氮、磷供给水平对丛枝菌根真菌生长发育的影响

为了研究营养元素氮、磷对丛枝菌根真菌（arbuscular mycorrhizal fungus）生长发育的影响,以黄瓜、番茄为宿主植物,采用半液培的方式,在LAN营养液的基础上,设置不同氮、磷供给水平的处理。结果显示,同一N、P处理水平条件下,接种处理对黄瓜植株地上部和根系的生物量未产生显著影响。不同N、P供应水平对菌根生长发育显著影响。提高供氮水平显著增加了菌根结构的数量,同时降低了植株地上部的磷含量;而磷处理对侵染结构的影响因不同供氮水平而有所差异,供N 0.3 mmol/L时,提高磷供给水平显著降低了侵染结构的数量,而当把供氮水平提高到N 3 mmol/L时,随着供磷水平的增加,菌根侵染结构数量显著增加。在此条件下,基于氮对菌根真菌和植株磷营养状况的影响的一致性,氮对菌根结构的作用可能源于氮、磷之间的交互作用。     

菌根化育苗对玉米生长和养分吸收的影响

【目的】丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)侵染作物根系形成菌根共生体系对于作物吸收磷具有重要作用,但该结果大多来源于室内受控试验,有限的田间试验因环境条件、试验材料与接种技术等差异致使AMF菌剂应用效果不一。本研究通过玉米菌根化育苗和田间移栽,分析了接种AMF对玉米生长、养分吸收、籽粒产量及养分含量的影响,以期推进菌根技术的实际生产应用。【方法】以自交品系玉米B73为供试作物,于2018年5月至10月在北京市延庆区进行了田间试验。田间小区设置基施磷(+P)和不施磷(–P)处理。供试AMF为Rhizophagus irregularis Schenck&Smith BGC AH01。玉米种子催芽后,分别播入加入AMF菌剂(+M)和菌剂过滤液(–M)的育苗钵内,培养两周后移栽至田间。玉米在田间条件下生长至拔节期时,使用便携式光合仪测定叶片光合速率与气孔导度,取样测定地上部与根部干重和养分元素含量,同时测定菌根侵染率;在玉米完熟期取样,测定籽粒百粒重、籽粒产量及养分含量。【结果】无论田间施磷与否,接菌植株根系的菌根侵染强度和丛枝丰度均显著高于不接菌植株。不施磷情况下,+M处理显著提高了玉米根系干重,玉米生长的菌根依赖性(163.7%)显著高于施磷情形(124.1%)。–P–M处理玉米叶片的光合速率和气孔导度显著低于其他3个处理。–P+M处理玉米叶片的光合参数、玉米地上部和根部磷含量与+P+M均无显著差异。与–P–M处理相比,–P+M显著提高了玉米籽粒产量和百粒重,同时也提高了籽粒中锌、锰、镁等矿质养分的含量,且与+P+M处理相比均无显著差异。【结论】玉米幼苗接种AMF后再移栽到田间,可以显著提高拔节期玉米根系的菌根侵染率,促进玉米地上部和根部对磷及锌、锰和镁的吸收,进而促进玉米的生长,提高籽粒产量和养分含量。本试验条件下,菌根化育苗可以达到与施磷同样的效果,在保障作物不减产的前提下减少磷肥施用量。     

