Domain: Engineering — Agricultural Engineering
Target concept: Place corn seedlings under unilateral light conditions, and observe and confirm that the stem bends toward the light source, while the shaded side remains upright, exhibiting a single direction of bending.

Video generation prompt: Fixed shot, time-lapse style. Plant healthy corn seedlings in pots. Place a single light source on one side. Keep the position of the seedlings unchanged. Record the growth process of the seedlings over time, with light always coming from one side. Emphasize the clear changes in the stem's orientation relative to the light source.

Evaluation guide:
(i) Target concept: Unidirectional phototropic bending in maize seedlings under asymmetric illumination.
Minimum mechanism: Light perception by photoreceptors (phototropins) → lateral auxin redistribution → differential growth rate across stem axis → sustained curvature toward light source; requires intact apical meristem, viable tissue, and absence of confounding tropisms (gravitropism must be neutralized by vertical orientation).
(ii)Storyline: Frame 1: Seedling upright, light source visible on one side, stem vertical and symmetrical. → Causal transition: Light stimulus initiates auxin asymmetry. → Frame sequence: Progressive increase in convex (outer-arc) curvature on the shaded side as it elongates faster than the lit side; the lit side stays straighter, forming the concave (inner-arc) side of the bend; no rotation or translation of base. → Perspective constraint: Fixed frontal view showing full stem length and light-source azimuth; no occlusion of stem apex or light direction. → Visibility constraint: Stem curvature must be resolvable at native resolution: no ambiguity between bending and parallax or perspective distortion.

Manual:
Experimental Procedure
1. Place one healthy corn seedling in a standard pot with moist soil.
2. Position a single directional light source on the left (or right) side only—no other lights.
3. Keep pot and seedling completely stationary; fix camera viewpoint directly facing the setup.
4. Record time-lapse video capturing stem orientation change over time.
Observation of Experimental Phenomena
The stem bends progressively and exclusively toward the light source; the shaded side elongates faster and develops the outer, convex curve of the bend, while the lit side elongates less and forms the straighter, inner curve.
Summary of Experimental Principles
Unilateral light triggers asymmetric auxin distribution in the coleoptile/stem, causing faster cell elongation on the shaded side—resulting in bending toward the light (positive phototropism).

Prompt Grounding rubric:
level_1: No corn seedling is present, no pot is visible, no unilateral light source is shown, no fixed camera framing is evident, and there is no time-lapse progression at all (e.g., a static single image or chaotic, non-sequential motion); none of the posted_prompt's setup elements are represented.
level_2: At least one of the seedling, pot, or unilateral light source is present, but not all three together; the camera framing shifts, pans, or rotates during the recording; there is no discernible sequential progression across frames (e.g., a single frame or jarring, disconnected cuts); at least two of the prompt's core setup elements are missing.
level_3: The corn seedling is shown in a pot; a light source is positioned on exactly one side of the setup; the camera framing stays fixed throughout; a visible, frame-to-frame change in stem orientation confirms a time-lapse progression is occurring, but one setup element is imperfect, such as the light's position relative to the seedling being ambiguous, a second light or bright reflection also illuminating the opposite side, or the pot/seedling shifting position between frames.
level_4: The seedling is present in its pot; a single light source stays fixed on one side only, with no competing secondary illumination; the seedling and pot remain stationary (no lateral shift or rotation) for the whole recording; the camera framing is fixed with no pan, tilt, or zoom; the time-lapse shows a continuous, visible change in stem orientation from start to finish, except for one minor, unrelated flaw, such as a brief flicker in light intensity or a short focus pulse.
level_5: The seedling is present in its pot; a single unilateral light source stays fixed on exactly one side for the entire recording, with no secondary or ambient light competing with it; the seedling's base and the pot remain completely motionless throughout; the camera framing is fixed with zero pan, tilt, or zoom; the time-lapse shows a smooth, unbroken progression of visible stem-orientation change from the first frame to the last; every setup element named in the posted_prompt (planting, unilateral light, stationary seedling, time-lapse recording) is fully and consistently instantiated.

