Structure of Transport Tissues (Cambridge (CIE) AS Biology): Flashcards
Exam code: 9700
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Define plan diagram.
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Define plan diagram.
A plan diagram shows the distribution of tissues in a section, with no individual cells drawn.
What are the rules for drawing a plan diagram (tissue map) of a transverse section?
Draw only the outlines of tissues.
Do not draw individual cells.
Keep tissues in the correct proportions, with no shading.
What is a herbaceous dicotyledonous plant?
A non-woody plant whose seeds contain two cotyledons (seed leaves).
Which three plant organs should you be able to draw in transverse section?
The stem, the root and the leaf.
A plan diagram shows the of tissues but not individual cells.
A plan diagram shows the distribution of tissues but not individual cells.
True or False?
Individual cells should be drawn on a plan diagram.
False.
A plan diagram shows only the outlines and distribution of tissues, never individual cells.
Define vascular bundle.
A vascular bundle is a strand of transport tissue containing both xylem and phloem.
Describe the distribution of xylem and phloem in a dicotyledonous stem.
Vascular bundles are arranged in a ring near the outer edge.
In each bundle the xylem is towards the inside and the phloem towards the outside.
Describe the distribution of xylem and phloem in a dicotyledonous root.
The vascular tissue is in the centre of the root.
The xylem forms a central X (star) shape, with phloem between its arms.
Describe the distribution of xylem and phloem in a dicotyledonous leaf.
Vascular bundles run through the midrib and veins.
The xylem lies on the upper side and the phloem on the lower side of each bundle.
In a dicotyledonous root, the xylem and phloem are found in the of the root.
In a dicotyledonous root, the xylem and phloem are found in the centre of the root.
In a dicotyledonous stem, the vascular bundles are arranged in a near the outer edge.
In a dicotyledonous stem, the vascular bundles are arranged in a ring near the outer edge.
Define xylem.
Xylem is the tissue that transports water and mineral ions from the roots up the plant, and provides support.
Describe the structure of a xylem vessel element.
It is a dead, empty cell with no cytoplasm or organelles.
The end walls have broken down to form a continuous hollow tube (lumen).
The walls are thickened with lignin and contain pits.
Relate the structure of a xylem vessel to its function.
No end walls and no cytoplasm give an uninterrupted, low-resistance column for water flow.
Lignin strengthens the walls, giving support and stopping them collapsing under tension.
Pits allow water to move sideways between vessels.
Define lignin.
Lignin is a strong, waterproof substance that thickens and strengthens xylem cell walls.
What are pits and why are they important in xylem vessels?
Pits are non-lignified gaps in the vessel wall.
They allow water to move sideways between neighbouring vessels.
Xylem vessel walls are strengthened and waterproofed by .
Xylem vessel walls are strengthened and waterproofed by lignin.
True or False?
Xylem vessel elements are living cells.
False.
Xylem vessel elements are dead and empty, with no cytoplasm, which allows free water flow.
Define phloem.
Phloem is the living tissue that transports assimilates, such as sucrose and amino acids, around the plant.
Describe the structure of a sieve tube element.
A living cell with little cytoplasm and no nucleus.
Its end walls form perforated sieve plates.
The cells are joined end to end into a continuous tube.
Define sieve plate.
A sieve plate is the perforated end wall between sieve tube elements, whose pores allow sap to flow through.
How is a companion cell adapted to its function?
It has dense cytoplasm and many mitochondria.
These provide the ATP needed to actively load sucrose into the phloem and to carry out the metabolism of the sieve tube element.
Why do sieve tube elements need companion cells?
Sieve tube elements have no nucleus and few organelles.
The companion cell carries out the metabolic functions that keep the sieve tube element alive and working.
The perforated end walls between sieve tube elements are called .
The perforated end walls between sieve tube elements are called sieve plates.
Companion cells contain many to provide ATP for loading sucrose.
Companion cells contain many mitochondria to provide ATP for loading sucrose.
How is the structure of a sieve tube element related to its function?
It has no nucleus and only a thin layer of cytoplasm around the edge.
This maximises space and reduces friction, allowing assimilates (sap) to flow through with little resistance.
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