Chapter 9- Transport in plants

Question 1

What is the need for transport for plants?

Answer 1

Metabolic demand
Size
Small SA:V ratio

Question 2

What is the need for transport in plants?

Answer 2

Metabolic demand
Size
Small SA:V ratio

Question 3

What are Dicotyledonous plants (Dicots)?

Answer 3

Make seeds that contain two organs that act as food stores(cotyledons)

Question 4

What are the 2 main types of dicots and their features?

Answer 4

Herbaceous- soft tissues and a relatively short lifecycle

Arborescent- woody and long life

Question 5

What is parenchyma?

Answer 5

Packing and supporting tissue which transports food and tannin deposits

Question 6

What are tannins?

Answer 6

A bitter chemical in parenchyma that deters predators

Question 7

What is plasmodesmata?

Answer 7

Microscopic channels in the cell walls which links to the cytoplasm for substance transport

Question 8

What are the 2 ways for water to move from the roots to the xylem of a plant?

Answer 8

Symplast pathway

Apoplast pathway

Question 9

What is the symplast?

Answer 9

Continuous cyptoplasm of living cells that is connected through plasmodestamta

Question 10

What is the symplast pathway?

Answer 10

1- Water moves through the symplast by osmosis
2- Water potential is high as joining cells do not contain water
3- After water leaves, water potential falls maintaining a steep concentration gradient

Question 11

What is the apoplast?

Answer 11

Space between cell walls and intercellular spaces

Question 12

What is the apoplast pathway?

Answer 12

1- Water fills between cavities
2- As H2O moves through cell walls, more water is pulled through apoplast due to cohesive forces between molecules.
3- The pull of water creates tension and a continuous flow of water

Question 13

What is suberin?

Answer 13

Waxy layer that lines the endodermis

Contains a waterproof layer that is called the casparian

Question 14

What is the transpiration pull?

Answer 14

1- Water molecules evaporate out of mesophyll layer surface through stomata into the air
2- Creating a lower H2O potential in that layer- H2O from cell below moves up
3- This process moves up into the xylem
4- Water molecules form hydrogen bonds with carbohydrates in the walls, this is called adhesion
5- Water molecules form the hydrogen bonds with each other and tend to stick together, this is called cohesion
6- Combined effects of adhesion and cohesion result in water capillary action which causes the H2O to rise up a narrow vessel against gravity

Question 15

What is the cohesion tension theory?

Answer 15

The model of water moving in a continuous stream up the xylem

Question 16

What is active loading?

Answer 16

Loading sucrose into sieve tube elements

High conc. of sugar in companion cells cause sucrose to diffuse into sieve tube elements

Question 17

What is translocation?

Answer 17

1- Hydrogen ions are transported from inside the companion cells across the membrane against the concentration gradient to the leaf tissue, this uses energy so is active
2- Hydrogen + ions and sucrose are diffused back into the companion cell down a concentration gradient. They are transported by a cotransporter protein
3- There is now a higher concentration of sucrose in the companion cells than the phloem which the sucrose diffuses into
4- As a result of the movement of sucrose, water moves into the cell via osmosis which increases turgor pressure due to rigid cell walls
5- Water moves into the tubes pf the sieve tube elements which reduces pressure in the companion cells

Question 18

What are xerophytes and their adaptions?

Answer 18

Plants in desert regions or icy and cold places
Adaptions- thick waxy cuticles, sunken stomata, reduced stomata, reduced leave/curled leaves, hairy leaves, leaf loss and deep reaching tap roots

Question 19

What are hydrophytes and their adaptions?

Answer 19

Found in water
Have floating leaves for photosynthesis
Adaptions- very thin waxy cuticle, many open stomata with inactive guard cells, reduced structure, large flat leaves, large SA:V ratio

Question 20

What is aerenchyma?

Answer 20

Supporting tissue found in stems and roots
Makes leaves and stems buoyant
Forms low resistance pathway for movement of substances

Question 21

What are mesophytes?

Answer 21

Land plants that have a waxy cuticle and green leaves

Well developed root systems that provide anchorage and allows for efficient absorption of H2O and minerals