Plant bioassays

Grant WF (1994) The present status of higher plant bioassays for the detection of environmental mutagens. Mutat Res 310 175-185 Grant WF, Owens ET (2001) Chromosome aberrations in Pisum for the study of environmental mutagens. Mutat Res 488 93-118 Kalweit S, Utesch D, von der Hude W, Madle S (1999) Chemically induced micronucleus formation in V79 cells-comparison of three different test approaches. Mutat Res 439 183-190... 

Anticytokinins Elicit Responses in Several Plant Bioassays... 

The first plant bioassay [Avena sativa L (oat) coleoptile test] was employed by F.W. Went in the 1920 s to demonstrate the existence of and to quantitatively assess the first growth-modifying substance [indole-3-acetic acid (IAA)] isolated from plants.122 Plant bioassays have been extremely useful and intimately linked to the discovery and characterization of the major classes of plant hormones. In fact, many of the bioassays used now were developed for PGRs. Bioassays have been used to screen, evaluate phytotoxicity or plant growth promotion, study mode... 

Since the use of techniques to measure IAA, bioassays have been important to discover PGR activity of many other compounds. Several bioassays for the PGR gibberellic acid (GA3) have been developed. One bioassay was based on reduction of amaranthin levels in Amaranthus caudatus (tassel flower) seedlings.63 This method was sensitive to GA3 from 0.01 to 1 mg L"1. GA3 was also bioassayed, based on anthocyanin reduction in tomato (Lycopersicon esculentum L.).62 Reduction of anthocyanin in tomato seedlings was linear from 10"5 to 10 mg L 1, and thus, this latter plant bioassay method was more sensitive. A multitude of bioassays for nonvolatile and volatile plant growth regulator compounds have been developed and their uses and limitations have been discussed.129 Since many allelochemicals have been shown to have relatively weak phytotoxicity (especially compared to herbicides), some of these bioassays that have been developed for detecting and quantitatively measuring PGR activity may be useful in allelopathy. 

The herbicidal effects have been documented, and there has been some work published regarding the persistence of dichlobenil in the soil. Barnsley and Rosher (1) measured the persistence of dichlobenil under both tropical and temperate conditions, using plant bioassay to measure residues. They found that dichlobenil disappeared rapidly, within a few days, when it was applied to the soil surface but was not worked in. However, when the chemical was incorporated in the soil, it persisted... 

Many other phytotoxins not presented here have been structurally characterized and tested In some plant bioassay systems. Numerous other reported phytotoxin studies are In the "active fraction" stage and structure elucidation of the active components has not been achieved. Nevertheless, from the data presented. It can generally be concluded that diverse microbes produce a broad range of chemistries with phytotoxic activities chemical and biochemical synthesis of almost all of these compounds Is unknown (but derivitizatlon studies to alter phytotoxic activity have been used In a few Instances) knowledge of the spectrum of species susceptible to these compounds Is Incomplete (many weed and crop species have not been tested some compounds are toxic to organisms other than plants) and the molecular mode of phytotoxin action Is unstudied or unknown for most. The major exception Is the vast amount of data on blalaphos, phosalacine, and phosphinothricin, which have achieved commercial status. 

The early USDA efforts to isolate hormones from corn pollen were not very fruitful. The USDA finally terminated the pollen research project in 1944 due to lack of (a) suitable plant bioassay systems to detect the hormones present in pollen and (b) proper analytical methods to isolate and identify the pollen hormones. 

Field studies with single applications of phenoxyalkanoic acid herbicides have indicated that breakdown is rapid under temperature and moisture conditions that favour microbiological activity (5). Enhanced degradation of these herbicides, under field conditions, was first noted in the late 1940s. The use of plant bioassay procedures, led to the discovery that the persistence of 2,4-D, but not 2,4,5-T, was decreased,by pretreatment of the soil with 2,4-D (26, 27). This enhanced breakdown was later confirmed using (14C)2,4-D and radiochemical analytical techniques (29). The breakdown of the (14C)2,4-D being more rapid in soil from the treated plots, tested 8 months after the last field application, than in soil from plots treated for the first time. 

Grant WF, The present status of higher plant bioassays for the detection of environmental mutagens, Mut. Res., 310, 175, 1994. 

Detection of genotoxic effects of heavy metal contaminated soils with plant bioassays. Mutat Res 420 37-48. 

Gehringer M M, Vijayne K, Nadya C (2003). The use of Lepidium sativum in a plant bioassay system for the detection of microcystin-LR. Toxicon. 41 871-876. 

Other studies (64) done in the greenhouse showed that paraquat applied to a loamy sand at rates of 50, 100, and 200 Ib/acre was readily absorbed in toxic amounts by blueberry plants. Bioassays with cucumber seedlings showed that the herbicide persisted in the soil long after the blueberry plants had been removed. 

Herbicide resistance is at present one of the most commonly used traits in commercial cultivars of GM crop plants [1], Since this resistance operates via the production of an enzyme to break down the herbicide and bees lack such substrates, they are extremely unlikely to be harmed by these plants. Bioassays with the purified products of such genes have not been carried out, but some experiments with GM plants have (see Chapter 15). 

Field Plant Bioassay Plant Weeks Growth in 72 h... 

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