Flora Flashcards
Australia’s Biodiversity: A mega-diverse country
- 8% of World’s species
* Many species endemic
Australia’s Fauna
- Bird
- Lizard
- Mammals
Australia’s Unique Flora
Flowering plants•> 21,000 species•> 90% of Australian species are endemic
What was the origin and history of this unusual Australian biota?
They observed that related plants and animals occurred also in the southern hemisphere, ‘linking’the continents.
Where plants lived in the past -clues to history
- showed evidence of ancient forests
- included leaves, stems, roots of seed fern Glossopteris
- Permian age (286-248 mya)
- Dominant trees
- Grew in swamps that formed coal deposits
- Fossils also in India, South America, South Africa & Australia (many species)
Explanation of a southern biota -its fossils and current distribution patterns
- Old idea(up to 1960’s): recent long distance dispersal over waterways land bridges that connected stationary continents, e.g. ratites walked!
- Modern theoryof continental drift -sea floor spreading and plate tectonics explain old union of land masses and their later movement apar
Moving continents
- Earth has experienced a number of tectonic cycles of continents coming together and moving apart
- Last major cycle started c. 320 mya, by c. 230 mya continents were coalesced into supercontinent Pangea
- Within Pangea, northern land masses joined to form Laurasia; southern lands formed Gondwana
- Pangea began to break up in mid Jurassic (c. 160 mya)
Gondwana break up
- NZ started separating c. 80 mya
- Australia separated by 35 mya
- South America separated c. 30 mya or later
Example of southern hemisphere distributions
- Bony-tongue freshwater fishes
- Ratites (flightless birds)
- Nothofagus -flowering plant(southern beech trees)
Consequences of drifting northwards Climates
Climate changes
•Warm, humid, rainforests initially widespread
•Circum-polar current: cooling of Antarctica
•Reduced wind-bearing rains over Australia and increased aridity from Oligocene (30 my ago)
•Contraction of rainforest decreased
•Evolution and expansion of more arid-adapted plants, e.g. sclerophylls, and animals adapted to them
Consequences of drifting northwards landform
- Old land surface, little mountain building or volcanic activity
- Weathering during warm-wet periods leached nutrients from soils
- Soils became low in nutrients e.g. Phosphorus
- Drier cooler periods increased wind erosion. Mobile dunes; inland lakes dried up & became salt plains
- Evolution further favouredarid-adapted flora & fauna
Consequences of drifting northwards Fire
- Evidence from charcoal and pollen fossil record
- Infrequent but present in wetter periods
- Caused by lightning, volcanoes
- Increased frequency with aridity
- Rainforest contracted further, sclerophyllsfire-adapted
Pleistocene “Ice ages”
- World-wide fluctuating interglacial(warm) and glacial(cold) periods 2.5 my -present
- Australia warm wet/cool dry periods, virtually no glaciation (ice)
- Mobilisationof sands and expansion of desert regions
- Changes in sea level
Arrival of humans
- Genetic evidence: 50 kya
- Archaeological evidence: 49-65 kya
- Possible indirect evidence: charcoal deposits ?100-120 kya
- Fire-stick farming
Megafaunal extinctions
•Concentrated 35-48 kya
Climate change?Hunting?Human use of fire?
Southwest WA: why is it so rich in endemic species?
-Long history of isolation
-Isolation through marine incursions at times of higher sea levels
-•Periods of high sea level: 42–34, 27–21, 16–14 mya
•Limestone deposits created soil (edaphic) barriers
Isolation through climate
-Patterns of species diversity are shaped by evolution –this is influenced by earth history (including climate & geology)
Important of AUSTRALIAN RAINFORESTS
- Surviving remnants of Gondwanan flora & fauna
- Provide a glimpse back in time to vegetation of Gondwana
- High conservation value, NE Queensland Wet Tropics World Heritage Area
- Species rich -50% Australian ferns in rainforests
- 13 of the most primitive flowering plant families
- Austrobaileya-pollen similar to oldest angiosperm fossils (120 million years old)
- Animals withprimitive features
Austrobaileya
- Genus of 1 species (A. scandens)
- Usually placed in its own family (Austobaileyaceae)
- has pollen similar to oldest angiosperm fossils (120 million years old)
TROPICAL RAINFORESTS
- Lowland -most species rich
- 100-200 tree species per hectare
- 1000 beetle species per tree
- Many ferns and palms
- Trees with large leaves (>12.5 cm)
TEMPERATE RAINFORESTS
- Fewer species, South, few vines
- Fewer layers, simpler structure
- Smaller leaves (2.5-7.5 cm)
- Cool temperate rainforests in Vic. & Tas. with single species often dominant:
Lowland tropical rainforests
Climate uniformly warm wet
•Rainfall >1800 mm, alt.<1000 m
•Rapid nutrient cycling
•Regional differences in composition
Leaf adaptations in rainforrest
- Large leaves
- Smooth surface and drip tip prevent moisture accumulating & fungal growth
- guttation: Pores on leaf edge drip water -root pressure forces water (& mineral nutrients) up plantWhen humidity high, little evaporation & transpiration stream
- large compound leaves
Compound leaves in rainforests
Can provide good surface area for capturing light, but also light penetration to lower branches
•Can be “cheaper” to produce than branches
Buttress and prop roots
- Structural support -shallow root system (feedingroots near surface)
- ?competition
Cauliflory
flowering on woody stems where pollinators can easily reach flowers
Epiphytes
a plant growing on another sDendrobium
•Advantage: can access light without investing in stems etc.
