topic 6 - Plant Structures And Their Functions

Question 1

light intensity law

Answer 1

light intensity ∝ 1/distance^2

Question 2

light intensity law explained

Answer 2

distance increases —> light intensity decreases

light intensity decreases in proportion to the square of the distance

Question 3

what does increasing CO2 do to photosynthesis

Answer 3

increases rate of photosynthesis up to a point

after the graph flattens out, CO2 is no longer the limiting factor

as long as there’s a lot of CO2, then light or temperature is the factor limiting photosynthesis.

Question 4

core practical to investigate photosynthesis

Answer 4

get a lamp
put pondweed in a flask
get a ruler to measure distance between the flask and the lamp
set a timer for 1 min
count the bubbles that are rising to the surface
(this allows you to measure volume of oxygen produced)
repeat at diff distances

Question 5

how to improve the core practical

Answer 5

use a gas syringe. counting bubbles can be inaccurate

Question 6

variables controlled on the core practical

Answer 6

volume of water, CO2 concentration, external light

Question 7

what are the two types of transport vessels in a plant

Answer 7

xylem and phloem

Question 8

plant adaptations - hair

Answer 8

cells on surface of plant root grows into hairs which stick out into soil

they give the plant a large surface area for absorbing water and mineral ions from the soil

concentration of mineral ions is usually higher in the root hair cells than in the soil, so mineral ions are absorbed by active transport

water is absorbed via osmosis

Question 9

what does phloem transport

Answer 9

sucrose

Question 10

what does xylem transport

Answer 10

water

Question 11

what is xylem

Answer 11

made of dead cells

carry water and mineral ions from roots to the stem and leaves

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

Question 12

what is transpiration

Answer 12

transpiration is the loss of water caused by the evaporation and diffusion of water from a plants surface. happens at the leaves mostly.

Question 13

what happens when transpiration happens

Answer 13

water is drawn up from the roots through the xylem vessels to replace the shortage of water on the leaf

there’s a constant transpiration stream of water through the plants

transpiration stream carries mineral ions that are dissolved in the water along with it

Question 14

what is stomata

Answer 14

tiny pores on the surface of a plant
mostly found in lower surface of leaves
allow CO2 and oxygen to diffuse directly in and out of leave
allow water vapour to escape during transpiration

Question 15

why do plants have stomata

Answer 15

so gases can be exchanged easily
because there’s more water inside the plant than in the air outside, the water escapes from the leaves through the stomata via diffusion

Question 16

what is stomata surrounded by

Answer 16

guard cells which change shape to control the size of the pore

when turgid (swollen with water) stomata are open

when flaccid (low on water and limp) stomata are closed

Question 17

how transpiration rate is affected (light)

Answer 17

brighter light — greater transpiration rate

stomata closes as it gets darker.
photosynthesis doesn’t happen in the dark so they don’t need to be open to let CO2 in.

very little water escapes when stomata is closed.

Question 18

how transpiration rate is affected (temperature)

Answer 18

warmer — faster transpiration

water particles have more energy to evaporate and diffuse out of the stomata

Question 19

affect transpiration rate (air flow)

Answer 19

better air flow — greater transpiration rate
good airflow — water vapour swept away, maintaining low concentration of water in air outside the leaf
diffusion then happens

Question 20

order of plant structure on a leaf

Answer 20

first layer: waxy cuticle
2. upper epidermis
3. palisade mesophyll tissue
4. spongy mesophyll tissue
5. lower epidermis

Question 21

what’s the acronym u made for the order of the layers

Answer 21

we used pork shit lmao

Question 22

what is palisade layer

Answer 22

lots of chloroplasts
near top of leaf for lots of light

Question 23

what is upper epidermis

Answer 23

transparent so light can pass through it into the palisade layer

Question 24

why is waxy cuticle there

Answer 24

helps reduce water loss by evaporation

Question 25

what does spongy layer contain

Answer 25

air spaces which increase rate of diffusion into and out the leaf’s cells

Question 26

lower epidermis has lots of what

Answer 26

stomata to diffuse CO2 directly into the leaf

Question 27

plant adaptations

Answer 27

small leaves or spines to reduce surface area for water loss

thick waxy cuticles — reduce water loss

curled leaves or hairs — reduces air flow, trapping water vapour and reducing diffusion from leaf to the air

fewer stomata that or stomata only open at night — reduce water loss

thick stem which stores water

Question 28

what are auxins

Answer 28

plant hormones which control growth at the tips of shoots and roots

Question 29

when do auxins do their job

Answer 29

in response to light (phototrophism)
in response to gravity (gravitrophism)

Question 30

how do shoots react to light

Answer 30

positively phototrophic (grow towards light)
when shoot tip is exposed to light, it gets more auxin on the side that’s in the shade
makes cells grow faster on shaded side so it bends towards light

Question 31

shoots react to gravity how

Answer 31

shoot produces more auxin on the lower side of the tip which causes lower side to grow faster which bends the shoot upwards

Question 32

roots react to gravity how

Answer 32

positively gravitrophic
a root growing sideways have more auxins on its lower side
this inhibits growth meaning cells on the top elongate faster which bends the root downwards

Question 33

roots react to light how

Answer 33

negatively phototrophic
root exposed to light — auxins gets on shaded sided
this inhibits elongation on shaded side so root bends downwards back in the ground

Question 34

Where does filtration occur?

Answer 34

In the glomerulus

Question 35

What is small enough to pass into the bowman’s capsule?

Answer 35

Urea, water, ions and glucose