Domain: Natural Science — Cell & Developmental Biology
Target concept: Under the microscope, osmotic stress induces plasmolysis in onion epidermal cells.

Video generation prompt: Under the light microscope, an onion epidermal peel is placed on a slide, and a concentrated salt solution is added from the edge while observing how the cells respond as the solution spreads beneath the peel.

Evaluation guide:
(i) Target concept: Osmotically driven water efflux causing reversible physical separation of plasma membrane from cell wall in plant cells.
Minimum mechanism: Intact semipermeable plasma membrane; rigid cellulose cell wall; hypertonic external solute gradient; aqueous diffusion pathway along extracellular space between peel and slide.
(ii)Storyline: [Phase 1] Static shot: peel centered on slide, no liquid present, cells turgid and contiguous. [Phase 2] Dropper enters frame, positions adjacent to peel edge, releases solution — liquid contacts slide edge beside peel. [Phase 3] Within same field-of-view: plasmolysis appears first in cells immediately adjacent to wetted edge, showing distinct wall-cytoplasm gap. [Phase 4] Gap expands contiguously to neighboring cells in direction away from edge, preserving cellular geometry and wall integrity. [Phase 5] Unexposed distal region remains fully turgid throughout; no plasmolysis occurs outside diffusion path. Perspective: Fixed microscope view (circular FOV), top-down; peel must remain fully in-frame; dropper visible only in periphery (not occluding FOV).

Manual:
Experimental Procedure
1. Place fresh onion epidermal peel flat on clean glass microscope slide.
2. Using a dropper, apply concentrated salt solution to one edge of the peel.
3. Observe under light microscope as solution diffuses beneath peel.
Observation of Experimental Phenomena
Cells near the salt-treated edge show clear separation between rigid cell wall and shrunken cytoplasm; unexposed cells remain turgid and fully filled; plasmolysis advances progressively from edge inward.
Summary of Experimental Principles
Osmotic stress from hypertonic salt solution causes water to exit onion epidermal cells via osmosis, resulting in cytoplasmic shrinkage and detachment from cell wall — plasmolysis.

Prompt Grounding rubric:
level_1: No onion epidermal peel is shown, no glass slide appears, no salt solution or dropper is shown being applied, and no top-down or angled microscope field of view of the slide is shown.
level_2: The peel, the slide, or a solution/dropper appears, but the three never come together as a set: none of placing the peel on the slide, adding salt solution at its edge, or holding a steady view of the slide actually happens, or the objects have no spatial relationship (e.g., the peel floats unsupported, or the slide stands on its edge).
level_3: The onion epidermal peel lies flat on the glass slide, a dropper or pipette is positioned at the slide's edge, and the microscope field of view (rounded frame, visible cell texture) is shown; the sequence proceeds peel placement, then dropper approaching the edge, then liquid touching the edge, in that order.
level_4: In addition to everything required for a 3, the salt solution visibly touches the slide right at the peel's edge rather than on top of the peel or away from it, the peel stays fully inside the field of view before and during contact, the dropper tip points toward the slide edge rather than up, down, or sideways, and no object appears or disappears partway through the sequence.
level_5: In addition to everything required for a 4, the dropper holds the same position relative to the slide edge once it has approached, without repositioning again; the peel lies flat and undisturbed for the whole sequence; the microscope field of view never zooms, pans, or rotates; and every object keeps a consistent size, position, and orientation from frame to frame.

Scientific and Causal Correctness rubric:
level_1: No plasmolysis appears: cells stay turgid and unchanged, no gap opens between the wall and the cell contents, and there is no visible difference between cells near the salt and cells far from it.
level_2: Cells change, but not correctly: the cell walls are missing or misshapen, the cell contents have no clear boundary, or the shrinkage bears no relation to where the salt solution touched the slide (e.g., cells far from the wetted edge shrink while cells near it do not).
level_3: Cell walls and an internal cytoplasmic mass are both visible; once the salt solution reaches the edge, cells near that edge show a clear gap opening between the wall and the shrinking contents, while cells farther away stay turgid, giving a visible contrast between the two regions.
level_4: In addition to everything required for a 3, the plasmolysis starts only at the wetted edge and advances inward from there over time, rather than appearing all at once or in scattered cells; the cell contents stay intact with no fragmenting or dissolving, and the cell walls keep sharp, continuous outlines throughout.
level_5: In addition to everything required for a 4, the plasmolysis stays confined to cells near the wetted edge, with no isolated cells shrinking far from it; no cell swells back or reverses during the sequence; the shrunken contents stay visibly denser than the surrounding medium; and the onion cells keep their natural pale color, with no artificial staining tint appearing.

Spatiotemporal Consistency rubric:
level_1: Objects teleport between frames (e.g., the peel jumps from hand to slide in one cut), the slide or dropper flickers or vanishes and reappears, the lighting suddenly changes with no cause, the cell texture disappears and comes back, or the field of view abruptly jumps or rotates.
level_2: A clear break in continuity occurs: the peel deforms unnaturally (e.g., it folds like paper and then snaps flat), the dropper jumps more than its own length between frames, the cell boundaries pulse or flicker, or a shadow's direction reverses with no light source moving.
level_3: All objects move smoothly: the peel is lowered onto the slide gradually, the dropper approaches the edge in one continuous motion, and the plasmolysis spreads gradually and contiguously outward from the wetted edge with no cells skipped or shrinking in isolation; no cell wall or slide surface tears or warps.
level_4: In addition to everything required for a 3, the dropper's approach and the shrinkage of the cell contents keep a steady pace with no sudden speeding up or stopping, the slide surface stays flat and rigid with no bending or rippling, and the cell walls keep a constant thickness and alignment across frames.
level_5: In addition to everything required for a 4, the motion of the dropper and the spreading plasmolysis shows no visible stutter or double-image effect, the dropper stays at a consistent apparent depth in front of the slide throughout, the lighting keeps the same brightness and direction across the whole sequence, and the dropper's shadow tracks its position and the implied light source consistently.