What is a leaf in terms of its tissue organisation?
A plant organ made of different tissues working together.
AQA GCSE Combined Science: Trilogy (8464) — Biology — Higher · 4.2.3.1
Revise AQA GCSE Combined Science: Trilogy (8464) — Biology — Higher specification point 4.2.3.1, Plant tissues, with free active-recall flashcards. Flip through the set or review every question and answer below.
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What is a leaf in terms of its tissue organisation?
A plant organ made of different tissues working together.
How are the epidermis, palisade mesophyll and spongy mesophyll arranged in a leaf?
The epidermis covers the leaf. Palisade mesophyll lies beneath the upper epidermis, with spongy mesophyll below it.
What do spaces in the spongy mesophyll connect with?
Stomata in the epidermis.
What cells surround each stoma?
Guard cells.
Which two transport tissues do leaf veins contain?
Xylem and phloem.
What does the arrangement of leaf tissues achieve for photosynthesising cells?
It brings them light, gases and water and connects the leaf to transport tissues.
What process is palisade mesophyll specialised for?
Photosynthesis.
What are the shape and arrangement of palisade mesophyll cells?
They are elongated and closely packed.
How are palisade mesophyll cells adapted to absorb light?
They contain many chloroplasts.
Where is palisade mesophyll located in a leaf?
Near the upper surface.
Through which leaf tissue does light pass to reach the palisade mesophyll?
The epidermis.
How are spongy mesophyll cells arranged in a leaf?
They are loosely arranged, with large air spaces between them.
How do air spaces in the spongy mesophyll help gases diffuse through a leaf?
They allow carbon dioxide to reach photosynthesising cells, and oxygen and water vapour to move towards the stomata.
What is the role of chloroplasts in spongy mesophyll cells?
They enable the cells to carry out photosynthesis.
How does the number of chloroplasts in spongy mesophyll cells generally compare with that in palisade cells?
Spongy mesophyll cells generally have fewer chloroplasts.
What type of cells does meristem tissue contain, and what can they continue to do?
Unspecialised cells that can continue to divide by mitosis.
Where are the meristems that support root and shoot growth located?
At the growing tips of roots and shoots.
How do meristems support the growth of roots and shoots?
They produce new cells, allowing these regions to grow.
What can new cells produced by meristems become as a plant develops?
They can differentiate into specialised plant cells, supplying tissues needed for development.
What is the role of epidermal tissue on plant surfaces?
It forms a covering that protects the tissues beneath.
How are leaf epidermal cells generally arranged, and what is their appearance?
They form a closely packed, transparent layer.
Why is the transparency of the leaf epidermis important?
It allows light to reach photosynthesising cells.
What is the role of the waxy cuticle on the outer surface of the leaf epidermis?
It reduces water loss by evaporation.
What is translocation in plants?
The transport of dissolved sugars between parts of a plant by phloem.
In phloem transport, what are sugar sources and where are sugars transported to?
Sources are regions where sugars are produced or released from storage. Sugars move to regions where they are used or stored.
In which direction can sugars travel through a plant in the phloem?
In either direction.
How are phloem sieve tubes formed?
Living cells join end to end.
What are sieve plates, and what do they allow?
They are perforated end walls that allow dissolved substances to move between sieve-tube cells.
What is the role of companion cells in phloem?
They support sieve-tube cells and provide energy for loading and unloading substances.