hormone contents. The largest difference in total root length and surface area among the three N rates was found at the silking stage: the total root length and surface increased by 51.36% and 42.58% under N180 and by 7.8% and 30.14% under N360, respectively, compared with N0, and the root/shoot ratio and root bleeding sap significantly increased under N180 and N360 compared with N0. The auxin and jasmonic acid levels of roots under N180 and N360 were higher than N0. N application rates also affected root microstructure and ultrastructure. Compared with N0, the proportions of root aerating tissue under N180 and N360 were decreased by 32.42% and 11.92% at silking. The root tip cell structure was damaged under N0, and intact under N180 and N360. Moreover, the 15N allocation proportions to root and grain under N180 and N360 were increased compared to N0. Grain yields under N180 and N360 increased by 20.44% and 16.6% compared with N0, respectively. It can be concluded that optimized-N application decreased root aerated tissue and thus improved root length and root surface area through regulating auxin and jasmonic acid levels and affected N uptake and grain yield of N-efficient spring maize variety.

Selection for nitrogen (N)-efficient crops is considered to be an effective approach for minimizing the input and the loss of N fertilizers in agricultural fields. This study investigated the hypothesis that nitrate supply may induce changes in root morphology so that N uptake efficiency can be influenced. Different levels of nitrate concentration (0.04, 0.2, 2, and 4 mM) were supplied to five maize (Zea mays L.) inbred lines that had shown different N efficiencies. Possible correlations between N-uptake efficiency and several root parameters of root morphology were evaluated. The two N-efficient varieties, 478 and H21, had higher shoot and root weight and absorbed more N than the two N-inefficient lines, Wu312 and Zong31, especially under low N supply. In general, high nitrate levels (2 and 4 mM) increased the total length of lateral roots (LR), but limited the total length of primary roots (PR) (including seminal and nodal roots) as well as the average length of primary roots. As a result, the total root length (TR) increased with the increasing of nitrate levels. Total N accumulation had significant positive correlations with the root dry weight, TR, and PR at low N supply (0.04–2 mM). At high N supply (4 mM), however, only LR was to some extent correlated to N accumulation. It is concluded that, under N deficient situation, a larger root system (total root length and root surface area) that resulted mainly from the longer primary roots contributed to the efficient N accumulation. At sufficient N supply, longer lateral roots are the main factor contributed to N accumulation.

