The purpose of this experiment is to determine how plant hormones affect the growth and development of Bibb Lettuce in a microgravity environment.
This project is significant because it tests how microgravity affects plants. In addition, based on last year's results, there was an upset in the plant's growth hormones, so this project will also focus on regulating the plant's hormones for optimal growth.
H0: Exposure to various levels of hormones in the plants will have no significant bearing on growth compared to the control.
H1: The plants exposed to an elevated level of auxins will have elongated stem growth compared to the control.
H2: The plants exposed to an elevated level of cytokinins will have more leaves compared to the control.
H3: The plants exposed to an elevated level of both auxins and cytokinins will have elongated stem growth and more leaves compared to the control.
H0: Exposure to both microgravity and variations in plant hormones will have no significant bearing on growth compared to the control.
H1: The plants exposed to both microgravity and an elevated level of auxins will have elongated stem growth compared to the control.
H2: The plants exposed to both microgravity and an elevated level of cytokinins will have more leaves compared to the control.
H3: The plants exposed to both microgravity and an elevated level of auxins and cytokinins will have elongated stem growth and more leaves compared to the control.
Photosynthesis
Photosynthesis is the process of using light energy to convert carbon dioxide and water into glucose and oxygen. The formula for photosynthesis is 6CO2 + 12H2O + Light Energy C6H12O6 + 6O2 + 6H2O, which means that six carbon dioxide molecules plus twelve water molecules combined with light energy produce a molecule of sugar, six molecules of oxygen, and six molecules of water. Photosynthesis occurs in the chloroplasts of the plant cell. During the process of photosynthesis, the plant releases oxygen, a vital element in life processes. As long as a plant receives its required amount of light, it should produce plenty of oxygen.
Microgravity
Microgravity is not the absence of gravity; it is simply any environment with gravity less than that of Earth’s. However, microgravity doesn’t just exist outside of Earth. On Earth, it is possible to create brief instances of microgravity. When roller coasters move in a steady up and down movement (parabolas), they give you a few seconds of microgravity. This is the same concept used to create the “Vomit Comet.”
Plants in Microgravity
One of the main affects of microgravity is the orientation of the roots and shoots of the plants. Microgravity confused the plant by not allowing it to detect where gravity is coming from. Very little is actually known about the extent of microgravity’s effects due to our current inability to create long-term microgravity conditions on Earth.
Microgravity Simulation and the Clinostat
A common instrument used to simulate microgravity is the clinostat. The clinostat is essentially a rotating wheel that contains compartments for plants. By rotating, it disrupts the plant’s sense of gravity (gravitropism), a effect similar to that of an actual microgravity environment.
Terraformation
Terraformation on Mars is something that may have a chance of becoming a reality. The current annual temperatures of Mars is -55oC, much too cold for human habitation. At one NASA conference, several ideas were thrown around. One possible solution came from Margarita Marinova, an MIT undergraduate at the time. Marinova suggested using perfluorocarbons (PFCs) to help initiate the planet’s warming process. Marinova has studied the effects of PFCs in partnership with Chris McKay of NASA’s Astrobiology Institute. There are several advantages to using PFCs. They are considered super greenhouse gases, so a small amount would warm the planet significantly. PFCs also have a long lifespan and they don’t have any negative effects on living organisms. In addition, PFCs don’t destroy ozone.
Plant Hormones
Two common plant hormones are auxins and cytokinins. Both are vital to a plant’s growth and development. Auxin’s primary functions are to stimulate cell elongation, cell division, differentiation, and root initiation; mediate phototropism and gravitropism; and delay leaf senescence. A common natural auxin is indole-3-acetic acid (IAA). Cytokinins, such as kinetin, affect root growth and differentiation; stimulate cell division and growth, germination, leaf expansion, shoot initiation, and bud formation; delay senescence; and release of apical dominance.