供磷水平对玉米丛枝菌根侵染及其对异质养分吸收的影响

【目的】 探究酸性土壤玉米丛枝菌根侵染对植物磷素吸收的促进作用,以加深理解根外菌丝对局部磷养分的获取如何受丛枝真菌侵染和环境磷养分的影响。 【方法】 以玉米为宿主植物,进行盆栽试验。在低磷酸性土壤上设置供P 0、50、500 mg/kg 3个水平 (P0、P50、P500),供试磷肥为磷酸二氢钾。每个处理再设置局部养分处理,即在每个重复中埋置两个各装有120 g灭菌土 (提前加 P 50 mg/kg) 的塑料小管,分别用孔径为0.45 μm(根系、菌丝均不能进入,以“–H”表示处理) 和50 μm(根系不能进入,菌丝可以进入,以“+H”表示处理) 的尼龙膜封住管口。测定了玉米的生长与磷吸收、土著丛枝菌根真菌的侵染和根外菌丝密度以及菌丝对局部磷养分的获取。 【结果】 1) 玉米株高、叶片SPAD值、全株干重、磷浓度及吸收量都随供磷水平升高而增加,以P50处理的根系干重最高,根冠比随供磷水平上升而降低。3个供磷水平下玉米根系均有不同程度的丛枝菌根真菌侵染。以P50处理的丛枝菌根侵染率、丛枝和孢囊结构发育最好;P0处理的丛枝菌根侵染率、丛枝丰度与P50处理没有显著差异,但孢囊丰度明显下降;P500处理虽然87.2%的根系具有侵染点,但整个根系形成的真菌结构、丛枝和孢囊比例远低于P0和P50处理,丛枝菌根的发育受到严重抑制。2) 土体土 (除塑料管之外的土) 菌丝密度随供磷水平升高而降低,但P0和P50处理差异不显著。–H处理塑料管中的菌丝密度在3个供磷水平下基本不变,保持在极低水平,而+H处理塑料管中的菌丝密度随供磷水平升高而下降。在相同供磷水平下,土体土的菌丝密度最高,其次是+H处理,–H处理的菌丝密度最低。根外菌丝从+H处理塑料管中获取的磷随环境供磷水平的升高而减少。 【结论】 酸性土壤条件下,适当地供磷可以促进玉米根系生长和丛枝菌根真菌的侵染。根外菌丝对局部磷养分的获取受环境磷养分的调控,在环境磷养分较低而局部磷养分高于环境磷养分时,较多的菌丝会进入局部区域获取磷。      

接种丛枝菌根真菌和施用磷石膏对烤烟生长及砷累积的影响

为了探讨丛枝菌根真菌（Arbuscular mycorrhizalfungi,AMF）对烤烟生长及磷石膏农用安全的影响,通过盆栽模拟试验研究了磷石膏（Phosphogypsum,PG）不同添加量[0、40mg·g^-1（PG0、PG40）1和接种两种AMF[Glomus massecle（GM）、G．aggregatum（GA）】对烤烟（KRK26）苗期生长及其磷（P）、硫（S）、砷（As）吸收的影响。试验结果表明：无论是否接种AMF,磷石膏的添加均显著增加了KRK26地上部生物量及其植株s含量、吸收量及吸收效率;除不接种处理（NM）的烤烟根系外,PG40处理显著增加了KRK26植株P含量、吸收量及吸收效率,并显著降低了NM处理的地上部As含量及吸收量,进而增加了磷砷吸收比。相同PG添加水平下,与不接种相比,接种GM和GA均显著增加了KRK26植株的生物量。除PGO处理的烤烟根系外,接种GM显著增加了KRK26植株P、S含量与吸收量及吸收效率,以及植株As含量及吸收量,并显著增加了PG40处理的植株磷砷吸收比;接种GA也显著增加了KRK26植株P、S含量及吸收量,并显著降低了PG0处理地上部As含量及吸收量。所有复合处理,以添加磷石膏40mg·g^-1和接种GA处理对KRK26的生长促进效果较好,对磷石膏施用造成的As污染有一定抵御作用。     

基于RHE元件和拟南芥转录组的根毛发育基因筛选

拟南芥根毛发育是分子发育生物学的重要模型。本试验通过分析拟南芥根毛突变体bst的芯片数据,并对筛选到的下调表达变化超过2倍的基因的启动子进行根毛顺式作用元件RHE(Root HairElement)的筛查,初步获得了根毛发育候选基因。结果表明,在bst中下调表达变化超过2倍的494个基因中,共有13个基因启动子中有RHE元件,其中5个为已报道的参与根毛发育基因,8个为本研究首次发现的参与根毛发育的候选基因。     

