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Adaptation - Adaptations in Plants (Xerophytes, Mesophytes, Hydrophytes)

Grade 6ICSE

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

🔑Concepts

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Adaptation is the process where a plant or animal becomes better suited to its environment through structural or functional changes.

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Hydrophytes are plants adapted to live in aquatic environments (H2OH_2O). They have features like aerenchyma (air cavities) for buoyancy and a waxy coating to prevent decay.

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Mesophytes are plants that grow in conditions with moderate H2OH_2O supply. They have well-developed root systems and stomata usually located on the underside of the leaves.

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Xerophytes are plants adapted to survive in habitats with very little H2OH_2O, such as deserts. They exhibit modifications like thick cuticles, sunken stomata, and succulent stems to store water.

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Transpiration is the loss of H2OH_2O vapor from the aerial parts of the plant. Xerophytes minimize this to conserve moisture, while Hydrophytes have limited or no stomata on submerged parts.

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In Xerophytes like Opuntia, the stem becomes flattened and green to perform photosynthesis, a condition known as phylloclade, while leaves are reduced to spines to prevent water loss.

📐Formulae

6CO2+6H2O→light/chlorophyllC6H12O6+6O26CO_2 + 6H_2O \xrightarrow{\text{light/chlorophyll}} C_6H_{12}O_6 + 6O_2

Rate of Transpiration∝1Humidity\text{Rate of Transpiration} \propto \frac{1}{\text{Humidity}}

Surface Area to Volume Ratio↓  ⟹  Water Loss↓\text{Surface Area to Volume Ratio} \downarrow \implies \text{Water Loss} \downarrow

💡Examples

Problem 1:

Why do the leaves of the Lotus plant (a Hydrophyte) float on the surface of H2OH_2O, and why is the upper surface waxy?

Solution:

The leaves contain large air spaces called aerenchyma for buoyancy, and the upper surface is coated with a waxy layer.

Explanation:

Aerenchyma allows the leaf to stay afloat to receive sunlight for photosynthesis. The waxy coating prevents H2OH_2O from clogging the stomata (which are on the upper surface) and prevents the leaf from rotting.

Problem 2:

Identify the type of plant that has 'sunken stomata' and explain its advantage.

Solution:

Xerophytes (e.g., Pine, Nerium).

Explanation:

Sunken stomata are located deep in the leaf tissue, which creates a pocket of moist air, reducing the diffusion gradient and thereby significantly lowering the rate of transpiration to conserve H2OH_2O.

Problem 3:

A plant has a taproot system that goes very deep into the soil. Which category does it likely belong to?

Solution:

Xerophyte.

Explanation:

Xerophytes develop long, extensive root systems to reach deep underground H2OH_2O tables in arid regions where the topsoil is dry.