Domain: Engineering — Agricultural Engineering
Target concept: Immerse the roots of corn seedlings in red ink, wait several hours to allow transpiration-driven uptake, then cut across the stem and confirm that the xylem vessels appear red while the phloem remains colorless, resulting in a distinct visual effect.

Video generation prompt: Immerse full-rooted maize seedlings in a container filled with red dye solution. After a period of time-lapse photography, remove one seedling and horizontally cut its stem with a blade. The structure of the cross-section is clearly visible, with particular emphasis on the internal vascular tissue structure.

Evaluation guide:
(i) Target concept: Differential vascular transport capacity in maize stems, demonstrated by selective xylem dye uptake.
Minimum mechanism: Red dye must be water-soluble, non-toxic to living tissue, and molecularly excluded from phloem sieve plates; xylem vessels must be structurally open and lignified to permit passive capillary ascent; stem must be physiologically active (intact roots, hydrated) to sustain transpiration-driven flow.
(ii)Storyline: [Phase 1] Maize seedling fully immersed (roots submerged, shoot above liquid), establishing baseline state. [Phase 2] Static immersion for observable time (no motion except minor liquid meniscus adjustment), enabling dye uptake. [Phase 3] Seedling lifted vertically without shaking, preserving dye in xylem. [Phase 4] Blade contacts stem at consistent height and cuts horizontally in single fluid motion, revealing fresh anatomy. [Phase 5] Cross-section presented upright, centered, unoccluded, with lighting enabling direct visual discrimination of red xylem vs. colorless phloem/cortex/pith. Perspective remains fixed-side frontal view throughout; no camera movement, zoom, or re-framing between phases.

Manual:
1. Experimental operation procedure: Submerge full-rooted maize seedling vertically in transparent container filled with red dye solution. Wait several hours (ideally overnight) to allow transpiration-driven capillary uptake of the dye through the xylem. Remove seedling. Horizontally cut stem near base with sharp blade. Place cut surface upright for viewing.
2. Observation of experimental phenomena: Cross-section shows discrete red-stained structures centrally located and radially scattered; surrounding tissues (cortex, pith, phloem) remain completely colorless—creating high-contrast visualization of xylem vessels only.
3. Summary of experimental principles: Xylem transports water and dissolved dyes upward via capillary action and transpiration pull; its lignified vessels retain red dye. Phloem transports sugars bidirectionally via living sieve tubes impermeable to large dye molecules—hence remains unstained.

Prompt Grounding rubric:
level_1: No maize seedling, red dye solution, or container appears anywhere in the video; no blade or cutting action is shown; no stem cross-section is ever displayed.
level_2: A maize seedling, red liquid, transparent container, or blade appears, but not arranged as the procedure requires; for example the seedling is never submerged, the blade never touches the stem, no horizontal cut is shown, or no cross-section appears afterward.
level_3: A maize seedling with its root system submerged in red liquid inside a container (its shoot held above the liquid surface) is shown, a blade contacts the stem, a horizontal cut is performed, and a stem cross-section is displayed; but at least one element is wrong (the plant is clearly not maize, the liquid is not red, the cutting tool is not blade-like) or the sequence is broken (the seedling is lifted out and left in air well before the cut, or the cross-section shown belongs to a different, previously detached stem piece rather than the one just cut).
level_4: The maize seedling's root system (and the base of the stem) sits fully submerged in the red dye solution inside a transparent container, while its shoot and leaves remain above the liquid surface in open air, throughout the immersion phase; the seedling is then lifted out of the liquid; a blade visibly contacts the stem and executes one continuous horizontal cut; the freshly exposed cross-section appears in the same shot and viewpoint immediately afterward, without cutting to a different setup or substituting a different stem; no object is misidentified and no step is shown out of order.
level_5: The seedling's roots stay completely submerged throughout the full immersion period, with its shoot held continuously above the liquid surface, sustaining the transpiration pull that draws dye up through the xylem; it is then lifted straight up out of the liquid without shaking or splashing, and the blade begins the horizontal cut promptly after lifting, with no extended air-exposure delay; the cutting motion happens with the stem held steady, so the internal pattern is not blurred by camera or object motion; the resulting cross-section is centered and fully unobstructed in frame; and the whole sequence plays as one uninterrupted take, with no visible splice, zoom cut, or overlay breaking the path from container to exposed cross-section.

