Effects of sterol biosynthesis-inhibiting fungicides and plant growth regulators on the sterol composition of barley plants

A number of sterol biosynthesis-inhibiting (SBI) fungicides and plant growth regulator analogs were applied as root drenches to barley seedlings and their effect on the total sterol composition of the roots and shoots was measured by gas-liquid chromatography. Prochloraz was found to be inactive in this system, probably because of poor uptake, while the other compounds could be divided into two groups according to their mode of action as assessed by sterol profiling. The morpholines tridemorph and fenpropimorph inhibited the enzyme cycloeucalenol—obtusifoliol isomerase whereas triadimenol, nuarimol, paclobutrazol, and triapenthenol (RSW 0411) inhibited the enzyme responsible for the removal of the C-14 methyl group. Effects of individual diastereo-isomers and enantiomers of some compounds on sterol profiles were compared with their known fungicidal and anti-gibberellin properties. Shoot growth was reduced by all the compounds tested, paclobutrazol, nuarimol, and triapenthenol being the most effective. As well as inducing accumulation of abnormal sterols, SBI fungicide treatment changed the ratio of campesterol to stigmasterol and sitosterol. It is hypothesized that this may reflect changes in membrane architecture and may offer an explanation for the increased frost hardiness sometimes observed with SBI fungicide-treated plants.     

The diastereomeric ratio in the triadimenol produced by fungal metabolism of triadimefon,and its role in fungicidal selectivity

The ratio of the two diastereomeric forms of triadimenol, produced by the reduction of triadimefon in various fungi, was studied. The reduction of triadimefon in fungi seems to be a concentration-dependent process, the virtual irreversibility of which is proved. Not only the degree of triadimefon reduction, but also the ratio of the triadimenol diastereomers produced, was characteristic for each of the fungal species. A direct correlation, between the production of the more active diastereomeric form and the sensitivity of the fungal species to triadimefon, was observed.     

Effect of diclobutrazol on the growth and sterol and photosynthetic pigment content of winter wheat

The effect of the fungicide, diclobutrazol, on the germination, growth, chloroplast pigment and sterol content of winter wheat seedlings has been studied. At 250 μEm it retards their germination and growth, producing smaller, darker green and apparently healthy young plants. This is largely due to the 2S,3S–enantiomeric component. The increased greenness is not due to a direct effect on chloroplast pigments. It inhibits sterol 14—demethylation, causing an increase in the content of 4α,14α–dimethyl sterols, and also increases the proportion of campesterol, a 24—methyl sterol, relative to that of the 24—ethyl sterols, stigmasterol and sitosterol. Both the 2R,3R– and 2S,3S–enantiomers appear to be able to cause these changes in sterol content.     

Toxic effects of cadmium,acetochlor and bensulfuron-methyl on nitrogen metabolism and plant growth in rice seedlings

The adverse effects of cadmium (Cd), acetochlor (AC), bensulfuron-methyl (BSM) alone and their coexistence on nitrogen metabolism and plant growth in rice seedlings were studied with aquatic culture experiments. The results demonstrated that in all exposure groups there were marked decrease in the fresh weight of rice seedlings and the activities of nitrate reductase (NR), glutamine synthetase (GS) in the roots and shoots, consequently leading to an increase in free amino acids content and decrease in soluble protein content and nitrate content in the roots and shoots. These results suggested that the toxicity of Cd, AC and BSM to the rice seedlings took place partly through the influence on nitrogen metabolism.     

