organisation in plants

Question 1

structure and function of the epidermal tissue

Answer 1

-covered in waxy cuticle to reduce water loss by evaporation

Question 2

structure and function of the upper epidermis

Answer 2

• it is transparent so that light can pass through to reach the palisade layer

Question 3

structure and function of the palisade layer

Answer 3

• contains lots of chloroplasts near the top so that they reach the most light and where photosynthesis takes place

Question 4

xylem and phloem functions

Answer 4

• carry water and nutrients to the leaf and take away glucose produced by photosynthesis. Also support the leaf.

Question 5

function of tissue of the leaves

Answer 5

• adapted for gas exchange, e.g the lower epidermis contains many holes called stomata that let co2 diffuse into the plant.

Question 6

what do the air sacs in the spongy mesophyll do

Answer 6

• increase the rate of diffusion of gases

Question 7

how is the opening of the stomata controlled

Answer 7

guard cells.

Question 8

describe structure and function of the phloem tubes

Answer 8

• elongated living cells, small pores in end walls to allow cell sap to flow.
• transport food mainly dissolved sugars made in leaves to the rest of the plant for immediate use or storage.
  transport goes in both direction, translocation

Question 9

definition of translocation

Answer 9

movement of materials in the plant from the leaves to other parts of it.

Question 10

describe structure of xylem/ function

Answer 10

• made of dead cells joined end to end, no end walls.
  Strengthened by lignin
  Carry water and mineral ions from roots to stem and leaves.

Question 11

Translocation stream definition

Answer 11

• movement of water from the roots through the xylem and out of the leaves

Question 12

describe transpiration

Answer 12

• caused by the evaporation/ diffusion of water from plants surface e,g leaves
  causes slight shortage in water and more water is drawn from rest of the plant by xylem vessels to replace it
  more water drawn from the roots and creates a constant transpiration stream of water

Question 13

what is transpiration rate affected by

Answer 13

• light intensity
  -temperature
  -air flow
  -humidity

Question 14

how are guard cells adapted?

Answer 14

• when plants have lots of water, the guard cells fill and turn turgid. Makes the stoma open for gas exhange for photosynthesis
• when there is a lack of water, guard cells lose water and become flaccid and the stoma close. Prevents too much water vapour escaping.
  Sensitive to light so they close at night to save water