Scientific and Causal Correctness rubric:
level_1: No color difference exists between xylem and phloem regions in the cross-section; the entire cut surface reads as uniformly red or uniformly colorless with no distinguishable vascular pattern; or, contrary to the real phenomenon, the outer tissue is red while the central vessels are colorless.
level_2: Red appears somewhere on the cut surface but is not confined to the internal vascular bundles; for example only the outer rind/epidermis is red, the red forms a diffuse wash across the whole section rather than sitting in distinct strand-like spots, or red shows up in clearly non-xylem tissue such as the cortex or the central pith.
level_3: Red appears as separate strand-like spots scattered through the stem's interior, roughly matching where maize vascular bundles sit, and the tissue immediately next to them stays colorless; but the effect is weak: the red is faint or low-contrast against the surrounding tissue, a few spots show reddish bleed into neighboring tissue, or a light pink tinge shows on the phloem side.
level_4: Red dye is confined entirely to the xylem strands: small, distinct, scattered points concentrated toward the stem's interior in the scattered-bundle pattern typical of maize; every other tissue region (phloem, cortex, pith, epidermis) is clearly colorless; the edge between each red point and the surrounding pale tissue is crisp enough to tell apart at a glance under normal lighting.
level_5: Beyond the sharp red/colorless split above, the red spots sit irregularly scattered across the section rather than forming one neat ring (matching maize's scattered-bundle anatomy rather than a ring-forming dicot stem); the tissue directly surrounding every red xylem strand, where the phloem sits, stays visibly colorless with no pink halo or bleed-through into it; and the red itself reads as a plausible aqueous dye tone (a red or pink food-dye/eosin look), not an unnatural neon, purple, or orange cast.

Spatiotemporal Consistency rubric:
level_1: Severe continuity break: the seedling appears to jump directly from being in the container to already being cut, with no visible transition between the two; the cross-section appears before any cut is shown; the room lighting or shadow direction changes abruptly between the immersion shot and the cutting shot; the container or stem shape changes discontinuously; or the video is clearly a patchwork of unrelated shots.
level_2: Noticeable continuity break: the cut happens off-screen and the video cuts straight to an already-exposed cross-section; the seedling shifts position relative to the container or liquid level in a way the liquid itself doesn't match; the stem's orientation rotates or flips by more than roughly a quarter turn between the immersion shot and the cutting shot; a shadow suddenly points a different direction with no matching change in light source; or light passing through the container and liquid looks inconsistent with an actual liquid being present.
level_3: Minor continuity break: a hand or tool briefly blocks the view and the cross-section appears right after, but it's unclear whether that object is actually the blade; there is slight jitter or shake during the cutting motion; there is a brief flicker in brightness; or the cross-section is shown rotated by more than roughly 30 degrees relative to the stem's orientation just before the cut, though it is still clearly the same stem.
level_4: All level-3 conditions hold, AND the seedling stays fixed in position within the container throughout the immersion phase, then is lifted straight out along one continuous path with no abrupt jump before cutting begins; the blade approaches and touches the stem along one consistent path; the cutting motion is smooth and follows the stem's own axis; the cross-section appears immediately after the cut, viewed from essentially the same side and angle as the stem just before cutting; and there is no jump in lighting, shadow direction, or camera perspective between the immersion and cutting portions.
level_5: Beyond the above, there is no visible jump-cut or mismatched frame anywhere in the sequence; no motion blur obscures the red-versus-colorless boundary in the cross-section; the container's edges and the stem line up consistently with no odd parallax shift while the camera holds its view; the stem's proportions look natural throughout with no flattening or stretching; and the liquid's surface level in the container stays steady and undisturbed for as long as the seedling remains immersed.