•Challenge: no access to soil -rely on water and dissolved nutrients in run-off•orchids, ferns, lichens; often xerophytic, mycorrhizal
2 leaf types advantage
Nest leaves collect litter for nutrients
Plant types found in TR
- Cauliflory
- Epiphytes
- Insectivorse plant
- woody vines (lianes)
- Parasitic plants
Simple leaves or compound leaf?
Look at positions of axillary shoots or buds New shoots (branches or inflorescences) arise from leaf axils
Fruit in the rainforrest
> 80% of tropical rainforest fruits are fleshy, often coloured
Frugivorous birds are common dispersers of rainforest fruits
• “Small” birds disperse 97% of fleshy-fruited species (seeds < 2 cm diameter)
• Mammals and cassowaries disperse other 3%
• Unlike any other rainforest
Animals capable of dispersing large fruit:
- cassowary
- musky rat-kangaroo
- white-tailed uromys
- tree kangaroos
Large seeds/fruit - an advantage?
Advantages:
• resistance to predation
• energy reserves for seedling establishment
Cassowary: unique role in gene flow?
- Largest vertebrate in Australian rainforests
- Only animal capable of long distance seed dispersal
- Up to 2 m tall
- 10 -13 cm claw on inner toe
- Seeds from cassowary gut: 96% germination rate
- No other treatment could do this
- Vital vector for large seed dispersal
- Currently being tracked by BioSciences’ cassowary team
Cyanogenesis: How it works
Cyanogenesis: Production of toxic HCN gas from CN containing compounds in plant; identified in > 2000 plants;
HCN inhibits respiration
Ant mutualism in Java Ash
Food bodies (epidermal structures that contain nutrients – can be removed by foragers): Ryparosa javanica (Java Ash) feed high energy fat to ants
Mymecotrophic plants - ant feeding plants
- Plant base bulbous,hollow chambers that house ants
* Debris & excretia provide plant with nutrients
Mutualisms upon mutualisms: Ant Farmers
- Golden ants collect eggs of endangered Apollo Jewell Butterfly
- Ants look after larvae, which enlarge domatia
- Larvae also secrete syrup like substance which ants eat
- Larvae pupate, hatch, fly away
- Some ants “farm” sap sucking insects in domatia
- Ant taking an aphid to “work”.
- Aphid delivers a drop of phloem sap when stroked by the ant’s antennae
Why is there high sepcies density in rain forrest?
High species diversity of tropical rainforests is linked to physical environment, their structural complexity and species interactions -many ways of living
Non-flowering plants: oldest fossils
Bryophytes prob. Late Silurian (>400 my)
Ferns Early-Mid Devonian (c. 350 my)
Cycads Early Permian (290-251 my)
Conifers Late Carboniferous (>300 my)
Australian conifers
- 44 species; 39 endemic (89%)
- 5 species not endemic are distributed in New Guinea or associated parts of Asia
- Fossil record suggests substantial contraction/extinction in most lineages
- Australian distribution is largely relictual, in mesic vegetation of low combustibility
Native cypress-pines
The only conifers in semi-arid/arid Australia
• Light-coloured foliage (reflects light/heat)
• Small leaves; Stems round in TS (reduces surface area for water loss)
• Woody female cones protect seeds from fire
Cycads
• 7 living families, 11 genera, c. 100 spp.