Residual effects of triadimefon in soil on powdery mildew and yield of spring barley

Residual triadimefon (or a breakdown product), from a spray application (2 kg/ha) to field soil in 1978, significantly decreased powdery mildew on spring barley throughout two subsequent growing seasons, with consequent yield increases of 42% in 1980 and 18% in 1981.
In other field experiments triadimefon applied to soil at rates >0.06 kg/ha decreased mildew in barley growing in the soil 11 months later. In these experiments triadimefon, but not benomyl, imazalil or prochloraz (all at 0.5 kg/ha) significantly decreased mildew up to harvest and increased yield by 22%.
Triadimefon incorporated into a loam soil and a peat-based compost at rates >0.1 ng/g significantly decreased mildew on barley grown in pots under glasshouse conditions. Plants grown in the treated compost at the same time but in isolated pots supplied with filtered moistened air and capillary watering required more triadimefon (>100 ng/g) in soil for significant mildew control.
Despite strong adsorption of triadimefon to soil (Kd 19.4), an active substance appears to remain available for uptake and translocation by barley plants over long periods. The sensitivity of barley mildew to extremely small residues of triadimefon is discussed in relation to the siting of field experiments on mildew control. The implications for widespread commercial use of formulations containing triadimefon are discussed in relation to disease control practice in cereal growing systems.     

Effect of mecoprop on plant growth and distribution of photosynthate in wheat (Triticum aestivum L.) seedlings

Foliar application of the phenoxy-acid herbicide, mecoprop, at four times normal field rate, caused decreases in root and shoot growth of wheat (Triticum aestivum L.). The shoot relative growth rate (RGR) was affected before that of the roots but subsequently the root RGR was significantly decreased. The roots of plants affected by mecoprop produced large numbers of short swollen laterals but the root system as a whole gradually recovered. Mecoprop treatment was associated with an immediate and lasting decrease in photo-synthetic ¹⁴CO₂ fixation. After a pulse of ¹⁴CO₂ in the light, the proportion of carbon moving to the roots in treated plants was always decreased but after a 24-h chase the proportion moving to the roots was initially decreased (2 days after spraying), then increased (9 days after spraying), but later became the same (17 days after spraying) as the water sprayed controls. Possible mechanisms involved with these mecoprop induced changes are discussed. Effets de l'herbicide mécoprop sur le développement végétatif et la répartition de produits photosynthétiques dans des plantules de blé (Triticum aestivum L.) Le mécoprop, acide phénoxypropionique, en application foliaire à quatre fois la dose conseillée, a amené une baisse dans la croissance des racines et des pousses du blé (Triticum aestivum L.). Le taux de croissance relative (RGR) des pousses a témoigné des effets plus tôt que les racines mais ultérieurement le RGR des racines a baissé de façon significative. Les racines des plantes touchées par le mécoprop ont produit de nombreuses ramifications courtes et renflées, mais le système racinaire s'est remis peu à peu. Les traitements au mécoprop sont associés à une baisse immédiate et prolongée dans la fixation du ¹⁴CO₂ photosynthétique. A la suite d'un marquage au ¹⁴CO₂à la lumière, la proportion de carbone qui s'acheminait vers les racines des plantes traitées a toujours fait voir une baisse mais au bout d'un intervalle de 24 h, la proportion qui s'acheminait vers les racines a d'abord diminué (2 jours après la pulvérisation) pour augmenter ensuite (9 jours après la pulvérisation). Plus tard (17 jours après la pulvérisation) cette proportion était semblable à celle des témoins ne recevant que de l'eau. Les mécanismea éventuellement enjeu dans ces changements provoqués par le mécoprop sont discutés. Wirkung von Mecoprop auf das Wachstum und die Verteilung von Assimilaten bei Jungpflanzen des Weizens (Triticum aestivum L.) Die Blattapplikation von Mecoprop in der 4 fachen Normaldosierung führte zu einer Abnahme des Wurzel-und Sprosswachstums des Weizens. Zunächst war das Wachstum des Sprosses, aber später auch das der Wurzeln herabgesetzt. Die Seitenwurzeln waren verkürzt und verdickt, aber nach und nach fand das Wurzelsystem zum normalen Wuchs zurück. Nach der Behandlung nahm die ¹⁴14C0₂-Assimilation für einige Zeit ab. 9 Tage nach der Behandlung nahm der Transport von Assimilaten in die Wurzeln wieder zu, so dass er 17 Tage nach der Behandlung dieselbe Höhe wie bei den Kontrollpflanzen erreichte. Der mögliche Mechanismus der von Mecoprop herbeigeführten Veränderungen wird diskutiert.     