PDF HTML阅读 XML下载 导出引用 引用提醒 降雨格局变化对白刺幼苗根系形态特征的影响 DOI: 10.5846/stxb201608161679 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（41361100，31560135，31360205，41461044）；甘肃省科技支撑项目（1604FKCA088）；中国博士后科学基金（2014M552514）；甘肃省高等学校科研项目（2015A-067，2015A-069） Response of the root morphology of Nitraria tangutorum seedlings to precipitation pattern changes Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探讨荒漠植物白刺幼苗根系形态对降雨格局变化的响应特征，设置3个降雨量梯度（W-、W、W+）和2个降雨间隔时间梯度（T、T+）进行人工模拟试验，结果表明，1）降雨量和降雨间隔时间对白刺幼苗根系形态有不同程度的影响，且降雨量的作用效应更大。2）降雨量相同时，延长降雨间隔时间均使白刺幼苗主根长、根系平均直径、根体积和根表面积减小，但总根长和根系生物量和总生物量却增加，在高降雨量条件下（W+）延长降雨间隔时间白刺幼苗比根长和比表面积分别增加了45.09%和20.20%，但差异均不显著。3）降雨间隔时间相同时，降雨量减少30%仅使主根长平均增加12.06%，总根长、根平均直径、根体积和根表面积等根系形态指标均显著减少，比根长和比表面积变化不大；降雨量增加30%仅使比表面积显著增加，其余各形态指标差异均不显著，低降雨量条件下（W-）主根长与根冠比达到最大，其他指标均在高降雨量条件下（W+）达到最大。4）对8个根系形态参数进行主成分分析，根系生物量、总根长、总根表面积、比根长、比表面积和根体积6个根系生态参数受降雨格局影响显著。 Abstract:A global climate model has predicted changes in precipitation patterns, with extended periods of time between precipitation events; larger individual precipitation events are expected to increase. Furthermore, with global climate change, local area rainfall patterns have also changed. Over 80 years, the annual precipitation in arid areas of central Asia has generally shown an increasing trend. Such an altered precipitation regime will significantly alter the temporal supply of water to desert ecosystems, and thus have important effects on ecological processes, which could ultimately affect species composition and biological diversity. Root growth of seedlings is the most important stage in plant regeneration and the most sensitive in the plant life cycle to environmental conditions. The responses of root morphology to changes in precipitation and the ability of seedlings to adapt can directly affect the success of subsequent seedling establishment, and may affect regeneration dynamics. Nitraria tangutorum, a super-xerophytic shrub, exhibits a strong tolerance for drought, cold, and saline-alkali soil. The shrub vegetation type in which N. tangutorum is the dominant species is an important vegetation type in the deserts of northwestern China. As a result, N. tangutorum is the key species for the revegetation of these arid and semiarid areas. Most research has examined the impacts of the amount of precipitation on this species rather than the effects of both the amount and interval of precipitation. To understand how climate-driven changes in precipitation can affect desert plants, especially the response of the root morphology to precipitation patterns change, we conducted a controlled experiment with two factors: precipitation quantity (natural precipitation as a control, reduction of 30% and increase of 30%) and interval (time elapsed between two precipitation events; 5 or 10 days). The results showed that root morphological characteristics were influenced by total precipitation and precipitation interval, the former playing a more significant role than the latter. Under the same precipitation condition, the main root length, root diameter, root volume, and root surface area were decreased, total root length, root biomass, and total biomass were increased by extended precipitation intervals, and specific root length (SRL) and specific root area (SRA) were considerably increased by 45.09% and 20.20% in high precipitation, respectively, but the difference was not significant. For the same precipitation condition interval, the main root length was increased by 12.06%, total length, diameter, volume and surface area were significantly decreased, and SRL and SRA were basically unchanged in precipitation reduced by 30% conditions. The SRA increased significantly, but the other index differences were not significant. The main root length and root-shoot ratio were largest in low precipitation, but others (total root length, root surface area, average root diameter, root volume, root biomass, SRL and SRA) were larger in high precipitation conditions. Eight characteristics of root morphology were analyzed using principle component analysis. The characteristics of root biomass, total root length, total root surface area, SRL, SRA and root volume were significantly affected by precipitation pattern changes. We suggested that the root morphology of N. tangutorum seedlings was mainly affected by the amount of precipitation. However, the precipitation interval could be as important as the amount of precipitation for the root morphology of N. tangutorum seedlings. Increasing the precipitation amount and extending the precipitation interval (less frequent but higher volume precipitation events) enhanced root growth and population regeneration. 参考文献 相似文献 引证文献

Morphological, physiological and metabolomic analysis to unravel the adaptive relationship between root growth of ephemeral plants and different soil habitats

Root morphological characteristics are important parameters for the evaluation of plant adaptation to stress environment. In this study, a pot experiment was conducted to investigate changes in the root morphology of Bothriochloa ischaemum intercropped with Lespedeza davurica under three soil water regimes and two phosphorus (P) fertilizer treatments. Results showed that root biomass (RB) per B. ischaemum plant decreased as its proportion increased in the mixtures. There were no significant differences in root:shoot ratio (RSR) among the mixture ratios, and P application did have consistent effects on the RSR. Bothriochloa ischaemum tended to have smaller root surface area (RSA), root average diameter (RAD), specific root length (SRL), and specific root area (SRA) under water stress conditions. There was a negative linear relationship between RB and RSA under each water and P treatment. Negative and positive linear relationships were found between RB and TRL (total root length), TRL and RSA, respectively, except under severe water stress without P application. P application decreased the RAD and increased the SRA and SRL of B. ischaemum under water stress. All these suggest two apparent response mechanisms for B. ischaemum under water stress and P application: an increase in length of small diameter roots and decrease in root weight density.

