Plant Osmoregulation - C6

Question 1

What are the main plant organs?

Answer 1

Roots, shoots (stem, leaf, bud, flower, fruit)

Question 2

What are the three kinds of non-replicating plant tissues?

Answer 2

Ground: support, storage & photosynthesis
Vascular: transport food & water
Dermal: protection – water loss

Question 3

Define meristematic

Answer 3

It consists of undifferentiated cells capable of cell division

Question 4

What are ground tissues responsible for?

Answer 4

In charge of support, storage and photosynthesis

Question 5

What are ground tissues made of?

Answer 5

Palisade mesophyll:
Elongated cells below epidermis (Main site of photosynthesis)
Spongy mesophyll:
(Below palisade cells
Fewer chloroplasts
Gaps allow gas movement (water vapour too))

Question 6

What are vascular bundles?

Answer 6

Transport food and water
Made of Xylem (water transport)
Phloem: sucrose (food) transport

Question 7

Which way do nutrients travel in the Xylem?

Answer 7

Up (roots to leaves)

Question 8

Is travel in the Xylem passive or active?

Answer 8

Passive, as the tissue is dead

Question 9

What carbohydrate within the walls stops gas and water exchange?

Answer 9

Lignin (cells die, leaving an empty tube)

Question 10

What does Phloem transport?

Answer 10

Sugar and mineral ions (Translocation)

Question 11

Is Phloem transport active or passive?

Answer 11

Active, as it goes both up and down

Question 12

What cells make up the Pholem tube?

Answer 12

Sieve cells, with sieve tubes at the ends, to allow sugar molecules movement (companion cells provide energy)

Question 13

What is the role of Dermal tissues?

Answer 13

Protection, homeostasis and gas exchange

Question 14

What are dermal tissues made of?

Answer 14

The Epidermis (preventing water loss)
Stomata (guard cells that exchange O2, Co2 and H2O)
Gas exchange means water loss as stomata are open - plants need to regulate this to avoid dehydration

Question 15

What are Stomata?

Answer 15

Holes between guard cells that allow gas exchange and transpiration. When open, they take in water and swell (turgid)
Blue light activates proton pump that lets in K+ and water follows due to concentration gradient. When closed, they lose water and shrink (flaccid). A high Co2 concentration/Abscisic acid from wilting leaves = K+ moves out and water follows due to concentration gradient

Question 16

What is transpiration?

Answer 16

Evaporation of water out of the spongy mesophyll through the stomata in leaves
Pulls water up the stem in the xylem
Works like a straw

Question 17

What is water movement from the roots to the leaves due to?

Answer 17

Root pressure (water moves in via diffusion constantly and pushes itself up part of the way)
Transpiration (evaporation of water from stomata means room for more water to fill the space)
Adhesion (attraction of polar water molecules inside xylem to the walls)
Cohesion (attraction of the water molecules to each other).
As water leaves via the stomata, the column us pulled up and continues to transport substances.

Question 18

What are the two ways for water to enter the roots?

Answer 18

Alloplastic (through the cell wall but not into cytoplasm)
Symplasmic (through cytoplasm)

Question 19

How long do root hairs (extra structures to pick up water) live

Answer 19

Less than a day

Question 20

What are the three factors effecting transpiration?

Answer 20

Humidity (low humidity increases the water potential gradient between the leaf and the air, increasing transpiration)
Light intensity (high light intensity makes stomata open to allow photosynthesis and allows more water to escape)
Wind (moves humid air away from leaf and increases transpiration - sweating)

Question 21

Give an example of osmoregulation in plants

Answer 21

Low water levels
Guard cells lose water = flaccid = stomata close
Closed stomata = less water loss via evaporation, but also less photosynthesis
Plant water levels maintained (not dropping further) until more water is obtained
Then guard cells fill with water, open and transpiration starts again