Integration of multiple stimuli in plant tropisms

Though rooted in place throughout their lifespans plants survive and prosper in harsh and changing environments, thanks to their remarkable abilities to identify available options, and select the preferable one. Such a task requires taking into account different types of sensory information and weighting conflicting needs.

The phototropic response of plants – the ability to reorient their growth trajectory based on light intensity and direction, is what allows them to maximize the amount of light they can absorb.

Plant shoots sense the direction of light via the light gradient across the organ and will respond to very small amounts of light.

Classic phototropic experiments employ unilateral lighting, this results in a clear and strong response which is easy to observe. However, in their natural environments plants are rarely exposed to such “clean” conditions, and are more often than not subjected to a variety of directional signals simultaneously.

Here we investigate the ability of plants to integrate multiple stimuli. We focus on the phototropic response of sunflower seedlings to two opposing light stimuli of different intensities, while taking into account the gravitropic effect. We then present a mathematical model which captures the experimental results.