丛枝菌根真菌对玉米锌、磷拮抗作用的影响

【目的】 利用丛枝菌根 (arbuscular mycorrhizal fungi,AM) 真菌与作物互利共生的关系来提高作物对锌的吸收是缓解锌、磷拮抗作用的途径之一,本试验在不同锌、磷浓度条件下,研究了接种AM真菌对玉米侵染和锌、磷吸收的影响,以期为揭示AM真菌影响锌、磷拮抗作用的机理提供理论依据。 【方法】 采用盆栽试验,设置三个施磷水平 (0、200 、400 mg/kg),两个施锌水平 (0、5 mg/kg),2个接菌水平[接菌 (+AM)和不接菌 (–AM)],共12个处理,每个处理4次重复。利用生物镝灯补充光照,在人工光照植物培养室内植株生长50天后,地上部与根部分别收获,测定其生物量、锌磷的含量和吸收量。 【结果】 施磷和接种AM真菌都显著提高了玉米植株生物量,不施锌条件下,施磷从0 mg/kg增加到400 mg/kg,玉米植株地下部和地上部生物量分别提高6.67倍、9.30倍。接种处理对玉米植株生物量的影响也有相同的趋势。在锌水平为5 mg/kg、磷水平为200 mg/kg的条件下,接种AM真菌玉米植株地下部磷的吸收量和含量分别增加了110%、55%;在同一锌、磷供给条件下,接种AM真菌显著提高了玉米对锌的吸收量,地下部和地上部分别是未接种处理的1.71倍和1.68倍。随着施磷水平的不断提高,玉米植株的锌含量会逐渐下降。不施锌条件下,施磷从0 mg/kg增加到200 mg/kg,玉米植株地上部锌含量降低36%,与之相反,接种AM真菌后地上部锌含量增加35%。但在高磷条件 (400 mg/kg) 下,接种AM真菌对玉米植株锌磷含量和吸收量影响均不显著。 【结论】 在本试验条件下,施磷抑制玉米对锌的吸收,接种AM真菌可提高玉米锌磷的含量和吸收量,有效缓解玉米锌磷拮抗作用,改善玉米的锌营养状况。      

减量施氮与间作模式对甜玉米AMF侵染和大豆结瘤及作物氮磷吸收的影响

通过4季(2014年秋季,2015年春、秋,2016年春季)大田定位试验,对比研究了两种施氮水平[300 kg·hm~(-2)(N1:减量施氮)和360 kg·hm~(-2)(N2:常规施氮)]和4种种植模式[甜玉米|菜用大豆2∶3(S2B3)、2∶4(S2B4)间作、甜玉米单作(SS)和菜用大豆单作(SB)]对华南地区甜玉米和大豆产量、甜玉米AMF侵染率、大豆根瘤菌等的影响。结果表明,减量施氮间作处理的甜玉米产量显著高于单作。2016年春季S2B3-N1处理大豆的根瘤数显著高于S2B3-N2处理;4季减量施氮和间作处理对大豆根瘤干重均没有显著影响。2015年春秋两季两种施氮水平间作处理的甜玉米生物量和氮含量均显著高于相应的单作处理;且减量施氮间作模式甜玉米AMF侵染率显著高于常规施氮处理。2015年秋季减量施氮间作模式处理甜玉米的磷含量显著高于单作处理。减量施氮与间作菜用大豆显著提高了甜玉米氮和磷含量、AMF侵染率、生物量及产量,是华南地区甜玉米资源高效利用的可持续生产模式。     

丛枝菌根真菌对青稞生长发育及磷营养的影响研究

青稞是大麦类作物中的一种，是西藏地区栽培面积最大、产量最多、分布最广的农作物品种。近年来，青稞的保健作用（富含-β葡聚糖和“生育三烯酚”）已得到国内外公认，因而青稞生产受到更广泛的关注。然而，根据西藏首次土壤资源调查结果，全自治区低磷（速效磷〈10mgkg^-1）土壤占总耕地面积的46．9％～72．3％（内部资料）。土壤供磷不足是限制青稞高产的重要潜在因素之一，同时西藏目前没有一家化肥厂，生产、科研所需肥料全靠从内地长途运输。寻找一条经济有效的途径缓解西藏地区农业生产肥料紧缺的状况成为一项迫切的任务。     