Scientific and Causal Correctness rubric:
level_1: The stem bends away from the light source, bends toward the lit side, bends randomly with no consistent direction, or shows no bending at all and stays rigidly vertical, contradicting the phototropic mechanism entirely.
level_2: The stem bends, but the direction doesn't match the light's position (e.g., the light is on the left, yet the stem curves right); curvature appears on both sides at once rather than being asymmetric; or the bend appears suddenly in a single frame rather than developing gradually, showing no coherent causal link between the light stimulus and the direction of growth.
level_3: The stem's upper portion visibly moves toward the light source over the sequence, with growth appearing more pronounced on the shaded side than the lit side, but the timing or magnitude is off, such as the full curve appearing within the first frame or two instead of developing gradually, or the curvature partially straightening or reversing partway through.
level_4: The stem's curvature develops gradually across the time-lapse: the shaded side visibly elongates and bows outward, forming the outer arc of the bend, while the lit side stays comparatively shorter and closer to straight, forming the inner arc; the stem tip progressively advances toward the light source; no unrelated curvature (such as drooping from gravity or a kink unrelated to light direction) appears, except for one minor deviation, such as a brief pause in the curving motion.
level_5: The stem's curvature develops smoothly and continuously toward the light across every frame: the shaded side elongates visibly more than the lit side, producing a longer, outward-bowing (convex) arc on the shaded side, while the lit side forms the shorter, straighter, inward (concave) arc; there is no reversal, no bending away from the light, and no secondary or competing curve anywhere in the sequence; the whole sequence is consistent with light-triggered asymmetric elongation driving sustained bending toward the light source.

Spatiotemporal Consistency rubric:
level_1: The corn seedling or its pot appears to jump to a different position between consecutive frames; the unilateral light source blinks on and off without cause; the stem visibly snaps or separates rather than curving smoothly; the time-lapse runs backward, freezes on a repeated frame for more than 3 frames, or the background itself shifts or changes color/texture; or the camera view itself pans, tilts, or zooms during the recording.
level_2: The pot or seedling shifts noticeably sideways (roughly its own width or more) between two consecutive frames with no bending-related cause; the light source's brightness or position flickers inconsistently more than twice across the sequence (e.g., its shadow vanishes then reappears without cause); the stem shows an abrupt kink or joint-like break instead of a continuous curve; or the shadow cast on the pot or soil disappears and reappears without a matching change in the light source.
level_3: The seedling's base stays fixed relative to the pot, and the pot stays fixed relative to the background and light source throughout; the stem curves smoothly from frame to frame without tearing or disconnecting; the cast shadow lengthens or shortens gradually in step with the stem's changing angle; the camera framing never shifts, but one small artifact is present, such as a single frame of motion blur that briefly obscures the exact moment the stem begins to bend, or a brief, harmless flicker in a background leaf or reflection that doesn't touch the seedling or light source.
level_4: Every continuity requirement from the 3-point level holds with no exceptions for the seedling, pot, and light source; in addition, the stem's apparent scale and perspective stay consistent with its actual growth and bending (no sudden size jumps), and the shadow's direction and length stay in visible agreement with the fixed light source and the stem's evolving curve in every frame, except for one very minor, isolated artifact, such as a single brief flicker in a background object or a faint lens-flare-like glint that never touches the seedling, pot, or light source.
level_5: Across the entire time-lapse, the seedling, pot, and light source keep perfectly consistent position, scale, and orientation from frame to frame; the stem's curvature unfolds as one continuous, biologically plausible motion with no visible snapping, sudden straightening, or reversal; the shadow cast by the seedling changes shape and length in exact step with the stem's evolving bend and the fixed light direction in every single frame, with no flicker, warping, or visible artifact anywhere in the sequence.