Exploratory Study: Phototropism

Phototropism is essentially how a plant grows in responds to light, either positive phototropism (towards the light) or negative phototropism (away from the light). I’d like to explore on the factors that contributes to the extent a plant grows towards (or away) a light source.

At each junction, a plant can decide to grow a leaf towards the right or left. With even exposure to light, the probability is 0.5 for each direction. With exposure to light biased to the right for example, the there’s a higher probability for a leaf to grow there. We can experiment different light sources by defining the intensity and shape. E.g., an outdoor plant will receive direct sunlight which is round and have high intensity while an indoor plant will receive sunlight from a rectangle window which may have day curtains, having low intensity.


Assuming even light exposure, we generate a probability tree using an algorithm. Each route starts from the same position, and based on a probability to turn left or right at multiple junctions, a route will be formed with a limit of n junctions. Since each decision at each junction is a probability, each route created will take different paths.

After, we try to add on the effect of light. We can input a single light source as a point or an area. Since intensity = 1/d^2, the further a plant is from a source, the less intense the light.

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