The Effect of Stomata Opening on Plant Transpiration
The purpose of this study is to find the effect of covered stomata on plant transpiration. The experiment was designed to examine the changes in texture of four Devil’s Ivy leaves (Epipremnum aureus) affected by covered stomata and rate of transpiration. One leaf was completely coated with Vaseline gel. The second leaf was coated only on the front surface, while the third leaf was coated on the back surface with gel. The fourth leaf was left uncoated as a control variable. The four leaves were hung on a rope (50cm. long), 10cm. apart from each other.
The leaves were exposed to the same amount of sunlight, temperature (32 degrees Celsius), and humidity (about 70 percent). The changes in the texture of the four leaves were observed over a one-week interval. The results showed slight loss of turgidity for the completely coated leaf, moderate flexibility and folding edges in partially covered leaves (front-surface and back-surface coated leaves), and tremendous flexibility, softness, and complete inward folding of the edges of the uncoated leaf. According to the results, it is concluded that the uncoated leaf with uncovered stomata had the higher rate of transpiration than the other completely and partially coated leaves.
Transpiration is the loss of water through stomata openings on the surfaces of plant leaves. It is crucial for the survival of plants since it aids in water transport through roots, stems, and leaves, creating a suction force. The stomata, minute pores controlled by guard cells, are also essential for gas exchange. Carbon dioxide enters these pores, and oxygen exits as a product of photosynthesis. Stomata generally open at daytime and close at nighttime. Many environmental factors also affect stomata openings for transpiration.
These factors include low humidity, wind, high temperature, and light, which increase the rate of transpiration. During dry conditions, cold weather, and high humidity, the plant decreases the rate of transpiration in order to preserve its water supply and keep its turgidity. Many plants have adapted to their environments by controlling the amount of water loss. Desert plants, such as cactus plants, have a waxy coating on the epidermal surface of their leaves to decrease water loss. Cactus plants open their stomata pores during the night where the air is cool and close their pores during the hot day. Without these adaptations, the plants will wilt and shrivel, losing an ample supply of water.
How do the covered stomata affect the rate of transpiration? The hypothesis of this experiment is if the stomata are uncoated and open, then the rate of transpiration will be higher than the coated stomata. The experiment was designed to observe the changes occurring in leaf texture affected by covered stomata and the rate of transpiration. Four healthy Devil’s Ivy leaves (Epipremnum aureus) were cut and hung on a rope with the two ends tied around two poles. The first leaf was coated with Vaseline gel on the front and back surfaces. The second leaf was coated with the gel at the front surface only, while the third leaf was coated with the gel at the back only. The fourth leaf was left uncoated as a control variable.
The leaves were exposed to the same intensity of sunlight, temperature (32 degrees Celsius), and humidity of about 70 percent. These leaves were observed and checked for changes in texture and turgidity over a one-week period. The dependant variable was the stomata openings (fully blocked by gel, partially blocked by gel, and completely opened). The independent variables were the sunlight, temperature (32 degrees Celsius), and humidity (about 70 percent). The prediction of this study is that the uncoated leaf with open stomata will have greater changes in texture than the completely and partially coated leaves due to the high rate of transpiration.
1. Four healthy Devil’s Ivy leaves (Epipremnum aureus)
2. Vaseline gel (94 grams)
3. One rope (50 cm. long)
4. Four paper clips
5. Two wooden stand poles (70 cm. long)
6. One cotton swab (used for coating the leaves with Vaseline gel)
8. Safety gloves
9. Safety goggles
1. Using your hands, cut four healthy Devil’s Ivy leaves (Epipremnum aureus) from the stem.
2. Tie the two ends of the rope (50cm. long) to the two wooden stand poles (each 70 cm. long).
3. Use the cotton swab to coat the first leaf with Vaseline gel at the front and back surfaces.
4. Coat the second leaf with Vaseline gel on the front surface only.
5. Coat the third leaf with Vaseline gel on the back surface only.
6. Leave the fourth leaf without coating.
7. Hang the four leaves on the rope, 10 cm. apart from each other.
8. Keep the leaves at a constant temperature (32 degrees Celsius), humidity (about 70 percent), and sunlight.
9. Observe any changes on the texture of the leaves over a one-week period.
10. To avoid any biological hazards, dispose the leaves in a garbage bin, and place the rope, clips, and wooden poles in the proper container after completing the experiment.
