Physiological basis of differential phytotoxic activity between fenoxaprop-P-ethyl and cyhalofop-butyl-treated barnyardgrass

This study investigated the physiological causes of differences in phytotoxic symptoms shown in barnyardgrass from foliar applications of the herbicides fenoxaprop-P-ethyl and cyhalofop-butyl. When these were applied to the third leaves of the whole plant, the chlorosis and desiccation in the third leaf was greater in fenoxaprop-P-ethyl than cyhalofop-butyl. However, initial growth inhibition of the fourth leaf was greater when using cyhalofop-butyl than when using fenoxaprop-P-ethyl. In the shoot regrowth test, regrowth at five days after treatment (DAT) was smaller in cyhalofop-butyl than in fenoxaprop-P-ethyl; the regrowth at 10 DAT exhibited the reverse trend. The chlorosis (decrease of chlorophylls: carotenoids ratio) in barnyardgrass leaf segments that were floated on herbicide solution was greater in the fenoxaprop-P-ethyl treatment. These results indicate that different herbicidal responses induced by the two herbicides are likely to be related to differential translocation and metabolism. The relatively light chlorosis and desiccation in treated leaves, severe cessation of initial growth (but a lower final herbicidal efficacy in the cyhalofop-butyl treatment) are probably related to its rapid translocation to the meristem region from the treated leaf, followed by faster metabolism. In contrast, the relatively greater chlorosis and desiccation compared to inhibition of initial growth in the fenoxaprop-P-ethyl treatment is likely to be related to its relatively slower translocation and metabolism in the treated leaf.     

齐墩果酸肟醚类化合物的合成及杀菌活性

为了开发潜在的氨基葡萄糖-6-磷酸合成酶（GlmS）抑制剂和杀菌剂,设计并合成了30个齐墩果酸肟醚类化合物,其中29个为新化合物,其结构均经1H NMR、13C NMR和高分辨质谱确证。采用Elson-Morgan法和菌丝生长速率法,分别测定了目标化合物对GlmS的抑制活性和杀菌活性。结果表明:在0.35 mmol/L下,大部分目标化合物对GlmS表现出一定的抑制活性,其中,化合物A-01、A-02、A-04、C-04和C-05对GlmS的抑制率在30%左右;部分化合物在50 μg/mL下对油菜菌核病菌Sclerotinia sclerotiorum（Lib.）de Bary、番茄灰霉病菌Botrytis cinerea Pers. 和稻瘟病菌Pyricularia oryzae Cav. 具有较好的杀菌活性,其中,化合物A-01、A-02、A-04、A-05和B-02对油菜菌核病菌的抑制率在88%左右,具有进一步研究的价值。     

新型芳氧吡啶肟醚类化合物的设计、合成和杀虫活性

以芳氧吡啶乙酮分子插件为基础,设计合成了一系列芳氧吡啶乙酮肟醚类化合物,其结构经核磁共振氢谱、碳谱及高分辨质谱等确证.初步杀虫活性测定结果表明,该系列化合物对棉蚜Aphis gossypii(Glover)具有较好的杀虫活性,其中化合物5a和6i在50 μg/mL下对棉蚜的致死率分别为76.8％和70.1％,具有作为先...     

Synthesis of spiroketal enol ethers related to tonghaosu and their insecticidal activities

This paper describes the syntheses and biological activities of a number of spiroketal enol ethers which are analogues of the plant extract tonghaosu. The insecticidal potential of this spiroketal system is assessed.     

新疆棉花品种次生代谢酶活性与诱导抗蚜性的关系

为了明确不同棉花品种次生代谢酶活性与诱导抗蚜性的关系,研究了不同类型棉花品种在棉蚜为害胁迫下,苯丙氨酸解氨酶(PAL)、过氧化物酶(POD)和多酚氧化酶(PPO)活性的变化及其对抗蚜性的影响。结果表明,未受蚜害时不同品种同一酶活性存在显著差异;受蚜害诱导后,抗蚜品种和感蚜品种3种酶活性均有不同程度的上升,抗蚜品种酶活性显著高于感蚜品种,诱导抗蚜性的强弱在不同品种间差异显著。     

Isolation of a phytotoxic isocoumarin from Diaporthe eres‐infected Hedera helix (English ivy) and synthesis of its phytotoxic analogs

BACKGROUND

The fungus Diaporthe eres was isolated from a fungal pathogen‐infected leaf of Hedera helix (English ivy) exhibiting necrosis. It is hypothesized that the causative fungus produces phytotoxins as evidenced by necrotic lesions on the leaves.

