Biotic and Abiotic Interactions

Question 1

Biotic interactions

Answer 1

interactions between living things

Question 2

Abiotic interactions

Answer 2

interactions between organism and non-living factors

Question 3

Biotroph

Answer 3

the pathogen is entirely dependent on the host for nutrition

Question 4

Necrotroph

Answer 4

kills host tissue as grows through them

Question 5

Steps of pathogen (disease)

Answer 5

Locate the host
Attachment/adhere
Penetration and entry
Colonization
Suppression or avoidance of host defences
Reproduction
Dispersal from host

Question 6

What do pathogens produce that causes part or all of the disease syndrome?

Answer 6

produce toxins

Question 7

Types of defences by host plant:

Answer 7

inducible and constitutive

Question 8

Detection systems

Answer 8

Resistance gene (plant) interacts with product of avirulence gene (pathogen).

Question 9

Detection systems

Answer 9

Resistance gene (plant) interacts with product of avirulence gene (pathogen). Elicitor activates defence response by plant receptor.

Question 10

Responses to pathogen recognition

Answer 10

Hydrogen peroxide
Hydroxyl radical
(through NADPH-dependent oxidases)

Question 11

What do hydrogen peroxide and hydroxyl radicals do in plant defence?

Answer 11

Initiate hypersensitive response

Directly kill

Question 12

What is the hypersensitive response?

Answer 12

Cells kill themselves at the site of infection to prevent further spread.

Question 13

When does the hypersensitive response work?

Answer 13

Biotrophs only

Question 14

What is systemic acquired resistance?

Answer 14

plant survives infection at one site the plant develops increased resistance at subsequent attack at sites throughout the plant

Question 15

What is the use of methyl salicylate in plant defence?

Answer 15

Important signalling molecule for systematic acquired resistance.
Thought to be important in local signalling of pathogen attack to other plants (transpiration from leaves).

Question 16

How is methyl salicylate transported around plant?

Answer 16

mostly likely through the vascular system

Question 17

What are pathogen-related proteins (plant)?

Answer 17

hydrolytic enzymes that destroy pathogens macromolecules

Question 18

Example of constitutive defence

Answer 18

For insect herbivory (deters feeding):
Terpenes – stored in resin canals or glandular hairs on plant surface
E.g. menthol

Question 19

Example of inducible defence

Answer 19

Triggered by substance in insect saliva, Jasmonic acid

• > Protease inhibitors (block protein digestion)
• > amylase (block starch digestion)
• > signals to local area (other plants)

Question 20

What are alkaloids?

Answer 20

constitutive defence molecule produced and stored by plants. Has a dramatic effect on vertebrate animals.
E.g. caffeine/nicotene…

Question 21

What are phenolic compounds?

Answer 21

constitutive defence
stored compounds that deter insect feeding or have anti-fungal effects
E.g. benzoic acid

Question 22

What are cyanogenic glycosides?

Answer 22

constitutive defence
Present in the vacuole and enzymes required to release cyanide in the cytosol.
E.g. apple seeds

Question 23

What are phytoalexins

Answer 23

Inducible defence
produced by de novo synthesis in response to stress, particularly pathogen attack
E.g. rishitin (potatoes)

Question 24

Two categories for response to abiotic stress

Answer 24

Adaptation

Acclimation

Question 25

Acclimation

Answer 25

aka plasticity

Physiological or metabolic response of individuals in response to changing environmental factors

Question 26

Adaptation

Answer 26

Constant or recurrent environmental challenges exert selective pressure driving evolution of traits that increase fitness under stress. Occurs over generations and across populations.

Question 27

Physio-chemical variables in the environment

Answer 27

Water (lack and excess)
Oxygen (and reactive derivatives)
Radiant energy
Mechanical influences

Question 28

Response(s) to water deficit and osmotic stress

Answer 28

Vacuolar accumulation of salts
Cytoplasm and organelles accumulated compatible solutes(sol. @ high conc. and non-toxic)
Stomatal closure (abscisic acid)

Question 29

Response(s) to flooding (excess water)

Answer 29

Generate ATP in glycolysis
Regenerate NAD+ through production of ethanol
Aerenchyma in roots to help O2 diffusion controlled by ethylene production
Suberin and lignin deposits at the hypodermis help stop O2 leaking out of the root

Question 30

Response(s) to cold stress

Answer 30

Accumulation of compatible solutes (osmoprotectants) allows cellular water to ‘super cool’ without freezing down to -40ºC.

Question 31

Response(s) to chilling sensitivity

Answer 31

more unsaturated fatty acids the membrane contains the lower the temperature at which the liquid to gel transition of cell membrane occurs.

Question 32

Response(s) to excess light

Answer 32

Light receive by violaxanthin then given to chlorophyll

When too much light, violaxanthin can be converted into zeaxanthin (reversible).

Question 33

Response(s) to high temperature stress

Answer 33

Heat shock proteins interact with proteins to:

• Stop aggregation of proteins
• Promote disaggregation of proteins
• Assist folding and refolding of proteins