3.3 Transport in Plants Flashcards

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1
Q

How many transport systems do plants have?

A

2 - xylem and phloem

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2
Q

Draw out where the xylem and phloem (vascular bundle) are located in the roots stem and leaves

A
  1. roots - xylem and phloem located in centre to provide support as they push through soil. find picture to check
  2. Stems - located near outside in a ring to provide structure and stop plant from bending. check with pic
  3. Leaves- make up network of veins to support thin leaves. check pic
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3
Q

What are the adaptations of a xylem?

A
  • made of xylem vessels which are long and tube shaped and have no end walls to allow water to pass up.
  • made of dead cells so have no cytoplasm and more room for water to pass up.
  • Holes in walls called pits that allow ions to move in/out.
  • walls supported by being thickened with lignin a woody substance to stop xylem walls from collapsing. Lignin can be deposited in spirals or rings.
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4
Q

What does the xylem do?

A

Transports water and mineral ions in a solution up a plant / up transpiration stream.

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5
Q

What is transpiration?

A

The loss of water vapour through evaporation via the stomata.

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6
Q

How does water movement through a plant happen from start to end (hint starts at root).

A
  1. water moves into roots
  2. water moves from roots to xylem
  3. water moves up xylem vessel towards leaves
  4. water is lost by transpiration
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7
Q

What are the two pathways in which water can enter roots.

A
  • symplast pathway
  • apoplast pathway
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8
Q

How does water enter the roots ?

A

by osmosis down a water potential gradient

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9
Q

Describe how water moves through the symplast pathway.

A

Water moved through the living part of the cell (cytoplasm) from cell to cell. Cells have channels called plasmodesmata which connect the cytoplasm between cells. It moved via osmosis.

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10
Q

Describe how water moves through the apoplast pathway.

A

Water moves through the dead part of the cells in the root (cell walls) by diffusion. However when water reaches the endodermis layer the cells have a band of waxy layer called the suberin this band is called the casparian strip. This stops water moving by cell walls and so water has to enter the symplast pathway.

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11
Q

How does transpiration happen?

A

Due to gas exchange.
Water at the top of a plant enters the leaves by the apoplast pathway from xylem.
The stomata open for gas exchange and water evaporates from a higher water potential out into the air where there’s a lower water potential.

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12
Q

What forces helps the water move up the xylem vessels and what are they?

A
  • Cohesion ( water molecules attracted) this reduces hydrostatic pressure causing a pull like motion of water molecules towards the stomata.
  • Adhesion (water molecules attracted to xylem walls) this helps water move up vessel
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13
Q

What are the limiting factors for transpiration?

A
  • Light intensity. (low)
  • Temperature. (low)
  • Humidity. (high)
  • Wind. (low)
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14
Q

Explain how light intensity is a limiting factor.

A

High light intensity allows the stomata to open so increases rate of evaporation. If light is low then it’s the limiting factor.

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15
Q

Explain how temperature is a limiting factor.

A

At higher temperatures, water molecules have more energy and so end up moving faster. If the temp is low the water molecules have less energy so slows down rate of transpiration.
also it increases the concentration gradient between the outside of the plant and the inside of the

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16
Q

Explain how humidity is a limiting factor.

A

If there’s a low humidity, the air is dryer, so there’s an increase in the water potential gradient. This increases the rate of evaporation. Therefore high humidity is a limiting factor as less water will be evaporated due to a less steep concentration gradient.

17
Q

Explain how wind is a limiting factor .

A

If there’s more wind, there’s more air movement, and this blows water away from stomata. This increases the water potential gradient. If there’s no wind this doesn’t happen.

18
Q

How are xerophytic plants adapted to live? Give an example of a xerophyte too.

A

Xerophytes are adapted to live in dry climates.
Include cacti and marram grass.
Have thick waxy layer on epidermis, spines not leaves to reduce SA, closed stomata in day, stomata in pits, hairs to trap moist air.
This all prevents too much water loss from transpiration.

19
Q

How are hydrophytic plants adapted to live in their conditions?
Give an example of one too.

A

Hydrophytes live in aquatic conditions.
Include water lilies.
Have air spaces, stomata only on upper surface of leaves, flexible leaves.
These help them to cope with low 02 levels.

20
Q

How is phloem tissue adapted?

A

Phloem tissue is made of living cells (sieve tube elements). They have a thin layer of cytoplasm but no nucleus. Sieve tube elements are joined together by sieve plates that have holes in to allow solutes to pass through.
Because sieve tube elements have no nucleus can’t survive on their own so each have a companion cell. These have a nucleus and lots of mitochondria.

21
Q

What is translocation?

A

The movement of assimilates to where they are needed in a plant via the phloem.

22
Q

Is translocation an active or passive process ?

A

Active as needs energy (ATP)

23
Q

Where do substances move to and from in translocation?

A

From the source to the sink

24
Q

what’s a source ?

A

Where a substance is made

25
Q

what’s a sink?

A

where the substance is used up

26
Q

What are assimilates?

A

Dissolved substances like sucros and amino acids ext.

27
Q

What is the mass flow hypotheses? (Draw it out)

A

check cards

28
Q

Explain the process of translocation and draw out the diagram.

A

check card paper
Diagram with source sink ect