This packet is everything a parent or guide needs to assess Unit 04 at home — learning targets, the answers that count as correct, the mastery rubric, calibration examples, and a clipboard score sheet. No multiple-choice test: the student shows mastery by measuring transpiration with a potometer and reasoning from water potential and cohesion-tension aloud.
By the end of the Water & Nutrient Transport unit, a student should be able to:
Six criteria, each judged Not yet / Approaching / Mastered (Page 3).
Measure water uptake under changing conditions.
The student reasons from water potential and cohesion-tension aloud (Page 4).
Uptake readings, conditions, and conclusions kept distinct.
You are making a decision, not adding up points. For each criterion, decide whether the work is Not yet, Approaching, or Mastered — the column language tells you which. A criterion counts as mastered only when the student can both take the measurement and justify the plant biology behind it. A student carries three tokens per term; one token buys a re-do of one criterion on another day, so a single bad afternoon never sinks the unit.
Accept any answer in the synonyms column — they are pre-approved as equivalent. The third column flags the confusions that look close but are not yet, so you can coach precisely.
| Canonical answer | Accepted synonyms | Common confusion / discriminator |
|---|---|---|
| Water movement | ||
| Water potential | Ψ ; water free energy | Water flows from high to low potential — the driving force |
| Transpiration | leaf water loss | Evaporation from the leaves that pulls the water column |
| Cohesion-tension | cohesion-tension theory | Pull from the leaves + water sticking together = lift |
| Xylem | water tissue | Carries the transpiration stream up; dead hollow cells |
| Stomata & phloem | ||
| Guard cells | stomatal cells | Swell and shrink to open and close a stoma |
| Stoma (stomata) | leaf pore | Balances CO₂ intake against water loss |
| Phloem | sugar tissue | Moves sugar from source to sink by pressure-flow |
| Pressure-flow | mass flow | Sugar loaded at the source raises pressure that pushes sap to sinks |
| Nutrition | ||
| Mineral nutrient | essential element | Pulled from the soil by roots; e.g. nitrogen, phosphorus, potassium |
| Source | sugar source | Where sugar is made and loaded into phloem (a leaf) |
| Sink | sugar sink | Where sugar is used or stored (a root, fruit, growing tip) |
| Root hair | absorptive cell | Where the root absorbs water and minerals — leaves don't absorb |
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Water potential | Thinks water simply moves “up” with no driving force. | Defines water potential but cannot predict flow direction from it. | Uses water potential to predict which way water moves between soil, root, stem, leaf, and air. |
| Transpiration & cohesion-tension | Believes the plant pushes water up from the roots. | Knows leaves lose water but not how that pulls the column upward. | Explains how transpiration at the leaves creates tension that pulls a cohesive water column up the xylem — roots absorb while leaves pull. |
| Stomatal control | Sees stomata as fixed holes that never change. | Knows guard cells open stomata but not what triggers it. | Explains how guard cells swell and shrink to open and close stomata, balancing CO₂ intake against water loss. |
| Phloem translocation & mineral nutrition | Confuses phloem transport with the xylem stream. | Knows phloem carries sugar but not the pressure-flow mechanism. | Explains pressure-flow from source to sink and names the essential mineral elements and their roles. |
| Lab technique (transpiration & the potometer) | Cannot seal the potometer or gets no measurable uptake. | Takes readings but ignores temperature, humidity, or air-flow effects. | Sets up a potometer, measures water uptake under changing conditions, and links the rate back to transpiration. |
| Integration (cross-domain) | Treats the science as isolated facts. | Names a link to history, reading, or writing but cannot defend it. | Connects the unit across History · Reading · Writing and defends why it matters. |
The split between Approaching and Mastered is pulled, not pushed: not just noting leaves lose water, but explaining how that loss lifts the whole column. Ask “so what actually moves the water — the roots or the leaves?”
Read these before you grade. They show what Mastered and Not yet actually sound like, plus the edge cases where you should coach rather than decide on the spot.
Student: ______________________________________ Date: _______________ Guide: _________________________
| # | Criterion | Decision | Notes |
|---|---|---|---|
| 1 | Water potential | NY / Appr / Mast | |
| 2 | Transpiration & cohesion-tension | NY / Appr / Mast | |
| 3 | Stomatal control | NY / Appr / Mast | |
| 4 | Phloem translocation & mineral nutrition | NY / Appr / Mast | |
| 5 | Lab technique (transpiration & the potometer) | NY / Appr / Mast | |
| 6 | Integration (cross-domain) | NY / Appr / Mast |
☐ No ☐ Yes — for criterion: __________ Tokens remaining: ☐ 3 ☐ 2 ☐ 1 ☐ 0
NY = Not yet · Appr = Approaching · Mast = Mastered · Unsure between two levels? Circle the lower one and note what a re-do would need.