The Wisdom of Survival: Phototropism

The phenomenon in which plants grow towards a light source under unilateral illumination is called phototropismFor sessile plants, this is not merely a physical movement but a sophisticated survival strategy. By growing towards light, plants maximize light capture, boost photosynthetic efficiency, and gain a competitive edge for spatial resources.

Experimental Model & Material Basis

To uncover the underlying logic, scientists introduced thecoleoptileas a research model. Through comparative experiments, they found that:taking a segment of a maize coleoptile and removing the top 2 mm to stop auxin productioncauses the plant to not only stop growing but also lose its phototropic response. This proves that the tip is both the light-sensing site and the source of growth signals.

• Synthesis Sites: Auxin is mainly synthesized in buds, young leaves, and developing seeds.
• Transport Mechanism: Under unilateral light, auxin undergoes lateral transport at the tip; in mature plant tissues, substances are also transported via the phloem throughnon-polar transport, together forming a complex regulatory network.