Biotic Interactions Flashcards
What are biotic interactions
Includes disease, herbivory and competition
Examples of disease organisms
Plant pathogens
Example of herbivory organisms
Pests
Examples of competition organisms
Weeds and neighbouring plants
What is the average percentage loss for major crops to disease
4
What is the average percentage loss for major crops to pests
3
What is the average percentage loss for major crops to weeds
3
What is disease
Damage to plants due to infection by plant pathogen micro-organisms like viruses and bacteria and fungi
Example of virus
Cucumber mosaic
What takes place in a lot of vitally infected plants
Chlorotic effect
Example of bacteria on pant s
Crown gall
Soft rots like in cabbage
Example of fungi causing disease
Potato blight
Southern leaf blight
Dutch elm disease
What are fungi a major problem in
Crops and many wild plants like anther smut
How is Dutch elm disease spread
A vascular wilt disease spread By bark beetles
When did Dutch elm disease transform the uk landscape
1960s - rarely see them in the country side anymore
What is a disease in our lifetime
Ashdie back - through the country to point it’s almost everywhere and is dangerous for trees and composition of flora and fauna. Maturing trees wilt and die back, stem rots, twigs are dead. Fungus sporalating through tree
Examples of plant eating animals
Vertebrates and invertebrates
Examples of invertebrates
Mites - attacking aerial
Nematodes - attacking roots
What are the different ways in which insect eat the plants
Attack different host tissue.
Chewers and sap suckers
How do chewers work
Boring through the centre of wooden stems of plants or down into bulbs or this ones if plants causing damage
How do sap-suckers work
black fly or green fly. Plug feeding part into flower forcing the content out into their mouth as honeydew
How does competition work
Limits the maximum size of a population or its biomass in a given habitat
What are the two competition interactions
Between individuals of he same species or individuals of different species
What are many plants
Aggressive competitiors
What is vital to understand in competition
It may be slow but it’s intense.
Interactions between crops within a monoculture for example.
Crop-weed interactions.
The structure and dynamics of natural vegetation.
How do competition, pathogens and pests affect plant growth
Interfer with host plants ability to acquire and utilise essential resources
What are essential resources for plants
Light (most important)
Water
Co2
Nutrients
Why is a plants ability to intercept and utilise the light important
To reproduce photosynthate to produce sugar for growth rate
What are plant growth and crop yield often seen as
Direct linear functions of cumulative light interception
What does light interception depend on
Leaf area:
The amount of leaf area and position of the leaves
How does the position of the leaves affect light interception
Horizontal leaves vs vertical leaves. Position within the canopy. Above is likely to intercept more light.
Examples of plant adaptations conferring strong competitive ability
Taller plants - on top of canopy so more light
Bigger plants - larger leaf area
Faster growing plants - go above and get light b4 others can shade you
How can pest and pathogens reduce yield
Reducing light interception - destroying leaf area.
Reducing efficiency with which light is utilised in photosynthesis. Bc the plant is chlorotic more energy used photosynthetically to bring colour back.
Both these thing combined is most fruqent and main long term effect.
How can plants respond to biotic interactions
Acclimation and adaptation
How can plants acclimate
Compensate for loss of photosynthate ability.
Reduce the probability and or severity of future attacks.
How do plants compensate for loss of photosynthate
Increase photosynthesis in undamaged leaves.
Rapid regrow this of new leaf tissue.
How do plants reduce the probability andnor severity of future attacks
Getting resistance developed through initial infection - systematically resistance of infection. E.g one leaf inoculated with rust disease and infection allowed to develop, one week later a second healthy leaf developed.
What are the 2 ways plants can adapt
Tolerance
Resistance
What is tolerance
The ability of the plant to endure the effects of herbivory (or infection by pathogen)
Example of tolerance
Always accumulate a lot of biomass as stored reserves that can be mobilised to support rapid re-growth after damage
What is resistance
The ability of the plant to rescue the severity of herbivory (or infection by a pathogen)
Example of resistance
Altering morphology
Chemical
Examples of altering morphology
Spines and thorns.
Layers in cell wall that prevent the penetration of fungal cells.
Change structure of the plant so it’s less attractive by changing the biochemistry.
Make it harder to break down and chew.
What is altering morphology
Increaed toughness and physical barriers
What is chemical resistance central to
Many plant defences against pests and pathogens and understanding how environmental change may affect ecosystem processes.
How do plants change their secondary chemistry in biotic stress
Producing different metabolites and different compounds to make plant less attractive or more toxic or gross and less able to be broken down by stress.
How do plants change their secondary chemistry for UV-B
Acclimate using uv-b compounds and they are the same type of compounds plants utilise as chemical mechanisms against biodecomposers.
Why is chemical resistance critical to think about
All the changes in the environment that could have the potential to have an impact on secondary chemistry. How they resit a whole plethora of consumers.