• Australia: 4 genera, 69 species
• All Aus species endemic (100%)
• Fossil record back to early Permian(c. 251-290 mya)
Seeds in cones or on loose clusters of female branches
• Genus Cycas has no Australian fossil record – recently colonised from
north?
• Fossils of other Australian genera indicate substantial range contraction
Diversity and endemism in Australian
ferns and bryophytes
• Ferns: ~450 species; 35% endemic
• Mosses: ~980 species; 26% endemic
• Liverworts & hornworts: ~870 species; 23-28% endemic
Fern and bryophyte species can be widespread, across ocean gaps
• Populations can show little morphological/genetic variation Dispersal stage of fern and bryophyte life cycles involves single-celled spores
Sexual reproduction in ferns and bryophytes involves flagellated
sperm swimming through free water to egg cells
Spores of bryophytes and ferns
- Produced in large numbers (>10 million/m2)
- Dust-like; mostly 5-70 µm
- Tolerate desiccation, high UV, temperature extremes
fern and byophytes species richness
Highest in wet forests
How do ferns and bryophytes survive in drier
habitats?
- Use sheltered micro-sites
- Infrequent sexual reproduction
- Asexual reproduction/vegetative propagules
- Persistent spores (can remain viable for > 15 years)
- Desiccation tolerance
- Expansion of liverwort thallus in response to water
Photosynthesis
6 CO2 + 12 H2O C6H12O6 + 6O2 + 6H2O
• < 1% of plant water use is in reactions of photosynthesis
Gas exchange requires open stomata
Stomatal aperture is controlled by turgor of the guard cells
Types of Plants that survive in drier environments
- Drought avoiding plants
- Drought tolerating plants (xerophytes) – with physical or physiological adaptations that maximise water uptake, minimise, water loss and maximise water use efficiency.
Drought avoidance
• Annual/ephemeral plants spend drier times as seeds
• Grow and reproduce quickly when moisture is available
maximising water supply: River red gum has deep root system; can access ground water
Xerophytes: drought tolerators
• Found in 20+ families of Australian plants
•evolved due to Increased aridity, increased fire frequency and weathering of soils during the last 30 my
-favoured the evolution and dominance of xerophytes
• Two major types: sclerophylls and succulents
Sclerophylls -
hard-leaved plants
More common than succulents
• Often small leaf size, short internodes
• Proportionally thick leaves
• Reduced surface area/volume ratio
Ø Anatomical features
Thick-walled cells (sclereids, fibres) - lignin in walls
Thick cuticle and waxy coating
the primary cell dies off to form a barrier
ØLeaf hairs reduce evapotranspiration: boundary layer
Why did sclerophylly first evolve?
Beadle’s hypothesis: Sclerophylly first evolved on soils of low nutrient level - especially low P
Why might sclerophylly be an adaptation to
low nutrient soils?
• Lack of nutrients can limit plant cell growth and metabolism, e.g., P is critically important, as backbone of nucleic acids, in ATP, cell membranes etc.
• slow growth, smaller leaves and internodes, carbohydrates channeled into lignin, thick cell walls = more efficient use of nutrients
Sclerophyllous plants evident before the onset of aridity in Australia, e.g. fossil
Banksia > 50 mya
slow growth, small cells, carbohydrates channeled into lignin, thick cell walls, which pre-adapted plants to increased aridity
Succulent plants
- Plants fleshy, with cells large & filled with watery sap; drought and salt tolerant
- Family Chenopodiaceae (saltbushes) of deserts; related to coastal saltmarsh plants
Adaptations: Chenopod shrub
- Surface colour reflects radiation
* Covered with bladder cells to excrete salt
Prickly Pear: pest attributes
Drought resistant (CAM, succulence, cuticle)
• Sexual and asexual reproduction (underground bulbs - some species)
• Pads and fruit can root (floods)
• Yummy fruit (seed dispersal)
The Solution to cacti?
• Slash and burn
• 100s of tonnes of arsenic pentoxide were used to kill the prickly pear to no affect.