Effect of propiconazole on growth and sterol biosynthesis by Sclerotium rolfsii

Germination of sclerotia ofSclerotium rolfsii on agar nutrient medium was delayed or slightly inhibited by concentrations of propiconazole between 0.4 and 4.0 μg ml^?1, but was strongly inhibited by 8 μg ml^?1 and completely inhibited by 16 μg ml^?1. On the other hand, growth of hyphae from the germinated sclerotia was strongly inhibited by propiconazole at 1 μg ml^?1 or greater. Hyphal growth from agar discs on agar medium was about 8 times less sensitive than hyphal growth from the sclerotia or from hyphal inoculum in liquid media. Propiconazole at 0.25 and 1.0 μg ml^?1 strongly inhibited ergosterol biosynthesis, but this was not associated with large accumulations of C-14 methyl sterols. The ratio of eburicol to ergosterol in hyphae grown in the presence of 0.25 μg ml^?1 propiconazole for 16, 30 or 45 h was 0.11, 0.13 and 0.04, respectively, for the three intervals while for hyphae grown in the presence of 1 μg ml^?1, the ratios were 0.29, 0.36 and 0.30, respectively, for the same intervals. In view of a ratio of 23.5 for¹⁴C-acetate incorporation into the two sterols during the initial 6 h growth period in the presence of propiconazole, it is believed that the lack of large accumulation of C-14 methyl sterols is due to the feedback inhibition by eburicol or to cell lysis when the content of ergosterol becomes too low in the actively growing cells.     

Effect of herbicide antidotes on glutathione content and glutathione S-transferase activity of sorghum shoots

The effects of the herbicide antidotes CGA-92194 (α-[(1,3-dioxolan-2-yl-methoxy)-imino]benzeneacetonitrile), flurazole [phenylmethyl 2-chloro-4-(trifluoromethyl)-5-thiazolecarboxylate], dichlormid (2,2-dichloro-N,N-di-2-propenylacetamide), and naphthalic anhydride (1H,3H-naphtho(1,8-cd)-pyran-1,3-dione) on nonprotein thiol content, glutathione content, and glutathione S-transferase (GST) activity in etiolated sorghum (Sorghum bicolor L.) Moench) shoots were examined. CGA-92194 and naphthalic anhydride had no effect on nonprotein thiol or reduced glutathione (GSH) content of sorghum shoots. In contrast, dichlormid and flurazole increased nonprotein thiol content of sorghum shoots by 24 and 48%, respectively. These increases were largely attributable to an increase in GSH. The antidotes increased GST activity less than twofold when using CDNB (1-chloro-2,4-dinitrobenzene) as a substrate. In contrast, when using metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] as a substrate, the increase in GST activity in response to antidote treatment was much greater: flurazole (30-fold), CGA-92194 (20-fold), naphthalic anhydride (17-fold), dichlormid (5-fold). The degree of protection from metolachlor injury conferred by a particular antidote was strongly correlated (R² = 0.95) with its ability to enhance GST activity, as evaluated with metolachlor as substrate. A comparison of GST activity in untreated and CGA-92194-treated seedlings, over a range of metolachlor concentrations (0.5–500 μM), indicated that the relative enhancement of enzyme activity by CGA-92194 was greater at lower metolachlor concentrations. The rate of nonenzymatic conjugation of metolachlor and GSH in vitro was much less (on a gram fresh weight equivalent basis) than the enzymatic rate. These results are consistent with the hypothesis that the above antidotes protect sorghum by enhancing GST activity which results in accelerated detoxification of metolachlor via GSH conjugation.     