Note: Wear safety gloves in order to avoid any contact with sap from the leaves which may cause allergies. Wear safety goggles to avoid contact of the eyes with the Vaseline gel, which may cause eye irritation.
According to the observations collected, the uncoated leaf showed the greatest change in texture among the other three leaves. On the first day, the completely coated, front-surface coated, back-surface coated, and uncoated leaves were firm and turgid, showing no change in their texture. During the third day of observation, the coated, front-surface covered, and back-surface covered leaves remained with no change. The uncoated leaf started to become flexible and supple in texture.
On the fifth day, the completely coated leaf remained unchanged, the front-surface and back-surface coated leaves started to become flexible and pliable, and the uncoated leaf edges started to fold inward. On the final seventh day, the completely coated leaf was mildly soft and flexible, losing some of its turgidity. The front-surface coated leaf edges started to fold downward, while the back-surface coated leaf edges started to fold upward. The uncoated leaf was markedly flexible, pliant, and bendable with the edges completely folded inward. These observations taken over a span of one week are recorded in the table on the next page.
How do the covered stomata affect the rate of transpiration? The hypothesis of this experiment is if the stomata are uncoated and opened, then the rate of transpiration will be higher than the coated stomata. The prediction of this study is that the uncoated leaf with open stomata will have greater changes in texture than the completely and partially coated leaves, due to the high rate of transpiration. From the observations collected, it is deduced that the leaf with the most changes in texture had the higher rate of transpiration due to the open stomata.
The completely coated leaf with Vaseline gel showed little changes in texture over the week such as mild flexibility and softness. The front-surface and back-surface coated leaves had moderate changes such as the pliable and supple texture of the leaves and the partial folding of the edges. The uncoated leaf; however, exhibited the most conspicuous changes such as the tremendously pliable and bendable leaves and the complete folding of the edges inward.
This concludes that the uncoated leaf with the open stomata will have a higher rate of transpiration than the completely and partially covered leaves; thus enforcing the hypothesis and confirming the prediction. The completely covered leaf with Vaseline gel had blocked the stomata pores and prevented water from escaping; thus, preserving most of its water supply and lowering the transpiration rate. The partially covered leaves (front-surface and back-surface covered leaves) allowed a considerable amount of water to escape because of the uncovered stomata on either side.
The uncoated leaf lost a great supply of water because all the stomata were uncovered and exposed. The Vaseline gel represents the waxy coating secreted by plants as one of many adaptations to a certain environment. This adaptation is crucial in hot desert climates, where preservation of water is imperative to insure the survival of the plant. From the data, it is inferred that the signs of water loss include soft, flexible, pliable, and supple leaf texture with folding edges. The weakness of this experiment includes many aspects.
When applied, the Vaseline gel may not have coated the entire surface; thus, leaving a few stomata pores exposed to the surrounding atmosphere. The experiment was performed only once; thus, making the results less reliable. Finally, the time span was not enough to measure the other changes resulting from greater water loss. This experiment may be improved in many vital ways. First, the experiment should be performed at least three more times to guarantee the reliability of the results. Second, the Vaseline gel should be smoothed out thoroughly to cover the entire surface as well as to provide an equal layer of coating.
The experiment should be extended to another week to measure the additional changes that may have been caused as a result of water loss such as the shriveling and dryness of leaves. An entire plant should be tested by the methods of this experiment to note any disparities in observation, and this experiment should be conducted on different plant leaves. Finally, other experiments should be conducted such as counting the number of stomata in plants, measuring the rate of transpiration by using a potometer, and describing the effects of other factors (wind, heat, humidity, and light) on transpiration rates.
These experiments will further increase the understanding of factors affecting transpiration. A botanist should be consulted for advanced knowledge of stomata effect on plant transpiration. The results of this study could be applied in many ways to agricultural improvement. Farmers should use the conclusions gained from this experiment to aid in growing plants efficiently. By understanding the factors affecting the rate of transpiration, farmers can place their plants in greenhouses to avoid exposure to these factors; thus, caring for plants proficiently.
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