A leaf is an organ: tissue layers have different tasks
| English | 中文 | Pinyin |
|---|---|---|
| palisade mesophyll/ˈpælɪseɪd ˈmesəfɪl/ | 栅栏叶肉 | zhà lán yè ròu |
| stoma/ˈstəʊmə/ | 气孔 | qì kǒng |
What would explain this observation?
- The upper leaf layer admits light while inner tissues exchange gases and photosynthesize. A leaf cross-section explains how several tissue types cooperate.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Epidermal tissue forms an outer covering. Palisade mesophyll 栅栏叶肉 has many chloroplasts and is suited to photosynthesis. Spongy mesophyll contains air spaces aiding gas movement. Xylem supplies water and mineral ions; phloem transports dissolved sugars. Guard cells surround stomata and change their opening. Meristems at growing shoot and root tips produce cells that can differentiate.
- palisade mesophyll: Leaf tissue with cells rich in chloroplasts; stoma 气孔: A leaf-surface opening bordered by guard cells.
Which tissue is especially associated with many chloroplasts?
A tissue is defined by its cells and role, while the whole leaf is an organ. Light reaching palisade cells supports photosynthesis, and a short gas pathway through air spaces supports exchange. A vascular bundle contains distinct transport tissues; it is not one tube carrying every substance in the same way.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- A tissue is defined by its cells and role, while the whole leaf is an organ. Light reaching palisade cells supports photosynthesis, and a short gas pathway through air spaces supports exchange. A vascular bundle contains distinct transport tissues; it is not one tube carrying every substance in the same way.
- Observe a prepared transverse leaf section or attributed micrograph. Draw visible layers with clear labels and a scale. Identify palisade versus spongy tissue from organization and spaces rather than colour alone. Include guard cells and stomata only where the actual section or supplied diagram shows them.
Which two habits make the investigation or model in this case more defensible?
Observe a prepared transverse leaf section or attributed micrograph. Draw visible layers with clear labels and a scale. Identify palisade versus spongy tissue from organization and spaces rather than colour alone. Include guard cells and stomata only where the actual section or supplied diagram shows them.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: a fictional microscope field covers 0.50 mm² and contains 12 stomata. Recorded density=12/0.50=24 stomata/mm². Compare several fields selected by a defined sampling rule, rather than choosing the field with the most stomata.
A field of 0.25 mm² contains 10 stomata. Calculate stomatal density. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
A field of 0.25 mm² contains 10 stomata. Calculate stomatal density.
The result is 40 per mm². Known: a fictional microscope field covers 0.50 mm² and contains 12 stomata. Recorded density=12/0.50=24 stomata/mm². Compare several fields selected by a defined sampling rule, rather than choosing the field with the most stomata.
Check the conclusion and its limits
- A stoma is the opening, while guard cells are the cells around it. Meristem is plant growth tissue, not a vessel moving sap. Every plant leaf need not have exactly the same arrangement as a standard schematic.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
A stoma and its surrounding guard cells are the same structure. This claim is false: A stoma is the opening, while guard cells are the cells around it. Meristem is plant growth tissue, not a vessel moving sap. Every plant leaf need not have exactly the same arrangement as a standard schematic.
A leaf is an organ: tissue layers have different tasks: A tissue is defined by its cells and role, while the whole leaf is an organ. Light reaching palisade cells supports photosynthesis, and a short gas pathway through air spaces supports exchange. A vascular bundle contains distinct transport tissues; it is not one tube carrying every substance in the same way.
A stoma and its surrounding guard cells are the same structure.
A stoma is the opening, while guard cells are the cells around it. Meristem is plant growth tissue, not a vessel moving sap. Every plant leaf need not have exactly the same arrangement as a standard schematic.
Leaf tissue with cells rich in chloroplasts: write the technical term.
palisade mesophyll means Leaf tissue with cells rich in chloroplasts.