This study aimed to evaluate the effects of phosphorus (P) deficiency on the lateral root growth of Fraxinus mandshurica seedlings and to reveal the potential molecular mechanisms involved. F. mandshurica seedlings were treated with various concentrations of P (0, 0.5, 1, and 2 mM KH2PO4) for 15 d. The growth of lateral roots was quantified by the number of lateral roots, total root length, total root surface area, and root : shoot ratio. Additionally, the levels of endogenous hormones and acid phosphatase were determined in the lateral roots of F. mandshurica seedlings using enzyme‐linked immunosorbent assay (ELISA). The transcription of 17 FmWRKYs and FmPHR1 was detected in the lateral roots of F. mandshurica seedlings using quantitative real‐time PCR (qRT‐PCR). F. mandshurica seedlings under P deficiency (0 mM) exhibited significantly higher number of lateral roots, total root length, total root surface area, and root : shoot ratio than those under P supply. P deficiency significantly decreased the levels of indole‐3‐acetic acid, brassinolide, and ethylene, and increased the levels of gibberellins 3, cytokinin, abscisic acid, and acid phosphatase in the lateral roots of F. mandshurica seedlings when compared to seedlings with P supply. In addition, the transcription of four FmWRKYs, including FmWRKY6, FmWRKY23, FmWRKY44, and FmWRKY71, as well as FmPHR1 were significantly higher in the lateral roots of F. mandshurica seedlings under P deficiency compared to seedlings treated with 1 mM P. Phosphorus deficiency promoted the lateral root growth of F. mandshurica seedlings and this process may be associated with the up‐regulation of FmWRKY6, FmWRKY23, FmWRKY44, FmWRKY71, and FmPHR1.

The objective of this study was to analyze K-efficiency and root morphology in two kinds of K-efficiency cotton genotypes. The results showed that K-efficiency of genotype 103 was 160.2 g g 1 and 47.5 g g 1 at low (4 mg L-1) and high (40 mg L-1) K levels while genotype 122 was 133.8 g g 1 and 37.9 g g 1. In addition, genotype103 had higher ability to transfer K to leaves than genotype 122. Under two K levels, Leaves K accumulation of genotype 103 was 84.6% and 62.6% of the whole plant, while that of genotype 122 was 63.4% and 56.0%. High K-efficiency genotype 103 had higher total root length, surface area and volume than low K-efficiency genotype 122 regardless of the K concentration treated. Especially when the concentration of K in the environment was low, genotype 103 still had better root system than genotype 122. When K was insufficient, the total root length and total root surface area of genotype 103 increased by 46.2% and 13.9%, while genotype 122 showed decreases in root parameters. Root system was classified into fine roots, middle roots and coarse roots according to root diameter. Low K condition limited the development of coarse roots. In genotype 103, coarse root length, surface area and root volume decreased by 54.0%, 62.8%, and 75.2%, respectively, meanwhile, genotype 122 also had a reducing coarse root parameters. Effect of low K condition on fine roots varied in different cotton genotypes. The fine root length, surface area and volume of genotype 103 increased by 69.0%, 77.0%, and 80.4%, compared with these in appropriate K treatment, and were 1.9, 2.3, and 2.6 times higher than these of genotype 122, respectively.

