Transport In Plants

Question 1

why do plants need transport systems?

Answer 1

• They have a small surface area to volume ratio.

- They have a high metabolic rate.

Question 2

What is the function of Xylem tissue?

Answer 2

• Transports water and mineral ion solutions.

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

Question 3

What is the function of phloem tissue?

Answer 3

• Transports sugars both up and down the plant.

Question 4

What does transverse mean?

Answer 4

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

Question 5

What is the structure of a root?

Answer 5

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

Question 6

What is the structure of a stem?

Answer 6

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

Question 7

What is the structure of a leaf?

Answer 7

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

Question 8

What is a xylem vessel?

Answer 8

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

Question 9

Adaptations of xylem vessels

Answer 9

• 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.

Question 10

Adaptations of phloem tissue

Answer 10

Contains…

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

Question 11

What are sieve tube elements?

Answer 11

• 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).

Question 12

What are companion cells?

Answer 12

• 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.

Question 13

How to perform a plant dissection p

Answer 13

• 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.

Question 14

How does water enter a plant?

Answer 14

• 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).

Question 15

Symplast pathway

Answer 15

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

Question 16

The apoplast pathway

Answer 16

• 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.

Question 17

How is water transported through leaves?

Answer 17

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

Question 18

How does cohesion and tension help water move up plants?

Answer 18

• 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.

Question 19

How does adhesion help water move up plants?

Answer 19

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