Phototropism
/ˌfoʊˈtɑːtrəˌpɪzəm/
Definition
Phototropism refers to a plant growth response to directional light, a biological process in which stems, leaves, or other organs bend as they grow. Shoots usually show positive phototropism by growing toward light, while some roots show negative phototropism by growing away from it. This differs from temporary leaf movement because phototropism involves unequal growth, often linked to the plant hormone auxin, rather than a quick reversible motion.
Biological Role
- Directional canopy shaping: In shoots, phototropism helps leaves and stems angle toward available light, which can improve light capture for photosynthesis and influence the overall form of a plant.
- Hormone-driven bending: The response is linked to auxin, a growth hormone that shifts within the organ and causes cells on one side to elongate more than the other, producing curvature.
- Different responses in roots and shoots: Many shoots bend toward light, while some roots show the opposite pattern or respond more strongly to gravity, so the visible effect depends on the plant part involved.
- Practical signs indoors: On windowsills or under one-sided grow lights, uneven illumination can lead to leaning growth. Rotating the pot regularly can help keep stems more balanced and upright.
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