Plant tissues and organs

Question 1

Give examples of plant organs and what they do?

Answer 1

Stems, roots and leaves are organs that work together to transport substances around the plant.

Question 2

Give examples of plant tissues.

Answer 2

Epidermal tissue - covers the whole plant
Palisade mesophyll tissue - where photosynthesis happens on the leaf
Spongy mesophyll
Xylem + phloem
Meristem tissue - found at growing tips of shoots + roots.

Question 3

How is the upper epidermis related to its function?

Answer 3

Transparent layer to let light through to the palisade layer.

Question 4

How is the palisade layer related to its function?

Answer 4

Has lots of chloroplasts - near the top of the leaf to get more light.

Question 5

How is the spongy mesophyll related to its function?

Answer 5

Contains air spaces which increase the rate of diffusion of gases.

Question 6

How is the stomata related to its function?

Answer 6

Lets gases diffuse in and out of the leaf. They are opened and closed in response to their environment - controlled by guard cells.

Question 7

What do xylem and phloem do?

Answer 7

Bring water and nutrients to the leaf and take away glucose produced by photosynthesis - also support leaf.

Question 8

What factors affect transpiration rate?

Answer 8

Air flow
Temperature
Humidity
Light intensity

Question 9

How does air flow affect the transpiration rate?

Answer 9

More windy, faster transpiration rate.
Fast moving air means that water vapour around the leaf is swept away, so higher concentration of water vapour inside leaf than outside - water will diffuse more quickly out of the leaf.

Question 10

How does temperature affect the transpiration rate?

Answer 10

Warmer, faster transpiration.

Because water particles have more energy, so they evaporate and diffuse out of the stomata faster.

Question 11

How does humidity affect the transpiration rate?

Answer 11

Humidity = a lot of water in air
Not much of a difference inside and outside the leaf - so diffusion won’t be very fast.
More drier around a leaf, faster transpiration.

Question 12

How does light intensity affect the transpiration rate?

Answer 12

Brighter the light, greater transpiration rate.

Photosynthesis can’t happen in the dark, so stomata close and very little water can escape.

Question 13

What is transpiration?

Answer 13

The loss of water from plants - caused by evaporation + diffusion from a plant’s surface, mainly leaves.

Question 14

What is a transpiration stream?

Answer 14

Movement of water from the roots, through the xylem and out of the leaves.

Question 15

Describe the process of transpiration.

Answer 15

1) Water evaporates from leaves + diffuses into the air.
2) Creates slight shortage of water in the leaf, more water is drawn up from the rest of the plant through the xylem tubes to replace it.
3) This means more water is drawn up from the roots.

Question 16

What do the phloem tubes do?

Answer 16

Transports dissolved sugar from leaves to rest of plant for immediate use or storage.
Composed of tubes of elongated cells - cell sap moves from one phloem cell to the next through pores in the end walls in both directions.

Question 17

What is translocation?

Answer 17

Movement of food molecules through the phloem.

Question 18

What do the xylem tubes do?

Answer 18

Transports water and mineral ions from the roots to the stems and leaves. (Made of dead cells)
Composed of hollow tubes strengthened by lignin with no end walls between cells.

Question 19

What is the structure and role of the stomata and guard cells?

Answer 19

To control gas exchange and water loss.

Question 20

How are root hair cells adapted for their role?

Answer 20

Adapted for the efficient uptake of water by osmosis, active transport

Question 21

How do guard cells control water loss and gas exchange?

Answer 21

When plant has lots of water, guard cells fill with it + get fat - this opens stomata so gases are exchanged for photosynthesis.
When plant is short of water, guard cells lose water + become floppy - stomata closes to help stop too much water vapour from escaping.