交联聚丙烯酰胺和丛枝菌根真菌对烟苗生长、养分吸收和生理指标的影响

利用漂浮育苗技术培育烟苗,在育苗基质中加入交联聚丙烯酰胺(crosslinked polyacrylate amine,CPA)和接种AM真菌,研究了它们对烟苗生长、养分吸收及有关生理指标的影响.结果表明,在不接种AM真菌的处理中,CPA显著促进烟苗生长,其原因可能是改善了烟苗的氮素营养,同时还提高了烟苗氮、磷、钾吸收置;但在接种AM真菌的处理中,CPA对烟苗生长无显著影响,显著降低AM真菌的感染率和烟苗硝酸还原酶活性.此外,接种AM真菌的烟苗生物量相似,不因菌株和基质CPA含量不同而发生变化.在-CPA的基质中,接种AM真菌的烟苗生物量显著高于不接种,增加磷、钾吸收量,提高硝酸还原酶活性;在+CPA的基质中,接种AM真菌后的烟苗生物量与不接种的相似,烟苗养分吸收、硝酸还原酶、几丁质酶和根系活力因菌株和CPA含量不同而异.由于降低AM真菌的感染率,不能进一步改善菌根烟苗生长,菌根效应可被CPA的促生作用掩盖甚至超过,故在实际育苗工作中,建议采用接种AM真菌或在基质中适量加入CPA一种方式即可.     

丛枝菌根真菌促进植物摄取土壤磷的作用机制

磷在土壤中易被固定沉淀,在植物磷利用率低的情况下,过度施肥会造成磷肥浪费,可能通过地表径流、地下水溶解等方式,造成水体富营养化产生面源污染,对人类生产生活造成较大影响。丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)和植物结合所形成的共生菌根可以显著增强植株对磷的吸收利用。通过AMF可以提高宿主植株对磷的吸收转运的特性,从AMF促进植株对磷元素的摄取机制、AMF促进植物磷摄取分子机理、AMF作用下根系分泌物对植株磷利用的影响与根际微生物对AMF磷元素利用的影响4个方面的研究进展进行分析总结。AMF可以通过改变宿主植株的根系形态和菌丝网络的形成,扩大植株对养分吸收范围;释放有机酸、磷酸酶和质子等根系分泌物改变土壤结构和理化性质,与根际微生物共同作用降解土壤中难溶性磷酸盐;诱导相关磷转运蛋白基因的特异性表达,提高植株对磷的转运能力而促进其吸收。     

The role of ethylene in root hair growth in Arabidopsis

Ethylene promotes root hair development in many higher plants. Recently the role of ethylene has been investigated in Arabidopsis because of the range of genetic resources available in this species. Root hairs in the Arabidopsis root form on specialized epidermal cells (trichoblasts) located in the cleft between underlying cortical cells. Hairless epidermal cells develop from atrichoblasts that are located over single cortical cells. Ethylene not only promotes root hair outgrowth but also causes cells that are normally hairless to form root hairs. This suggests that ethylene may play a dual function in the formation of root hairs. Firstly it may play a role in hair initiation and secondly may be required for the elongation of hairs. Alternatively it may suggest that these are two parts of the same process.     

The control of root hair formation: suggested mechanisms

Little is known about the physiological regulation of root hair development. Though the literature on the topic is fragmentary, with many gaps, it has been used to put forward some proposals for a central regulatory mechanism, taking note especially of the strong physiological influence of environmental factors on root hair formation. A hypothesis which implicates ethylene (ET) in this mechanism is proposed. This hypothesis is supported by numerous indications and observations in the literature about the effect of ET on cell wall formation and cell wall properties during the phase of root expansion and hair formation. It is assumed that environmental conditions control the effective ET concentration in epidermal hair-forming cells; they influence root development and ET production, while, through affecting the rhizosphere, they modify gas exchange at the root surface, accelerating removal of ET thereby limiting its function in hair formation. In such a way the effects of various specific factors (e.g. soil temperature, bulk density, gas exchange at the root surface or the effect of nutrients) might be manifestations of a central regulatory mechanism. The hope is that this hypothesis will stimulate further research and some suggestions are made as to the direction such research might take.     