• As can still be detected today
bounty on bird
Biological Control
• Study began in 1912 • 150 insects studied world wide • 52 brought to Australia • Tested for host specificity • 18 insects and 1 mite released • 9 insects and the mite survived stem boring moth – most effective against common and spiny pest pear
trait of cacti that help them to addapt to Australia
- Low area/volume ratio reduces water loss
- Extensive, shallow root system
- new rain root form rapidly
- full of water
CAM - the cactus advantage
- CAM - Crassulacean Acid Metabolism – a modification involving the delivery of CO2 to photosynthesis
- First identified in members of the family Crassulaceae
- Generally grow where water is scarce, with some exceptions
Some common CAMs
• Pineapple • Aloe • Orchids • 26 Angiosperm families • Cactaceae, Orchidaceae, Bromeliaceae, Liliaceae • Some ferns and at least one gymnosperm • About 7% of vascular plant species are CAM
How CAM works
- CO2 pumped into storage at night
- Pump = PEP carboxylase
- Storage = vacuole (malic acid)
- Stomata close in the early morning
- Water trapped in the plant
- CO2 concentrated in plant, used by photosynthesis
- Photosynthesis stimulated, Photorespiration is inhibited
- Little water is lost due to closed stomata
Photorespiration
: Rubisco catalyzes oxygenation of ribulose
bisphosphate (RuBP)
Rate of photorespiration increases with temperature
On the CO2 Trail
- Some insects can measure CO2 (moths, butterflies, flies, bees, mosquitoes, ticks)
- CAM plants “breath” in CO2 when all of the other plants are “breathing” out.
- Patches of prickly pear cannot hide from Cactoblastis
- There is an additional volatile signal from Opuntia
How do you spot a CAM
Taste Test: sour by night, sweet by day
Discrimination between 13CO2 and 12CO2
• 1.1% of biospheric and atmospheric C is 13C, a stable isotope
• The CO2 pump (PEP carboxylase) is less fussy about 13CO2
CAM can be switched on
- Obligate (or constitutive) CAM – plants that always perform CAM, independent of conditions (e.g. most Opuntia species)
- Facultative CAM – CAM expression depends on environmental and/or developmental cues (e.g. pineapple and other bromeliads)
CAM Idling – Under Extreme Stress
Stomata always closed
• No net CO2 uptake
• CO2 from night-time respiration used to make malate
• Same CO2 released during the day to run `photosynthesis
CAM Cycling – Saves Water
- CO2 collected from respiration at night when stomata are closed
- CO2 released during day from storage, so stomata do not have to open as much
- Less water lost
- More CAM cyclers are being discovered
: Australian CAM
Chenopodiaceae • Atriplex(salt bush) • Maireana(blue bush) Most known CAM plants in Australia are are epiphytes or lithophytes – at least 53 are orchids, but also ferns and other plant groups (e.g. Myrmecodia) • Some submerged aquatic plants show CAM (eg. Isoetes - quillworts) • During the day, photosynthetic algae rapidly deplete CO 2 in water • CAM gets around this by fixing CO 2 at night!
Plants differ in water use efficiency
C3 400-500
C4 250-300
CAM 50-100
C4 Photosynthesis
• In most (C4) grasses, a CO2 pump can “suck” CO2 in
through less open stomata, saving water
Spatial separation of
carbon fixation step
Why stay wet and cool in arid condition?
- High temperatures can lead to irreversible damage – proteins denature
- H2O evaporation used as cooling (latent heat loss)
- H2O needed for cellular functioning (maintaining turgor), nutrient transport, photosynthesis
Kangaroos – used 3 strategies to manipulate the
energy budget for survival
- reduce radiation load
- promoting latent heat flux
- promoted sensible heat flux
Plant Leaves adaptation to arid condition
n Leaf orientation
n Leaf shape
n Leaf amount-low leaf weight ratio (Mleaves/Mplant); drought deciduous plants
n Leaf optics
Adjusting leaf orientation
• Sun-tracking (diaheliotropic), or sun-avoiding (paraheliotropic), e.g. Hardenbergia
Leaf Angle
and Azimuth
- horizontal leaf absorbs most light
- vertical east-west almost as much
- vertical N-S much less
- paraheliotropism leaves always parallel to sun’s rays
- diaheliotropism leaves always perpendicular to sun’s rays
Leaf optics
• All Atriplex species (59 in Australia) are covered with unique bladder hairs
• Hairs have a balloon-like terminal bladder cell supported by a stalk cell
• Bladders accumulate high concentrations of salt
-lower leaves temperature
Adaptation to Promote Latent Heat Flux
- Maximise water supply
Includes adaptations for obtaining water, buffering water supply, increasing water use efficiency (to make less water last longer)
Radiation load
NET RADIATION
LOAD – Solar + heat
from surroundings
Maintaining physiological temperature: different form of heat loss
Sensible heat-Heat loss from warmer leaf (animal) to cooler air
Latent heat-Heat loss from evaporation of water
Maintaining physiological temperature
- possible to have sensible heat gain from warmer air
- Greater latent heat loss required to maintain temperature
equation to calculate water loss and heat loss
