Plants need to survive in a harsh and fluctuating environment, optimising their search for fluctuating nutrients, and predicting danger. They achieve this through complex response processes, such as decision-making, based on memory, or the capability to accumulate and compare past stimuli. For example, a plant shoot accumulates sensory information from various fluctuating light sources, decides which direction yields consistently most light for photosynthesis, and grows in that direction. Here we propose a reverse-engineering approach to investigating the underlying rules for the accumulation and integration of sensory inputs, relating macroscopic tropic dynamics to microscopic processes, while combining experiments with mathematical models.