柑橘丛枝菌根真菌生长与根际有效磷和磷酸酶活性的相关性

通过观测田间国庆1号温州密柑/枳和国庆4号温州密柑/枳根系菌根侵染率、孢子密度、根际有效磷和磷酸酶活性的年变化,探讨丛枝菌根真菌生长与根际有效磷和磷酸酶活性的相关性.结果表明,2种柑橘菌根侵染率和孢子密度的年变化均呈 “Λ”形,2月和12月较低,4月和10月居中,6月和8月较高;有效磷和中性磷酸酶年变化呈“V”形.2种柑橘的菌根侵染率都与孢子密度呈极显著正相关,与有效磷呈极显著负相关,说明较高的孢子密度和较低的有效磷对菌根侵染率有促进作用;2种柑橘的孢子密度均与有效磷呈极显著负相关,与中性磷酸酶和总磷酸酶呈极显著正相关,表明中性磷酸酶和总磷酸酶对孢子密度有刺激作用,而有效磷对其有抑制作用.柑橘树下有机磷矿化主要以中性磷酸酶为主.     

丛枝菌根结构与功能研究进展

丛枝菌根(arbuscular mycorrhiza,AM)是陆地生态系统中分布最广泛、最重要的互惠共生体之一,对提高植物抗逆性、修复污染生境、保持生态系统稳定与可持续生产力的作用显著.AM结构特征是判断菌根形成的主要指标,与其功能密切相关.本文总结了AM丛枝结构、泡囊结构、菌丝结构和侵入点结构等发育特征;分析了A型丛枝结构、P型丛枝结构、泡囊结构和根外菌丝结构与促进寄主植物养分吸收和生长、提高植物抗旱性、耐涝性、耐盐性、抗高温、拮抗病原物、提高植物抗病性、抗重金属毒性、分解有毒有机物、修复污染与退化土壤等功能的关系,及其所发挥的重要作用;探讨了影响AM结构与功能的因子,以及基于AM不同结构所发挥功能的作用机制.旨在为系统研究AM真菌发育特征、AM真菌效能机制,以及评价和筛选AM真菌高效菌种提供依据.     

柑橘丛枝菌根发育状况田间调查

对湖北省秭归县柑橘良种示范场、三溪河和邓加坡3个采样点的不同柑橘品种的菌根发育状况进行田间调查。结果表明,调查的柑橘均被丛枝菌根真菌侵染,其发育状况因品种、立地条件而异。在3个采样点中,以柑橘良种示范场的枳/罗伯逊脐橙36号/卡特夏橙菌根侵染率最高;以柑橘良种示范场的枳/罗伯逊脐橙36号/脐血橙根际的孢子密度最高。菌根侵染率与孢子密度间没有显著相关性。     

3种农业措施对柑橘丛枝菌根发育的影响

研究了土施N肥(2L 0.5%尿素)、覆草(5~6cm厚杂草)和翻耕(20cm表层土翻耕2次)三种措施,对田间条件下的国庆1号/枳和国庆4号/枳的菌根侵染率和孢子密度的影响。结果表明,覆草极显著地提高了2种柑橘根系的孢子密度,而对菌根侵染率无显著影响;施N肥极显著降低2种柑橘的孢子密度;翻耕极显著抑制了2种柑橘的菌根侵染率。2种柑橘的根系菌根侵染率和孢子密度间都存在显著或极显著正相关。     

南方红豆杉丛枝菌根(AM)的研究

研究了南方红豆杉根部丛枝菌根真菌(AMF)侵染情况、菌根形态结构以及根际土中AMF孢子的种类与数量.结果显示:南方红豆杉可与AMF形成典型的丛枝-泡囊型菌根,侵染率在71.2%~94.4%,但是历山、蟒河自然保护区的侵染强度优于人工栽培区;在南方红豆杉根际土中共分离鉴定出5种AMF,无梗囊霉属1种、球囊霉属4种,分别是:光壁无梗囊霉、地表球囊霉、地球囊霉、缩球囊霉、明球囊霉,其中光壁无梗囊霉为优势种;南方红豆杉的根由表皮、外皮层、内皮层、中柱组成,AMF只侵染表皮层、内皮层,不能侵染中柱.这为将来利用AMF接种技术进行南方红豆杉的繁殖、移植栽培以及紫杉醇的积累等研究提供了理论依据.     

