Plant nutrition

Question 1

What is plant nutrition?

Answer 1

The study of the chemical elements necessary for plant growth & the adaptations for obtaining these elements

Question 2

80-90% of a plant’s fresh mass is what?

Answer 2

Water

Question 3

4% of a plant’s dry mass is what?

What is the other 96%?

Answer 3

Inorganic substances from soil

From CO2 assimilated during photosynthesis

Question 4

What are essential elements?

Answer 4

Required for plants to survive (complete its life cycle) & reproduce

Question 5

What % do micronutrients make up in some species?

Answer 5

0.02% of dry weight

Question 6

What are most fertilisers?

Answer 6

NPK

= major macronutrients essential for healthy plant growth

Question 7

Give examples of macronutrients

Answer 7

Carbon
Oxygen 
Hydrogen 
Nitrogen 
Potassium 
Calcium 
Magnesium 
Phosphorous 
Sulfar

Question 8

Give an example of a micronutrient and what it’s used for

Answer 8

Manganese

- crucial for amino acid formation & photosynthesis

Question 9

Which is the most abundant macronutrient that isn’t C, H or O2?

Answer 9

Nitrogen

Question 10

What is N a component of?

Answer 10

Amino acids
Nucleic acids
Cofactors
Hormones
Alkaloids
Chlorophyll

Question 11

What is hydroponic culture used for?

Answer 11

Determining which chemical elements are essential

Question 12

What do symptoms of mineral deficiency depend on?

Answer 12

Nutrient’s function & mobility within the plant

Question 13

What does deficiency of a mobile nutrient affect?

Give an example

Answer 13

Older organs

Magnesium

Question 14

What does deficiency of an immobile nutrient affect?

Give an example

Answer 14

Younger organs

Iron

Question 15

Why are older organs affected more in mobile nutrient deficiency?

Answer 15

Mobile nutrients can be transported to actively growing young tissues from older tissues
- so older organs display the deficiency

Question 16

What are the most common deficiencies?

Answer 16

N
P
K

Question 17

What is a key factor that affect nutrient availability?

Answer 17

pH

Question 18

In which pH are there:
> major nutrient deficiencies?
> trace element deficiencies?

Answer 18

> Acidic

> Alkaline

Question 19

How do some species survive in acidic & alkaline soils?

Answer 19

> ability to interact w/ other orgs in soil

> can change chemistry of soil around them to facilitate getting hold of macronutrients

Question 20

Define chlorosis

Answer 20

Yellowing due to loss of chlorophyll

Question 21

Define necrosis

Answer 21

Death of plant tissue

Question 22

What are the symptoms of N deficiency?

Answer 22

> little growth

> yellowing of mature lower leaves

Question 23

What type of nutrient is N?

Answer 23

Mobile macronutrient

Question 24

What are the 2 forms N is acquired in?

Answer 24

> nitrate - favoured as benign & chemically unreactive

> ammonia - toxic as breaks down e- transport

Question 25

Soil is stratified into layers called...?

Answer 25

Soil horizons

Question 26

Which horizon plants obtain most of their water & minerals from?

Answer 26

A horizon | - topsoil

Question 27

What does topsoil consist of?

Answer 27

>mineral particles >living orgs >humus (decaying organic material)

Question 28

What are the basic physical properties of soil?

Answer 28

Texture | Composition (organic & inorganic)

Question 29

What is the B horizon made up of?

Answer 29

Less organic material than A | Less weathered than A

Question 30

What is the C horizon made of?

Answer 30

Partially broken down rock

Question 31

Why can clay particles hold onto water?

Answer 31

They're -vely charged

Question 32

How is soil formed?

Answer 32

By gradual disintegration of rocks | + decaying organic matter integrates into soil aggregates

Question 33

What are cations? Give examples. What do they do to soil particles & why?

Answer 33

+ve charged ions K+, Ca2+,Mg2+ Adhere to them Particles are -vely charged

Question 34

What happens in cation exchange?

Answer 34

Cations are displaced from soil particles by H+ ions produced directly or indirectly by plant roots - -> displace cations enter soil solution - -> can be taken up by plant roots

Question 35

How can H+ ions be released indirectly by plant roots?

Answer 35

CO2 from respiration released from plant roots - -> produces carbonic acid - -> releases H+ ions

Question 36

How can plant nutrition sometimes depend on mutualistic relationships w/ soil microbes?

Answer 36

> secretions from roots support microbes in nearby enviro | > microbes in rhizosphere help plant obtain nutrients

Question 37

What are endophytic bacteria?

Answer 37

Those that live between cells in plant roots

Question 38

What is the rhizosphere?

Answer 38

Layer of soil surrounding the growing root that is affected by the root - no sharp boundary

Question 39

What is rhizodeposition?

Answer 39

The secretion of organic compounds e.g. sugars, amino acids & organic acids by plant roots into the rhizosphere

Question 40

What do rhizodeposits consist of?

Answer 40

> sloughed off cells (by friction w/ soil) | > organic matter exuded (from living cells)

Question 41

Why is rhizodeposition of ecological importance?

Answer 41

> loss of C for the plant > input from organic C pool of the soil > field the soil microbiota

Question 42

What are rhizobacteria?

Answer 42

Bacteria that live in the rhizosphere

Question 43

What are the roles of rhizobacteria?

Answer 43

> produce hormone-like substances = stimulate plant growth > produce antibiotics = protect roots from disease > absorb toxic metals/ make nutrients more available to roots

Question 44

What are the roles of soil bacteria in plant N nutrition?

Answer 44

N-fixing bacteria e.g. Rhizobia (N gas --> ammonia) Ammonifying bacteria (humus --> ammonia) Nitrifying bacteria (ammonium --> nitrate) Denitrifying bacteria (nitrate --> N gas)

Question 45

Why isn't N directly available to plants?

Answer 45

Requires breaking of v stable covalent triple bond | plants can't do

Question 46

What are mycorrhizae?

Answer 46

Mutualistic associations of fungi & roots - increase absorption capacity of plant - fungi gain carbohydrates

Question 47

What are the 2 types of mycorrhizae?

Answer 47

Ectomycorrhizae - grows on surface of roots & between cells Endomycorrhizae (arbuscular mycorrhizae) - gets into cytoplasm of cell

Question 48

What are the nutritional adaptations using other orgs in a non-mutualistic way?

Answer 48

Epiphytes Parasitic plants Carnivorous plants

Question 49

What are epiphytes?

Answer 49

Plants that grow on surface of plants and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it.

Question 50

What are the different examples of types of parasitic plants?

Answer 50

Mistletoe = photosynthetic Dodder = non photosynthetic Indian pipe = non photosynthetic parasite of mycorrhizae

Question 51

Describe carnivorous plants

Answer 51

>Photosynthetic >Obtain N by killing & digesting insects >Adaptation to low nutrient enviro e.g. bogs >Traps = modified leaves

Question 52

What are the 2 types of traps & give examples

Answer 52

Active e.g. Venus fly trap Passive e.g. Pitcher plants

Question 53

What are the costs of botanical carnivory?

Answer 53

> underdeveloped root system > traps not v good at photosynthesis = trade-off between light capture & prey capture