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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
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
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