RESULTS

The fungus was isolated and grown in Czapek Dox broth culture medium and potato dextrose broth culture medium and identified as Diaporthe eres. The ethyl acetate extracts of the culture broths were phytotoxic to lettuce (Lactuca sativa) and bentgrass (Agrostis stolonifera). 3,4‐Dihydro‐8‐hydroxy‐3,5‐dimethylisocoumarin ( 1 ) and tyrosol ( 2 ) were isolated and identified as the phytotoxic constituents. Six analogs of 3,4‐dihydro‐isocoumarin were synthesized and shown to be phytotoxic. The synthesized 3,4‐dihydro‐8‐hydroxy‐3,7‐dimethylisocoumarin and 3,4‐dihydro‐8‐hydroxy‐3,3,7‐trimethylisocoumarin were two‐ to three‐fold more phytotoxic than the naturally occurring 1 in a Lemna paucicostata growth bioassay.

CONCLUSION

Synthesis and herbicidal activities of the several new analogs of 1 are reported for the first time. These promising molecules should be used as templates for synthesis and testing of more analogs. © 2017 Society of Chemical Industry     

Factors affecting phytotoxic activity of allelochemicals in soil

Allelopathy is the inhibitory or stimulatory effect of a plant (donor) on other plants (receivers) through the chemicals released from the donor plant to the environment, mostly into the soil. These chemicals may reach the receiver plants in various ways, including leaching from plant foliage, exudation from the roots, and decomposition of dead residue of the donor plants. However, allelopathy in soil is a complicated phenomenon that is affected by soil condition, growth condition of the donor and receiver plants and climatic condition. Allelochemicals in soil are adsorbed on soil solids, and metabolized by chemical and biological reactions during the movement in soil. This behavior is affected by various soil factors, such as soil texture, organic and inorganic matter, moisture and organisms, which affect the phytotoxic activity in soil. If an allelochemical can directly affect the growth of receiver plants in soil, then the allelochemical might be present in the soil water so that it is directly available for absorption by the plant. Thus, it is suggested the concentration of an allelochemical in soil water is a dominant factor directly determining the phytotoxic activity in soil, and the concentration is controlled by soil factors that affect the behavior of adsorption, desorption and degradation in soil.     

Use of phytotoxic rice crop residues for weed management

There is a general perception among Cambodian rice (Oryza sativa) farmers that, after harvesting, rice crop residues that are incorporated into the field benefit the growth of the subsequent rice crop. However, the effect of this action upon weed establishment and growth has not yet been considered. A series of pot and field trials were conducted to determine whether such action could inhibit weed establishment and/or growth. The pot studies first evaluated the response of the test plant (rice line ST‐3) and three weed species, barnyardgrass (Echinochloa crus‐galli), small umbrella sedge (Cyperus difformis), and water primrose (Ludwigia octovalves), to the residue of 16 rice lines and the field trials were later conducted to evaluate the response of the same test plants to the residue of seven putatively allelopathic rice lines and one non‐allelopathic rice line. The residue of all the studied rice lines, depending on how long they had been incorporated into the soil, reduced the establishment and growth of all three weed species, as well as the rice crop. However, if the residue's incorporation was delayed by 2 weeks or only a proportion of the residue was incorporated, the rice crop could withstand the growth‐inhibiting effect, while the inhibition of the establishment and growth of the three weed species was retained. These responses of rice and the weeds to rice crop residues might provide a basis for a weed management strategy, particularly in the resource‐poor rice‐production systems of Cambodia.     

Correlation between hydrolytic enzyme activities measured in bean seedlings afterTrichoderma koningii treatment combined with pregermination and the protective effect againstPythium splendens

An experimental protocol consisting in the colonisation of pregerminated bean seeds dressed withTrichoderma sp. was used in order to study the mechanisms correlated with the protective effect againstPythium splendens. Seed dressed with TH-11 (T. koningii) for 24 h presented a higher protective effect and a higher level of seed colonisation as compared to those dressed with TH-13 (T. longibranchiatum). The levels of seed coat colonisation by TH-11 and TH-13 was shown to be correlated with the carboxymethylcellulase activity, as measured in the seed coats retreived from germinating dressed bean seeds. The seed coat colonisation was also associated with an increased activities of endo-1,3--glucanase and endochitinase measured in seed extracts, and an inhibitory effect of seed extracts onPythium sporangia germination. Pretreatment of TH-13-dressed seeds with a commercial cellulase improved all parameters mentioned above, thus suggesting a role of cellulase activity in the colonisation process and the linked protective effect. The possible role of hydrolytic enzymes in the protective effects is discussed.     