Sensible heat Flux = gh(Tl – Ta)
Tl
, Ta = leaf, air temperature; gh conduction of air,gh – proportional to wind speed (thickness of boundary layer)
latent heat Flux = gw(Wl – Wa) Wl
, Wa = water vapour conc. in leaf, air. gw conductant to water vapor.gw – proportional to stomatal aperture
Plant adaptation to fire
Ø Effects of fire depend on temperature and duration (speed) of fire: very fast hot fire may deal
less damage than a slow long fire
Ø Plant adaptations include:
1. Tolerance of fire: protective features, even stimulated by fire to flower
2. Adult plant killed but seeds survive
3. Plants promote fire e.g. eucalypts with oil in leaves help fire to burn rapidly (less damage)
Plant adaptation to survive fire
Ø Thick fibrous outer bark (corky layers) protects living parts - phloem and cambium
- Dormant buds: 1. Aerial: epicormic
- Underground buds Lignotubers (eucalypts),Rhizomes (bracken)
Regeneration from seed after fire
Ø Seeds released from woody fruits (canopy seed bank)
Ø Soil seed bank - seeds with hard-coats, cracked by heat, imbibe water & germinate
Seeds with an elaiosome (fleshy funicle) provide a food reward for ants
Ø Ants harvest seed, bury underground, discard hard seed and eat reward. Both species benefit.
• Common in Australia, c. 87 genera, 24 families
Fire stimulates seed germination
-Many native plants are known to have low germination rates in the absence of fire
-Experiments showed that smoke was responsible for stimulating germination in many species
-Subsequently shown that a Butenolide, small carbon-molecule, by-product of burning cellulose:
-breaks seed dormancy
example:
Haemodoraceae
Anigozanthos, Conostylis, Anigozanthos
Proteaceae
Conospermum, Stirlingia, Grevillea,
Petrophile
Rutaceae
Philotheca, Geleznowia
Fire stimulates flowering
Smoke compounds act as hormones and may stimulate flowering (ethylene)
Fire as management tool to maximise biodiversity
Ø Burn too often (<5 year cycle), plants killed, grow from seed but cannot reach flowering age and set seed; only short-lived plants or sprouter with bulbs, rhizomes survive
Ø Long-time unburnt (>50 yrs), some shrubs die & some
grow large and dominate, shading out smaller plants
Biology of family Proteaceae
• 1500 species, > 800 spp in Australia
- a centre of diversity
• Forests, woodlands, heathlands on low nutrient soils e.g. Banksia, Grevillea
• Rainforests Macadamia, Telopea (waratahs)
• Sclerophyll woody shrubs and trees with corky bark, often lignotubers
• Fruits woody follicles or fleshy drupes
Age of Proteaceae
• Old Gondwanan family with fossil pollen 80 million years old
(Cretaceous)
The typical Proteaceae flower
- 4-lobed perianth (tepals)
- 4 stamens attached to tepals
- Ovary 1 or 2 compartments
- Style long & acts as pollen presenter (male phase) then receives pollen (female phase)
Banksia - fruits, seeds and fire
Proteacea
• Often only a few ovaries develop as fruits
• Fruit a woody follicle, usually opens after fire
• 2 winged seeds per follicle
Proteaceae & bush tucker
• Edible nuts - Macadamia rich in oils; only commercial crop based on a rainforest tree of Queensland
• Fleshy sweet drupes- geebung Persoonia
-Nectar - Banksia dentata, Grevillea juncifolia,
G. robusta
Alternative names/classifications of Legumes
3 families o Peas: Fabaceae o Cassias: Ceasalpiniaceae o Wattles: Mimosaceae Or 1 family Fabaceae with three subfamilies o Faboideae o Ceasalpinioideae o Mimosoideae
Australian Legumes
Fruits a pod - a legume
Ø Food plants - peas and beans
Ø Native species often toxic but used by Aboriginal people
Ø Some a source of medicinal compounds or genetic traits (e.g. drought tolerance) for crop legumes e.g. Glycine traits for soy beans
Australian Fabaceae
1100 spp. • trees • shrubs • herbs • creepers • climbers
Family Fabaceae - peas
Ø Seeds have hard resistant coats - survive fire
Ø Leaves often compound - 3 leaflets or more
Ø Sclerophyll forms leaves simple, reduced to spines or scales
Nitrogen fixing
Pea family Fabaceae
Butterfly flowers
5 petals: 3 free 2 united; 10 stamens
side petal know as wing, bottom two know as keel
Egg & bacon peas Insect pollinated
Fabaceae Standard petal large, showy Yellow attracts bees Markings are nectar guides Keel and wing form a landing platform for the bee (Some peas, e.g. red flowered, are bird pollinated)
Acacia -
- Known in Australia since the Early Miocene
- Acacia is the largest genus of woody flowering plants in Australia with 960 species
- Occur in rainforests and wet eucalypt forest e.g. Acacia melanoxylon (blackwood)
- Dominant in semi-arid and arid regions e.g. mulga lands
Wattles Acacia-ecomimic use
- Green Acacia seeds roasted 18-25% protein content
- Acacia gum - bush candy
- Timber, e.g. blackwood A. melanoxylon
- Important after fire - fix Nitrogen
- root nodules with bacteria: Rhizobium
Acacias - two foliage types
bipinnate leaves
phyllodes
Acacias Flower
- Cylindrical Flower spike
- Flowers in globular heads
Acacia pollination biology
Very small flowers, in clusters (heads or spikes).
