Phytotoxines

At high enough concentrations, PAN is a potent eye irritant and phytotoxin. On a smoggy day in the Los Angeles area, PAN concentrations are typically 5 to 10 ppb in the rest of the United States PAN concentrations are generally a fraction of a ppb. An important formation route for formaldehyde [50-00-0] HCHO, is reaction 9. However, o2onolysis of olefinic compounds and some other reactions of VOCs can produce HCHO and other aldehydes. 

C. W. Hesseltiue, Sixth International Symposium Mycotoxins and Phytotoxins, Pretoria, South Africa, 1985, pp. 1—18. 

Ricin [9009-86-3], a phytotoxin found in the seeds of the castor oil plant Acinus communis, conjugated to murine monoclonal antibody (Immunogen Corp.), has been approved by the U.S. Food and Dmg Administration (FDA) for the treatment of patients with B-ceU leukemia and lymphoma (59). 

A new method of stabilizing metalated epoxides through remote coordination has recently been introduced, allowing stereoselective access to a range of epoxylactones. Epoxylactone 216 was converted into the phytotoxin xylobovide (Scheme 5.50) [75]... 

The early literature on naturally occurring plant growth inhibitors and the influence one plant might exert on another by chemical means (allelopathy) is considered comprehensively in various reviews (12, 15, 36, 37, 48, 49, 61, 67, 94, 121, 162). Reviews of studies concerned with the influence of plant exudates on root-infecting fungi (130) and the effects of phytotoxins which arise as decomposition products (113) have appeared recently. Because of the excellent coverage of the topics by others, no attempt is made here to review the early literature exhaustively. Instead, consideration is restricted essentially to specific compounds and to some of the more recent literature. 

Ichihara A., Oikawa H. Biological Diels-Alder Reaction in Biosynthesis of Phytotoxins in Dyn. Aspects Nat. Prod. Chem. 1997 119, Eds. Ogoura K. and Sangawa U., Pb. Kodansha, Tokyo... 

Keywords biological Diels-Alder reaction In biosynthesis of phytotoxins, DIels-Alderase... 

Ichihara A., Oikawa H. Biosynthesis of Phytotoxins From Alternaria Solani... 

By necessity, herbivores have evolved GIT and systemic compensatory mechanisms that allow them to subsist on plant-based diets that have limited nutrient quality and include phytochemicals. Still, herbivores remain susceptible to some of the anti-nutrient and toxic phytochemicals. For example, several herbivores are sensitive to the phytotoxins associated with autumn crocus, which include colchicine (Yamada et al, 2000). As a consequence, herbivores tend to select species and portions of plants based on a combination of nutrient quality and concentrations of phytochemicals (Yeager et al, 1997), and this has an impact on habitat selection and plant ecology (Duncan and Gordon, 1999). Carnivorous species have not been under selective pressure to develop similar compensatory mechanisms, generally have only limited abilities to subsist on plant-based diets, and in many cases are less tolerant of phytochemicals. 

Ninety weed and crop species common to the southeastern U. S. were tested for phytotoxin content to discover candidates for an allelopathy testing program. Plants were collected in the spring, summer and fall in a three county area of northeastern Mississippi. Plants were maintained in sealed plastic... 

Comparison of the results of these two bioassays reported in table II illustrates the importance of the choice of the bloassay species, as well as the variability of results to be expected when "phytotoxins" are released into the environment. Treatments applied to the radish and tomato seeds were identical, but most treatments tended to inhibit radish growth and stimulate tomato growth. 

The results of the bloassays reported here Indicate that some of the species studied may release phytotoxins into the environment. Further work is needed to identify any active compounds and determine their influence in the field. 

Rye (Secale cereale L.) and Wheat Triticum aestivum L.) Mulch The Suppression of Certain Broadleaved Weeds and the Isolation and Identification of Phytotoxins... 

Microorganisms associated with the roots of certain plants may produce or facilitate release of phytotoxins. For example, microbes in the rhizosphere of chamise (Adenostoma fasciculatum H. A.) appear to contribute to suppression of herbs near these shrubs (21), a phenomenon previously attributed to toxins washed from the chamise foliage (22, 23). Similarly, hydrogen cyanide, a potent phytotoxin,... 

Once biological activity has been established (in the laboratory or the field) and once the chemical work has been accomplished, we need to confirm allelopathic activity in the natural environment. To accomplish this end, the effects of soil and microbial flora must be considered. Thus, the disciplines of soil chemistry and microbiology are required. The chapters in this volume deal primarily with the biology and chemistry of phytotoxins isolated from plants however, we hope that these topics will stimulate soil chemists and microbiologists to contribute to solving the problems associated with the study of allelopathy. Thus, the purpose of this volume is not only to bring before the scientific community a representation of research efforts in the area of allelopathy, but also to promote the relationships... 

Caffeine is the alkaloid that made coffee fruit and seed so much desired. Caffeine is probably also part of the defense system of the coffee seed, since caffeine has been recognized as an antifungal,149 a selective phytotoxin,150 and a chemosterilant toward certain insects.151... 

Dayan, F.E., Romagni, J.G. and Duke, S.O. (2000). Investigating the mode of action of natural phytotoxins. Journal of Chemical Ecology 26 2079-2094. 

The allelopathic effects of dominant plants on other plants in phytocoenosis are caused by phenolic phytotoxins present in all parts of plants, but the highest amount of these compounds is accumulated in the leaves. Leaves of dominant trees represent the main components of the litter in the forest, thus analysis of phenolic compounds and measurements of their content in leaves and leaf litter is considered as very important. 

During decomposition of plant remains, many phenolic compounds are released by leaching, microbial degradation or are synthesized by microbial activity. In forestry, problems of natural regeneration and reforestation are connected to the presence of phenolic substances deposited in the soil. Methods for extrachon and identification of toxic substances from different soil types (mineral or organic) are described. The method for extracting of soil phytotoxins is based on the use of ethylacetate and methanol (free phenolics) and alkaline hydrolysis (bound phenolics). 

Intercropping may facilitate weed control if intercrops are more weed competitive than sole crops or are able to suppress weed growth through allelopathy (the weed species is more susceptible to such phytotoxin than crops). If intercrops do not suppress weeds more than sole crops, they should provide yield advantages due to better utilization of resources or by converting resources than in case of sole crops (Liebman and Dyck 1993). 

Liebman M, Sundberg DN (2006) Seed mass affects the susceptibility of weed and crop species to phytotoxins extracted from red clover shoots. Weed Sci 54 340-345 Lin D, Sugitomo Y, Dong Y, Terao H, Matsuo M (2006) Natural herbicidal potential of sauru-raceae (Houttuynia cordata Thunb.) dried powders on paddy weeds in transplanted rice. Crop Prot 25 1126-1129... 

S. Nara, H. Toshima, A. Ichihara, Asymmetric Total Syntheses of (+)-Coronafacic Acid and (+)-Coronatine, Phytotoxins Isolated from Pseudomonas Syringae Pathovars, Tetrahedron, 1997, 53, 9509-9524. 

We wondered about the nature of the corematal message. Was HD simply the male s way of announcing his presence to the female, or was the molecule conveying more subtle information Specifically, we asked whether the derivation of a pheromone from phytotoxin might have... 

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