Introduction:
It is the photosynthesis of plants that converts CO2 and water into organic matter and O2, which provides energy and nutrients for all life on Earth and keeps the components of the atmosphere relatively stable. In today's experiment we are going to find out how plants photosynthesize with SCI module, light sensor and CO2 sensor.
Materials:
SCI DAQ Module x 1 https://www.dfrobot.com/product-2655.html
SEN0228 Ambient Light Sensor x 1 https://www.dfrobot.com/product-1620.html
SEN0536 Infrared CO2 Sensor x 1 https://www.dfrobot.com/product-2646.html
4pin Wire x 2
Type-C Cable or Battery Holder
Small Transparent (Glass/Plastic) Bottle/Bag x 1
Fresh Spinach Leaves x 5
Notice:
1) If you choose a bottle, the diameter of the bottle top should be at least 3cm so that two sensor can be put into the bottle. It would be better if the bottle has a cap.
2) The volume of the bottle or bag should be large enough to hold two sensors and the spinach leaves.
Setup:
1. Power the SCI module from either battery or Type-C port.
2. Connect the light sensor and infrared CO2 sensor to Port 2 and Port 3 respectively. The sensors will be automatically identified and their data will be displayed on the screen.
3. Place the spinach leaves and sensors in the bottle or bag and seal.
Experiment:
1. Set Data Refresh Rate:
In the previous courses we have learned that the data refresh rate can be adjusted as desired. During this experiment, where the changes of sensor data are accurate, we should switch to a relatively high data refresh rate, 1S.
1) Press S button to enter the setting menu.
2) Select Set Refresh Rate.
3) Select 1S and press OK to confirm.
2. Explore how plants photosynthesize
Photosynthesis takes place in chloroplasts, which are usually found in the leaves of plants. This is why we choose spinach leaves instead of spinach stems as our experimental material.
1) Lay the bottle or bag with sensors and leaves in it down exposed to sunshine or other light sources. Please insure that the light sensor is facing directly to the light source to collect exact data.
2) Press R button and collect data for 10 minutes. Press R button again to pause collecting.
3. Explore how plants breathe
1) Lay the bottle or bag with sensors and leaves in it in a dark room or a opaque box. Please keep the container sealed to avoid gas exchange.
2) Press R button and collect data for 10 minutes. Press R button again to stop collecting.
4. Data analysis
1) Export data: connect SCI module to your computer, and download the CSV file named after the latest timestamp.
2) Clean data: During the data collection process, some incorrect, duplicate or incomplete data may be collected. Data cleansing refers to the removal of these erroneous or unwanted data by filtering, de-duplicating, and filling in missing values.
For example, the first few lines of data are obviously incoherent with the following ones, which may be caused by unstable sensors. The same situation may occur again at the moment when leaves switch to dark environment. A blank line separates the data of leaves’ photosynthesis and respiration so it’s easy to find out. Delete these disturbing data.
3) Visualize data: Draw a line graph about how the light intensity and CO2 concentration change over time.
5. Conclusions
The leaves’ photosynthesis and respiration can be obviously divided from the significant difference of light intensity. When the light is strong, CO2 concentration in the container is declining, indicating that the leaves are doing photosynthesis and consuming CO2. When the light is type of week, CO2 concentration in the container is rising, indicating that the leaves are doing respiration and producing CO2.
6. Extensions: Greenhouse Intelligent Light Control System
The experiment tells us that light is an essential determinant to photosynthesis. But different colors of light don’t effect equivalently. The graph below demonstrates the absorbance of chlorophyll, the energy absorbing pigment in plants critical for photosynthesis, to different colors of light.
Previous studies show that chlorophyll absorbs red and blue light and reflects green light. In modern agriculture, red and blue lights are often installed in greenhouses to increase the rate of photosynthesis in crops and improve yields. Let’s try to create an intelligent light control system for your one plants with the help of micro:bit controller.
Materials:
micro:bit x 1
LED Ring Lamp x 1
3pin Wire x 1
Setup:
1. Connect the SCI module from the I2C output port to the I2C port on the micro:bit expansion board.
2. Connect the LED ring lamp to the P2 port on the expansion board.
3. Power the micro:bit and SCI module using the power plug on the expansion board.
4. Connect the micro:bit to your computer using a USB cable to begin programming.
Programming:
The micro:bit will control the LED ring lamp to glow red and blue when the environment light intensity is lower than 100lx.
