SB6 Plant Structures and their Functions

Question 1

Photosynthesis Equation

Answer 1

6CO2 + 6H20 —> C6H1206 + 6O2

Question 2

Why is photosynthesis endothermic?

Answer 2

Because it takes in energy from the surroundings, such as light

Question 3

Plant adaptations for photosynthesis

Answer 3

Chloroplasts contain chlorophyll which absorbs light

Question 4

What does glucose do in a plant?

Answer 4

Used to make larger, complex molecules that the plant needs to grow and makeup the organism’s biomass

Question 5

Define rate of reaction

Answer 5

The speed at which the reaction is occurring

Question 6

How does temperature affect the rate of photosynthesis?

Answer 6

Enzymes work slow at lower temperatures. But if the plant gets too hot, the enzymes will denature. If the enzymes are at the optimum temp., then something else is the limiting factor

Question 7

How does light intensity affect the rate of photosynthesis?

Answer 7

Light transfers the energy needed for photosynthesis. If the reaction has plenty of light, then it will react up to a certain point before something else is the limiting factor

Question 8

How does carbon dioxide concentration affect the rate of photosynthesis?

Answer 8

CO2 is needed for photosynthesis. Increasing the amount of CO2 you have increases the rate of reaction, up to a point. Then something else becomes the limiting factor

Question 9

List the limiting factors to photosynthesis

Answer 9

temperature, light intensity and carbon dioxide concentration

Question 10

Why is the rate of photosynthesis indirectly proportional to the distance of a light source?

Answer 10

The closer the light source, the greater the light intensity.

Question 11

What is the impact of more than one factor on the rate of photosynthesis?

Answer 11

The temperature must be just right, too little CO2 slows it down, and not enough light also slows down the rate of photosynthesis. All factors must be perfect

Question 12

Root hair cell adaptations

Answer 12

Cells on surface of roots grow into “hairs” that sick out into the soil. Each branch is covered with microscopic hairs. This gives plant large SA to absorb mineral ions and water

Question 13

Define a concentration gradient

Answer 13

An area of higher concentration to an area of lower concentration

Question 14

How do molecules move by osmosis? eg in root hair cells

Answer 14

Water is absorbed by osmosis as it goes from the soil which is has a higher concentration of water, across the cell membrane to an area of lower concentration

Question 15

Define transpiration in plants

Answer 15

Transpiration is caused by the evaporation and diffusion of water from a plant’s surface, so more water is drawn up the xylem to replace this, creating a constant transpiration stream

Question 16

Define translocation in plants

Answer 16

Happens in phloem tubes transporting food substances

Question 17

Xylem adaptations

Answer 17

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

Question 18

Phloem adaptations

Answer 18

• made of columns of elongated living cells with small pores in the end walls to allow stuff to flow through
• transport food substances (sucrose) made in the leaves to the rest of the plant for immediate use or for storage

Question 19

Environmental factors effecting the rate of transpiration

Answer 19

Light intensity - brighter light, greater transpiration rate
Temperature - the warmer it is, the faster transpiration happens
Air flow - better the air flow around a leaf, greater transpiration rate

Question 20

How do you measure the rate of transpiration?

Answer 20

A potometer measures water uptake by a plant, but it’s assumed that water uptake by the plant is directly related to water loss from the leaves

Question 21

Define stomata

Answer 21

Stomata are tiny pores on the surface of a plant, mostly found on the lower surface of leaves, allowing CO2 and O2 to diffuse directly in and out of a leaf

Question 22

Adaptations go a cactus

Answer 22

• small leaves / spines reduces SA
• curled leaves or hairs on surface reduces air flow
• thick waxy cuticle reduces water loss by evaporation
• thick fleshy stem stores water
• fewer stomata / stomata that only open at night reducing water loss

Question 23

Adaptations to a leaf

Answer 23

• upper epidermis is transparent so light can pass through
• palisade layer has lots of chloroplasts
• epidermal tissues are covered with waxy cuticle

Question 24

Define tropism

Answer 24

A tropism is a growth response to a one sided stimulus

Question 25

How is fruit artificially ripened?

Answer 25

The fruit is picked unripe and then a ripening hormone (ethene) is added in transportation

Question 26

How are gibberellins used?

Answer 26

1) Seeds can be treated with gibberellins to make them germinate at any time of year
2) Gibberellins are applied to unpollinated flowers, the fruit will grow but seeds won’t
3) Used to control plant hormones that stimulate seed germination, so it can control flower and fruit formation

Question 27

Shoots grow towards the light

Answer 27

POSITIVELY PHOTOTROPIC

When exposed to light, more auxins accumulate on the side that’s in the shade, making the cell grow (elongate) faster on the shaded side, causing it to grow towards the light

Question 28

Roots grow away from light

Answer 28

NEGATIVELY PHOTOTROPIC

If a root is exposed to some light, more auxins accumulate on the shaded side. The auxins inhibit cell elongation on the shaded side, so the root bends back down into the ground

Question 29

How are auxins used?

Answer 29

1) Selective weed killers only affect broad-leaved plants and don’t disrupt crops and grass
2) Adding auxins to parts of a plant you have cut off will make it produce roots and grow into a new plant

Question 30

Advantages of using hormones in fruit farming

Answer 30

Control when the seeds grow, when they ripen, whether they have seeds