Sunflower seedlings bend toward a light illusion, not the brightest direction
Kempinski A, Porat A, Rivière M, Meroz Y
Plant Signaling
If your windowsill seedlings lean at an odd angle under two lamps or a window plus a grow light, this work explains why: they add up signals from each side rather than following the brightest source, so balanced lighting on opposite sides keeps stems growing straight.
Plants have no brain, so each patch of stem senses light on its own and the plant blends those signals into one growth direction. Sunflower seedlings react to the sum of these signals, not the raw brightness, so they can lean somewhere that isn't where the light is strongest. When two equal lights shine from opposite sides, the pulls cancel and the seedling stands straight; a weak third light is enough to tip the balance.
Key Findings
A model where light is sensed locally around the shoot, transduced nonlinearly, and summed as vectors predicted sunflower seedling growth under unilateral, bilateral, and out-of-plane lighting.
Seedlings respond to the vector sum of transduced signals, not the physical sum of incident light, so growth direction can deviate systematically from the direction of maximal illumination, similar to an optical illusion.
Symmetrical opposing light cues cancel each other, and a weaker symmetry-breaking light source was experimentally shown to shift growth direction as predicted.
chevron_right Technical Summary
Sunflower seedlings don't simply grow toward the brightest spot. They convert light from each side of the stem into a signal, then add those signals up as directions, so the growth angle can differ from where the light is strongest. Equal light from opposite sides cancels out, and the seedling grows straight up.
Abstract Preview
Original paper
Nonlinear distributed sensing of light patterns leads to perceptual distortions in plants.
Many organisms lack centralized sensory-processing systems, navigating complex environments through local integration of spatially distributed stimuli (e.g., chemotaxis of cells, bacteria, or growi...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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