Activity 1 -- Constructing the PGC
Introduction
The CUE-TSIPS growing system has been designed to simulate the conditions under which plants will be grown pre-flight and in-flight on the Space Shuttle mission. The system uses readily available, low-cost materials with which students can construct their own Plant Growth Chambers.
Each group of students will need one PGC for experimental plants. Control plants will be grown separately in additional PGCs. For pollination and fertilization activities, each class will need at least 16 extra plants (two PGCs) to serve as controls.
Time Frame
Teachers may choose to have their students construct PGCs prior to the start of the CUE-TSIPS activities or use the "CUE-TSIPS Mission Calendar" to time the construction with the Shuttle mission.
Working in groups of four, construction of the PGC components (lid and base) would take about one 50 minute class period. Assembly of the components once students are ready to plant will take about 15 minutes.
Learning Objectives
This activity is largely technology-based. In participating in this activity students will:
- learn to construct experimental equipment; and
- make accurate measurements.
1. PGC Lid Construction
Materials
- transparent acrylic sheet, 2 mm (1/8") thick (comes in various dimensions, illustrated as a sheet 70 cm x 80 cm), or other clear plastic sheets (e.g., report covers, overhead transparencies, etc.)
- cutter for acrylic sheet (such as Red DevilR) and/or scissors for plastic sheets
- 2 cm wide clear adhesive tape
- fine tipped permanent marker
- metal or wood file, or sand paper
Procedure
1. Use a marker to mark the cut lines on the acrylic sheet as shown. For other types of clear plastic make appropriate measures and cuts.
Each PGC lid includes pieces in the following dimensions:
- two pieces 20 cm x 21.5 cm (front and back panels), and
- two pieces 20 cm x 5.6 cm (side panels).
A 70 cm x 80 cm acrylic sheet can be cut as shown at right to yield pieces for four PGC lids.
2. Cut the acrylic sheet with the cutter (or with a circular table saw with a hardened blade). Peel off the protective plastic film.
Caution: Acrylic sheet cutters and saws are very sharp and should be used with care.
Tips:
- Smooth off sharp edges of the cut acrylic pieces using a file or sand paper.
- For thin plastic sheets, cut the front panel to be shorter to access plants.
3. Assemble the PGC lid as follows:
- Use two pieces of clear adhesive tape to attach the back panel to one of the side panels. Place one piece of tape about 2 cm from the top and one about 4 cm above the bottom edge on each side-back joint.
- Use two pieces of tape to attach a side panel to the other side of the back panel. Again, place one piece about 2 cm from the top and the other about 4 cm above the bottom edge. Three of the four panels should be taped together at this point.
- Tear off two additional pieces of tape. On each piece, fold over one end about 1 cm to make a flap. Place one of these two pieces of tape on each side of the front panel, with the flap end on the front panel. By peeling back these pieces, the front panel can be removed and replaced, allowing easy student access to the plants inside the PGC.
- If using thin plastic sheets, support them by taping panels to bamboo grilling skewers at the corners. The skewers can be poked into the styrofoam film can wick pot holder (page 35).
2. PGC Base Construction
The basic growing system utilizes peatlite (peat moss:vermiculite, 1:1) as the root medium, and a capillary wicking system to provide water and nutrients to the plants in film can wick pots. Although the peatlite medium and film can wick pot system is not being used in the Space Shuttle Plant Growth Chambers, it is recommended as the most reliable system in which AstroPlants can be grown.
Materials
- two plastic drawer organizers (22 x 7.6 x 5.1 cm), the first to be a base which will hold the film can wick pots and the second to act as a reservoir
- four 35 mm black film cans for wick pots
- capillary wicking material
- styrofoam block (2.5 cm thick, 21 cm long x 5.5 cm wide), cut from builder's insulating foam
Procedure
1. Melt or drill an approximately 5 mm diameter hole in the center of the bottom of each film can.
Caution: Melting plastic produces noxious fumes; perform this step in a well-ventilated area. Wear safety goggles if using a drill.
2. From the capillary wicking material, cut four diamond wicks (3 cm x 1 cm), with tapered ends, for the film can wick pots.
3. From the capillary wicking material, cut a wick strip to be 30 cm long and 1 cm wide, with tapered ends.
4. From the capillary wicking material, cut a capillary mat to fit the bottom of one of the drawer organizers (21 cm x 5.5 cm).
5. With a hot soldering iron or large hot nail melt two 2 cm slots in the bottom of one of the drawer organizers to
accommodate the capillary wick; this organizer will become the base for the growing system.
Caution: Melting plastic produces noxious fumes; perform this step in a well-ventilated area.
6. From 2.5 cm (1 inch) thick insulating styrofoam, measure and cut, with a fine blade saw (hacksaw or utility saw), a rectangular block 21 cm long by 5.5 cm wide. Rough edges where the styrofoam is cut may be smoothed with sandpaper.
7. With a pen and a film can, trace four equally spaced circles on the top surface of the styrofoam block (this block will hold the film can wick pots).
8. Using a 33 mm (1.25 inch) circular "keyhole" cutter in an electric drill, cut four holes equally spaced in the styrofoam block. Alternatively the hot flamed rim of a PyrexR test tube (18 to 22 mm diameter) may be used to melt the four holes. Other forms of film can wick pot holders, such as wooden blocks, are satisfactory.
Caution: Melting styrofoam produces noxious fumes; perform this step in a well-ventilated area. Wear safety goggles if using a drill.
