Allelopathic Effects in Biology

Introduction

Considering the beneficial properties of plants, not only to us, but the environment as well, it is important to understand the nature of Allelopathy and how it affects plant ecology. According to the Topics in Biology Laboratory Manuel, allelopathy refers to “the beneficial or harmful effects of one plant on another plant, by the release of chemicals from plant parts in both natural and agricultural systems.” By secretion of biochemical materials, allelopathy involves a plant’s ability to inhibit germination or growth of the surrounding germination.

In our exercise, we tested for the presence of allelopathic chemicals in plant shoots and the effect of the allelopathic chemicals (our I. V. ) on the germination and growth (our D. V. ) on radish seeds. The question proposed became, “Does Rose seed extract affect the germination and growth of radish seeds? ” Keeping the allelopathic effects in mind, our working hypothesis became, “If radish seeds get exposed to the rose leaf extract, then their percent successful germination and the average length will be less than the percent successful germination and the average length of the radish seeds which do not get exposed to the Rose leaf extract.

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Materials: For week 1 and week 2 the following materials were used: 10 grams of fresh leaves (rose), sandwich-type plastic bag, a scale, a blender, 100 mL of distilled water, folded cheesecloth, a funnel, one stock bottle, 3 pieces of filter paper, two Petri dishes, and 40 radish seeds.

Methods

According to the Topics in Biology Laboratory Manuel, the experiment was conducted as follows:

First we needed to collect fresh leaves from one plant species, and fill up a plastic sandwich bag, which we were to bring with us to the lab.

Next in groups we were to weigh 10 grams of leaves from the one plant species and place the measured sample in a blender. Next we added the 100 mL of distilled water to the blender. Holding the lid of the blender, we blended the mixture completely. Then we placed some folded cheesecloth into a funnel and sat it into a stock bottle. Finally we poured the blended mixture through the funnel/cheesecloth to filter the solution. To test the Allelopathic effects, we then needed to place 3 pieces of filter paper in each of the bottoms of the two Petri dishes.

In one Petri dish (labeled with the leaf extract) we added 10 mL of the filtered solution, so that it soaked the filter paper layers. In the second Petri dish (labeled control), we added 10 mL of distilled water so that the water soaked the filter paper layers as well. Next in each of the Petri dished we added 20 radish seeds on top of the 3 pieces of filter paper, evenly spaced. Then we placed another piece of filter paper on top of the seeds in both dishes. Finally, we placed the lids on top of both Petri dishes to prevent excessive evaporation and stored them at room temperature, giving them a week to germinate, then be evaluated.

Results

For our results, after careful observations and measurements, the percentages of successful germination were as follows: For the Experimental group, that is the group treated with extract, had a 70% success rate in which 14 of the 20 radish seeds had sprouts. However, the Control group, which had been treated with distilled water, had an 85% of successful germination in which 17 of the 20 seeds had sprouted. When comparing the seedlings length, the experimental group recorded 3. 0 mm being the shortest, and 13. 0 mm being the longest, making 4. mm the average length of the seedlings, all which is indicated on the following two pages by bar graph representations on average seed length and percentage rates of both groups. When looking at the control group, however, the shortest length measured was 12. 0 mm and the longest was 62. 0 mm, making their average 42. 0 mm. When observing each of the radish seed’s conditions, it was obvious that the control group produced healthier, more vibrant seedlings with an extended root system and hair. However the experimental group contained more so dry, yellowish seeds with little to no root hair.

Discussion

When observing the results of the Allelopathy experiment, it is evident that the results reflect and indeed support my hypothesis which stated that, “If radish seeds get exposed to the rose leaf extract, then their percent successful germination and the average length will be less than the percent successful germination and the average length of the radish seeds which do not get exposed to the Rose leaf extract. ” So again when comparing the average length of seedlings between the control group and the experimental group, there really is no comparison; the experimental group had a mere 4. mm length verses that of the control group which had a remarkable 42. 0 mm length. Although noted both had a high percentage rate of germination, it really comes down to Allelopathy and the competitive “chemical warfare,” present in our experimental group. As for leaving room for error, a number of problems could have taken place, such as if small amounts of water needed to be added to re-saturate the filter paper, or if fungus appeared due to the high temperatures, etc. Over all I believe the experiment did a good job of explaining and demonstrating the Allelopathic effects on plant economy.