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The experiment Method

The experiment started with the collection of 120 Petri dishes, 60 for each laboratory, the collection of 10 Raphanus Sativus seeds per Petri dish (1200 seeds), the collection of the bark, leaves and seeds of Juglans Nigra. Further, pipettes, parafilm and 120 filter paper discs were also gathered. 25 grams of the bark, leaves and seed extracts of Juglans Nigra were then blended in a blender containing 100 milliliters of distilled water to create 100% of the three different treatments to be used. Prior to filtration, the extracts were ground for 5 minutes, with the resulting diluents filtered through cheese cloth to remove as much residual solid as possible. The process was the same for all three extracts: the bark, the seeds as well as the leaves. From the 100% solution, further concentrates of 50%, 25%, and 12.5% solutions were created through dilution. For instance, in order to create 50%, 25 milliliters of the 100% solution was added to 25 milliliters of distilled solution. In order to create the 25% solution, 25 ml of the 50% was added to 25 ml of distilled water. Further, plain distilled water was also used to represent 0% concentration of the treatment and therefore acted as the control experiment. Each of the three treatments (bark, leaf, and seed) therefore generated 5 concentrations (100%, 50%, 25%, 12.5%, 0%), each put in 4 Petri-dishes per laboratory, translating to 8 Petri dishes per concentration of each extract. The controls (24) in the experiment were mainly used as markers, or points of comparison, as they were assumed to be free from any allelopathic chemicals, unlike the other concentrations. The control therefore, acts as a reference point against which the findings demonstrate the effects of the allelopathic chemicals in Juglans Nigra, but against which the degree of the effect based on the concentrations can be compared.

Before putting the seeds in the Petri dishes, each was turned upside down and lined with a single layer of filter paper and labeled with the name of the extract as well as the concentration to be applied. 10 Raphanus Sativus seeds were then added to each filter paper disc in a circular pattern close to the disc’s edge. 6 milliliters of each concentration was then added to each Petri dish depending on its label and the Petri dishes sealed with parafilm in order to prevent the experiment from drying. The experiment was then allowed to incubate for a period of one week and the number of seeds that had germinated in each Petri dish assessed at the end of the one week. Germination was measured in terms of the breaking of the seed coat, as well as the length of the germinated root to the nearest tenth of a centimeter. As such, the data in each of the 8 Petri dishes per concentration of each of the 3 treatments, was collected in terms of the number of seeds that germinated, as well as the mean radical length per dish. Calculations for each of the concentrates as well as for each of the individual treatments (extracts was then done and measures of central tendency as well as the analysis of variance done using excel as demonstrated by the instructor. Further, graphical methods were also used to provide a pictorial depiction of the findings, as well as to allow for a regression analysis of the findings.