Domain: Natural Science — Biochemistry & Molecular Biology
Target concept: Iodine staining of illuminated leaves, showing starch accumulation

Video generation prompt: A green leaf exposed to intense light is placed in hot water and alcohol for decolorization, then spread out and stained with iodine solution on its surface.

Evaluation guide:
(i) Target concept: Visualization of starch accumulation via the iodine-starch reaction across a leaf that was uniformly light-exposed, after its chlorophyll has been removed.
Minimum mechanism: The leaf must have undergone light exposure across its whole blade (implied by its green color and the experimental context); chlorophyll must be removed by the hot-water-then-alcohol decolorization to expose the starch already stored in the tissue; iodine must contact the starch-rich mesophyll to produce blue-black color; no competing pigments or chemical interferences present.
(ii)Storyline: [Frame 0–2] Green leaf immersed briefly in hot water, then transferred into an alcohol container → [Frame 3–4] Leaf removed, visibly pale/white, placed flat → [Frame 5–6] Iodine solution dispensed and contacts leaf surface → [Frame 7–9] Blue-black color develops across the whole leaf blade, with the veins remaining visibly paler than the surrounding tissue; fixed overhead or oblique viewpoint maintained throughout; leaf remains fully visible and unoccluded; all transitions occur via continuous motion or seamless cut; lighting remains constant and directional to support shadow consistency and color perception.

Manual:
Experimental Procedure
1. Place a green leaf that has been exposed to intense light into hot water briefly, then transfer it into alcohol for decolorization.
2. Remove the decolorized leaf and spread it flat on a surface.
3. Apply iodine solution evenly to the leaf surface.
Observation of Experimental Phenomena
The decolorized leaf turns blue-black across its whole blade, with the veins remaining visibly paler, because starch accumulated throughout the leaf during its uniform exposure to light before decolorization.
Summary of Experimental Principles
Starch produced during photosynthesis binds iodine to form a blue-black complex; decolorization removes chlorophyll so this color change becomes visible across the whole leaf.

Prompt Grounding rubric:
level_1: No leaf is present; neither a hot-water container nor an alcohol container appears; no iodine-application step is shown; the scene contains no recognizable decolorization or staining action at all.
level_2: A green leaf (matching the prompt's starting appearance) is present, but it is never placed into any liquid: no hot-water immersion and no alcohol immersion is shown; an iodine solution may appear, but it is never applied to the leaf; at most one of the required props (leaf, hot-water container, alcohol container, iodine dropper) is used correctly.
level_3: The leaf is placed into a liquid container for decolorization, later removed and laid flat, and iodine solution is visibly applied to its surface, but only one of the two required liquids (hot water OR alcohol) appears rather than both in sequence: the second immersion step is missing, the two are merged into a single step, or their order is reversed.
level_4: The leaf is shown immersed in hot water, then transferred to and immersed in alcohol (both steps present, in that order), then removed, spread flat, and stained with a visibly brownish-yellow iodine solution applied by dropper or swab; all four core props (leaf, hot-water container, alcohol container, iodine solution) appear with correct visual identity; no step is skipped, duplicated, or substituted, and the leaf is never swapped for a different leaf between steps.
level_5: Every 4-point condition holds, and in addition the leaf's identity and orientation carry over continuously from one step to the next: the same leaf shape and edges are recognizable across the hot-water step, the alcohol step, the spreading step, and the staining step, with no substitution; the hot-water and alcohol containers keep consistent size and shape whenever shown, the camera viewpoint stays fixed through the whole sequence, and the transfer from the hot-water container to the alcohol container is shown as a distinct hand-carried motion rather than the leaf appearing already inside the second liquid.

