The Role of Fungal Symbioses in the Adaptation of Plants to High Stress Environments

All plants studied in natural ecosystemsare symbiotic with fungi that either resideentirely (endophytes) or partially(mycorrhizae) within plants. Thesesymbioses appear to adapt to biotic andabiotic stresses and may be responsible forthe survival of both plant hosts and fungalsymbionts in high stress habitats. Here wedescribe the role of symbiotic fungi inplant stress tolerance and present astrategy based on adaptive symbiosis topotentially mitigate the impacts of globalchange on plant communities.     

Arbuscular mycorrhizal fungi, rhizobia, available soil P and nodulation of groundnut (Arachis hypogaea) in Zimbabwe

Arbuscular mycorrhizal fungal (AMF) colonization and nodulation of groundnut were examined in nine soils collected from subsistence farmers’ fields in Zimbabwe. Nodule number, shoot dry weight, shoot N and P contents, and AMF colonization were assessed after 6 weeks growth. Both nodule number and AMF colonization differed by an order of magnitude among the nine soils. Soil available P explained almost all the variability in nodule number (r² = 0.98), but had no significant effect on percent AMF colonization. By adding P to one soil, nodule numbers increased four-fold resulting in a significantly higher N content in the shoots. Similar, but smaller, effects were obtained by increasing the abundance of AMF through an inoculation with Glomus intraradices, suggesting that nodulation in this soil was limited by AMF abundance and that the fungi could, to a limited extent, substitute for P fertilizer.     

To enhance the reproduction of Phanerochaete chrysosporium by adding natural lixiviums in liquid medium

Great promotion to the reproduction of white rot fungus Phanerochaete chrysosporlum by adding natural lixiviums such as from wood, maize core and potato in liquid medium was found in this research. Incubated in the liquid medium contained 10 mg/L glucose as carbon source with natural lixiviums for three days, the production of myeelium pellet reaches more than 80 g/L, which is 5 times more than that of without natural lixiviums. Incubated in the liquid medium contained 5 mg/L glucose as carbon source with natural lixiviums for three days, the production of myeelium pellet can reach 69.5 g/L, while the production in the medium without natural lixiviums is very low. When the liquid medium contained 1-20 g/L glucose as carbon source, the production of myeelium pellet in 3 d can only reach 12.5 g/L to 14.5 g/L. The fungus in the medium with potato lixiviums are easily contaminated by other microorganisms and in the medium with maize core lixiviums are easily bulking, while in the medium with wood lixiviums are neither easily contaminated nor bulking. Medium with wood lixiviums can produce more pellet than other medium, endure contamination and keep better sedimentation capacity. So that, wood lixivium is borer additive to the culture of white rot fungi in liquid medium. Addition of the mixture of wood, maize core and potato lixiviums is of advantage to the productian of mycelium pellet. The difference of the production in the medium with different amount of wood lixiviums showed little in the first 3 d, while it esnanded after 3 d. Wood lixiviums stimulate the growth of P. chrysosporium instead of supply organies which fungi need.     

丛枝菌根化大青杨苗木根际微域环境的研究

对接种AM菌根真菌的大青杨苗木根际微区进行系统研究，发现AM菌根真菌对宿主根际微域环境产生了重要影响：试验中选用的Glomus mosseae、G.intraradices、G.sinuosa、G.versifopme等4种AM菌根真菌都与盆栽大青杨苗木形成了菌根复合体。其中G.mosseae、G.intraradices侵染效果最好，侵染率分别是64．4％、67．4％。受两种菌侵染的苗木的生物量分别是对照处理的2．59、2．13倍。AM菌根对根际土壤微生物种群数量没有产生影响，但使根面、根系上的细菌、放线菌、固氮菌的数量显著增加。AM菌根增加了根际土壤磷酸酶、脲酶、蛋白酶的活性，各种酶活性增加量与苗木菌根侵染率呈显著相关。AM菌根使根际pH值降低，与菌根侵染率呈显著负相关。接种苗木的根际土壤中，可直接被植物吸收利用的N、P元素出现富集现象，与菌根侵染率呈极显著相关。     

白腐真菌对土壤中多环芳烃(PAHs)降解的研究

研究白腐真菌对多环芳烃(PAHs)的降解,结果表明,温度、培养基、氧气浓度、水土比对PAHs的降解均有影响.温度为25℃、营养液为查氏培养基、通气量为60L·d-1、水土比为5∶1为最优水平组合.对降解不同时期各种因素的重要性及其最优水平的分析表明,各种影响因素在降解实验的不同阶段的影响程度不同,降解实验初期,培养基是最重要的影响因素,而氧气在整个实验中均为重要的影响因素.     

