Allelopathic effect of phenolic acids from humic solutions on two spruce mycorrhizal fungi:Cenococcum graniforme andLaccaria laccata

The aim of this investigation was to determine the impact ofp-hydroxyacetophenone,p-hydroxybenzoic acid, catechol, and protocatechuic acid on respiration of two spruce mycorrhizal fungi:Laccaria laccata andCenococcum graniforme. These phenols are produced byVaccinium myrtillus,Athyrium filixfemina, andPicea abies, predominant species of spruce forests in the Alps, and they are also present in humic solutions at 10^–10 M or 10^–5 M. Respiration of the two fungi was inhibited by the four phenolic acids, even at concentrations ranging from 10^–5 M to 10^–7 M. These data show phenolic acids from humic solutions have biological activity at extremely low concentrations, suggesting a contribution ofV. myrtillus, A. filixfemina, andP. abies to allelopathic inhibition of mycorrhizal fungi.     

丛枝菌根(AM)对水稻生长促进及化肥减量研究

为了考察丛枝菌根(Arbuscular Mycorrhiza,AM)对水稻生长促进及化肥减量效果,以摩西球囊霉(Glomus mosseae)为实验材料在不同丛枝菌根真菌(Arbuscular mycorrhizal fungi,AMF)含量的基质中进行水稻盆栽试验.对比分析了水稻根部AMF的侵染状况,及其对水稻生长的促进作用,并在此基础上探讨了AMF强化在农业面源污染化肥减量中的作用.结果表明:自然基质中土著G.mosseae普遍存在,并可与水稻根系形成菌根结构,但其对水稻的影响与AMF空白基质相比差异并不显著.AMF强化能显著提高其对水稻根部的侵染率.与自然基质相比,AMF强化使水稻的株高、总生物量、根系总表面积及产量分别提高了20.6%、30%、36.6%、45.3%.经计算,每生产100kg水稻,AMF强化相对于自然条件下氮肥、磷肥、钾肥施用量分别减少3.14kg、1.88kg、2.42kg,削减程度高达47%.AMF强化能够有效促进水稻生长并提高其产量,而且在农业面源污染化肥减量方面具有重要作用.     

Beyond Photoprotection: The Multifarious Roles of Flavonoids in Plant Terrestrialization

Plants evolved an impressive arsenal of multifunctional specialized metabolites to cope with the novel environmental pressures imposed by the terrestrial habitat when moving from water. Here we examine the multifarious roles of flavonoids in plant terrestrialization. We reason on the environmental drivers, other than the increase in UV-B radiation, that were mostly responsible for the rise of flavonoid metabolism and how flavonoids helped plants in land conquest. We are reasonably based on a nutrient-deficiency hypothesis for the replacement of mycosporine-like amino acids, typical of streptophytic algae, with the flavonoid metabolism during the water-to-land transition. We suggest that flavonoids modulated auxin transport and signaling and promoted the symbiosis between plants and fungi (e.g., arbuscular mycorrhizal, AM), a central event for the conquest of land by plants. AM improved the ability of early plants to take up nutrients and water from highly impoverished soils. We offer evidence that flavonoids equipped early land plants with highly versatile “defense compounds”, essential for the new set of abiotic and biotic stressors imposed by the terrestrial environment. We conclude that flavonoids have been multifunctional since the appearance of plants on land, not only acting as UV filters but especially improving both nutrient acquisition and biotic stress defense.     

丛枝菌根真菌在有机污染物污染土壤植物修复中的应用

综述了丛枝菌根真菌-植物体系在有机物污染土壤修复中的效果;分析了丛枝菌根真菌促进植物修复的机理;并探讨了影响丛枝菌根真菌在有机物污染土壤植物修复作用的因素。文章最后总结了目前这一技术存在的问题,并提出了相关建议。     

镉污染土壤的菌根修复研究

以玉米为试验材料，采用盆栽方法模拟土壤Cd污染状况，分别将丛枝菌根真菌Glomus diaphanum和Glomus mosseae接种于镉污染土壤中，研究两种菌根真菌对玉米生长及对Cd吸收、分配的影响．结果表明：与未接种的对照相比，接种Glomus diaphanum菌根使玉米的生物量增加了5．79倍，地上部镉含量降低了53．9％，地上部磷含量增加了4．6倍．菌丝侵染使植物将镉滞留在根部，抑制了镉向地上部的转移．其中，接种Glomus diaphanum菌显著于接种Glomus mosseae菌．因此，在镉污染土壤原位修复中，接种Glomus diaphanum菌有助于抑制重金属迁移．     

Grain mineral concentrations and yield of wheat grown under organic and conventional management