Cultivars of hot pepper (Capsicum annuum L.) differ widely in their fruit cadmium (Cd) concentrations. Previously, we suggested that low-Cd cultivars are better able to prevent the translocation of Cd from roots to aboveground parts, but the corresponding mechanisms are still unknown. In this study, we aimed to improve understanding of the root morphological characteristics of the mechanisms involved in two low-Cd and a high-Cd cultivar. Seedlings were grown in nutrient solutions containing 0 (control), 2, and 10 μM Cd for 20 days, and Cd contents for the three cultivars were compared with changes in root morphology. The total root length (RL), root surface area (SA), number of root tips (RT), and specific root length (SRL) of all cultivars were decreased significantly by the 10 μM Cd treatment with the exception of the SA in JFZ, which showed no obvious change. For each cultivar, the 10 μM Cd treatment decreased significantly RL and SA specifically in roots with diameters (RD) of RD ≤ 0.2 mm or 0.2 mm < RD ≤ 0.4 mm, and increased significantly RL and SA specifically in roots with diameters of 0.6 mm < RD ≤ 0.8 mm. Hot pepper cultivars differ greatly in Cd accumulation and root morphology. In the 10 μM Cd treatment, root volume (RV), SA, and RT of all cultivars were negatively correlated with Cd concentration and amount in roots. However, RL, SA, RV, and RT of all cultivars were positively correlated with Cd concentration and amount in shoots, and translocation rate of Cd. The two low-Cd cultivars of hot pepper had less root tips, shorter root length, and smaller root surface area than the high-Cd cultivar in 10 μM Cd treatment, which may play a vital role in reducing root-to-shoot Cd translocation.

Root Morphology and Nitrogen Uptake of Maize Simultaneously Supplied with Ammonium and Nitrate in a Split-root System

A localized supply of phosphorus may affect root morphology and architecture, and thereby affect phosphorus uptake by rice plants. In the present study, we attempted to test this hypothesis using two rice cultivars representing upland and lowland ecotypes grown in specially designed split and stratified soil cultures with a low-phosphorus red soil. Our data indicate that a localized supply of phosphorus increased both total root length and root fineness, particularly in the high-phosphorus zone. In split culture, plants roots tended to preferentially grow on the high-phosphorus zone, with about 70–75% of the total root length allocated to the high-phosphorus compartment. The total root length on the high-phosphorus side in the split-phosphorus treatment was significantly longer than that in the homogenously high-phosphorus treatment, implying that a phosphorus-deficiency signal from the low-phosphorus side may stimulate the growth of the roots located in the high-phosphorus zone. In stratified soil culture, changes in root morphology and architecture were also observed as indicated by increased total root length, root fineness and relative root allocation in the high-phosphorus layers, again suggesting altered root morphology and preferential root proliferation in the high-phosphorus regions. The induced changes in root morphology and architecture by localized phosphorus supply may have both physiological significance and practical implications in that plants can meet the demand for phosphorus with parts of the roots reaching the high-phosphorus zone, hence localized fertilization methods such as side dressing or banded application of phosphorus fertilizers may both minimize phosphorus fixation by the soil and increase phosphorus uptake efficiency from the fertilizers.

The root system plays an important role in the growth and development of cotton, and root growth is closely related to shoot growth, both of which are affected by N availability in the soil. However, it is unknown how N affects root growth and the root–shoot relationship under various N rates in the Yellow River Basin, China. Thus, the aim of this study was to assess the impacts of the application rate of N on root growth and the root–shoot relationship, to provide insight into the N regulation of root and shoot growth and N efficiency from the perspective of the root system. A field experiment conducted in 2014 and 2015 was used to determine the effects of N rates (0, 120, 240, and 480 kg ha–1) on root morphology, root distribution, the root–shoot relationship, and cotton yield. A moderate N fertilization rate (240 kg ha–1) increased root length, root surface area, and root biomass in most soil layers and significantly increased total root growth and total root biomass by more than 36.06% compared to the 0 kg ha–1 treatment. In addition, roots in the surface soil layers were more strongly affected by N fertilization than roots distributed in the deeper soil layers. Total root length, total root surface area, and root biomass in the 0–15 cm layer were significantly correlated with shoot biomass and boll biomass. In the 60–75 cm layer, total root length, total root surface area, and root length were significantly positively correlated with seed cotton yield. The application of a moderate level of N markedly increased total shoot biomass, boll biomass, and seed cotton yield. Our results show that increased shoot and boll biomasses were correlated with a significant increase in the root system especially the shallow roots in the moderate N treatment (240 kg ha–1), leading to an increase in cotton seed yield.

Zinc uptake and accumulation in winter wheat relative to changes in root morphology and mycorrhizal colonization following varying phosphorus application on calcareous soil