Comparison of root and root hair growth in solution and soil culture

Aerated solution culture is frequently used for studying plant growth. Few comparisons have been made of root growth in solution with that found in soil. The objective of this study was to compare root growth and root hair development in these two mediums. Corn (Zea mays L.) grown in aerated solution at two temperatures (18 and 25°C) and three P concentrations (2, 10, and 500 μmol L^‐1) was compared with that in three soils, Raub (Aquic Argiudoll) and two Chalmers (Typic Haplaquoll) silt loams, in a controlled climate chamber over 21d. Corn plant weight and root growth were similar in solution culture and Raub soil when grown at an air and soil temperature of 18°C. At 25°C both yield and root growth were greater in Raub soil, even though P uptake by corn was 7‐fold greater in solution culture. The same difference was found when corn grown at 25°C in solution culture at 3 different P concentrations was compared with that grown in Chalmers soil at two P levels. Percentage of total root length with root hairs, root length and density and consequently root surface area, were all greater in the Chalmers soil than in solution culture. An increase in soil P, resulted in a decrease in root hair growth. No such relationship was found in solution culture. Although the recovery and measurement of plant roots and root hairs is more convenient in solution culture, results from this study indicate that the usefulness of solution culture for determining those factors which control root growth and root hair development in soil is limited.     

Root trait plasticity and plant nutrient acquisition in phosphorus limited soil

To overcome soil nutrient limitation, many plants have developed complex nutrient acquisition strategies including altering root morphology, root hair formation or colonization by arbuscular mycorrhizal fungi (AMF). The interactions of these strategies and their plasticity are, however, affected by soil nutrient status throughout plant growth. Such plasticity is decisive for plant phosphorus (P) acquisition in P‐limited soils. We investigated the P acquisition strategies and their plasticity of two maize genotypes characterized by the presence or absence of root hairs. We hypothesized that in the absence of root hairs plant growth is facilitated by traits with complementary functions, e.g., by higher root mycorrhizal colonization. This dependence on complementary traits will decrease in P fertilized soils. At early growth stages, root hairs are of little benefit for nutrient uptake. Regardless of the presence or absence of root hairs, plants produced average root biomass of 0.14 g per plant and exhibited 23% root mycorrhizal colonization. At later growth stages of maize, contrasting mechanisms with functional complementarity explained similar plant biomass production under P limitation: the presence of root hairs versus higher root mycorrhizal colonization (67%) favored by increased fine root diameter in absence of root hairs. P fertilization decreased the dependence of plant on specific root traits for nutrient acquisition. Through root trait plasticity, plants can minimize trade‐offs for developing and maintaining functional traits, while increasing the benefit in terms of nutrient acquisition and plant growth. The present study highlights the plasticity of functional root traits for efficient nutrient acquisition strategies in agricultural systems with low nutrient availability.     

Growth and nutrient uptake of temperate perennial pastures are influenced by grass species and fertilisation with a microbial consortium inoculant

Background: The low fertility of sandy soils in South‐Western Australia is challenging for the establishment of temperate perennial pastures. Aims: To assess whether microbial consortium inoculant may improve plant growth by increasing nutrient supply, root biomass and nutrient uptake capacity. Methods: Five temperate perennial pasture grasses–cocksfoot (Dactylis glomerata L. cv. Howlong), phalaris (Phalaris aquatica L. cv. Atlas PG), tall fescue (Festuca arundinacea L. cv. Prosper), tall wheatgrass (Thinopyrum ponticum L. cv. Dundas), and veldt grass (Ehrharta calycina Sm. cv. Mission) were tested in a controlled environment on the growth and nutrition with the microbial consortium inoculant and rock mineral fertiliser. Results: Veldt grass produced the highest shoot and root growth, while tall fescue yielded the lowest. Rock mineral fertiliser with or without microbial consortium inoculant significantly increased root and shoot biomass production across the grass species. The benefit of microbial consortium inoculation applied in conjunction with rock mineral fertiliser was significant regarding shoot N content in tall wheatgrass, cocksfoot and tall fescue. Shoot P and K concentrations also increased in the five grass species by microbial consortium inoculation combined with rock mineral fertiliser in comparison with the control treatment. Arbuscular mycorrhizal (AM) colonisation decreased with rock mineral fertilisation with or without microbial consortium inoculant except in cocksfoot. Conclusions: The response to microbial consortium inoculation, either alone or in combination with rock mineral fertiliser, was plant species‐dependent, indicating its potential use in pasture production.     