no petals (more like small inconspicuous petal)
1. Female phase style elongates,
2. Male phase
pollen shed
Acacia bird pollination
extra-floral nectaries on leaves or phyllodes; showy inflorescence of many flower clusters
-floral nectaries can also attract ants
-ant does not pollinate
• Keep plant relatively free of fungal spores
• Ward off herbivorous insects
Acacia fruits and seeds
- Fruit a legume (pod)
- seed coat hard - seed won’t take in water and germinate until this is cracked (e.g. by heat of fire)
- often have an eliasome - ants take seeds underground
Family Myrtaceae example and uses
• In Australia: bottlebrushes, tea trees, paperbarks, lilly pillies; eucalypts dominate forests and woodlands
• Used traditionally for wood for canoes, bark, honey, water (mallee roots)
• Modern uses- horticulture, timber, paper, oils, spices - cloves (Syzygium aromaticum
flower buds)
• Fruit - scrub cherries, Guava, Feijoa
Characteristics of Family
Myrtaceae leaves and fruit
• All have leaves with aromatic oils in oil glands
• Anti-herbivory; increases flammability
Dry-fruited forms e.g. eucalypt capsule opens by valves (splitting of top of ovary
Ø Fleshy-fruited forms e.g. rainforest lilly pilly
Myrtaceae typical flower
Ø Flower regular in shape, 4-5 sepals, 4-5 petals
Tea tree
Ø Many stamens
Ø Inferior ovary
Tea tree flower
- White, open flowers
* Pollinated by flies, beetles, bees
The eucalypts
Ø 700+ species in Australia
Ø Forest, woodlands and mallee shrublands
Ø All habitats except rainforest, alpine and arid desert
The eucalypts - uses
• Timber - building, furniture E. marginata (jarrah) WA E. regnans (mountain ash) EA • Pulp for paper • Fuel • Oils • Ornamentals • Reforestation of degraded land e.g. red gums, blue gums in salted areas • Habitats for animals e.g. hollows in tree trunks for possums
Mountain ash
- The tallest flowering plant in the world
- 100+ m height, 400 years old, nest hollows a resource for animals
- After fire, regenerates from seed stored in canopy in woody fruits
Eucalypt fossils
Australia
Ø Flowers & Fruits 30 mya
Ø Pollen 60 mya
South America c. 50 mya
Three eucalypt genera
Angophora Corymbia Eucalyptus
13 spp 100+ spp 600+ spp
Eucalyptus flowers
have protective caps (opercula
homologous to sepals and petals
Eucalypt flower and fruit development
1 sepal operculum shed
2 petal operculum shed
Anthesis, stamens displayed, pollen shed
Style extends Stigma receptive, fertilisation,
style withers ovary swells
Eucalypt fruit
-woody capsule
aids species identification
Eucalyptus leaves
Eucalypts have distinctive foliage at various life stage
Juvenile: often leaf opposite, sessile, held horizontally, dorsiventral anatomy
Petiole twists during development and leaf hangs vertically
Eucalyptus adult leaf isobilateral anatomy
Some Eucalyptus species retain juvenile foliage
Identifying eucalypts
- Fruit shape and size
- Bark type
- Leaf shape and size (including juveniles)
- Flower bud shape/number