Lighting and Plants
Plants require light in order to grow. They use light energy to convert carbon dioxide and water into glucose and oxygen (6CO2 + 12H2O + Light Energy C6H12O6 + 6O2 + 6H2O). White light contains all wavelengths of light. Plants use very little of the yellow and green wavelengths of light, reflecting them instead, which is why they appear green. They mostly use red and blue wavelengths, requiring more red than blue. Incandescent bulbs are discouraged because while they release a lot of red light, they are a poor source of blue light (Trinklein). “Cool-white fluorescent tubes produce a small amount of red rays in addition to orange, yellow-green, and blue rays. However, the red light produced usually is not enough for plants unless windows or other artificial lights produced additional red rays…. Special fluorescent tubes have also been developed for growing plants. These have a higher output in the red range to balance out the blue output (Trinklein).” The plants should receive 16-18 hours of light if that is the only light they are receiving. If they are receiving light from another source, 12-14 hours is sufficient. If plants do not receive adequate lighting, they may have longer stems and lengths between leaves. The leaves may be smaller than those that receive adequate lighting. The coloring may be a pale green and some leaves, typically lower ones, may yellow and drop (Trinklein).
Bibb Lettuce
Bibb Lettuce is a loose headed type lettuce. It is leafy with a “buttery appearance.” When healthy, it has bright green leaves. Bibb Lettuce will become bitter if temperatures rise above 95oF.
Hydroponics
Hydroponics is the study of growing plants in materials other than soil. There are a plethora of different medias available besides soil, including, but not limited to, expanded clay, rockwool, perlite, vermiculite, sand, and gravel. There are several techniques useful for a hydroponics environment such as continuous flow, flood and drain (ebb and flow), and top irrigation.
Medias
Choosing the hydroponics medium is important as all plants need some kind of support. Here are some descriptions of the aforementioned medias:
Expanded Clay
Expanded clay is clay baked into different shapes, usually balls or pebbles. They can be reused for multiple plants.
Rockwool
Rockwool is basalt rock, heated at high temperatures and spun into different shapes, usually cubes. It is important to avoid inhalation as it may cause irritation.
Perlite
Perlite is volcanic rock heated into lightweight glass pebbles.
Vermiculite
Similar to perlite, it has been heated until expanded into pebbles. It also holds more water than perlite.
Sand
Sand is often highly discouraged as a medium as it doesn’t drain well, can clog up roots, and has to be sterilized between uses.
Gravel
If using gravel, wash it thoroughly before use. It has many advantages as it’s cheap, easy to clean, and won’t waterlog.
Techniques
The technique used for hydroponics can have a profound effect on the plant. The following are some of the most common and most effective techniques used in hydroponics:
Continuous Flow
In the continuous flow technique, nutrient solution constantly flows past the roots of the plants.
Ebb and Flow
The ebb and flow technique generally consists of using a reservoir filled with nutrient solution which will pump solution up for a set time then let it drain and repeat.
Top Irrigation
Top irrigation consists of periodically applying a nutrient solution to the surface of the medium.
Chemical safety
For all chemicals
1. During the part of the experiment that will be performed at school, all chemicals will be used in accordance with the MSDS.
2. The use of all chemicals will be done while wearing gloves, aprons, and goggles.
3. All chemicals that release fumes will be placed under the fume hood to prevent the release of fumes into the classroom.
4. A fire blanket, fume hood, fire extinguisher, eyewash station, and shower are available for use.
5. Upon leaving the lab, hands will be washed and all chemicals will be stored in a locked ventilated chemical storeroom.
Chemical Disposal
FloraNova Grow
Completely dissolve each substance in water in a separate container. Rinse this solution down the drain with a tenfold excess of water. Then rinse the solution of a second substance down the drain with a tenfold excess of water. Repeat as necessary.
Europonic Rockwool Conditioning Solution
Completely dissolve each substance in water in a separate container. Rinse this solution down the drain with a tenfold excess of water. Then rinse the solution of a second substance down the drain with a tenfold excess of water. Repeat as necessary.
Indole-3-Acetic Acid
The organic acid may be diluted by adding it slowly to a 20-fold excess of water with stirring, neutralizing the resulting solution with sodium carbonate or sodium hydroxide solution, checking the pH with pH paper. Stir the solution until all solid organic acids have dissolved.
Kinetin
Completely dissolve each substance in water in a separate container. Rinse this solution down the drain with a tenfold excess of water. Then rinse the solution of a second substance down the drain with a tenfold excess of water. Repeat as necessary.
