Comparing Plant Growth For Two Pre-germination Methods

Throughout the past semester, I have been interning in Dr. Stuarts lab, working with Echinacea angustifolia. I performed two experiments during my time there. One comparing the differences in growth for two pre-germination methods. For this experiment, I measured the hight of the plant on three separate dates in order to determine the plant success for five cohorts.

No analysis was performed on Cohorts 4 and 5 because there was no growth for any of these plants. All plants with a height of 0 at the last day of measurement were considered dead.

We performed an ANOVA using R to compare the mean heights of Cohorts 1 and 2 at each age at which they were measured. After performing analysis for Cohorts 1 and 2, we found that there was no significant difference in the heights of the plants germinated using the Blotter method than those plants germinated using the Agar method. These results were similar for each of the three ages at which the plants were measured: 14, 28, and 35.

In addition to the three measurements performed on each of the plants, I also chose a single day in which to measure all of the plants. On March 19, I measured each of the 418 plants. We performed an ANOVA analysis on the mean heights of living plants on this single day in order to see if there was a cohort effect on the measurements. We found that there was no difference in measurements of the plants among treatments, but that height does differ among cohorts 1 and 2, according to a linear model, which we had expected.

There is much more analysis which can be done with the data collected and which we hope to do in the future, including comparisons for rate of emergence, timing of emergence, and survival of individual plants.

This image shows a dish of achenes pre-germinated using the blotter method.

This image shows a dish of achenes pre-germinated using the agar method.

I will also be working on the analysis of my second experiment throughout the summer, involving the comparisons of plant growth and plant morphology for four crosses between Echinacea angustifolia and Echinacea pallida. So keep an eye out for updates!


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