Isolation of feeding deterrents against argentine stem weevil from ryegrass infected with the endophyteAcremonium loliae

Infection of ryegrass (Lolium perenne) by an endophytic fungus (Acremonium loliae) confers resistance against the Argentine stem weevil (Listronotus bonariensis). Extracts from ryegrass clones, infected and uninfected withA. loliae, were compared in a feeding choice bioassay, and several fractions were identified which affected stem weevil feeding behavior. One stem weevil feeding deterrent, peramine C₁₂H₁₇N₅O, has been isolated from infected ryegrass and partially characterized as a basic indole derivative. Extracts from culturedA. loliae had no effect on stem weevil feeding behavior nor was peramine detected in the fungal cultures examined. Peramine and the other active substances are hydrophilic in contrast to the lipophilic properties reported for the neurotoxic lolitrems also isolated from ryegrass infected withA. loliae and associated with causing ryegrass staggers disorder in livestock. It is suggested that ryegrass staggers and stem weevil feeding deterrency may arise by different biochemical mechanisms.     

Plant tolerance to diesel minimizes its impact on soil microbial characteristics during rhizoremediation of diesel-contaminated soils

Soil contamination due to petroleum-derived products is an important environmental problem. We assessed the impacts of diesel oil on plants (Trifolium repens and Lolium perenne) and soil microbial community characteristics within the context of the rhizoremediation of contaminated soils. For this purpose, a diesel fuel spill on a grassland soil was simulated under pot conditions at a dose of 12,000 mg diesel kg^− 1 DW soil. Thirty days after diesel addition, T. repens (white clover) and L. perenne (perennial ryegrass) were sown in the pots and grown under greenhouse conditions (temperature 25/18 °C day/night, relative humidity 60/80% day/night and a photosynthetic photon flux density of 400 μmol photon m^− 2 s^− 1) for 5 months. A parallel set of unplanted pots was also included. Concentrations of n-alkanes in soil were determined as an indicator of diesel degradation. Seedling germination, plant growth, maximal photochemical efficiency of photosystem II (F_v/F_m), pigment composition and lipophylic antioxidant content were determined to assess the impacts of diesel on the studied plants. Soil microbial community characteristics, such as enzyme and community-level physiological profiles, were also determined and used to calculate the soil quality index (SQI). The presence of plants had a stimulatory effect on soil microbial activity. L. perenne was far more tolerant to diesel contamination than T. repens. Diesel contamination affected soil microbial characteristics, although its impact was less pronounced in the rhizosphere of L. perenne. Rhizoremediation with T. repens and L. perenne resulted in a similar reduction of total n-alkanes concentration. However, values of the soil microbial parameters and the SQI showed that the more tolerant species (L. perenne) was able to better maintain its rhizosphere characteristics when growing in diesel-contaminated soil, suggesting a better soil health. We concluded that plant tolerance is of crucial importance for the recovery of soil health during rhizoremediation of contaminated soils.     

Determination of lignin in the presence of ester-bound substituted cinnamic acids by a modified acetyl bromide procedure

The lignin content of plant materials can be determined spectro-scopically but the presence of ester-bound substituted cinnamic acids in the cell walls of some plant families, particularly the Gramineae, gives elevated values. Pre-treatment with either pyrrolidine : pyridine or 0-5 m sodium methoxide selectively removes the ester-bound acids leaving intact the true lignin. The treatments have been applied to cellulose powder, immature perennial ryegrass stems, oat straw and forage rape stems. The pyrrolidine : pyridine treatment removes a slightly higher proportion of these non-lignin components but the sodium methoxide treatment appears to cause less damage than the heterocyclic bases to other cell wall constituents and is preferred if the residues are to be used for other purposes.     

绿肥混合翻压还田对土壤性状及烟叶品质的影响

为明确不同绿肥翻压模式产生的生态效应,设计了3个处理：黑麦草单独翻压处理（20 000 kg/hm²）、紫云英单独翻压处理（21 000 kg/hm²）、黑麦草和紫云英混合翻压处理（黑麦草5000 kg/hm²,紫云英15 000 kg/hm²）,测定了绿肥翻压还田30、60、120 d后不同处理土壤养分含量,微生物生物量和酶活性,分析了绿肥腐解动态及对烟叶品质的影响。结果表明,不同处理下绿肥腐解速率变化趋势均为先升高后降低,在60 d时达到最大值。绿肥翻压还田后30~60 d,黑麦草和紫云英混合翻压处理显著提高了土壤速效磷含量（p<0.05）,而单种绿肥翻压效果不显著。绿肥翻压还田后120 d,与单种翻压相比,混合翻压处理显著提高了土壤脲酶、淀粉酶活性和土壤微生物量碳、氮、磷含量（p<0.05）,且烟叶总氮、烟碱、钾含量和钾氯比总体适宜,达到优质烟标准。因此,与单种绿肥翻压还田处理相比,紫云英和黑麦草混合翻压还田更能提高植烟土壤供磷能力,改善土壤微环境,促进烟叶优质品质的形成。     

Effect of fungal metabolite peramine and analogs on feeding and development of argentine stem weevil (Listronotus bonariensis)

Peramine, a pyrrolopyrazine alkaloid produced by the fungal endophyte of perennial ryegrassAcremonium lolii, deterred the feeding of both adults and larvae of the graminacious herbivore, the Argentine stem weevil (Listronotus bonariensis), at 0.1 g/g and 10 g/g, respectively. In a no-choice test fewer stem weevil larvae fed and developed on diet containing as little as 2 g/g peramine. The proportion of larvae which did not develop beyond the first instar was higher on diet containing peramine and appeared to be due to a higher proportion of larvae which did not feed. For larvae which fed on the peramine-containing diet, feeding scores and times to pupation were not significantly different from those of controls. A number of simple peramine analogues showed feeding-deterrent activity against adult weevils, indicating the importance of the pyrrolopyrazine ring system of peramine in determining feeding-deterrent activity.     