Saccharin-induced protection against powdery mildew in barley: effects on growth and phenylpropanoid metabolism

Treatment of barley ( Hordeum vulgare ) with 3 m m saccharin, applied as a foliar treatment to the first leaf or as a soil drench, provided significant control of powdery mildew ( Blumeria graminis f.sp. hordei ) on first and second leaves. This was unlikely to be the result of a direct effect of saccharin on the fungus, as application of the chemical to first leaves 2 h before inoculation did not affect conidial germination or formation of appressoria. Saccharin treatment had no significant effect on plant growth, except for a reduction in total leaf area in plants treated with a saccharin drench 14 days before inoculation with mildew. Phenylalanine ammonia-lyase activity was reduced significantly in second leaves 18 and 48 h after inoculation in plants treated with saccharin 14 days earlier. Peroxidase activity increased significantly in plants challenged with mildew within 6 days of saccharin application, although changes were not apparent until 48 h after pathogen challenge. On these occasions, treatment with saccharin resulted in a 33% increase in peroxidase activity compared with controls. In plants inoculated 10 or 14 days after saccharin application, cinnamyl alcohol dehydrogenase (CAD) activity increased prior to, and 18, 24 and 48 h after, inoculation of the barley plants with mildew. CAD activity increased approximately twofold compared with controls. However, in contrast to peroxidase, CAD activity was significantly higher in saccharin-treated plants prior to and after inoculation with powdery mildew, suggesting that saccharin primes CAD activity prior to pathogen challenge.     

Effect of acetochlor treatment on Fusarium wilt and sugar content in melon seedlings

Pretreatment of soil with the herbicide acetochlor at 0.1–1g g^–1 significantly decreased incidence of wilt due toFusarium oxysporum f. sp.melonis in melon seedlings. Glucose, fructose and sucrose increased in leaves of inoculated and uninoculated melon plants following acetochlor treatment. The increase in sugar levels in stems and roots was less pronounced. Light intensity affected sugar content and disease incidence. The percentage of diseased plants was significantly higher in untreated plants grown under 165E m^–2 sec^–1 compared to plants grown under 300E m^–2 sec^–1. Lowering light intensity resulted in reduction of levels of total sugars on the third and sixth day after inoculation. Acetochlor had little or no effect on growth rate or sporulation of the pathogen in culture. The colonization rate of diseased plant stems by the pathogen was similar in herbicide-treated and untreated plants, thus excluding the possibility that disease reduction by the herbicide is related to direct fungitoxicity.Contribution from the Agricultural Research Organization. No. 1560-E, 1995 series.     

欧李内生促生菌分离、鉴定及促生、耐盐碱特性

为获得欧李(Cerasus humilis)根系优良内生促生菌,以欧李根系为研究材料,采用组织匀浆法分离纯化可培养内生细菌,测定其固氮、解磷、溶磷、合成植物生长素IAA(吲哚乙酸)和耐盐碱特性,并通过16S rRNA序列系统发育分析进行初步鉴定.结果显示:分离的7株菌均表现出一定的促生潜力,菌株固氮酶活性在50.64～...     

Effect of analogues of plant growth regulators on in vitro growth of eukaryotic plant pathogens

FGA (furfurylamine; 1,2,3,4 tetra- O -acetyl-β- d -glucose; adipic acid monoethyl ester), a chemical mixture of three analogues of plant growth regulators that increases the protection of tomato plants against phytopathogens, was demonstrated to have direct antimicrobial activity. It reduced the growth in vitro of the filamentous fungi Alternaria solani and Botrytis cinerea , and the oomycetes Phytophthora capsici and Phytophthora citrophthora (ED₅₀ 0·18–0·26% w/v, depending on species). The components of this mixture were also active against these phytopathogens, but sensitivity to the compounds was different for each pathogen. Adipic acid monoethyl ester (E) showed the highest and widest range of activity. Experiments on B. cinerea and A. solani indicated that this compound prevented spore germination in addition to mycelial growth and at high concentrations (0·5% w/v), inhibiting both the yeast Saccharomyces cerevisiae and the bacterium Escherichia coli . This ester retarded A. solani infection of tomato leaves, providing evidence for its efficacy in a biological context and its potential use in plant disease prevention.     

