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Plants - Structure of Leaf and Roots

Grade 6Cambridge (IGCSE)

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Photosynthesis is the process by which plants make food using light energy, which primarily occurs in the leaves containing chlorophyll.

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The Waxy Cuticle is a waterproof layer on top of the leaf that prevents excessive loss of H2OH_2O through evaporation.

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The Palisade Mesophyll consists of tall, cylindrical cells packed with chloroplasts to maximize the absorption of light for photosynthesis.

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The Spongy Mesophyll has large air spaces between cells to allow for the efficient diffusion of gases like CO2CO_2 and O2O_2.

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Stomata are small pores, mostly on the underside of the leaf, controlled by guard cells to regulate gas exchange and the loss of water vapor (transpiration).

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Vascular Bundles contain the Xylem, which transports H2OH_2O and minerals from roots to leaves, and the Phloem, which transports glucose/sucrose produced during photosynthesis.

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Root Hair Cells have long, finger-like projections that significantly increase the surface area for the absorption of H2OH_2O via osmosis and mineral ions via active transport.

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The Root Cap protects the growing tip of the root as it pushes through the soil.

📐Formulae

Carbon Dioxide+Water→Light energyGlucose+Oxygen\text{Carbon Dioxide} + \text{Water} \xrightarrow{\text{Light energy}} \text{Glucose} + \text{Oxygen}

6CO2+6H2O→C6H12O6+6O26CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2

Rate of Photosynthesis∝Light Intensity\text{Rate of Photosynthesis} \propto \text{Light Intensity}

💡Examples

Problem 1:

Explain why most of the stomata are found on the lower epidermis of a leaf rather than the upper epidermis.

Solution:

To reduce water loss through transpiration.

Explanation:

The upper surface of the leaf is directly exposed to sunlight, which increases temperature. By having stomata on the cooler, shaded underside, the plant minimizes the evaporation of H2OH_2O while still allowing CO2CO_2 to enter for photosynthesis.

Problem 2:

How does the structure of a root hair cell help in the uptake of H2OH_2O and minerals?

Solution:

The long extension increases the surface area to volume ratio.

Explanation:

A higher surface area allows more H2OH_2O molecules to pass through the cell membrane at once via osmosis. It also provides more space for carrier proteins involved in the active transport of mineral ions like NO3−NO_3^- (nitrates) from the soil.

Problem 3:

Identify the chemical symbol for the gas required by the spongy mesophyll for photosynthesis and the gas produced as a byproduct.

Solution:

Required: CO2CO_2; Produced: O2O_2.

Explanation:

Plants take in Carbon Dioxide (CO2CO_2) from the atmosphere and release Oxygen (O2O_2) as a waste product of the photosynthetic reaction.