Ryegrass uptake of carbamazepine and ibuprofen applied by urine fertilization

Human urine is a potential alternative fertilizer for agriculture. However, its usage is associated with a risk of spreading pharmaceutical residues to fields. The individual and combined behavior of carbamazepine and ibuprofen was investigated by GC/MS analysis in a greenhouse experiment using ryegrass fertilized with pharmaceutical-spiked urine. Only carbamazepine could be detected in soil, roots, and aerial plant parts. Fifty-three per cent of carbamazepine originally present in the urine was recovered in soil samples taken after three months. Additionally, 34% of carbamazepine was found in aerial plant parts and 0.3% in roots. Model calculations showed that neither roots nor Casparian strip posed a considerable barrier to uptake. Carbamazepine transport was clearly driven by transpiration. Ibuprofen was not detected in the soil or in any plant parts after three months. This was assumed to be due to biodegradation of ibuprofen. Carbamazepine and ibuprofen, singly or in combination, did not adversely affect the growth of ryegrass.     

Composition and digestibility during ageing of consecutive leaves on the main stem of Italian ryegrass plants,growing undisturbed or regrowing after cutting

For modelling of grass digestibility throughout the growing season, the impact of cutting on individual leaves needs to be quantified. Therefore, a glasshouse experiment was carried out with Italian ryegrass (Lolium multiflorum Lam) grown from seed. Half of the plants were grown undisturbed until leaf stage 8, while the other half were cut at leaf stage 4, after which they were allowed to grow until leaf stage 9. The composition and digestibility characteristics of leaves 6, 7 and 8 on the main shoot of plants from both treatments were quantified. In the uncut plants, leaf blade length and mass and specific cell wall (CW) and organic matter (OM) mass (mg cm⁻²) was higher for consecutive leaves. During leaf ageing specific CW mass remained unchanged, while specific OM mass and CW digestibility declined, resulting in a decline of OM digestibility. CW digestibility of leaves decreased to c 78%, a value also found in an earlier experiment. The newly formed leaves after cutting had a reduced leaf size and specific leaf mass (SLM, mg DM cm⁻²). Leaf 6, that was damaged by cutting, showed a lower initial CW content and a rapid decline of specific CW and OM mass and of digestibility during ageing. Its low specific mass and digestibility of CW could have been related to cessation of CW synthesis during its growth after cutting, as was evidenced by the lower CW thickness of sclerenchyma cells. The later-formed leaves, 7 and 8, had digestibility characteristics similar to those of the uncut plants. Since leaf 6 hardly contributed to the total plant dry matter mass, the cut and the uncut plants differed only slightly in digestibility of the total leaf fraction. It can be concluded that cutting sets back leaf size and growth rate but has little effect on digestibility characteristics during ageing. © 1999 Society of Chemical Industry     

Effects of Sodium Fertiliser on the Chemical Composition of Grass and Clover Leaves,Stems and Inflorescences

Sodium fertiliser was applied to dairy cow pasture to investigate the effects on the chemical composition of grass and clover leaves, stems and inflorescences. The effect of sodium fertiliser varied between fractions, with grass leaves and stems generally being more responsive than grass inflorescences or clover fractions. The sodium content of all fractions was already high in the control treatment, and was increased to an excessive level by sodium fertiliser in all fractions except grass stems. Grass leaves were most affected. Potassium content was reduced in grass leaves and stems, but not in other fractions. The effects on calcium and magnesium varied between fractions but the K: (Ca+Mg) ratio, the most sensitive index of susceptibility to hypomagnesaemia, was reduced in grass leaves, but increased in other fractions. DM digestibility was decreased in grass and clover leaves by sodium, probably because of the high sodium content. MAD fibre content was also increased in these fractions. Crude protein content was decreased by sodium fertiliser in grass leaves, in particular. Therefore, when applied to pasture which is naturally high in sodium, sodium fertiliser had detrimental effects on pasture macronutrient content. However, beneficial effects were still observed on mineral ratios for plant and animal nutrition. It is concluded that if sodium fertiliser increases herbage sodium concentrations above 5 g kg⁻¹ DM, improvements in mineral ratios that could affect ruminant health may be offset by reductions in the nutritive value of the herbage. It is therefore recommended that the herbage sodium concentration should be known before sodium fertiliser is applied.     

青蒿素对黑麦草种子萌发和幼苗生长的影响

运用室内培养皿法,分析不同质量浓度的青蒿素浸种后黑麦草种子萌发、根系活力、幼苗生长等指标的变化。结果表明,青蒿素对黑麦草种子萌发有抑制作用,且浓度越高,抑制作用越显著。与无菌水对照相比,随着青蒿素质量浓度的增加,根系活力和可溶性蛋白含量逐渐降低,而黑麦草幼苗的苗高、根长、鲜质量、干质量、根冠比及叶绿素含量呈先升高后降低的趋势。20~30 mg/L青蒿素处理对黑麦草幼苗各项指标的影响与PP333对照相似。