干旱对小麦幼苗Cu、Mn含量的影响及其机理研究

采用液体培养法,研究了不同干旱处理方法,即每天间断干旱1 h2、h、3 h、4 h和连续干旱24 h,对小麦幼苗两种微量元素Cu、Mn的吸收、分布及叶绿素含量的影响。结果表明:间断干旱1 h、2 h处理,小麦幼苗根、茎、叶的Cu、Mn含量及叶绿素含量均有所增加,间断干旱2 h处理增加更显著;间断干旱3 h4、h和连续干旱处理均使小麦幼苗根茎叶中Cu、Mn含量及叶绿素含量降低,连续干旱处理降低最显著。随着干旱程度的增加,小麦幼苗Cu、Mn含量呈"钟型曲线"变化,即先随干旱程度增加而增加,当干旱达到一定程度后随干旱程度增加而减少。小麦幼苗Cu、Mn含量和叶绿素含量变化趋势一致,三者高度相关。说明适度的干旱处理可增加小麦幼苗中Cu、Mn两种微量元素的含量,而过度干旱则导致小麦幼苗中Cu、Mn含量降低。     

The effect of bacterial fermentation of couch grass rhizomes and Fusarium culmorum on the growth of barley seedlings

Phytotoxic concentrations of acetic acid were found in extracts of decaying rhizomes of couch grass ( Agropyron repens ) kept in sand at different moisture levels. Leaf extension of barley seedlings was inhibited by inoculating the radicles before planting with Fusarium culmorum and this inhibition was increased by 5 mM acetic acid. Seed dressings of benomyl and thiram alleviated the inhibition of leaf growth of seedlings grown in sand containing rhizomes inoculated with F. culmorum .     

多效唑对2年生沙地柏生长和生理特征的影响研究

多效唑是一种赤霉素抑制剂,通过调控植物的生长、生理过程,提高其抗逆性.文中在盆栽控水的条件下,采用多效唑溶液灌根(0,50,200,400,600,800mg/L),研究多效唑对2年生沙地柏生长和生理特征的影响.结果表明:多效唑显著抑制沙地柏地上部分的生长,增大叶厚,促进地下根系生长;显著增大叶绿素a和b的总含量,减小了叶绿素a/b和水分饱和亏缺,提高光合产物积累、叶片相对含水量及肉质化指数等.多效唑可以提高植物的适应能力和抗逆性,并对提高干旱、半干旱区植被盖度及植被恢复具有重要意义.综合效应最佳处理浓度范围是200～ 600mg/L.     

聚乙二醇胁迫下赤霉素浸种对番茄种子萌发和幼苗生长的影响

以番茄幼苗为材料,研究了50 mg/g 的赤霉素(GA3)和清水浸种后用不同浓度的聚乙二醇(0、40、80、120 mg/g)胁迫对番茄种子萌发及幼苗生长的影响.结果表明:40 mg/g的聚乙二醇胁迫对番茄种子的萌发率、发芽指数、幼苗株高、根长有促进作用,120 mg/g的聚乙二醇明显抑制种子的萌发率、发芽指数、幼苗株高、根长;不同浓度的聚乙二醇胁迫明显降低了幼苗的叶绿素含量.用50 mg/g GA3浸种后明显增加聚乙二醇胁迫下番茄种子的萌发率、发芽指数、幼苗株高、根长和叶绿素含量.用50 m g/g GA3浸种对番茄幼苗的生长有一定的促进作用.     

