This lesson focuses on one factor that affects plant growth: light. We know that plants require light in order to perform photosynthesis, but not all types of light are needed for plant growth, and the light requirement vary plant by plant. In this lesson the students will learn colors of light (light spectrum) and the effect of different colors of light on plant growth.
Wio Link board, LED strip, Reading Material
Ask the students why greenhouses are transparent. Explain to the students that a greenhouse usually needs to maximize the amount of light going in, so that the plants can use the light to perform photosynthesis. If there is not enough light, what can greenhouses do?
Well, it turns out that we can use artificial light sources. Connect the LED strip and turn it on without letting the students see the code. The LED strip turns on and only shows two colors - red and blue. Why is that? Actually, most of the plant grow lights are red and blue. See this Google Image Search result.
Why are are these commercial grow lights also red and blue? The Reading Meaterial explains it perfectly:
Plants have adapted, over millions of years, to use sunlight as their source of energy to grow through the process of photosynthesis. In photosynthesis a plant produces sugar when a plant’s chlorophyll is exposed to light with a wavelength of in the visible part of the light spectrum of 400–700 nanometers. The amount of sugar is almost directly proportional to the intensity of the light. We can use this knowledge to expose plants to light of a specific frequency during each phase of its development.
Why red and blue lights?
It is important to note that all visible colors of the light spectrum are used by plants but blue and red are very important for plants. The reason is that the chlorophyll cells in plants are very good at absorbing and using both blue and red light. Blue light drives the photosynthesis process and promotes good root development. If plant is receiving plenty of blue light it should have thick leaves, strong stems and will be shorter (but healthier). Red light also helps a plant grow but is particularly important for flower production.
Now that we know why we need red and blue lights, let’s turn on our grow lights. In this course, it is a general rule that you can interact with a device with these three steps (refer to the cheat sheet).
from displays import GrowLight gl = GrowLight(port=1) gl.on()
Refer to the documentation on GrowLight and finish the following challenges:
For challenge 3, you may use this website RGB Color Picker useful in choosing your colors.
For challenge 4, the use of quotation marks
"" is very important!
Please upload your final code to Google Classroom. Save your file in the format of