On the low‐P soils in southeastern Australia, organic crops differ from conventional ones primarily in the use of relatively insoluble, as opposed to soluble, P fertilisers and in the non‐use of herbicides. As organic management, particularly elimination of soluble fertilisers, is often claimed to enhance grain mineral concentrations, we examined grain from wheat on paired organic and conventional farms in two sets of experiments: (1) four pairs of commercial crops (1991–1993); and (2) fertiliser experiments on one farm pair where nil fertiliser was compared with 40 kg ha^?1 of P as either relatively insoluble reactive phosphate rock or more soluble superphosphate (1991 and 1992). All wheat was grown following a 2–6 year legume‐based pasture phase. Both conventional management and the superphosphate treatment greatly increased yields but reduced colonisation by mycorrhizal fungi. While only minor variations occurred in grain N, K, Mg, Ca, S and Fe concentrations, conventional grain had lower Zn and Cu but higher Mn and P than organic grain. These differences were ascribed to: soluble P fertilisers increasing P uptake but reducing mycorrhizal colonisation and thereby reducing Zn uptake and enhancing Mn uptake; dilution of Cu in heavier crops; and past lime applications on the organic farm decreasing Mn availability. These variations in grain minerals had nutritional implications primarily favouring the organic grain; however, organic management and, specifically, elimination of soluble fertilisers did not induce dramatic increases in grain mineral concentrations. In addition, organic management was coupled with yield reductions of 17–84 per cent due to P limitation and weeds. The impact of large regional variations in the characteristics of organic and conventional systems on the general applicability of the results from this study and other similar studies is discussed. Copyright © 2004 Society of Chemical Industry     

Mycorrhizal colonization and grain Cd concentration of field‐grown durum wheat in response to tillage,preceding crop and phosphorus fertilization

BACKGROUND: A 3‐year field trial was conducted to investigate the effect of agricultural management practices including tillage, preceding crop and phosphate fertilization on root colonization by arbuscular mycorrhizal (AM) fungi and grain cadmium (Cd) concentration of durum wheat (Triticum turgidum L.). The relationship between grain Cd and soil and plant variables was explored to determine the primary factors affecting grain Cd concentration. RESULTS: Mycorrhizal colonization of the roots was reduced by conventional tillage or when the preceding crop was canola (Brassica napus L.), compared to minimum tillage or when the preceding crop was flax (Linum usitatissimum L.). In contrast, grain Cd was not consistently affected by any treatment. Grain Cd was generally below the maximum permissible concentration (MPC) of 100 µg Cd kg^?1 proposed by WHO. Grain Cd varied substantially from year to year, and could be predicted with 70% of variance accounted for by using the model: grain Cd concentration = ? 321.9 + 44.5× ln(grain yield) + 0.26× soil DTPA‐Cd + 182.5× soil electrical conductivity (EC)? 0.98× grain Zn concentration. CONCLUSIONS: These common agricultural management practices had no effect on grain Cd concentration in durum wheat though they impacted mycorrhizal colonization of roots. Grain yield and to a lesser extent soil conditions of EC and DTPA‐Cd and grain Zn influenced grain Cd, whereas mycorrhizal colonization levels did not. Copyright © 2010 Crown in the right of Canada. Published by John Wiley & Sons, Ltd     

Nutrient use efficiency and arbuscular mycorrhizal root colonisation of winter wheat cultivars in different farming systems of the DOK long‐term trial

BACKGROUND: For organic farming, cultivars are required with high nutrient use efficiency under nutrient limited conditions. Arbuscular mycorrhizal fungi (AMF) are known to contribute to nutrient uptake under low input conditions. We compared nutrient use efficiency (NUE) of old and modern organically and conventionally bred cultivars in organic and conventional systems and assessed AMF‐root colonisation (AMF‐RC) in relation to nutrient concentrations. RESULTS: Cultivars and systems had a statistically significant effect on nitrogen (N) and phosphorus (P) concentrations and NUE parameters, whereas no genotype × environment interactions appeared. In contrast to N and P uptake, the NUE parameters were higher under organic than under conventional conditions. NUE for N increased with the year of release of cultivars. In the organic systems, the organically bred cultivars could not outperform the conventionally bred cultivars in grain yield and NUE parameters. AMF‐RC was higher in the organic than in the conventional system, but did not differ among cultivars. CONCLUSION: Cultivars achieving high NUE in the organic systems were found among modern cultivars, irrespective of the breeding programme. Nutrient conditions during the breeding programme did not affect AMF‐RC. No clear evidence was found that AMF symbiosis contributed more to nutrient concentrations under low input than under high input conditions. Copyright © 2010 Society of Chemical Industry