钦州湾红树林丛枝菌根初步研究

海漆 (Excoecaria agallocha)、桐花树 (Aegiceras corniculatum)、秋茄 (Kandlia candel)、白骨壤 (Avi-cennia marina)是钦州湾分布广、生长量大的 4种红树植物 ,该项研究初步调查了丛枝菌根真菌在这四种植物根系的定居情况。在这四种植物的根际土壤均分离到丛枝菌根真菌孢子 ,其孢子密度以海漆根际的最高 ,其次为桐花树、秋茄、白骨壤。同时 ,海漆根系的侵染率和物种丰富度也最高 ,但在所取的白骨壤根样中没有观察到丛枝菌根的侵染。菌根侵染主要是以根内菌丝、胞内菌丝膨大扭曲、泡囊等形态出现。海水和土壤质地是影响菌根侵染率的主要因素。在所采土样中仅发现球囊霉属 (Glomus)、无梗囊霉属 (Acaulospora)丛枝菌根真菌 ,计有 1 7种和多个未确定种。     

山珊瑚内生菌根的研究

山珊瑚内生菌根真菌在人工培养基上分离培养不能生长。侵染菌丝由山珊瑚侧根表皮侵入,在皮层中部形成侵染通道。进入皮层细胞后形成丛枝吸器。被侵染的寄主细胞仍是生活细胞,但细胞质变稀,蛋白质、RNA含量很少。近中柱的6至8层皮层细胞壁增厚并木质化。丛枝吸器含有丰富的红淀粉,少量的中性脂肪、碱性蛋白质和D NA。菌丝丛枝干幼龄期电子致密,周围有界面物质包围,在衰老时泡囊化,界面物质亦瓦解。吸器由五边形结构组成。寄主细胞在被侵染前含淀粉质体、线粒体、高尔基体、内质网和核糖体,在被侵染后,淀粉质体消失,其它细胞器数量明显减少,而主要是微丝和小液泡及多泡体。文章讨论了山珊瑚菌根与天麻和泡囊-丛枝菌根的异同。     

V-A菌根真菌对柑桔吸收钙素效应的研究初报*

应用放射性同位素~(45)Ca示踪来探明泡囊—丛枝菌根真菌对柑桔吸收钙素的作用。两次盆栽试验,施用含~(45)Ca(NO_3)_2的Hoagland营养液,分别在红壤及无土基质人工接种菌根真菌Glomus citricolum于枳(Poncirus trifoliata)和构头橙(Citrus aurantium)实生苗根系,以不接种为对照。结果表明在红壤中接种2个月后,枳已形成菌根,5个月的菌根感染率为24.5％。在无土基质中,菌根的形成更好;接种3个月后,构头橙的菌根感染率为49.5％,并且发生丰富的泡囊。在红壤中,有菌根枳实生苗的地上部从肥料中吸收的钙素和全钙含量都比无菌根的增加75％左右。在无土基质中,有菌根的枳和构头橙实生苗地上部含钙量及放射性强度都比无菌根的显著增高。放射性自显影直接地显示了菌根真菌将吸收的~(45)Ga运转至地上茎叶中,对构头橙的效应更明显。     

V-A菌根真菌对柑桔吸收钙素效应的研究初报

应用放射性同位素~(45)Ca示踪来探明泡囊—丛枝菌根真菌对柑桔吸收钙素的作用。两次盆栽试验,施用含~(45)Ca(NO_3)_2的Hoagland营养液,分别在红壤及无土基质人工接种菌根真菌Glomus citricolum于枳(Poncirus trifoliata)和构头橙(Citrus aurantium)实生苗根系,以不接种为对照。结果表明在红壤中接种2个月后,枳已形成菌根,5个月的菌根感染率为24.5％。在无土基质中,菌根的形成更好;接种3个月后,构头橙的菌根感染率为49.5％,并且发生丰富的泡囊。在红壤中,有菌根枳实生苗的地上部从肥料中吸收的钙素和全钙含量都比无菌根的增加75％左右。在无土基质中,有菌根的枳和构头橙实生苗地上部含钙量及放射性强度都比无菌根的显著增高。放射性自显影直接地显示了菌根真菌将吸收的~(45)Ga运转至地上茎叶中,对构头橙的效应更明显。     