Scientific and Causal Correctness rubric:
level_1: No starch-related color change occurs; the iodine step produces no blue-black anywhere on the leaf; the leaf stays green, or turns uniformly brown/black without ever passing through a pale decolorized stage; there is no visible causal link between the light exposure, the decolorization, and the iodine staining.
level_2: Iodine is applied, but the leaf shows no blue-black color anywhere; or the leaf darkens uniformly to black, purple, or gray rather than the blue-black specific to a starch-iodine complex; or the dark color appears on the container or background rather than on the leaf; or iodine is applied while the leaf is still green, i.e., the hot-water/alcohol decolorization step is skipped.
level_3: After the iodine step, blue-black color appears somewhere on the leaf's blade, and this occurs only after a visibly pale, white decolorized leaf is shown beforehand; however, the blue-black coverage is patchy or only partial across the blade in a way the vein network does not explain (e.g., large blank patches of undyed lamina), or the resulting color is washed-out and low-contrast rather than a clear blue-black.
level_4: The leaf is pale/white and uniform immediately before staining, with no green patches remaining; after the iodine solution is applied, blue-black color develops across essentially the whole leaf blade (the tissue between the veins), not just one corner or patch, consistent with the entire leaf having been uniformly exposed to light; the veins themselves may remain visibly paler or yellower than the surrounding tissue; no unrelated discoloration (no yellow, brown, or purple artifacts) appears; the causal chain is visible: decolorization → pale leaf → iodine contact → blue-black coloring of the whole blade.
level_5: Every 4-point condition holds, and in addition the leaf is shown fully green before decolorization and fully pale/white with zero residual green patches immediately before staining; the blue-black coloring after iodine reaches a high-contrast, saturated hue continuously across the entire leaf blade up to its edges, without fading out toward the margins, while the vein network stays visibly distinguishable as lighter lines; no other color artifact appears anywhere: no browning at the edges, no partial bleaching, no color bleeding into the background; every frame is consistent with the full causal chain from light exposure through starch accumulation to the iodine-starch complex forming across the whole blade.

Spatiotemporal Consistency rubric:
level_1: The leaf disappears and reappears at a different size, orientation, or location between shots; the hot-water or alcohol container's position or orientation changes between shots without any hand moving it; the iodine droplet appears already sitting on the leaf with no dropper or delivery motion shown; the bench lighting jumps from bright to dim between two consecutive shots with no dimming visible; or the leaf visibly tears, splits, or warps in an unnatural way.
level_2: At least two of the following occur: the leaf rotates a large angle between shots with no visible turning motion; the iodine bottle appears full, then empty in the next shot with no pouring or dropper motion shown; the decolorized leaf's surface texture changes inconsistently, e.g., glossy in one shot and matte in the next, with no explanation; or the lighting flickers, or a shadow jumps to the opposite side, with no corresponding light-source movement.
level_3: One minor spatiotemporal flaw occurs: e.g., the leaf is briefly hidden behind a hand or container during a transfer, breaking visual continuity for a moment; or the leaf's position shifts slightly between the decolorization-removal shot and the spreading shot with no visible sliding motion; or steam above the hot-water container appears or vanishes abruptly between shots while the container itself stays fixed; otherwise the leaf and both containers keep their shape intact, and their positions change only through visible motion rather than an instantaneous jump.
level_4: The leaf, the hot-water container, and the alcohol container each keep a consistent position, scale, and orientation whenever they reappear; the leaf's motion (being lifted, transferred, and laid flat) follows a smooth, physically plausible path rather than jumping between poses; every transition is either continuous motion or a clean cut that does not hide an incomplete step; the liquid level and any steam above the hot-water container change gradually rather than discontinuously; the leaf's surface texture and sheen stay consistent between the pre- and post-decolorization shots aside from the expected color change.
level_5: Every 4-point condition holds, and in addition the leaf's whole path is shown with continuous, natural motion: lifted from the hot water, carried through the air, and lowered into the alcohol with no gap in the motion; the alcohol's surface visibly settles after the leaf enters it; the iodine droplet forms at the dropper tip, detaches, falls, and spreads across the leaf surface in one unbroken motion; the shadow the leaf casts stays on a consistent side matching a single unmoving light source throughout every step; and the camera viewpoint stays fixed with no mismatch between the leaf and the containers behind it.