The effect of mycorrhizal inoculation and phosphorus application on the growth and mineral nutrient status of apple seedlings

Apple seedlings cv. Antonovka were grown in soil taken from an orchard with a distinctive specific apple replant disease. The influence of the different available soil phosphorus (P) level (0, 20, 40 and 80 mg P dm^?3 of soil) and arbuscular mycorrhizae fungi (AMF) inoculation on the vegetative growth, chlorophyll fluorescence, and the frequency of mycorrhizae were assessed. Moreover, leaf and root mineral composition was ascertained by means of the inductively coupled plasma mass spectrometry (ICP-MS) method. The inoculation with AMF influenced seedlings growth as well as the biomass production and partitioning. The method of inoculation (granular, quick root dip or irrigation) had a great impact on the frequency of mycorrhizae (83.3, 98.8 and 100%, respectively) as well as on the abundance of arbuscules (36.4, 62.9 and 67.3%) as compared to the control (11.7%). The beneficial effect of AMF on leaf PSII efficiency was established. AMF inoculated plants had a significantly higher content of nitrogen, potassium, phosphorus and boron (N, K, P and B) in the shoots and a higher content of nitrogen, sulfur, copper, iron, manganese, molybdenum and titanium (N, S, Cu, Fe, Mn, Mo and Ti) in the roots. Although roots showed a higher concentration of aluminium, barium, lithium, cadmium, lead and vanadium (Al, Ba, Li, Cd, Pb, and V) but upon AMF inoculation, the concentration of these cations was much lower.     

Mycorrhizal function on soil aggregate stability in root zone and root-free hyphae zone of trifoliate orange

Arbuscular mycorrhizal fungi (AMF) influence soil aggregate stability through their hyphae, roots, and glomalin-related soil protein (GRSP); however, the individual effect of these factors is difficult to distinguish. Pots separated by a 37-μm mesh bag buried in the middle of each pot was used to establish root zone (root + hyphae) and hyphae zone (roots free), where the Poncirus trifoliata seedlings were colonized by Funneliformis mosseae or Paraglomus occultum in root zone. AMF inoculation significantly increased shoot, root, and plant’s total biomass, soil organic carbon, GRSP fractions, 2–4 and 1–2 mm size water-stable aggregates, and mean weight diameter (MWD) in root or hyphae zone. Within root zone, root colonization and biomass presented stronger relationship with MWD than GRSP fractions. While, within hyphae zone, total of GRSP fraction was significantly correlated with MWD. The study, suggested further that root biomass and colonization were the main mechanisms in root zone for improving aggregate stability, whereas total of GRSP fractions was of paramount importance in hyphae zone. Mycorrhizal effect on aggregate stability was observed to be contrastingly different between root zone and hyphae zone.     

The influence of root hairs on the uptake of phosphate

Abstract

The uptake of phosphate from stirred solution by roots was not affected by root hairs. In contrast to this, root hairs appreciably increased the uptake of phosphate from a clay soil.     

Effects of avocado (Persea americana Mill.) scion on arbuscular mycorrhizal and root hair development in rootstock

Grafting is an important process to propagate horticulture plants; however, the mechanism through which the scion affects the absorption of rootstock remains poorly understood. The effects of the scion on AM fungi types in the rhizosphere soil of rootstock and the absorption of mycorrhizal root were determined in this study. Composition of arbuscular mycorrhizal (AM) fungi, soil assessment, spore density, hyphal length density, glomalin-related soil protein (GRSP) content in rhizosphere soil, root hair morphology and AM colonisation rate were measured among ‘Kampong’ avocado rootstocks grafted with five scions and ‘Kampong’ seedling trees. Results showed the main types of AM fungi in avocado seedling trees and trees grafted with five scions were nearly identical. However, the proportion of main genera exhibited differences. In addition, alkali-hydrolysable N, alkali-hydrolysable P and available K in rhizosphere soil, root hair density, AM colonization, spore density, hyphal length and GRSP content suggested the absorption of ‘Kampong’ rootstocks grafted with ‘Monroe’, ‘Wilson seedless’, ‘Hass’ and ‘Tonnage’ possessed stronger absorption than ‘Kampong’ seedling trees because of high AM colonisation and root hair density. This study suggested scions regulated both the AM and root hair development systematically and laid the foundation for future research of AM-enhancing avocado production.