The incredible fungal genus —Drechslera — and its phytotoxic ophiobolins

ManyDrechslera species that haveCochliobolus sp. as a perfect stage produce a related group of ophiobolins, sesterterpenoids (C-25’s), which are phytotoxic to a wide range of plants. One of the most toxic ophiobolins is 6-epiophiobolin A and it is produced by all of theDrechslera species thus far studied. On the other hand, some novel ophiobolins have been found inD. oryzae: ophiobolin J, 6-epiophiobolin I, and 8-deoxyophiobolin J. Potentially, genetic crosses made between these fungi could yield novel organisms, producing novel combinations of the ophiobolins, and thus new pathotypes. Ophiobolins are being used in tissue culture systems to screen plants for sensitivity to these toxins. Paper presented at the Bat-Sheva Seminar on Host - Fungus Interaction, Jerusalem, Israel (March 14–25,1988).     

Residual thenylchlor concentration in soil water and its phytotoxic activity in soil

The phytotoxic activity of soil-applied thenylchlor (2-chloro- N -[3-methoxy-2-thenyl]-2',6'-dimethylacetanilide) on the growth of rice seedlings and its behavior in two different types of soil, Ryugasaki soil and Tsukuba soil, after application was investigated with emphasis on the concentration in the soil water. The greatest inhibition of thenylchlor on the growth of rice seedlings was found immediately after application to both the Ryugasaki and Tsukuba soils. The phytotoxic activity decreased with time in both soils. However, the rate of decrease in phytotoxic activity was slower in the Ryugasaki soil than in the Tsukuba soil. The concentration of thenylchlor in soil water, the amount adsorbed on the soil solid, and the amount in the total soil reduced with time after application to both soils. The amount of thenylchlor adsorbed on the soil solid phase was more persistent than that in the soil water in both soils and the concentration in the soil water was higher in the Ryugasaki soil than in the Tsukuba soil at any given time. The residual phytotoxic activity of thenylchlor on the growth of the rice seedlings in the soil was highly correlated with its concentration in the soil water but not with the amount in the total soil. These results suggested that the residual phytotoxic activity of thenylchlor in the soil is determined by its concentration in the soil water after application.     

Pyrimidinyl-substituted amides and thioureas: syntheses, crystal structure and herbicidal activities

BACKGROUND: The high herbicidal activities of [1,2,4]triazolo[1,5-c]pyrimidine and 2H-1,2,4-thiadiazolo[2,3-a]pyrimidine derivatives suggested the development of new fused heterocyclic compounds for application as herbicides. RESULTS: Three series of pyrimidinyl-substituted thioureas (4) and amides (5, 6) were synthesized, and the typical crystal structure of a 2H-1,2,4-thiadiazolo[2,3-a]pyrimidine derivative (5a) was determined by X-ray diffraction. All the compounds were tested for herbicidal activity against selected weeds. CONCLUSION: The series of fused heterocyclic amides 5a to 5d exhibited high herbicidal activities both against monocotyledonous weeds (Echinochloa crus-galli L., Sorghum bicolor (L.) M?nch., Digitaria sanguinalis (L.) Scop) and against dicotyledonous weeds (Amaranthus retroflexus L. and Brassica campestris L.) in pre-emergence treatments. In particular, compound 5b at low concentration still showed high inhibitory activity against A. retroflexus in pre-emergence treatment. Different substituents at the meta positions of the pyrimidine ring were found to affect the herbicidal activity.     

Antagonistic effect of photosynthetic electron transport inhibitors on peroxidizing phytotoxic activity

It is shown that a number of new 2-benzylamino-1,3,5-triazines have a similar antagonistic effect to diuron on the phytotoxic activity of peroxidizing herbicides.     

