Organisation - Plant Cells 73-77

Question 1

what are plants made of

Answer 1

made of organs like stems, roots and leaves

Question 2

what are some examples of plant tissues and what is there role
5 points

Answer 2

1) epidermal - this covers the whole plant
2) palisade mesophyll - this is the part of the leaf where most photosynthesis happens
3) spongy mesophyll - this is in the leaf and contains big air spaces to allow gases to diffuse in and out of cells
4) xylem and phloem - they transport things like water, mineral ions and food around the plant
5) meristem - this is found at the growing tips of shoots and roots and is able to differentiate into lots of different types of plant cell

Question 3

what tissues does a leaf contain
3 points

Answer 3

1) epidermal
2) mesophyll
3) xylem and phloem

Question 4

label a leaf cell

Answer 4

look on page 73 of bio book

Question 5

what are the epidermal tissues covered with why does this help
2 points

Answer 5

1) covered with a waxy cuticle
2) which helps to reduce water loss by evaporation

Question 6

what are the features of the upper epidermis
2 points

Answer 6

1) it’s transparent
2) so that light can pass through it to the palisade layer

Question 7

what are the features of the palisade layer
2 points

Answer 7

1) it has lots of chloroplasts
2) which means they’re near the top layer of the leaf where they can get lots of light

Question 8

what are the features of the xylem and phloem in a leaf
3 points

Answer 8

1) they form a network of vascular bundles,
2) which deliver water and other nutrients to the entire leaf and take away the glucose produced by photosynthesis
3) they also help support the structure

Question 9

how are the tissues of leaves adapted for efficient gas exchange
3 points

Answer 9

1) the lower epidermis of full of little holes called stomata which let CO2 diffuse directly into the leaf
2) the opening and closing of stomata is controlled by guard cells in response to the environmental conditions
3) the air spaces in the spongy mesophyll tissue increase the rate of diffusion of gases

Question 10

what do phloem tubes transport

Answer 10

food

Question 11

describe features of phloem tubes
3 points

Answer 11

1) made of columns of elongated living cells with small pores in the end walls to allow cell sap to flow through
2) they transport food substances made in the leaves to the rest of the plant for immediate use or for storage
3) the transport goes in both directions

Question 12

what is the process of transportation in the phloem called

Answer 12

translocation

Question 13

what do xylem tubes transport

Answer 13

water

Question 14

describe the features of the xylem tube

Answer 14

1) made of dead cells joined end to end with no end walls between them and a hole down the middle
2) they’re strengthened with a material called lignin
3) they carry water and mineral ions from the roots to the stem and leaves

Question 15

what is the transpiration stream

Answer 15

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

Question 16

what is transpiration

Answer 16

the loss of water from the plant

Question 17

where does most transpiration happen

Answer 17

at the leaves

Question 18

describe the process of transpiration

Answer 18

1) its caused by the evaporation and diffusion of water from a plant’s surface
2) this evaporation creates a slight shortage of water in the leaf
3) and so more water is drawn up from the rest of the plant through the xylem vessels to replace it
4) this in turn means more water is drawn up from the roots
5) so there’s a constant transpiration stream of water through the plant

Question 19

what is the purpose of a stomata

Answer 19

so gases can be exchanged easily

Question 20

why does water escape through the stomata
2 points

Answer 20

1) because there is more water inside the plant than in the air out side
2) so water escapes through the stomata by diffusion

Question 21

what is the rate of transpiration affected by
4 points

Answer 21

1) light intensity
2) temperature
3) air flow
4)humidity

Question 22

how does light intensity affect the rate of transpiration
3 points

Answer 22

1) the brighter the light, the greater the transpiration rate
2) stomata begin to close as it gets darker. Photosynthesis can’t happen in the dark so the don’t need to be open to let CO2 in
3) when the stomata are closed, very little water can escape

Question 23

how does temperature affect the transpiration rate
2 points

Answer 23

1) the warmer it is, the faster transpiration happens
2) when it’s warm the water particles have more energy to evaporate and diffuse out of the stomata

Question 24

how does airflow affect the transpiration rate
4 points

Answer 24

1) the better airflow around a leaf, the greater the transpiration rate
2) if airflow around a leaf is poor, the water vapour just surrounds the leaf and doesn’t move away
3) this means there’s a high concentration of water particles outside the leaf as well as inside it so diffusion doesn’t happen as quickly
4) if there’s good airflow, the water vapour is swept away, maintaining a low concentration of water in the air outside the leaf, diffusion then happens quickly

Question 25

why does humidity affect transpiration rate
3 points

Answer 25

1) the drier the air around a leaf, the faster transpiration happens
2) if the air is humid there’s a lot of water in it already, so there’s not much of a difference between the inside and the outside of a leaf
3) diffusion happens fastest if there’s a really high concentration in one place and a really low concentration in the other

Question 26

what does a potometer estimate

Answer 26

1) it can estimate the rate of transpiration
2) by measuring the uptake of water by a plant because it is directly related to transpiration rate

Question 27

what are guard cells

Answer 27

they are specialised cells shaped like kidneys which open and close the stomata

Question 28

what happens to the guard cells when a plant has lots of water
2 points

Answer 28

1) the guard cells fill with water and go plump and turgid
2) this makes the stomata open so gases can be exchanged for photosynthesis

Question 29

what happens to guard cells when the plant is short of water
2 points

Answer 29

1) the guard cells lose water and become flaccid making the stomata close
2) this helps stop too much water vapour escaping

Question 30

how are guard cells adapted
3 points

Answer 30

1) they have thin outer walls and thick inner walls to make opening and closing work
2) they’re sensitive to light so they close at night to save water
3) more stomata on the underneath of a leaf because it’s shaded and cooler so less water loss