tropism

The directional growth or movement responses of organisms to environmental stimuli. The response depends on stimulus direction and can be positive (toward the stimulus) or negative (away). The most typical examples of this phenomenon might be phototropism (growth toward light), gravitropism (growth in response to gravity), and thigmotropism (response to touch). These movements are regulated by signal transduction pathways that guide growth based on external cues. Tropisms play a critical role in optimizing resource acquisition and survival.

Similarly, neurotrophism refers to the growth and guidance of neurons toward specific targets via neurotrophic factors (e.g., nerve growth factor, NGF). Both processes depend on chemical gradients (e.g., auxins in plants, neurotrophins in neurons), enable adaptive responses to environmental cues (resources for plants; synaptic connections for neurons), and involve receptor-mediated signaling to regulate growth trajectories.