For the past decade, he has used the phototropic properties of cyanobacteria to produce images in Petri dishes.
Algebraical summation of geotropic and phototropic effects: Experiment 194.
Thus the leaflets of Mimosa pudica acted on by light from above fold upwards, the phototropic effect being positive.
We shall find in the next chapter that the intensity of phototropic effect is proportional to the quantity of incident light.
This has even led to assumption that there are phototropic particles which function like statoliths in geotropic organs.
But we cannot conceive of light suddenly losing its phototropic effect by an increase of intensity.
As the responsive movement is towards light, the phototropic effect must be regarded as positive.
But the same leaflets acted on by light from below exhibit a folding upwards, the phototropic effect being now negative.
As the curvature is towards the stimulus, the phototropic curvature thus remains positive, even under continued stimulation.
Thus the phototropic curvature increases, within limits, with the duration of stimulation.