Topic 6- Plant Structures And Their Functions

Question 1

equation for photosynthesis

Answer 1

Carbon dioxide +water -> glucose + oxygen

Question 2

how to investigate the light intensity

Answer 2

• a source of light is placed at specific distances from the pondweed
• the pondweed is left to photosynthesise for a set amount of time
• as the pond weed photosynthesises oxygen is released and will be collected in the gas syringe

Question 3

what are the limiting factors of photosynthesis?

Answer 3

• not enough light
• too little carbon dioxide
• temperature too high or low

Question 4

equation for light intensity

Answer 4

Light intensity ∝ 1 ÷ distance (d)²

Question 5

root hairs

Answer 5

• absorb water and mineral ions in soil
• have millions of microscopic hairs
• large surface area

Question 6

phloem tubes

Answer 6

• columns of elongated living cells
• they transport food substances (mainly sucrose)
• this is a process called translocation
• transport goes both ways

Question 7

functions of xylem

Answer 7

• made of dead cells joined end to end
• strengthened with lignin
• they carry water and mineral ions from the roots to the stem and leaves
• this process is called transpiration stream

Question 8

definition of transpiration

Answer 8

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

Question 9

stomata

Answer 9

• stomata are tiny pores on the surface of a leaf
• they allow for gas exchange
• surrounded by guard cells

Question 10

what 3 environmental factors affect the rate of transpiration?

Answer 10

• light intensity
• temperature
• air flow

Question 11

how are leaves adapted for photosynthesis?

Answer 11

•broad leaves
Increase surface area to get more light for photosynthesis

•palisade layer has lots of chloroplasts

•upper epidermis is transparent
Let’s light pass through

•waxy cuticle
Reduce water loss

Question 12

how are leaves adapted for gas exchange?

Answer 12

•stomata
-let’s carbon dioxide diffuse directly into the leaf

•spongy mesophyll
-has air spaces which increases the rate of diffusion

Question 13

how are some plants adapted to extreme climates?

Answer 13

•small leaves
Reduces surface area for water loss

•curled leaves or hairs
Reduces air flow and traps water vapour

•thick waxy cuticles
Reduce water loss

•thick fleshy stem
which stores water

Question 14

auxins

Answer 14

Plant hormones which control growth at the tip of shoots and roots

Question 15

definition of positively phototropic

Answer 15

• grows towards light
• when a shoot tip is exposed to light it accumulates more auxin on the side which is in the shade
• it will then grow faster on the side which is shaded
• so it grows towards light

Question 16

definition of negatively phototropic

Answer 16

• grows away from light
• if a root is exposed to light more auxin accumulate on the shaded side
• so the root grows downwards

Question 17

definition of positively gravitropic

Answer 17

•grows towards gravity

Question 18

definition of negatively gravitropic

Answer 18

•grows away from gravity

Question 19

how to investigate the effect of light intensity on growth

Answer 19

• Canadian pond weed is put in a flask
• a light source is placed at a specific length away from the flask
• at a specific time see how much gas has been produced (gas syringe on top of the flask)
• repeat with different lengths

Question 20

how do weedkillers work?

Answer 20

Selective weed killers have been developed from auxins, which only affect broad leaved plants

They disrupt their normal growth patterns

Question 21

how are rooting powders used?

Answer 21

By cutting of part of the plant and adding rooting powder(contains auxins) it will then produce roots

This enables growers to produce clones

Question 22

how are flower and fruit formation controlled?

Answer 22

Using gibberellins

A plant hormone that stimulates stem growth, seed germination and flowering

Question 23

how are seedless fruit produced?

Answer 23

Adding plant hormones

Eg. Gibberellins
Some citrus fruit is grown like this

Question 24

how is ripening in fruit controlled?

Answer 24

The fruit is picked unripe

Then ethane is added to ripen the fruit