Topic 6 - plant structures and their functions

- photosynthesis - factors affecting photosynthesis- plant cell organisation - transpiration and translocation- plant hormones (auxins and commercial uses)

What substance absorbs energy required for photosynthesis

Chlorophyll

In what part of the plant/cell does photosynthesis take place

Leaves, chloroplast

What is the word equation for photosynthesis

Carbon dioxide + water = glucose + oxygen

What is the chemical equation for photosynthesis

What type of reaction is photosynthesis

Endothermic

What can glucose made in photosynthesis be used for

• Cellular respiration (break down glucose to release energy)

• Make cellulose (used to make strong cell walls)

• Make starch (used to store glucose)

• Make amino acids (used to make proteins)

• Make lipids (store energy as fats or oils)

How do plants get carbon dioxide for photosynthesis

Diffuses from the air into the leaves via stomata

How do plants get water for photosynthesis

Diffuses from soil into root hair cells by osmosis

What makes starch a useful long term storage molecule

• easily broken down when needed

• Compact

• Insoluble in water

What else do plants need to make amino acids other than glucose

Nitrate ions

Which useful energy transfer happens overall in photosynthesis

Light → chemical

Why may plants not produce enough chlorophyll

• lack required nutrients

• Have a disease

List three environmental factors that effect the rate of photosynthesis

• light intensity

• Temperature

• amount of carbon dioxide

• Carbon dioxide concentration

• Light intensity

Temperature

Carbon dioxide concentration

Plateaued

• temperature

• Light intensity

Describe and explain how the rate of photosynthesis varies with temperature

• rate initially increases with temperature

• Because particles have more energy and move faster so react more frequently

• Highest rate is at optimum temp for enzyme action

• At higher temps the rate decreases as bonds holding the enzyme together being to break and so the enzyme changes shape

• Rate falls to zero as enzymes denature

How can farmers ensure that photosynthesis takes place 24 hours a day

Use artificial lighting

What are the two benefits of paraffin heaters

• heat

• Carbon dioxide

What are the four levels of plant organisation

Cells → tissues → organs → organ systems

Give an example of an organ on a plant

Leaf

The root, stem and leaves make up what

Organ system

What is a guard cell and example of

Cell

The palisade mesophyll layer is an example of what

Tissue

Draw and label/ name the parts of a cross section of a leaf

Which structures help minimise water loss

• Guard cells that close stomata

• Waxy cuticle

At night time is the stomata open or closed

Closed

What is Meriden tissue and where is it found

• stem cells helping plant growth

• Tips of roots and shoots

What part of the leaf is glucose produced in

leaf

What is the movement of sap up and down the plant called

Translocation

What do phloem cells have in their end walls to allow cell sap to pass along the phloem tube

Pores

What does xylem transport in a plant

Water and dissolved mineral ions

How do root hair cells absorb water from the soil

Osmosis

How do root hair cells absorb mineral ions from the soil

Active transport

Which substance are xylem cells reinforced with to make them stronger

Lignin

What is transpiration

Evaporation of water form leaves

What happens to the transpiration rate as the temp increases

Increases

Are stomata open or closed during the night

Closed

Why does the rate of transpiration increase if the light intensity is increased

The stomata is open wider to let more carbon dioxide into the leaf for photosynthesis

What happens to the rate of transpiration if the wind increases

Increases

Why does water loss slow down is a plant is pour into a plastic bag

Humidity increases

What influences rate of transpiration to vary

• humidity

• Temp

• Light intensity

• Air flow

What stimuli can plants detect

• gravity

• Touch

• Light

Do plants have a nervous system

No

Do plant hormones act locally (a certain area)

Yes

What is a family of plant hormones produced in the tips of roots and shoots called

Auxins

Which way do auxins diffuse

Backwards from the tip of shoots and roots

What refers to the growth of plants in response to gravity

Geotropism/ gravitropism

What side do auxins accumulate on

• lower side

• Shaded side

Shoots are considered

• positively phototropic

• Negatively geotropic

What is phototropism

A response to light

What happens to make a root grown in the direction of the force of gravity

Top side grows more than the bottom side

What is positive phototropism

Plants grow towards light source

What effects do auxins have on plants

Shoot cell growth and root cell inhibition

Name the plant hormones

Gibberellin

Auxins

Ethene

What are auxins

A family of plant hormones

What are three uses of auxins in agriculture and horticulture

In weed killers, rooting powders and to promote growth in tissue

Auxins stimulate cells to grow and divide so how can they be used as weed killers

Stimulated too much growth, disrupting growth process and kills the plant when too much is used.

What is the benefit of selective weedkillers

kill some plants but not all

What is dormancy

Seeds are inactive and don’t grow or develop

What is the process of germination

Seeds develop and grow

Which pant hormone can stimulate a plant to germinate in

Gibberellin

Which hormone is responsible for inducing fruit to ripen

Ethene

Explain how ethene is used in the transport of food

Ethene stimulates fruit to ripen

Fruit is picked unripe so it’s still hard and isn’t damaged during transport or storage

Ethene used to ripen fruit for sale