Lecture 11 RH Flashcards
What are some biotic stress factors that affect plants?
Weeds- endemic vs invasive (different categories)
Pests and diseases (flowering trees and seed bearing trees)
How are weeds controlled?
Biological: Includes using animals or other natural enemies to feed on the weeds.
Cultural: Farming systems
Physical: Mulching, hand removal
Chemical: Herbicides
What are some abiotic stress factors?
Drought
Floods
Salinity (evaporation of water from the soil could be problematic)
Low nutrient soils (Australia has a problem with mineral nutrients such as phosphorus and nitrogen)
Fire (Australia has severe fires in summer and autumn)
Why do some plants have mycorrhizal association?
Increases nutrient uptake
Fungus brings in usable nutrients to the plant
Plant breaks down fungus, and obtains nutrients
What are the factors affected by fire?
Physical properties
Chemical properties
Nutrients (decrease in potassium and calcium levels in the soil)
Soil temperature
Soil moisture
Soil biota
What are adaptations that plants have to regular fires?
Resprouters grow from burned trunks
Reseeders produce more trees. (Some seed testa are so rigid that fire is necessary for them to emerge)
How are resprouters adapted to fires?
Rapidly developing buds are formed (At the terminal and can either be naked or have accessories)
Bark produced (some buds form under bark stimulated by hormones during dry seasons)
Underground organs such as lignotubers and tubers
Resprouters use mycorrhizal associations
Other adaptations include scleromorphology adaptations
When does the red bean orchid flower?
After fires
What do naked buds do?
Stalked buds in leaf axils with 1 - 3 per axil.
These buds develop with terminal buds reestablishing canopy cover quickly.
What do accessory buds do?
Secondary buds formed near primary buds
What is the benefit of having bark?
Increases the thickness of the wood and charred bark is shed
What does bark contain that can be used by humans?
Oils (Eucalypts)
Tannins (eg Redwoods)
Sap
What are lignotubers?
Bulbous mass of buds:
Large woody stem swelling
Basal stem tuber bearing many buds
Embedded in bark
Above or below ground
What are tubers?
Underground storage organs and is deep in soild making it protected from fire.
They are normally used for asexual reproduction for regeneration and is dependent on time of fire.
Which trees typically form lignotubers?
Eucaypts (mostly Mallee eucalypts)
What is the function of lignotubers?
They persist throughout the life of plants and are important to fire response and environmental stress response
What is serotiny?
Cones can withstand wildfire. Extreme temperatures open cones and distribute seeds
What happens to leaf morphology in response to fires?
They become hard and rigid with short internodes.
Small plant size
Sclerenchyma tissue is abundant in leaves
What is the origin of scleromorphology?
Probably evolved on margins of rainforest communities in heath vegetation
What are some water conservation strategies for plants?
Small air spaces
Less stomata
Sunken stomata
Small vascular bundles
Fewer vascular bundles
Usually only mesophyll present (no palisade cells)
What is required for germination of new plants?
Testa rupture
Water uptake
What treatments can increase germination?
Temperature: Heat
Physical abrasion
Nutritional smoke water, mycorrhiza
What does burning vegetation do to stimulate seed germination?
Produces cyanohydrins that liberate cyanide and stimulate seed germination
What are the largest angiosperm families in Australia?
Fabaceae 12% (dicot Acacia)
Myrtaceae 9.3% (Dicot Corymbia)
Asteraceae 8.0% (Dicot Goodenia)
What are Casuarinaceae?
She-Oaks which form trees or shrubs
What do causuarinaceae leaves look like?
Reduced to fused teeth on stems
Number of teeth around the stem are diagnostic of
How are casuarinaceae geographically separated?
Northerly form casuarina
Southerly form Allocasuarina
How are casuarinaceae pollinated?
Wind pollination
What do casuarinaceae fruit look like?
Woody cone. Bracts become woody (fire resistant)
Seeds are released when desiccated
What type of flowers do casuarinaceae produce?
Males: 1 bract 2 scale like perianth parts and 1 stamen
Females: 1 bract, 2 bracteoles, ovary of 2 carpels, 2 long reddish styles
What are chenopodiaceae?
Saltbushes
What kind of habitat do chenopodeaceae live in?
Saline habitats, coastal vegetation
What kind of vegetation do chenopodiaceae have?
Shrubs or herbs
What are the vegetative characteristics of chenopodiaceae?
Leaves are simple, alternate or clustered, exstipulate
What do chenopodiaceae flowers look like?
5 persistent sepals (swelling at fruiting into wings or spines or fleshy)
5 stamens
Superior ovary
K(5) C0 A5 G(2_)
What do chenopodiaceae fruit look like?
Dry cluster of follicles