Plant Tissues, Organs and Systems

This section covers plant tissues, organs and systems. Including structure and functions of leaves and stems and roots and xylem and phloem transport systems. 

Photosynthetic Organism

Plants are photosynthetic organisms, meaning they produce their own food using photosynthesis. This process occurs in the chloroplasts of plant cells, where chlorophyll absorbs light energy to convert carbon dioxide and water into glucose and oxygen.

Key Points:

• Photosynthesis provides the plant with glucose for energy and growth.
• Oxygen is released as a by-product and used by living organisms for respiration.
• The rate of photosynthesis is affected by light intensity, carbon dioxide concentration, and temperature.

Leaves: Structure and Function

The leaf is the primary site of photosynthesis and is adapted for efficient gas exchange and light absorption.

Leaf Adaptations:

• Large Surface Area – Maximises light absorption.
• Thin Structure – Reduces diffusion distance for gases.
• Chloroplasts in Palisade Cells – Contain chlorophyll for photosynthesis.
• Stomata on Lower Epidermis – Allow gas exchange and control water loss.
• Waxy Cuticle – Reduces water loss via evaporation.

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Stem and Roots

The stem and roots play essential roles in transport and support:

• Stem: Supports the plant and transports water, minerals, and food.
• Roots: Absorb water and minerals from the soil and anchor the plant.
• Root Hair Cells: Specialised for absorption due to a large surface area and thin walls.

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Xylem and Phloem: Transport Systems

Plants contain two key transport tissues: xylem and phloem.

Xylem (Water Transport)

• Transports water and minerals from the roots to the leaves.
• Made of dead cells forming hollow tubes.
• Strengthened with lignin to provide structural support.
• Uses the transpiration stream, where water evaporates from the leaves, creating a continuous flow.

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Phloem (Food Transport)

• Transports sugars (e.g., glucose) and amino acids from the leaves to other parts of the plant.
• Made of living cells with perforated ends, forming sieve tubes.
• Uses translocation, an active process requiring energy.

Root Hair Cells

Root hair cells are specialised for absorbing water and minerals efficiently:

• Large surface area increases absorption.
• Thin walls allow quicker diffusion.
• Mitochondria provide energy for active transport of minerals from soil.

The structure of plant tissues, organs, and systems ensures efficient photosynthesis, transport, and growth. Understanding these adaptations helps explain how plants survive and function in different environments.