不同砧木对柑橘幼树生长和叶片糖含量的影响

以体细胞杂种红橘 枳和红橘 粗柠檬、有性杂种Troyer枳橙和Swingle枳柚、枳(对照)作砧木的‘国庆4号’温州蜜柑2a生嫁接苗为试材,通过盆栽试验研究了砧木对柑橘幼树生长和叶片糖含量的影响。结果表明,4种处理的生长势比对照旺盛;红橘 枳处理的花量极显著多于对照,其余3种砧木处理的则极显著少于对照。在光合色素含量上,Troyer枳橙处理最高,对照最低。不同砧木处理对叶片可溶性糖含量的年变化动态特征影响明显;不同砧木处理的叶片淀粉含量年变化动态特征相似。在不同时期,不同砧木处理对叶片可溶性糖和淀粉含量有明显的影响。初步评价了体细胞杂种红橘 枳和红橘 粗柠檬用作柑橘砧木的利用价值。     

Characterization of Mycorrhizas Formed by Glomus sp. on Roots of Hypernodulating Mutants of Lotus japonicus

Lotus japonicus hypernodulating mutants, Ljsym78-1 and Ljsym78-2, by the arbuscular mycorrhizal fungus Glomus sp. was characterized. The mutants are defective in systemic autoregulation of nodulation and nitrate inhibition, and form an excess of nodules and lateral roots. The percent root length colonized by the arbuscular mycorrhizal fungi was significantly higher for the mutant than wild-type roots. Detailed assessment of the colonization indicated that the percentage of colonization by arbuscules was increased, but that by external hyphae, internal hyphae and vesicles was decreased, in the mutant roots compared with the wild-type. The succinate dehydrogenase activity of arbuscules, external hyphae and internal hyphae showed similar trends. In addition, the majority of individual arbuscules that formed on the mutant roots had a well-developed and seemingly tough morphology. The results suggest that mutation at the Ljsym78 locus positively stimulates the growth and activity of arbuscules, but leads to reduced growth and activity of hyphae. We report the first identification of Lotus japonicus mutants that show significantly increased arbuscule formation and termed these mutants Arb⁺⁺. Received 8 August 2000/ Accepted in revised form 19 October 2000     

Electron microscopy of vesicular-arbuscular mycorrhizae of yellow poplar. III Host-endophyte interactions during arbuscular development.

Scanning- and transmission-electron microscopy were used to examine developing and mature functional arbuscules in mycorrhizal roots of yellow poplar. Arbuscules developed from intracellular hyphae which branched repeatedly upon penetration into the host cells. Intermediate and late stages of developemnt were characterized by the production of numerous, short, bifurcate hyphae throughout the arbuscule. Mature arbuscules exhibited a coralloid morphology which resulted in a considerable increase in the surface area of the endophyte exposed within the host cells. Distinctive ultrastructural features of arbuscular hyphae included osmiophilic walls, nuclei, abundant cytoplasm, glycogen, and numerous small vacuoles. All arbuscular components were enclosed by host wall material and cytoplasm during development and at maturity. In infected cells, host nuclei were enlarged and the cytoplasm associated with the arbuscular branches typically contained abundant mitochondria, endoplasmic reticulum, and proplastids. Ultrastructural observations suggested that nutrient transfer may be predominantly directed toward the fungal endophyte during arbuscular development and while mature arbuscules remain functional.     

