除草剂安全剂作用机理研究进展

除草剂安全剂是一类可在不影响除草剂对靶标杂草活性的前提下,有选择性地保护作物免受除草剂伤害的特殊用途化合物,有关安全剂作用机理的研究对新安全剂的开发具有重要意义。目前关于除草剂安全剂的作用机理主要有4种观点:1）影响除草剂在作物体内的吸收和转运;2）与除草剂竞争靶标位点;3）影响靶标酶的活性;4）增强作物对除草剂的代谢。文章对近年来安全剂作用机理及安全剂对杂草的影响等研究进展进行了综述,并分析了当前存在的问题及未来的研究方向,旨在为深入研究安全剂的作用机理及新安全剂开发提供参考。     

Phosphorus amendment decreased cadmium (Cd) uptake and ameliorates chlorophyll contents,gas exchange attributes,antioxidants, and mineral nutrients in wheat (Triticum aestivum L.) under Cd stress

A 28-day pot (sand culture) experiment was carried to evaluate the effects of phosphorus (P) application in alleviating Cd phytotoxicity in wheat plants. Different levels of P (0, 10, and 20 kg ha^?1) were applied without and with 100 µM Cd. The results showed that 100 µM Cd concentration decreased plant biomass, chlorophyll contents, gas exchange attributes, and mineral nutrients in wheat plants. Cadmium stress increased tissue Cd and H₂O₂ concentrations. The activities of superoxide dismutases (SOD), peroxidase (POD) enzymes, increased while the activities of catalase (CAT), ascorbic acid (AsA), α-tocopherol, and phenolics decreased under Cd stress. Phosphorus supply increased shoot biomass, leaf area, photosynthetic pigments, and mineral nutrients and decreased Cd and H₂O₂ concentrations in shoots. Phosphorus application improved antioxidant enzyme activities and gas exchange attributes which emerged as an important mechanism of Cd tolerance in wheat. We conclude that P application contributes to decreased Cd concentrations in wheat shoots and increased gas exchange attributes and antioxidant enzymes and could be implemented in a general scheme aiming at controlling Cd concentrations in wheat for sustained production of this important grain crop.     

Phytotoxic Effects of Residual Glufosinate on the Nitrogen Assimilation of Transplanted Rapeseed Seedlings

Herbicide application is an efficient method to control weed growth in modern agriculture production, but there is concern about the ecological impact of unwanted herbicide residues in the soil. Rapeseed varieties ZS11 and D148 were used to evaluate the phytotoxic effects of residual glufosinate on the assimilation of nitrogen (N) in rapeseed seedlings transplanted to untreated [0 g hm^?2 glufosinate] or treated [450 g hm^?2 and 900 g hm^?2 glufosinate] soils. Glutamine synthetase (GS) and glutamate dehydrogenase (GDH) activities, the contents of ammonium (NH₄⁺), free amino acids (FAA), and soluble protein (SP), and seedling dry weight (DW) were determined at 5, 8, 11, 20, 40, and 70 d post-transplant. Both concentrations of glufosinate induced physiological phytotoxicity on the N assimilation of transplanted seedlings of both varieties, as their leaves and roots presented reduced GS activities and SP contents, and increased GDH activities, and NH₄⁺ and FAA content. Glufosinate phytotoxicity on the N assimilation of transplanted seedlings reached a plateau at 11 to 20 d. further, GDH in roots and GS in leaves were still significantly different at 70 d. Meanwhile, ZS11 might be more sensitive to glufosinate than D148 since ZS11 had more variation than D148 at the same treatment, and the overdose of glufosinate more strongly inhibited N assimilation than the recommended dose. Therefore, it is essential to apply a suitable glufosinate dose to the transplanted variety, to minimize adverse effects on crops and the environment.

Abbreviations: N, Nitrogen; GS, Glutamine synthetase; GDH, glutamate dehydrogenase; NH₄⁺, ammonium; FAA, free amino acids; SP, soluble proteins; DW, Dry weight; ANOVA, one-way analysis of variance; NO₃^?, nitrate; OECD, Organisation for Economic Co-operation and Development; PPT, phosphinothricin; USEPA, United States Environmental Protection Agency     

An evaluation of pre-emergent herbicides for container-grown ornamental plants

Two applications of 5 herbicides were evaluated during spring and summer for weed control and phytotoxicity on 25 species of trees, shrubs and herbaceous perennials. Weed control was considered to be effective if herbicide-treated pots contained at most 20% of the weeds in untreated pots. Oxyfluorfen applied at 1.25, 2.5 and 5.0 kg ha^?1 provided effective control of grass and broad-leaved weeds for 8 weeks after the first application, and the 2 higher rates effectively controlled all weeds for 12 weeks after the second application. Oxadiazon at 2.0, 4.0 and 8.0 kg ha^?1 effectively controlled all weeds for 8 weeks after the first application, but only the highest rate was effective 12 weeks after the second application. Napropamide at 5.0, 10.0 and 20.0 kg ha^?1 effectively controlled grasses for up to 12 weeks, but only effectively controlled broad-leaved weeds at the 2 higher rates for 8 weeks after the first application and failed to control them after the second application. Alachlor at 4.0, 8.0 and 16.0 kg ha^?1 and oryzalin + trifluralin at 0.5, 1.0 and 2.0 kg ha^?1 provided effective control of grasses for 8 weeks after the first application. These herbicides at the highest rate also controlled broad-leaved weeds for 8 weeks after the first application. However alachlor and oryzalin + trifluralin failed to provide effective control of any weeds after the second application.Competition from weeds reduced the shoot dry weight (SDW) of unweeded control pots by 20% compared with hand-weeded control pots. None of the herbicides produced visible clamage in any plants. The SDW of 8 species treated with some of the herbicides was significantly lower than the corresponding hand-weeded control plants, and for 6 of these species some herbicide treatments were identified as being possibly phytotoxic. Oxyfluorfen appeared to inhibit the growth of Photinia and Coleonema, and alachlor inhibited the growth of Photinia, Eriostemon, Azalea ‘Splendens’, Lavendula and Coleonema. Oryzalin + trifluralin appeared to inhibit the growth of Bauhinia, and napropamide and oxadiazon inhibited the growth of Coleonema.     

