Tests with contaminated leaves

It is clear that the plant leaves exposed to the oil field burns are loaded with contaminants compared to the control (unexposed plant) leaf. This was comfirmed by a simple test using a commercial microwave device (8) exposure time was 2 minutes. The dry palm - tree leaves exposed to environmental pollution by oil field burns contaminant showed severe weight loss compared to the conventional control (dry palm - tree unexposed leaves). Figure 4 shows details. More details are available elsewhere (9). 

If the chemical composition of the samples is known or at least partly known (in a stepwise TIE approach) or existing data allow for QSAR calculation, the samples can be ranked by TUs. Arts et al. (2006) studied, in 12 outdoor ditch mesocosms, the effects of sequential contamination with 5 pesticides in a regression design. They applied dosages equivalent with 0.2%, 1%, and 5% of the predicted environmental concentration (PEC) subsequently over 17 weeks. Endpoints recorded over 30 weeks included community composition of macroinvertebrates, plankton, and macrophytes, and leaf litter decomposition as functional ecosystem parameters. TUs were calculated in relation to acute toxicity data for the most sensitive standard species Daphnia magna and Lemna minor. Principal response curves (PRCs), a special form of constrained PCA, and Williams test (NOEC, class 2 LOEC) were used to identify the most sensitive taxa. Next to direct effects on certain species, also indirect effects, for example, how the change in abundance of a sensitive species affects the abundance of another, more tolerant species, can be detected only in mesocosm or in situ experiments. All observed effects were summarized in effect classes in a descriptive manner. 

In addition, unidentified wild strains of bacteria were collected from nest boxes by swabbing the nest and nest cavity with sterilized cotton swabs dipped in sterilized distilled water. Each contaminated swab was carried back to the laboratory in a sterilized tube. Sterilized nutrient medium was innoculated with the standard strains or wild strains, and then each experimental plate was incubated in the presence of a 1 cm piece of sterilized leaf material. There were three replications for each plant tested and a control (i.e., a plate innoculated with bacteria but without leaf material). Our presumption was that any bacteriocidal compounds present in the leaves would diffuse into the nutrient medium and inhibit bacterial growth. Plants were scored as strongly bacteriocidal if there was a bacteria free zone around leaf pieces greater than 1 cm. Plants were scored as moderately effective if a bacteria free zone was apparent, but less than 1 cm. Plants were scored as ineffective if no apparent inhibition of bacterial growth was observed. 

Castor is a very hardy plant and in some areas an invasive weed. It is susceptible to numerous insect and microbial pests, but castor germplasm is available for resistance to many of these pests. One key to successful breeding is the ability to screen large numbers of plants quickly. In the case of leafminer resistance, Anjani et al. (2010) found that resistance was correlated with high phenolic content as reflected by purple leaf coloration. Over 100 castor plant accessions, of 1979 tested, proved to be resistant to Fusarium (Fusarium oxysporum f. Sp. ricini) wilt based on their limited susceptibility to wilting in a contaminated field (Anjani et al., 2014). 

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