Topic 6 - Plant Structures and their Functions

Question 1

Why are photosynthetic organisms producers of biomass

Answer 1

Because they use energy from the sun to produce glucose

Question 2

What substances are produced from glucose and their roles in the plant

Answer 2

energy which is used for respiration

Question 3

recall the equation for photosynthesis

Answer 3

6CO2 + 6H2O —> C6H12O6 + 6O2

Question 4

Why is photosynthesis an endothermic reaction?

Answer 4

AS energy is taken in during the reaction

Question 5

How are leaves and their cells adapted for photosynthesis

Answer 5

Palisade layer has lots of chloroplasts so theyre near the top of the leaf
broad with large surface area exposed to light for photosynthesis

Question 6

What are the effects of temperature, light intensity and carbon dioxide concentration on the rate of photosynthesis

Answer 6

Light intensity- when high intensity, rate of photosynthesis speeds
Carbon dioxide- two little slows it down as its a raw material needed
Temperature- If too hot enzyme denatures too low enzymes dont work

Question 7

Why is the rate of photosynthesis inversely proportional to the distance from light source?

Answer 7

because as distance increases the photosynthesis rate decreases 1/distance 2

Question 8

How are root hair cells adapted to their functions

Answer 8

millions of microscopic hairs which gives plant large surface area to absorb mineral ions through active transport and osmosis

Question 9

what are the 3 transportational processes

Answer 9

osmosis diffusion and active transport

Question 10

what is the concentration gradient

Answer 10

The direction osmosis and diffusion take from a high to low concentration.
active transport goes against the concentration gradient

Question 11

What is active transport used for

Answer 11

To transport food molecules such as sucrose from a low to high concentration

Question 12

How is a Xylem tube adapted for its function

Answer 12

dead cells joined together end to end with no end walls to take water from roots to stem and leaves.
strengthened with lignin
carry mineral ions too up the transpiration stream

Question 13

What is the transpiration stream

Answer 13

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

Question 14

Why is the phloem tube adapted to its function? What is translocation

Answer 14

Elongated living cells with small pores on end walls so food substances can diffuse through.
they transport food substances made in leaves to other parts of the plant through process of translocation

Question 15

What is transpiration

Answer 15

caused by evaporation and diffusion
occurs usually in leaves
its the loss of water from a plant

Question 16

What effects the rate of transpiration

Answer 16

Light intensity- brighter light the greater the rate as stomata close when its dark.
Temperature- warmer means faster transpiration as particles have more energy to evaporate and transpire
Air flow- better the air flow the more transpiration as water vapour is swept away maintaining low water concentration on surface of leaf so diffusion occurs faster

Question 17

How can you measure the rate of transpiration

Answer 17

using a potometer and record position of air bubble. start time and measure distance moved. calculate the speed of bubble

Question 18

What are the different tissues in a leaf

Answer 18

Waxy cuticle, upper epidermis, palisade mesophyl tissue, lower epidermis, stomata on base

Question 19

What are the functions of these layers of leaves

Answer 19

Waxy cuticle- reduces water loss
upper epidermis- light is allowed through as this layer in transparent
Palisade layer- lots of chloroplasts near top so lots of light
Spongy mesophyll tissue- contains air space which increases the rate of diffusion
lower epidermis- lots of stomata which lets CO2 diffuse directly into the leaf

Question 20

What are some adaptations plants have to living in extreme conditions

Answer 20

• Small leaves or spines to reduce surface area to reduce evaporation and stop predators eating
• Curled leaves/hairs to reduce air flow on surface which reduces diffusion
• Thick waxy cuticles to stop water loss by evaporation
• Few stomata that only open at night to reduce evaporation
• Stomata in sunken pits to reduce air flow to them

Question 21

What are the names of 3 plants hormones

Answer 21

-gibberellins ethene and auxins

Question 22

Identify positive and negative tropisms

Answer 22

Positive phototropisms- Shoots
Negative- roots

positive gravitropsims- Roots
negative shoots

Question 23

How do auxins cause phototropism

Answer 23

auxins in tips of shoots makes all side elongate so a taller shoot gets more light

Question 24

How can plant growers use auxins

Answer 24

selective weed killers- only effect broad leaf plants- disrupts plant growth
growing cuttings from rooting powder- conatins auxins which produce shoots very quickly and can create clones

Question 25

How can plant growers use Gibberellins

Answer 25

-controlling seed germination- make plants flower earlier or under conditions they wouldnt normally flower it stimualtes SEED GERMINATION
(can also reduce flower formation to improve fruit quality)
-proudcing seedless fruit- applied to unpollonated flowers to so fruit grows but seeds dont
-Controlling seed germination - getting seeds to germinate at time of year they would normally

Question 26

How can we artificially ripen fruit with hormones

Answer 26

Controlling ripening of fruit- ethene is added to fruit on the way to the supermarket so when they get there the fruit will be perfect on the shelves

Question 27

Advantage of using plant hormones in fruit farming?

Answer 27

• Get fruit at times of year where conditions wouldnt usually be right,
• produce seedless fruit
• produce clones of one plant

Question 28

Disadvantages of Plant hormones in fruit farming

Answer 28

• Harmful to environment- fertilisers and chemicals can leak into waters
• fruit may be poor quality
• traditional farmers out of business