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 — Foundation · 4.2.3.1
Revise AQA GCSE Combined Science: Trilogy (8464) — Biology — Foundation 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 is the role of epidermal tissue in plants?
It covers and protects plant surfaces.
How is the epidermis of a leaf usually arranged?
It is usually a single layer of closely packed cells.
Why is the upper epidermis of a leaf transparent?
It allows light to reach the mesophyll.
What is the function of the waxy cuticle on a leaf?
It reduces water loss.
What are stomata, and what cells surround each one?
Stomata are pores in the epidermis, each surrounded by a pair of guard cells.
How do changes in guard cells open or close a stoma?
Changes in their water content alter their shape, opening or closing the pore.
What do stomata regulate by opening and closing?
Gas exchange and water loss.
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 is translocation in plants?
The transport of dissolved sugars and other organic substances around the plant through the phloem.
How are phloem sieve tubes formed?
Living sieve tube cells join end to end.
What are sieve plates, and how do they allow substances to move?
They are sieve tube cell end walls with pores through which substances can move.
What role do companion cells play in phloem transport?
They support sieve tubes and supply energy for transport.
Between which regions do substances move during translocation?
From regions where they are produced or released to regions where they are used or stored.
In which direction can substances travel through the phloem?
In either direction through the plant.
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.