Paper 2 - Topic 6, Plant Structures And Their Function

Question 1

What are auxins

Answer 1

A group of plant hormones that inhibit growth in plant roots and stimulate growth in shoot tips

Question 2

What is biomass

Answer 2

The total mass of organic material, measure in a specific area over a set period

Question 3

Which hormone stimulates ripening in fruits

Answer 3

Ethene

Question 4

What is gravitropism

Answer 4

A plants growth response to gravity

Question 5

What are guard cells

Answer 5

Cells that surround the stomata and change shape depending on the volume of water, they control the rate of transpiration by becoming turgid or flaccid

Question 6

What is lignin

Answer 6

A material that strengthens the walls of xylem cells

Question 7

What is a limiting factor

Answer 7

A variable that limits the rate of a particular reaction

Question 8

What is the lower epidermis

Answer 8

A layer of cells on the leaf’s lower surface that contains stomata and guard cells

Question 9

What is negative plant tropism

Answer 9

The growth of a plant away from a stimulus

Question 10

What is the palisade mesophyll layer

Answer 10

The main photosynthesis tissue in plants located below the upper endodermis, it receives the most light so contains the greatest concentration of chloroplasts

Question 11

What is the phloem

Answer 11

A transport tissue found in plants that is specialised to transport sugars from the leaf to the rest of the plant in both directions

Question 12

What is photosynthesis

Answer 12

An endothermic reaction that takes place inside photosynthetic organisms and converts light energy into chemical energy

Question 13

What is the equation for photosynthesis

Answer 13

6CO₂ + 6H₂ ——> C₆H₁₂O₆ + 6O₂

Question 14

What is phototropism

Answer 14

A plants growth response to light

Question 15

What is plant tropism

Answer 15

The growth response of a plant to a stimulus

Question 16

What are root hair cells

Answer 16

Specialised cells responsible for the uptake of water and minerals from the soil, they have long hair-like extensions known as root hairs, provide a large surface area for absorption

Question 17

What is the spongy mesophyll layer

Answer 17

A type of loosely packed mesophyll tissue with air pockets specialised for gas exchange, also contains chloroplasts for photosynthesis

Question 18

What is the stomata

Answer 18

Small holes found on the surface of a plant that can be opened or closed by guard cells to control water loss and gas exchange

Question 19

What is translocation

Answer 19

The movement of sugars up and down a plant from photosynthetic to non-photosynthetic tissues via the phloem

Question 20

What’s transpiration

Answer 20

Water loss from plant leaves and shoots via diffusion and evaporation

Question 21

What is the rate of transpiration affected by

Answer 21

Light intensity, temperature and air flow

Question 22

What is the upper epidermis

Answer 22

A layer of transparent cells that allows light to strike the palisade mesophyll tissue

Question 23

What’s the waxy cuticle

Answer 23

A waxy layer that reduces water loss from the surface of leaves

Question 24

What’s the xylem

Answer 24

A transport tissue in plants that is specialised to transport water and dissolved materials from the roots of the plants to the leaves

Question 25

What’s the word equation for photosynthesis

Answer 25

Carbon dioxide + water ——> glucose + oxygen

Question 26

How does temperature affect the rate of photosynthesis

Answer 26

-Increase in temp, rate of photosynthesis increases - reaction is controlled by enzymes so only continues up till a certain temp before enzyme denatures

Question 27

How does light intensity affect the rate of photosynthesis

Answer 27

Higher the light intensity, the faster the rate of rsa toon

Question 28

How does carbon dioxide concentration affect the rate of photosynthesis

Answer 28

- carbon dioxide is needed to make glucose so as concentration of carbon dioxide increases the rate of reaction increases

Question 29

How can you measure the oxygen production of a plant and calculate the rate of photosynthesis

Answer 29

- pondweed placed in test tube full of water, top is sealed with a bung. A capillary tube also containing water leads into the test tube and is attached to a syringe - a lamp is placed at a measure distance from the test tube - as it photosynthesises, oxygen is produced forming gas in the capillary tube -distance bubble has moved is measure using a ruler to calculate volume of oxygen produced - variables that can be changed : temp (using water bath) time pondweed is left, light intensity (distance of lamp from plant) - control all factors that may affect photosynthesis apart from IV

Question 30

How are root hair cells adapted to its specific function

Answer 30

- specialised to take up water by osmosis and mineral ions by active transport from the soil as they are found in the tips of roots - have large SA due to root hairs (more water can move in)

Question 31

How are xylem cells adapted to their specific function

Answer 31

- specialised to transport water and mineral ions up the plant from roots to shoots -

Question 32

How are phloem cells adapted to their specific function

Answer 32

Specialised to carry products of photosynthesis to all parts of the plant

Question 33

Why do plants loose water

Answer 33

Through transpiration, as the stomata’s are open, water evaporates at the open stomata on the leafs surface

Question 34

What do the guard cells do when lots of water is available to the plant

Answer 34

The cells fill and change shape opening the stomata (they are also light sensitive), this allows gases to be exchanged and more water leave the plant via evaporation - more stomata found on bottom of leaf as cool and shaded so there is less water loss

Question 35

Where does translocation occur

Answer 35

Only in the phloem

Question 36

What are the adaptations of a leaf

Answer 36

- stomata: able to close to minimise water loss and open to increase evaporation and transpiration also allows gas exchange to occur when open - chlorophyll: chlorophyll = green most efficient colour for absorbing light - ss: leaves are very thin so there is a short distance for carbon dioxide to enter the leaf and short distance for oxygen to diffuse out - large surface area: leaf can absorb more light at once

Question 37

How does an increase in temperature affect the rate of water uptake and transpiration

Answer 37

- molecules move faster, evaporation happening at a faster rate so transpiration increases - rate of photosynthesis increase, more stomata are open for gaseous exchange, so more water evaporates and rate of transpiration increases

Question 38

How does an increase in relative humidity affect the rate of water uptake and transpiration

Answer 38

If relative humidity is high, there will be reduced concentration gradient between concentrations of water and vapour inside and outside leaf, resulting in slower rate of diffusion and decrease in rate of transpiration

Question 39

How does an increase air movements (wind) affect the rate of water uptake and transpiration

Answer 39

- if air moving away from leaf, concentration of water vapour surrounding leaf will be lower - there is a steeper concentration gradient resulting in diffusion happening faster, increasing rate of transpiration

Question 40

How does an increase in light intensity affect the rate of water uptake and transpiration

Answer 40

- increased rate of photosynthesis, so more stomata open, more water can evaporate and and increased rate of transpiration

Question 41

How do most plants show positive phototropism when they grow towards a light source

Answer 41

- plant exposed to light on one side - auxin (growth hormone) moves to shaded side of root - auxin stimulates cells to grow more here - shoot bends towards light - plant receives more light so faster rate of photosynthesis

Question 42

How do most shoots show negative gravitropism as they grow away from gravity

Answer 42

- auxin moves to lower side - cells of the shoot grow more on the side with most auxin - makes shoot bend and grow away from ground

Question 43

How do most roots show positive gravitropism as they grow towards gravity

Answer 43

- auxin moves to lower side - cells of the root grow more on side with less auxin - makes the root bend and grow downwards