Plant structures and their functions

Question 1

What is the equation for photosynthesis

Answer 1

carbon dioxide + water -> glucose + oxygen

–>
light

Question 2

Chemical formula for glucose

Answer 2

C₆H₁₂O₆

Question 3

What is biomass?

Answer 3

The materials in an organism

Question 4

Where does photosynthesis occur

Answer 4

plants and algae

Question 5

What kind of reaction is photosynthesis?

Answer 5

endothermic, takes more energy than it releases

Question 6

What factors affect photosynthesis and how

Answer 6

• Temperature: As temperature increases so does the rate of photosynthesis. This increases until the enzymes denature
• Light intensity: Higher the light intensity, faster the rate of reaction
• Carbon dioxide concentration: As the concentration of CO₂ increases, the rate of reaction increases

Question 7

What is a limiting factor in terms of photosynthesis?

Answer 7

If one factor which affects the rate of photosynthesis is low(or too high like temperature), the increase in rate of reaction of photosynthesis will be restricted.
The relationship between a factor and the rate of photosynthesis will plateau after a limiting factor stops it.

Question 8

How can we investigate the effect of light intensity on photosynthesis? (CP)

Answer 8

• Add 20 algal balls to a set amount of hydrogen carbonate indicator. Have many bottles. Cover one in foil as a control.
• Keep each bottle a set distance away from a lamp by using a ruler
• Keep a tank of water between the lamp and the algal balls as a heat shield to prevent temperature being a factor.
• Wait a few days.
• The indicator will show how much CO2 indicator is there in the bottle.
• orange is high
• red is atmospheric
• purple is low
• The higher the CO2 levels, lower the rate of photosynthesis

Question 9

how does distance affect light intensity

Answer 9

depends on inverse square law which is
light intensity = 1/d^2

Question 10

How is the root hair cell structured to absorb water and mineral ions?

Answer 10

• Large surface area to diffuse more water and minerals
• mitochondria for energy for active transport of mineral ions
• Large permanent vacuole
• Thin cell walls

Question 11

What is the xylem?

Answer 11

A tube that carries water and mineral ions (dissolved in water) from the root to the stem and leaves. Goes up. Uses transpiration

Question 12

How is the xylem adapted to its function

Answer 12

• The xylem is full of dead cells which are joined together without cell walls
• Lignin kills these cells, making them hollow and lignified
• Lignin is deposited in spirals, which provides support for the xylem.

Question 13

What is the phloem?

Answer 13

Tube which transfers food substances (sucrose) from the leaves to the rest of the plant. Goes up and down. Uses translocation

Question 14

How is the phloem adapted to its function?

Answer 14

• Made of elongated living cells.
• Small pores in each cell’s end walls to allow things to flow through.
• Each cell has a companion cell which has mitochondria for energy, since translocation requires energy.

Question 15

What is transpiration?

Answer 15

Loss of water from the plant

Question 16

How does transpiration work?

Answer 16

• Water leaves the cell through stomata
• Water molecules are attracted to other molecules, causing it to pull more molecules up the xylem. Called capillary action.
• Results in more water coming through the roots
• Leads to a constant transpiration stream.

Question 17

What are stomata and what does it do

Answer 17

Pores on the surface of a plant. Usually under a leaf. Allow CO2 to diffuse in and out of a leaf

Question 18

How do guard cells work?

Answer 18

• If the guard cell is turgid, the stomata opens. Allows water and gas to leave
• When flaccid, the stomata close, reducing water loss

Question 19

What is translocation?

Answer 19

Transportation of food substances, made in the leaves up and down the phloem.
Requires energy supplied by companion cells.

Question 20

What are the layers of a leaf from top to bottom?

Answer 20

• Waxy cuticle
• upper epidermis
• Palisade mesophyll tissue
• Spongy mesophyll tissue
• lower epidermis

Question 21

How are plants adapted for photosynthesis and gas exchange? Give a shit ton of reasons

Answer 21

• Thin leaves: carbon dioxide only has a small distance to travel into the leaf and oxygen has a small distance to diffuse out
• Stomata: Close to reduce water loss and open to increase evaporation and gas exchange
• Large surface area: absorb more light at once
• Xylem and Phloem - xylem takes water to leaves, phloem takes away the sucrose
• Waxy cuticle: prevents water loss through evaporation
• Upper epidermis: Transparent so light can reach palisade mesophyll tissue
• Spongy mesophyll: empty space, increases diffusion into and out of leaf cells

Question 22

What factors affect transpiration and how?

Answer 22

• Light intensity: Brighter light, greater transpiration rate. Stomata close when dark as CO2 is not required because photosynthesis don’t happen.
• Temperature: Warmer, faster transpiration happens. More energy goes to particles, meaning they diffuse out of stomata faster
• Air flow: Good air flow means better transpiration rate. When diffusion happens, water moves outside the leaf. If there is less air flow, the water hangs around the leaf and diffusion is slow. If there is good air flow, the water particles get moved away.

Question 23

How can you estimate transpiration rates?

Answer 23

• Use a potometer. Air bubble is placed at the start of a capillary tube filled with water. Measure how far the air bubble moves. Divide how far the bubble has moved by the time taken for it to move. This is the rate of transpiration

Question 24

How do some plants survive in extreme environments?

Answer 24

• Small leaf size: reduces volume of water lost by transpiration
• Has a waxy cuticle: Prevents evaporation of water
• Stomata: fewer stomata or stomata which only open at night.

Question 25

What is an auxin and how does it work

Answer 25

Plant hormones which control growth at the tips of shoots and roots. Move through the plant in a solution. Promotes growth at shoots, inhibits growth at roots. Auxins move away from light

Question 26

What is phototropism and how does it work and explain its types

Answer 26

• Positive phototropism is when an shoot grows towards the light. The auxins accumulate on the underside of the shoot and make those cells grow, pushing the plant upwards
• Negative phototropism is when a root grows away from the light

Question 27

What is gravitropism and how does it work, explain its types

Answer 27

• Positive gravitropism occurs in roots, as they follow gravity and move downwards. Auxins accumulate on the lower side and inhibit the growth of that side. Makes other side grow downwards.
• Negative gravitropism occurs in shoots. This is because they grow upwards.

Question 28

What are gibberellins?

Answer 28

Plant hormones which stimulate germination, stem growth and flowering

Question 29

What plant hormones are used commercially?

Answer 29

• Auxins
• Gibberellins
• Ethene

Question 30

Where are auxins used commercially?

Answer 30

• Weed killers: Weedkillers have auxins in them. When put over plants, they target broad leaved plants (weeds). The auxins cause the weeds to grow too fast, killing them.
• Rooting powder: A cutting is taken from the plant. The cutting is placed in the soil. Rooting powder, with auxins, causes the roots to grow fast. Causes the plant to grow like actual plants

Question 31

Where are gibberellins used commercially?

Answer 31

• Used to make plants flower and/or germinate earlier than they would normally
• Used to make fruits bigger
• Gibberellins can cause unpollinated flowers to grow fruits without seeds.

Question 32

How is ethene used commercially?

Answer 32

• Ethene makes a fruit ripen
• Helps transport fruit: The fruit is picked when unripe and transported easily because they are still firm. When they reach the supermarket they are sprayed with ethene to ripen them quickly.