土壤中酞酸酯(PAEs)对丛枝菌根化植物生长的影响

以豇豆 (Vignaunguiculata )为供试植物 ,分别接种AM真菌Acaulosporalavis(光壁无梗球囊霉 ,菌号 :3 4)和Glomuscaledonium (苏格兰球囊霉 ,菌号 :90 0 3 6) ,通过温室盆栽试验 ,观察 2、10和 5 0mg·kg-1DEHP和DBP对菌根化植物生长的影响。试验结果表明 ,土壤添加DEHP和DBP后 ,植物地上和地下部分干重均有不同程度下降 ,高浓度DEHP和DBP还使植物叶绿素a和b的含量及根瘤数降低 ,接种AM真菌后明显促进了植物的生长 ,尤其对植物早期地下部分和植物后期地上部分的促进作用较为明显 ;同时 ,也增加了植物叶绿素a和b的含量及根瘤数     

白腐菌在固体培养基下对吲哚和吡啶的降解

研究了稻草秆粉介质中白腐菌对吲哚和吡啶的降解.实验结果表明,质量浓度分别为200、80 mg/L左右的吲哚可被白腐菌去除99%以上,质量浓度为74 mg/L吡啶的去除率为61.5%;白腐菌在稻草秆粉培养体系中对吲哚和吡啶的降解,符合零级反应动力学,其中反应速率常数K(高浓度吲哚)＞K(低浓度吲哚)＞K(吡啶);高低浓度吲哚和吡啶3个降解体系的漆酶活力在第6天达到最大;漆酶在吲哚和吡啶降解过程中起着较重要的作用,但酶活的变化与吲哚和吡啶的相对去除率不呈线性相关,稻草秆粉培养基中的介质和培养环境在降解过程中可能也起着重要作用.     

Degradation of Benzo[a]Pyrene in Soil with Arbuscular Mycorrhizal Alfalfa

Mycorrhizal and non-mycorrhizal alfalfa (Medicago sativa) was grown in pots containing soil artificially contaminated with various levels of benzo[a]pyrene (B[a]P)(0, 1, 10 and 100 mg kg^–1). Soil and plants were sampled after 30, 40, 50, 60 and 90 days and compared with unlanted pots. The percentage of mycorrhizal root length colonized by Glomus caledoniun was not significantly affected by the addition of B[a]P up to 10 mg kg^–1 but was significantly lower at 100 mg kg^–1B[a]P compared with low concentrations (p < 0.05). There was no difference in soil polyphenol oxidase and dehydrogenase activity among the controls and applications of 1 and 10 mg kg^–1 of B[a]P. However, enzyme activities were significantly higher at 100 mg kg^–1B[a]P compared with the other three treatments, and there was no mycorrhizal effect. Over a period of 90 days the concentration of B[a]P in soil in which alfalfa was grown was significantly lower than in unplanted soil (p < 0.05). Degradation rates of B[a]P added at 1, 10 and 100 mg kg^–1 without G. caledonium were 76, 78 and 53%, and with mycorrhizal inoculation were 86, 87 and 57%. The degradation rate in unplanted soil was significantly lower than in planted soil, and was significantly higher in medium- and low-B[a]P treatments than in the high B[a]P concentration tested. There is a possibility of enhancement phytoremediation of PAHs in rhizosphere soil with arbuscular mycorrhizal fungi.     

微量元素对红豆杉菌根菌生长的影响

微量元素对植物的生长发育有着十分重要的意义。对太行山野生红豆杉(Taxus chinensis var.mairei)菌根菌菌丝在分别加有硫酸锌、钼酸铵以及硫酸亚铁的PDA培养基中的生长发育状况进行了试验研究。所得数据同PDA对照组进行比较分析后,结果表明:Mo元素对红豆杉菌根菌菌丝的生长发育有很好的促进作用;Fe元素明显地促进红豆杉菌根菌菌丝的生长发育;Zn元素在一定范围内对红豆杉菌根菌菌丝的生长发育有一定的抑制作用。实验结果揭示出红豆杉菌根菌生长发育的一些营养因素。     

黄孢原毛平革菌反复脱色模拟染料废水的试验研究

研究了白腐真菌黄孢原毛平革菌在35℃、150r／min条件下培养3d后，培养基类型、染料浓度以及反复脱色次数对其脱色的影响。玉米芯浸出液是首选的可替代营养源的物质，培养3d的黄孢原毛平革菌6h脱色率即达92％。黄孢原毛平革菌能够在短时间(6h)基本脱色较高浓度(40mg／L，60mg／L)的活性艳红K-2BP模拟染料废水，对于低浓度(10mg／L，20mg／L)脱色作用则比较缓慢，浓度超过150mg／L即显示出对菌的毒性作用。玉米芯浸出液培养3d的菌可以重复脱色模拟废水6次以上，每批脱色率均在82％以上，但菌球的沉降性能变差。