Mycorrhizal status and diversity of fungal endophytes in roots of common buckwheat (Fagopyrum esculentum) and tartary buckwheat (F. tataricum)

To determine the mycorrhizal status and to identify the fungi colonising the roots of the plants, common buckwheat (Fagopyrum esculentum) and tartary buckwheat (F. tataricum) were inoculated with an indigenous fungal mixture from a buckwheat field. Root colonisation was characterised by the hyphae and distinct microsclerotia of dark septate endophytes, with occasional arbuscules and vesicles of arbuscular mycorrhizal fungi. Sequences of arbuscular mycorrhizal fungi colonising tartary buckwheat clustered close to the Glomus species group A. Sequences with similarity to the Ceratobasidium/Rhizoctonia complex, a putative dark septate endophyte fungus, were amplified from the roots of both common and tartary buckwheat. To the best of our knowledge, this is the first report of arbuscular mycorrhizal colonisation in tartary buckwheat and the first molecular characterisation of these fungi that can colonise both of these economically important plant species.     

Mycotrophy of Annona cherimola and the morphology of its mycorrhizae

The mycotrophic character of Annona cherimola (Magnoliales), a tropical/subtropical plantation crop of interest, is described for the first time. This crop seems to depend on mycorrhizae (arbuscular) for optimal growth, with Glomus deserticola being the most effective endophyte tested. Study of the morphology of the arbuscular mycorrhizae in Annona roots showed exclusively intracellular hyphal development, with cell-to-cell fungal passage and an abundance of arbuscules and coiled hyphae within cells. Intercellular distributive hyphae were not observed. The morphology and the pattern of spread of the mycorrhizal colonization were similar for the different endophytes involved and appeared to be dependent on the host root. Such features of mycorrhizal colonization are characteristic of host species lacking intercellular air channels and have been described for some species of ecological interest, but they are not commonly noted in the mycorrhizal literature, especially that dealing with crop species. Some ecophysiological consequences of this pattern of colonization are discussed.     

Infection of hairy roots of strawberry (Fragaria x Ananassa Duch.) with arbuscular mycorrhizal fungus

Summary Hairy root cultures of strawberry (Fragaria x ananassa Duch.) were induced with the Agrobacterium rhizogenes strain A4. Cultures were maintained on B50 medium but could also grow on a minimal medium, which did not inhibit the growth of arbuscular mycorrhizal fungi. The growth and nutrient uptake were characterized in shake flasks and in a bioreactor. Spores of the native Finnish arbuscular mycorrhizal fungus Glomus fistulosum V128 were used to infect strawberry (Fragaria x ananassa Duch. Senga Sengana) hairy roots in vitro. During cultivation, vegetative spore formation was observed. At the end of the cultivation, hyphae and arbuscules were observed in the stained roots.Abbreviations AM arbuscular mycorrhiza - AMF arbuscular mycorrhizal fungus     

X-ray microanalysis of elements of VA mycorrhizal and non-mycorrhizal Pennisetum pedicellatum roots

Chemical composition of inter and intracellular hyphae was elucidated in Pennisetum pedicellatum roots colonized by Gigaspora margarita by employing energy dispersive X-ray microanalysis. Maximum amount of phosphate was estimated in polyphosphate granules present in the roots. Amount of phosphate was low in fungal hyphae, arbuscular trunks and degenerated arbuscules. Elements S, K and Ca were present in the hyphae, arbuscular trunk and degenerated arbuscules.     

濒危药用植物桃儿七根的显微结构及其菌根真菌分布研究

本文研究了桃儿七Sinopodophyllum hexandrum根的显微结构及其真菌分布。结果表明,桃儿七的根为根状茎,节状,不定根形成的须根系发达。根的结构主要由表皮、皮层、维管柱三部分构成,其中,皮层所占比例最大,超过80%。根的木质部有四原型和五原型两种类型,五原型较为常见;四原型的根和五原型的根在皮层细胞形态上存在一定差异。在桃儿七的不定根和其上的侧根观察到真菌菌丝分布,其数量和种类与根的直径有关,在不定根较细(先端)的部位真菌以暗色有隔内生真菌(DSE真菌)为主,侵染率为77.9%;而较粗根中真菌菌丝为无隔菌丝为主,分布很少且仅存在于皮层细胞的一至二层,不侵染皮层深部和维管柱。不定根侧根中真菌以丛枝菌根真菌为主,丛枝菌根常常占据大部分的皮层细胞,侵染率高达90%以上。桃儿七根中没有发现根毛存在,因此,侧根中共生的丛枝菌根真菌可能是桃儿七养分和水分吸收的主要途径。