Lecture 9- Coping with aridity and drought III

Question 1

What structure allows Cactoblastis cactorum to find the prickly pear?

Answer 1

labial palsp located in either side of the proboscis can measure CO2 with a resolution of 1ppm
-that is how cactoblastus found the opuntias

Question 2

Can Cactoblastis cactorum be a problem?

Answer 2

• Cactoblastis introduced to South Africa, Hawaii, Bahamas
• Moved from Bahamas to Florida
• Advancing across SE USA and Mexico
-cactoblastis may be a problem for where prockly pear occurs naturallly

Question 3

What are the basic principles of how to survive in a desert?

Answer 3

• Stay wet • Stay cool • Tolerate dehydration • Tolerate over-heating

• water is the key to survival, have to stay wet and cool
• helps to tolerate dehydration and over-heating

Question 4

Why is water important for organisms in the desert?

Answer 4

• 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

Question 5

Do plants sweat?

Answer 5

• yes
• transpiration
• latent heat loss as it takes lot of energy with it
• 99% of water that gets into a plant is evaporated
• only a little bit is used in photosynthesis

Question 6

Is there a connection between rainfall levels and plant productivity?

Answer 6

productivity of plants is highly correlated with amount of rainfall

• the ability to make dry matter= grow
• this is globally
• hyperbolic relationship

Question 7

Where do you get radiation from when outside?

Answer 7

• you will pick up radiation when you are outside= comes from the sun (solar) and from the surroundings (from absolute heat, everything above absolute zero emit it)
• net radiation load= the total amount of the two

Question 8

What is the net radiation load?

Answer 8

the sum of solar heat and heat from the surroundings

Question 9

What is sensible heat loss?

Answer 9

• e.g. from warmer leaf to cooler air
• as you get hot and rise above the air temperature= that heat is transferred to the surrounding, both inanimate and animate objects heat up and trasfer it to the air

Question 10

What is latent heat loss?

Answer 10

-via evaporation of water, takes lot of energy from the organism

Question 11

What does survival in the desert and elsewhere depend on?

Answer 11

• involves manipulation of load and/or disipation/loss processes
• go to the shade or something like that

Question 12

What is the sauna experiment?

Answer 12

• Set sauna at 110 C • Sit still and appraise
fluxes • Large sensible heat gain • Large latent heat loss
• Boundary layer reduces sensible flux
-hotter than you so get sensible heat gain
-sweat= latent heat loss
-boundary layer= aerodynamic boundary layer= boundary of still air that imposes a resistance to sensible heat gain
-that is why it is good not to move

Question 13

What is a boundary layer and how is it important in maintaining temperature?

Answer 13

• boundary layer= aerodynamic boundary layer= boundary of still air that imposes a resistance to sensible heat gain
• that is why it is good not to move

Question 14

What balance maintains body temperature within set physiological range

Answer 14

-the balance: the sensible and latent heat maintain body temperature in physiological range

Question 15

What are the strategies of avoiding heat in kangaroos?

Answer 15

survival strategy 1: reduce radiation load

• kangaroos licking their forearms= veins close to surface, lick and latent heat loss= cool down
• dig the soil so can get to the cooler ground underneath
• wet areas have lower sensible heat flux
• hide in the shade as well
• solar radioation(shade), latent heat(licking) and sensible heat(ground)= have to balance

Question 16

What are the factors on a plant that can be manipulated to deal with temperature change?

Answer 16

! Leaf orientation ! Leaf shape ! Leaf amount ! Leaf optic