生物降解膜覆膜节水对沙砾土壤含水量及葡萄幼苗生长的影响

为了提高干旱半干旱地区水资源的利用率,加快生物降解膜的应用,以葡萄扦插苗为材料,在吐鲁番市二堡乡设置覆膜区和无覆膜区,其中覆膜区采用生物降解膜节水种植技术和3种不同膜（完全生物降解膜、半生物降解膜、普 通膜）处理,持续观测90 d,以无覆膜及覆膜区内普通膜为对照,分析生物降解膜作用下沙砾土壤含水量及葡萄幼苗生长的变化。结果表明：覆膜区比无覆膜区节水可达到60%;覆膜作用下可明显增加10～40 cm沙砾土层含水量,保水性能均高于无覆膜对照;覆膜区完全生物降解膜作用明显增加了葡萄幼苗的发芽数、叶片数、叶面积、新梢宽度生长量、新梢节数生长量;半生物降解膜明显增加了幼苗的发芽数、叶片数、叶面积、新梢叶片数生长量,但叶片多为展开的新叶,叶面积较小;普通膜明显增加了幼苗的发芽数、新梢节数生长量。覆膜对幼苗基径、新梢宽度、新梢长度、新梢节数及新梢叶片数、新梢长度生长量影响不显著。研究认为覆膜区完全生物降解膜不仅具有较好的保水性,还能促进大部分幼苗生长指标,综合效果最佳。     

Action of benzimidazole fungicides on resorcinolic lipid metabolism in rye seedlings depends on thermal and light growth conditions

The content and homologue composition of alkylresorcinols were investigated in rye seedlings (Secale cereale L.) treated with benzimidazole fungicides and grown for 5 days under various thermal and light conditions. The fresh and dry biomasses of green and etiolated plants were greatly increased by benomyl and carbendazim at 29 °C. At 22 and 15 °C benomyl had an inhibitory action on growth of rye, whereas the effects caused in the presence of carbendazim were slightly dependent on external stimuli. On the other hand, benomyl enhanced resorcinol biosynthesis in green seedlings grown at all temperatures, while carbendazim only at 29 °C. In plants kept in the darkness, both fungicides increased content of alkylresorcinols at 29 °C and decreased its at 22 and 15 °C. The qualitative pattern of resorcinolic homologues was also significantly modified in the presence of benomyl and carbendazim and depended on other physical stimuli.     

植物生长调节剂对烟草生长发育及钾素吸收与分配影响研究

通过盆栽试验,采用不同钾素水平,在烟草植株打顶后夹吸不同的植物生长调节剂对烟草生长发育进行研究。研究表明,不同钾水平对烟草植株的株高、最大叶面积、根体积、倒二叶叶面积均没有显著的促进作用,但是能够显著增加根鲜重,而烟株打顶后夹吸生长调节剂能显著地促进烟草植株的株高、最大叶面积、根体积、根鲜重、倒二叶叶面积的增长。同时,植物生长调节剂能明显提高不同部位烟叶中的钾含量和各部位钾素的积累量,促进钾素从根、茎部向叶部的转移,显著提高烟草的品质,其中表油菜素内酯(BR)与赤霉素(GA3)处理效果最为明显。     

Effect of tricyclazole on growth and secondary metabolism in Pyricularia oryzae

Tricyclazole [5-methyl-1,2,4-triazolo (3,4-b)-benzothiazole] controls rice blast disease caused by Pyricularia oryzae at concentrations (5–10 μg/ml) which do not inhibit growth of the pathogen in vitro. However, concentrations of 1 μg/ml or less inhibit melanin formation in the fungus. Production of pyriculol by the pathogen is usually enhanced by 10 μg/ml of tricyclazole, whereas production of 3,4-dihydro-4,8-dihydroxy-1(2H)-naphthalenone is strongly inhibited or markedly reduced and delayed. Evidence suggests that tricyclazole blocks aspects of polyketide metabolism in P. oryzae which may have a role in pathogenicity.