How I came up with the idea of this investigation: There was a day when there was a mosquito flying near the plants in my house and I tried to catch it, so I found the nearest large plastic lid and placed it on top of the bamboo plant with the mosquito on its leaves. I accidentally left the lid on the plant overnight and the next morning, I finally remembered and when I lifted the lid, I saw drops of water on the bamboo leaves. Therefore, I recalled this incident when I was assigned the topic of observing plant growth and decided to research on the subject.
In this self-directed study, I hope to be able to observe how higher and lower levels of humidity and transpiration can cause the green bean sprouts to exhibit the process of guttation, which is when the appearance of drops of water are exuded from the hydathodes at its tips. When a plant experiences a high soil moisture level, water will enter the roots of the plant because the water potential of the roots is lower than that in the soil. Next, the water begins to build up in the plant, resulting in a slight root pressure. Following that, the root pressure forces some water to exude through the tip of the leaf called hydathodes, which are often found at the end of vascular bundles.
Guttation occurs when the atmospheric conditions cause a decline in transpiration and an augment in humidity; therefore, I hope to investigate whether the green bean sprouts placed inside enclosed containers will perform the process of guttation as the interior of the containers should contain a higher humidity and lower rate of transpiration.
The purpose of this experiment is to examine how changes in the level of humidity and transpiration can cause the green bean sprouts to demonstrate the process of guttation where water is exuded from the hydathodes at its tips. The differences in temperature in the exposed and enclosed containers may cause more or less water to be exuded through guttation. Guttation occurs when the atmospheric conditions cause a reduction in transpiration and an increase in humidity.
If plants usually perform the process of guttation under conditions of high humidity and low transpiration, then the leaves of the green bean sprouts grown inside the enclosed containers should exude more water than the ones grown in the exposed containers because there is greater humidity and less transpiration inside the enclosed container, causing the leaves of the green bean sprouts to experience a high soil moisture level where water would accumulate and create a slight root pressure so that water will exude from the hydathodes (a type of tissue in the leaves).
I predict that the green bean sprouts grown in the enclosed containers will experience higher humidity and a lower transpiration rate; therefore, they will perform the process of guttation by exuding beads of water through its hydathodes. On the other hand, I predict that the green bean sprouts grown in the exposed containers will not go through the process of guttation as they will experience lower humidity and a higher transpiration rate.
o The number of beads exuded from the leaves of the green bean sprouts
o Level of humidity\transpiration
* Variables to be controlled:
o Soil – should be the same type (brand) and quantity (grams)
o Water – should be the same amount (in mL) and temperature (ï¿½C)
o Light – should be the same amount and intensity
o Time – all plants should be watered and observed at the same time and for the same duration (minutes); measurements of growth for each plant should be made at the same time
o Size of container for each plant should be the same
o Type of plant in each pot should be the same
MATERIALS AND METHODS:
* 6 green bean sprout seeds of the same variety
* 6 containers of the same type and size
* Soil from backyard (50g for each container)
* Water (10mL for each plant each day)
* Hygrometer (to measure humidity)
* Balance (to weigh soil)
* Ruler (to measure height of plants)
* Dessertspoon that holds 10mL
* Plastic wrap
* Natural light
* 3 larger plastic containers
* 3 plastic covers
* Teaspoon that holds 5mL
1. I obtained over 50 potential green bean sprout seeds for growth, but only chose the best six. (best = appears healthiest)
2. I dug up soil from the same area of my backyard. Then, I equally divided the soil into six portions (50g for each container).
3. I obtained six containers, each with a diameter of 10cm and height of 15cm. Next, I placed the divided portions of soil into each of the containers.
4. I labeled the containers with a permanent marker. Container labels were: A, B, C, D, E, F. Containers A, B, C were placed in the containers enclosed with plastic wrap (high humidity) and D, E, F being the ones exposed (low humidity).
5. I watered the plants (10mL for each plant) during each observation. I decreased the amount of the water (from 10mL to 5mL) for the plants in the wrapped containers after two days because the soil continued to be very moist.
6. I observed the growth of the six plants each day at 6pm. (June 1st to June 11th) Data was collected from measuring plant growth with a ruler and counting the beads of water exuded. Any necessary photographs were taken.
7. Note – This was not part of the original procedure but it was necessary in order to continue the experiment: After Day 5, the plants in containers A, B, C were already coming into contact with the plastic wrap; therefore, I had to remove the plastic wrap from containers A, B, and C in order to allow space for them to grow. I substituted the plastic wrap with a plastic container (please refer to figure 1.)
The control of variables:
Controlling the following variables is necessary to acquire the most accurate results (these are listed in no particular order as each one is important):
* same type (found in the same location)
* same quantity (50g for each container)
Reason: Differences in the soil may alter plant growth; the amount of soil may speed up or slow down the rate of growth as well
* same amount (10mL for each plant)
* same source (taken from the same location – kitchen tap)
* same temperature (5C)
Reason: As a result of receiving more or less water, plants may grow rapidly or slowly. To ensure that plants receive the same treatment, the same amount, source, and temperature of water should be noted
* same amount
* same intensity
There is the assumption that the amount of intensity of light is kept constant because the plants are placed within the same area the light should therefore be distributed evenly to each plant.
Reason: The even distribution of light is important as light is a major factor of plant growth and should therefore be controlled.
* observed at the same time and for the same duration
* watered at relatively the same time
Reason: Watering the plants at different times of the day may cause plants to grow at different rates because some plants may absorb more or less water throughout different time periods of the day. Observing the plants at the same time is a fair way to obtain data because plant conditions may change as often as every minute.
* Same type
* Same size
Reason: Containers made of different materials may alter plant growth because a plant’s surrounding environment (in this case, the container in which it grows in) is extremely important to its growth – the environment should be controlled. In addition, different sizes of containers may allow for more or less light to make contact with the plant and thus result in unwanted inaccuracies.
o Type of plant
* Same type or variety
* Very similar in size
Reason: As we know, different plants grow very differently. Some may sprout on the day it is planted while others may take several days to germinate.
* Each variable above has the ability to alter the development and growth of a plant; therefore, in order to ensure a fair test of the process of guttation in the plants, each plant must receive the same treatment.
Methods of collecting sufficient relevant data:
* The experiment is ongoing for 11 days, which should allow for the collection of enough relevant data
a. Multiple trials should be able to verify that results are consistent and precise
b. Repeating the experiment several times should ensure that the outcome is not a coincidence or accident
* By using six plants (three for each category), there is a higher probability that the results will be reliable
a. Observing more than one plant will allow for dependability of data
b. Using more than one plant is a good idea as there is always the possibility that some plants may die midway through the experiment