*All chemicals are to be used in experimentation and are therefore not subject to any of the disposal methods described above.*
Electrical Power Safety
1. Limit the use of high power devices around water.
2. Never use frayed or cut wires when plugging in a device.
3. Never overload the outlet and use a surge protector.
4. All electrical devices should have an emergency cut off switch or “kill” switch.
5. Shut off and unplug all devices when not in use or when you leave the room unattended.
Sharp Object Safety
1. Use caution when using a sharp object.
2. Restrict the use of sharps to a minimum.
3. Do not use bent or broken needles, knifes, or razor blades
4. Cover or cap needle after every use.
5. Discard used syringes, needles, and scalpels into an approved sharps container.
6. Bring all needles in a sharps container to a local fire station for disposal.
Preparing the Clinostat
1. Clean the clinostat.
2. Set up the plant compartments.
3. Check to make sure system is working.
4. Check to make sure lights are working.
5. Condition the rockwool.
6. Fill the tray with hydroponics nutrient solution.
7. Once plants are ready, move them into environment.
Preparing the Hydroponics Systems
1. Clean all the hydroponics trays.
2. Set up the pump system.
3. Test the pump system.
4. Check to make sure the lights are working.
5. Conditioning the rockwool.
6. Fill the bucket(s) with hydroponics nutrient solution.
7. Once plants are ready, move them into environment.
Cultivating the Bibb Lettuce, Lactuca sativa
1. Plants will be split into several different groups: 20 mL water, 5 mL kinetin/15 mL water, 10 mL kinetin/10 mL water, 15 mL kinetin/5 mL water, and 20 mL kinetin. There will be 100 plants total, 20 per group.
2. Plants will be germinated in petri dishes containing the above mixtures of hormones.
3. Plants will then be placed in their separate environments.
4. Plants will mature in their environment.
5. While plants are maturing, they will be given an injection of their hormone(s).
Collecting the Data
1. Measurements will take place every Tuesday until the end of experimentation.
2. Measurements will include leaf count, coloration of the leaf, and height of the plant measuring from the end of the root to where the stem splits for leaves.
Analyzing the Data
1. Data will first be organized in a date table based on groups or variables.
2. The mean or average for each group or variable will be calculated.
3. A z-test will be performed on each group using last year’s hydroponics control as the standard of comparison.
Critical Value: 1.96
Leaf Count
Clinostat Control: -7.2
Clinostat Kinetin: -7.8
Clinostat IAA: -7.5
Clinostat Kinetin/IAA: -7.3
Hydroponics Kinetin: -1.9
Hydroponics IAA: -2.3
Hydroponics Kinetin/IAA: -4.2
Clinostat Control: 8
Clinostat Kinetin: 12
Clinostat IAA: 11
Clinostat Kinetin/IAA: 14
Hydroponics Kinetin: 2
Hydroponics IAA: 3
Hydroponics Kinetin/IAA: 2
Clinostat Control: -7.2
Clinostat Kinetin: -7.8
Clinostat IAA: -7.5
Clinostat Kinetin/IAA: -7.3
Hydroponics Kinetin: -1.9
Hydroponics IAA: -2.3
Hydroponics Kinetin/IAA: -4.2
For the plants solely exposed to hormones, the null hypothesis was rejected. There were differences in growth. The first hypothesis was accepted. Plants germinated in indole-3-acetic acid (IAA) did show elongated stem growth compared to the control, as did the other groups. The second hypothesis was rejected. Plants germinated in kinetin did not show higher numbers of leaves compared to the control, as well as the other groups. The third hypothesis was rejected. Plants germinated in a mixture of kinetin and IAA showed elongated stem growth compared to the growth, but had less leaves.
For plants exposed to both hormones and microgravity, the null hypothesis was rejected. There were differences in growth. The first hypothesis was accepted. Plants germinated in indole-3-acetic acid (IAA) and grown in a microgravity environment did show elongated stem growth compared to the control, as did the other groups. The second hypothesis was rejected. Plants germinated in kinetin and grown in a microgravity environment did not show higher numbers of leaves compared to the control, as well as the other groups. The third hypothesis was rejected. Plants germinated in a mixture of kinetin and IAA and grown in a microgravity environment showed elongated stem growth compared to the growth, but had less leaves.