梨叶部病害与梨叶早衰脱落相关性分析

为明确南方梨产区造成梨早衰落叶的原因,本研究对梨叶部病害的发生与早期落叶间的关系进行了调查分析。结果显示:4种叶部病害(梨斑点病、褐斑病、黑斑病和黄脉病)中,除黄脉病外,不同年份间其余3种病害的发生程度与早期落叶率均呈显著正相关;不同品种、果园和时段间这3种病害均呈极显著正相关;7-9月间梨早衰脱落叶片斑点病发病率均达到100%,显著高于其他3种病害;病害防控对减少梨叶部病害发生和降低早期落叶率具有同效性,由此认为防治以斑点病为重点的叶部病害,是控制梨树落叶早衰问题的关键。     

阿拉善荒漠区植物多样性与土壤理化性质相关性研究

为了弄清阿拉善荒漠区的植物多样性特征,初步阐明调控荒漠植被空间分布的土壤理化指标,本文对阿拉善荒漠流动沙地、固定沙地、砾质沙地和盐碱地四种生境下植物多样性与土壤理化性质的关系进行了研究,并确定了不同生境下植物多样性与土壤理化指标的逐步回归方程。研究结果表明:固定沙地和砾质沙地的植物多样性明显高于流动沙地和盐碱地;在砂粒含量较高的流动沙地和砾质沙地,灌木物种的Shannon-Wiener指数明显大于草本物种;逐步回归方程表明,土壤pH及砂粒含量显著影响流动沙地的植物多样性,固定沙地和砾质沙地的植物多样性与土壤中全磷、全钾含量密切相关,而土壤中全磷和总盐量则显著影响盐碱地的植物多样性。     

Isolation and identification of two phytotoxic compounds from the medicinal plant Cassia alata L.

Cassia alata (Caesalpiniaceae), an ornamental shrub, has many biological properties such as antifungal and antibacterial activities. Several bioactive and phytotoxic compounds have already been isolated from C. alata. Phytotoxic substances from plants have drawn attention as an alternative biological approach to control weeds. Thus, we conducted this research to explore other phytotoxic compounds in C. alata leaves. Aqueous methanol extracts of C. alata leaves strongly inhibited the seedling growth of broccoli, cabbage, cress, radish and rapeseed, in which the level of inhibition correlated with concentration. Two active compounds were isolated through chromatographies and identified using spectral data as (S)‐4‐(3‐hydroxybutyl)phenol [(+)‐rhododendrol] and (E)‐4‐((1R,4R)‐4‐hydroxy‐2,6,6‐trimethylcyclohex‐2‐en‐1‐yl)but‐3‐en‐2‐one [3‐hydroxy‐α‐ionone]. These two active compounds inhibited the growth of cress seedlings in a concentration‐dependent manner. The required concentrations for 50% growth inhibition (I₅₀ value) of cress seedlings were 192.0–296.1 μM for (+)‐rhododendrol and 132.4–195.3 μM for 3‐hydroxy‐α‐ionone. These results indicate that the two phytotoxic compounds play a part in the phytotoxic activity of C. alata leaves.     

Studies in phytotoxicity: The detection of incipient phytotoxic effects of sulphur preparations

In a study of the relationship between carbon dioxide assimilation in the light, respiration in the dark, and temperature, the carbon dioxide content of air drawn over dwarf beans treated with lime sulphur or sulphur dust in light or darkness was continuously monitored coulometrically. Sulphur dust had only a negligible effect on carbon dioxide assimilation in the light or on respiration in the dark. Lime sulphur at 15 and 22°c also produced only small differences but at 30°c there were marked changes in net assimilation. Those treatments which caused changes in carbon dioxide assimilation in the light or respiration in the dark were directly associated with the degree of damage estimated visually. The method may be valuable for the detection of phytotoxic effects of other fungicides and insecticides.     

Synthesis and precocious-metamorphosis-inducing activity of 3-pyridyl ethers

A new series of 5-(substituted phenoxy)pentyl 3-pyridyl ethers induced precocious metamorphosis in larvae of the silkworm, Bombyx mori. Both 2- and 4-pyridyl ethers were inactive, indicating that the 3-pyridine moiety was essential for the activity. Octyl, dodecyl and farnesyl 3-pyridyl ethers had no activity. Among the compounds tested so far, 5-(4-propylphenoxy)pentyl 3-pyridyl ether showed the highest activity. The activity fell off with increasing or decreasing length of the carbon chain between two oxygen atoms. Introduction of a methyl group at the 6 position of the pyridine ring completely eliminated the activity. Precocious metamorphosis induced by 3-pyridyl ethers was fully reversible by a simultaneous application of a small amount of tebufenozide, an ecdysteroid agonist, or methoprene, a JH agonist. © 1998 SCI.