The Effect Of Temperature On Plant Growth Essay Examples

Introduction

There are a number of environmental factors that affect plant productivity and growth. One of those factors is temperature. The effect of temperature on a plant will depend on whether the plant is a warm-season plant or a cool-season plant. Adverse temperatures can cause a plant to have stunted growth and poor quality. For example, if the growing temperature is too low for a warm-season plant, it will prevent the plant from fruiting. At temperatures that are too low, the rate of photosynthesis slows down. On the other hand, if the temperature is too high, it can cause pollen to become inviable, and the plant will fail to pollinate.
In this experiment, I will look at the effect of temperature on the growth of corn. Corn is a traditional summer season crop, which means that it thrives under warm conditions. Using a 100W UV light bulb as a heat source, I will be measuring the growth of four corn plants placed at varying distances away from the bulb.

Question

How does temperature affect the growth of corn?
Hypothesis
I predict that the corn plants closest to and furthest from the heat source will have stunted growth compared to the plants placed between the two. My reasoning is that the plant nearest the heat source will be too warm, while the plant furthest from the heat source will be too cold, which will result in poor growth in both plants. However, the middle two plants will be at an optimum growing distance from the heat source, and these plants will be taller than the closest and furthest plants.

Variables

Independent variable: the distance of each plant from the heat source (measured in centimeters)
Dependent variable: the height of each corn crop (measured in centimeters)
Control variable: A single corn plant will be grown at room temperature.
Principle of Method
Materials
1. UV light
2. UV light stand
3. Base (40cm x 1m)
4. Meter stick
5. Plastic plant pot (x5)
6. High grade, store-bought soil
7. Pencil
8. Paper
9. Heat gloves
10. Digital thermometer
11. Ruler

Diagram

(Please see the attached illustration.)

Safety

Because the surface of the bulb can exceed temperatures of 100 °F, heat gloves were worn whenever the bulb had to be touched.

Procedure

The bottom of each plant pot was covered with an even two-inch layer of soil. Three corn seeds were placed on top of the layer of soil, and then another half-inch of soil was added to the pot.
The UV light was attached to the light stand and connected to the base. The height of the UV light was 7 inches from the base.

The light was turned on for 10 hours a day, between 7:45 am and 5:45 pm.

Distances of 15 cm, 25 cm, 35 cm, and 45 cm were measured and marked, and pots were placed at each distance.
The fifth pot was placed behind the heat source, at room temperature.
The plants were grown over a period of two weeks. Each pot was given 20 ml of water at 5 pm every day.
Every two days, at the same time the plants were watered, the temperature of the soil was measured with a mercury thermometer.
After the temperature of the soil was taken for each of the five pots, the temperatures were measured again two more times. The temperatures of the pots were measured in the same order for each of the three readings. (As in; first pot 1, then pots 2, 3, 4, and 5; then pot 1 again, then 2, 3, 4, and 5; and so on.)
Every two days, the height of the seedlings was measured with a ruler, and the height of the tallest seedling was recorded.

Tables

Pot 1: 15 cm from light source
Pot 2: 25 cm from light source
Pot 3: 35 cm from light source
Pot 4: 45 cm from light source
Pot 5: behind light source (control)
Heights of Tallest Seedlings
Observations
There were several things that I noticed throughout this experiment. For instance, I noticed that the soil in pots 1 and 2 was always very dry just prior to watering. Pot 1 didn't see any growth at all. Pot 3 was also consistently dry, but less dry than pots 1 and 2. Pots 4 and 5 (the control pot) didn't seem to have as much difficulty retaining moisture.

Graph

Figure 1: Heights of tallest corn seedlings measured in two-day intervals over two weeks.

Calculations

For this experiment, we use Spearman's Rank Correlation Coefficient to determine the degree of correlation between temperature and plant height.

Spearman's Rank Correlation Coefficient formula is:

Where n is the number of data pairs (5). Using the D2 values calculated above, we arrive at a correlation coefficient value of 1-(6*38/5*24) = -0.9. This result indicates a very strong negative correlation between temperature and measured height.

Discussion

My hypothesis turned out to be only partially correct. As I predicted, the plant closest to the heat source did undergo stunted growth – in fact, it didn't grow at all! The second closest plant grew but only to a final height of 1.2 centimeters, and its growth stalled after the tenth day. This indicates that pots 1 and 2 were too close to the heat source for the corn seedlings to thrive.
The plant that experienced the greatest and most rapid growth was the one in pot 4, at a distance of 45 cm from the heat source. The average temperature of the soil in pot 4 over the two weeks was 75.2 degrees. The plant in pot 5, the control pot at room temperature, experienced a rate of growth similar to the rate of the plant in pot 4. This indicates to me that the ideal temperature for corn to grow in is around or somewhat slightly above room temperature.

Evaluation

I feel that my methods for measuring and recording data values were not particularly prone to error. However, I believe that the accuracy of this experiment could be improved if I had used more than five pots. For example, if I had used ten pots instead of five, I would have a larger spread of data points, and this would allow me to calculate a more precise value of the Spearman's correlation coefficient.
A potential source of error for this experiment was in the measuring of the heights of the seedlings. The markings on the ruler that I used to measure the height were only 0.25 cm apart. Sometimes, it was difficult to hold the ruler steady to get an accurate measurement. If I were to repeat this experiment, I might use a caliper instead of a ruler.

Conclusion

The evidence from the data suggests that temperatures higher than 78 or 79 degrees Fahrenheit will have a detrimental effect on the growth of corn plants. The Spearman Rank Correlation Coefficient that was calculated for this experiment was -0.9. This suggests a highly negative correlation between temperature and plant growth. In other words, the higher the temperature, the lesser the growth of the plant. However, more data is needed to verify the accuracy of this correlation value. Future experiments should use a larger range of data points, with plants closer to and further away from the heat source, to determine a more accurate value of the correlation coefficient.

References

1. Weisstein, Eric W. "Spearman Rank Correlation Coefficient." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/SpearmanRankCorrelationCoefficient.html
2. Went, F. W. “The effect of temperature on plant growth.” Annual Review of Plant Physiology 4.1 (1953): 347-362.