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Flip to reveal answersWhich leaf layer carries out most of the photosynthesis?
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All 12 Flashcards — Leaf structure for photosynthesis
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Question
Which leaf layer carries out most of the photosynthesis?
Answer
The **palisade mesophyll** — tall cells packed with chloroplasts near the top of the leaf.
Question
How do you identify the palisade mesophyll on a leaf cross-section?
Answer
Look for a layer of **tall, column-shaped cells packed with chloroplasts, just below the upper surface**.
Question
What is the palisade mesophyll?
Answer
A layer of **tall, chloroplast-packed cells** just under the upper surface that does **most of the leaf's photosynthesis**.
Question
What is the spongy mesophyll, and how does it help photosynthesis?
Answer
A layer of **loosely-packed cells with large air spaces**; the spaces let **CO₂ diffuse** to every photosynthesising cell.
Question
Why are the waxy cuticle and upper epidermis transparent?
Answer
They have **no chloroplasts**, so they are clear and let **light pass through** to the palisade cells below.
Question
Why is a leaf broad and flat?
Answer
To give a **large surface area** for absorbing light (and for gas exchange).
Question
Why is a leaf thin?
Answer
So light and **CO₂ only travel a short distance** to reach the chloroplasts.
Question
Where is the palisade mesophyll positioned, and why there?
Answer
**Near the top**, just below the upper epidermis — where the **light is brightest**, so it absorbs the most light.
Question
What do the veins (xylem and phloem) do for photosynthesis?
Answer
**Xylem** brings **water** (a raw material); **phloem** carries away the **sugars** made.
Question
Which three raw materials/conditions does a leaf supply for photosynthesis?
Answer
**Light** (captured by the broad, transparent-topped leaf), **CO₂** (in through stomata) and **water** (up the xylem).
Question
How can you tell the palisade mesophyll from the spongy mesophyll?
Answer
**Palisade** = tall, packed cells near the **top**; **spongy** = loose, rounded cells with **air spaces lower down**.
Question
What lets CO₂ enter the leaf to reach the chloroplasts?
Answer
The **stomata** (pores controlled by **guard cells**), mainly on the lower surface.
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Topic 3.3 hub
Photosynthesis
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