A comparison of crop and non-crop plants as sensitive indicator species for regulatory testing

The effectiveness of regulatory non-target plant testing using crop species to predict the phytotoxicicity of herbicides to non-crop species was evaluated for eleven herbicides. These herbicides were representative of eight chemical classes and six modes of action. Data for non-crop plants from pre-emergence and post-emergence efficacy screening studies were compared with those for the most sensitive crop species defined by regulatory tests conducted to meet US EPA requirements. Testing under pre-emergence conditions for ten compounds indicated that for five of the compounds (K-815910, trifluralin, pyridyloxy A, pyridyloxy B and cyanazine), the most sensitive crop species was more sensitive than all the non-crop species evaluated. For metsulfuron-methyl, chlorimuron-ethyl, hexazinone and bromacil, only one of the non-crop species evaluated was more sensitive than the most sensitive crop species from regulatory tests. Data for the tenth compound, chloroacetamide, showed that four of 32 non-crop species tested in efficacy screens had at least one rate at which greater visual effects were observed than were observed for the most sensitive crop response in a regulatory test. The results of post-emergence exposure comparisons for five of the compounds (pyridyloxy A, cloransulam-methyl, chlorimuron-ethyl, cyanazine and hexazinone) indicated that the most sensitive crop species were more sensitive than all the non-crop species evaluated. Data for pyridyloxy B, metsulfuron-methyl and bromacil indicated that only one of the non-crop species evaluated was more sensitive than the most sensitive crop species. For trifluralin, three of the eight non-crop species were more sensitive than the most sensitive crop species. Data for K-815910 indicated that four of the fourteen non-crop species tested were marginally more sensitive than the most sensitive crop, but were within the same range of sensitivity. These results indicate that the current regulatory test batteries and methods using crop species effectively provide suitable sensitive indicator plants for the eleven diverse herbicides evaluated. This comparison indicates that crop species sensitivity to test substances is likely to be representative of non-crop herbaceous species response, regardless of chemical class, mode of action and magnitude or route of exposure.     

Selectivity and mode of action of carfentrazone-ethyl,a novel phenyl triazolinone herbicide

Post-emergence application of carfentrazone-ethyl at rates as low as 2·2 g ha^-1 caused greater leaf injury and growth reduction in ivyleaf morningglory (Ipomoea hederacea) and velvetleaf (Abutilon theophrasti) than in soybean (Glycine max). The herbicide was more rapidly metabolized in the crop than in the weed species, with 26·7, 54·3 and 60·6% of the parent compound remaining in soybean, ivyleaf morningglory and velvetleaf, respectively, 24 h after exposure. The free acid metabolite, carfentrazone, was present in all species and accounted for 21·2–27·4% of the total radioactivity. Unknown metabolites (R_f 0 and 0·22) were four to five times more abundant in soybean than in the weed species. Carfentrazone-ethyl induced more leakage from leaf discs from the weeds than those from soybean and the degree of injury correlated with the amount of protoporphyrin IX (Proto IX) present in the treated tissues. Both carfentrazone-ethyl and carfentrazone were potent inhibitors of protoporphyrinogen oxidase (Protox). Therefore, the selectivity of this herbicide may, at least in part, be attributed to the lower accumulation of Proto IX in soybean than in the weeds, probably because of the ability of soybean to metabolize more carfentrazone into unknown metabolites than the weeds. © 1997 SCI.     

不同浓度鸡粪嫌气发酵液对万寿菊生长和代谢的影响

每天用不同浓度的鸡粪嫌气发酵液（ＡＤＣＭＥ）处理种在温室中的万寿菊植株。结果,用１．６８％～３．３６％ＡＤＣＭＥ处理的植株地上部鲜重最高,开花最多,但用０．５６％浓度处理的根鲜重最高。收获时取植株中部叶片和根作为样品进行生理生化分析,发现叶片和根中细胞膜相对透性和Ｐｉ含量,过氧化物酶、Ｍｇ＾２＋－ＡＴＰ酶和Ｃａ＾２＋－ＡＴＰ酶活性以及根中蛋白质、ｐＨ和多酚氧化酶活性在一定范围内随着ＡＤＣＭＥ处理浓度的提高而提高。地上部鲜重较高、开花较多的处理,植株叶片中的叶绿素、类胡萝卜素和Ｐｉ含量,根中的多酚氧化酶活性以及根、叶中过氧化物酶、Ｍｇ＾２＋－ＡＴＰ酶和Ｃａ＾２＋－ＡＴＰ酶活性也较高。出现盐中毒症状的处理,植株根中的细胞膜相对透性和过氧化酶活性以及叶片中的Ｍｇ＾２＋－ＡＴＰ酶和Ｃａ＾２＋－ＡＴＰ酶活性显著高于其它处