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8 Cards in this Set

  • Front
  • Back

Cacti Arrive in Australia

Opuntia (prickly pear) first imported to support the growth of cochineal insects (and to maintain spiffy red coats on parade), it subsequently, and briefly, lent ambience to early vineyards


Rate of advance = 100 ha per hour!

The Solution?

Slash and burn •100s of tonnes of arsenic pentoxide were used to kill the prickly pear to no affect.

Prickly Pear – Environmental Weed

Environmental weeds - those species that invade native communities or ecosystems - they are undesirable from an ecological perspective, but not necessarily an economic one.




•Serious environmental weeds - those that cause major modification to species richness, abundance or ecosystem function.




•Very serious environmental weeds - those that can totally and permanently destroy an ecosystem.

CAM - the cactus’ advantage?

• CAM - Crassulacean Acid Metabolism wFirst identified in members of the family Crassulaceae wGenerally grow where water is scarce, with some exceptions wCAM is not wide-spread in Australia. common cams (Pineapple •Aloe•Orchids)







Why is CAM so good?

CAM plants have stomata


• When they open to let CO2in, H2O escapes


• CAM plants open stomata at night


Slashing was more effective at night

Study to kill the cacti

Cactoblastis cactorum (stem boring moth – most effective against common and spiny pest pear) •Dactylopius spp. (cochineal mealybug – 5 species)


•(Females spend life attached to plants; covered in waxy secretion; yield redish colour when crushed.


government gave farmers heaps of these eggs to kill the cacti

Why stay wet and cool?
Good solvent at physiological temperatures •Maintain structure (turgor)
•Cooling (latent heat loss)
•Transport
•Price of fixing CO2
•Substrate for photosynthesis
•High temperatures can lead to irreversible damage
Survival Strategy 1: Reduce Radiation Load

Leaf Angle- horizontal leaf absorbs most light


Paraheliotropism leaves always parallel to sun’s rays. dia is opposite


Leaf orientation


Leaf shape


Leaf amount


Leaf optics