Bio173 Plant data worksheet

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Feb 20, 2024

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Bio173 Plant data worksheet- 10 points, due at the start of next week’s lab 1) Start by opening the file “Plant Data W23.xlsx” on Canvas. The file should open to the “all sect” tab. This is a cut-and-paste from individual section data, captured in other tabs. Data here are corrected for species reversals (e.g., recording tomato data in the alfalfa column). N/A has been replaced with 0 or a blank cell; clearly erroneous values have been deleted. On the right, upper side of the sheet, you can see the average aggregate weights for each plant in each pot. These are what you will use to make your DeWit graphs. Also shown here is the mean weight per plant. It is calculated by dividing the average aggregate weight by the average number of plants. Only data for the monocultures (e.g., 40 Oats) and 20/20 mixed cultures is shown. 2) Go to the tab for the combination you are assigned by your GSI. This is a subset of the average data already calculated, but it will simplify your subsequent analysis. Make four DeWit series graphs for the two species and two conditions (yellow = full sun and gray = partial shade). In Excel this is as simple as i) highlighting the relevant cells (i.e., “Pot” and “weight of plant (g)” and then choosing Insert > Chart > Line. Once you have the charts, rename the title to reflect the two species present (even if the data are for just one of the species) and the light regime. It will help if you make the lines consistent with the color scheme used in the file (double-click on the line, and then the paint bucket and choose a color). You can reverse the values on the x-axis (double click on the x-axis, choose “axis options”, choose the columns tab, and then click the box for “categories in reverse order”). Lastly, you can set the maximum value for weight on the y-axis to be the same for each graph with the same species of plant (double click on the y-axis, choose “axis options”, choose the columns tab, and then enter a maximum value for “Bounds”). I suggest 30 g for oats, 50 g for tomato, and 3 g for alfalfa. This will make it easier to see the difference between full sun and partial shade.

3) Start by looking at the numbers for full sun vs. partially shaded. Under which condition did plants grow better? Plants need light, but the high sun can also place plants under water or other nutrient stress. How would you explain the result for each of your two species? Note these results were sometimes, but not always, statistically significant (T-tests not shown in your data file). - In full sun the tomato plant grew better compared to when the species had access to shaded light. This conclusion can be made based on the fact that the graph of tomato plants with the full sun was overall higher in comparison to the partial shade graph. - The graph also demonstrates that oats do better with access to full sun, as the overall weight for the oat plant was higher in the presence of the sun compared to partial access to the sun. - Both of the plants growing better with the full sun can be explained by the species' biological tendency to capture the maximum amount of sunlight to help them grow tall.

4) Look at the shape of your DeWit curves. From this, determine whether intra- or interspecific competition is stronger for each of your two species. Do you get the same result in full sun vs. partial shade? More light could change how well each species grows and thus, the competition results. Record and explain below. - The DeWit replacement series consists of planting numerous pots containing two species each in different proportions that all add up to the same density. When making conclusions about the species' interactions with one another data regarding when the plants are in equal proportions must be considered- 20 oat seeds and 20 tomato seeds. - The pot containing the 1:1 proportion that had access to the full sun yielded different growth between species. While the tomato seeds only grew about 13 plants, the oat seeds exceeded the tomato growth by 2 additional plants. While there isn't a significant difference in plant growth it seems as though interspecific competition affected tomato plants more than oats. When the species were in this proportion it was also found that access to the full sun was more beneficial for the oats whereas partial access to partial shade better benefited the tomato plants. - The tomato monoculture demonstrated intraspecific competition. Additionally, access to partial sun seemed to benefit the tomato plant growth more compared to access to full sun. This conclusion can be made based on the fact that 32 plants grew in shade and only 30 in full sun. It would be expected that the total weight of the shaded plants would be greater given that more plants grew, however this was not the case. The shaded tomato plants' total weight measured a weight of 40g whereas the plants with access to full sun measured 46g. This could show that while the number of tomato seeds for both lighting conditions are around the same number, access to the full sun could decrease the effects of intraspecific competition as the weight of all the seeds in full sun was 6g above the weight of all the seeds in partial light. - In addition to the tomato plant monoculture, the oat monoculture also demonstrated intraspecific competition. When the plants had access to the full sun a total of 30 oat seeds grew whereas when in the shaded light 31 plants grew. The total weight of the oat plants with access to the full sun measured 30g however, the plants in shaded light measured a mass of 25g. This could show that while the number of oat seeds is relatively close to one another, the shaded lighting also could decrease the effects of

intraspecific competition amongst oat plants. 5) Now look at the per-plant weights. Which species did better in a monoculture, and which did better in a mixed culture? This is an indicator of which species is the superior competitor. Is this consistent with the DeWit results? Record and explain below. This is the heart of your lab report. - Using the total weights measured we were able to identify the weight per individual plant. The yielded mass per oat plant with access to full light was 1.12g in the pot containing 20 oat seeds whereas the monoculture oat plants' individual mass was 1.01g. When the growing species were placed in the shade however each oat plant was found to have a weight of 0.85g when 20 oat seeds were present, however, the monoculture plants had an individual mass of 0.80g. - For both lighting types of oats that were mixed in a 1:1 ratio with both species present it was found that oats in this ratio had a greater individual mass compared to the oats in the monoculture. This shows that oats grew better when in a smaller population of its own species. - In regards to the tomato plants with access to the full sun, the weight per individual in the monoculture pot was 1.52g whereas when only 20 tomato seeds were planted the mass was 1.19g. The monoculture placed in the shade however grew plants each with an individual weight of 1.26g. The shaded pot containing only 20 tomato seeds had an individual weight of 0.74g. For both lighting types tomatoes had a higher mass per individual plant when they were in a monoculture. This shows that tomato plants are the inferior species in an interspecific interaction with oat plants. This makes sense as oats serve as the superior competitor in the species x species interaction, which explains why oats do worse in a monoculture- where intraspecific competition is at play. This is consistent with the DeWit results because, in the oat graphs, we can see that when there is a 1:1 ratio of each species in one pot (20 oat seeds and 20 tomato seeds) the average seed number is somewhat higher or equal for both lighting conditions than compared to tomato. Tomato and Oat Plant Interaction: Effect of Competition on Plant Growth

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