Transport In Plants Flashcards

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1
Q

why do plants need transport systems?

A
  • They have a small surface area to volume ratio.

- They have a high metabolic rate.

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2
Q

What is the function of Xylem tissue?

A
  • Transports water and mineral ion solutions.

- these substances move up the plant from the root to the leaves.

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3
Q

What is the function of phloem tissue?

A
  • Transports sugars both up and down the plant.
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4
Q

What does transverse mean?

A
  • The sections are cut through each structure at a right angle to its length.
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5
Q

What is the structure of a root?

A
  • Xylem and phloem are in the centre to profile support for the root at it pushes through the soil.
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6
Q

What is the structure of a stem?

A
  • Xylem and phloem are near the outside to provide a sort of ‘scaffolding’ that reduces bending.
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7
Q

What is the structure of a leaf?

A
  • Xylem and phloem make Iona network of veins which support the thin leaves.
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8
Q

What is a xylem vessel?

A
  • The part of the tissue that actually transports the water ions.
  • Very long, tube-like structures formed from cells joined end to end.
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9
Q

Adaptations of xylem vessels

A
  • No end walls, making an uninterrupted tube that allows water to puss up through the middle easily.
  • Cells are dead, so they contain no cytoplasm.
  • Cell walls are thickened with lignin which helps to support the walls and stops them collapsing inwards.
  • Lignin is deposited in a spiral which allows flexibility and prevents the stem the stem from breaking.
  • There are small pits so water and mineral ions move into and out of the vessels whenever.
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10
Q

Adaptations of phloem tissue

A

Contains…

  • Phloem fibres.
  • Phloem parenchyma.
  • Sieve tube elements.
  • Companion cells.
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11
Q

What are sieve tube elements?

A
  • Living cells that form the tube for transporting sugars through the plant.
  • They are joined end to end to form sieve tubes.
  • The ‘sieve’ parts are the end walls, which have lots of holes in them to allow solutes to pass through.
  • They have a thin layer of cytoplasm and few organelles to make it easier for solutes to pass though).
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12
Q

What are companion cells?

A
  • Lack of a nucleus and organelles means sieve tube tube elements can’t survive on their own.
  • Therefore, there is a companion cell for every sieve tube element.
  • Companion cells carry out the living functions for both themselves and their sieve cells.
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13
Q

How to perform a plant dissection p

A
  • Use a scalpel to cut a cross-section of the stem.
  • Use tweezers to gently place the cut sections in water until you come to use them.
  • Add a drop of water to a microscope slide, add the plant section and add one or two drops of a stain.
  • Carefully apply a cover slip so you have created a wet mount.
  • View the specimen under a light microscope and draw a labelled diagram of what you observe.
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14
Q

How does water enter a plant?

A
  • Water enters through the root hair cells (root) and the passes through the root cortex, including the endodermis, to reach the xylem.
  • Water is drawn into the root via osmosis.
  • Water moves from an area of high water potential to low water potential, down a water potential gradient.
  • Roots tend to have a high water potential and leaves have a lower water potential (because water constantly evaporated from them).
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15
Q

Symplast pathway

A
  • Water moves through the cytoplasm. The cytoplasm of neighbouring cells connect through plasmodesmata. (Via osmosis).
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16
Q

The apoplast pathway

A
  • Water Goes through non-living parts of the cell (cell walls).
  • When Water gets to the endodermis cells in the root, it’s path is blocked by a waxy strip in the cell walls, called the Casparian strip.
  • This forces the water down to the symplast pathway (cytoplasm). This is useful because it means water has to go through a plasma membrane which is partially permeable and it able to control whether or not substances in the water get through.
17
Q

How is water transported through leaves?

A
  • Water moves through Apoplast pathway.
  • When the stomata open, water evaporates (diffuses out the leaves down the water potential gradient) into surrounding air.
18
Q

How does cohesion and tension help water move up plants?

A
  • Watee evaporates from the leaves at the top of the xylem (transpiration).
  • This creates a tension (suction) which pull more water to the leaves.
  • Water molecules are cohesive (stick together) so when some are pulled into the leaf, others follow.
19
Q

How does adhesion help water move up plants?

A
  • Water molecules are attracted to the walls of the xylem vessels, which helps water to rise up through the xylem vessels.