Mechanism of ventilation

Adaptation of Air Sacs for Gaseous Exchange

 

Adaptation for all transport :

1) large number of alveoli -> vary large surface area

2) thin layer of epidthellium -> short distance for diffusion

Adaptation for diffusion :

3) moist, covered by mucus -> dissolve and diffuse rapidly

4) covered by network of capillary -> oxygen can delivered to body rapidly , CO2 can delivered out the body rapidly,  create steeply concentration gradient to fasten diffusion

5) low blood pressure in nearby capillary -> stay longer time for gaseous exchange

Structural Adaptation of Leaves for Photosynthesis and Gaseous Exchange

 

-photosynthesis require light, CO2 and H20 as substrate

1) Thin flat shape :

light :

• Maximized the area explosed to light
• Minimized the distance of light to mesophyll cell

CO2 :

• Minimized the distance of CO2 to mesophyll cell

2) Epidermis :

light :

• thin layer
• transpiration, allow light to penetrate

water :

• covered by cuticle , reduce water loss

3) Palisade mesophyll cell :

light :

• closely packed
• lots of chloroplast

4) Spongy mesophyll cell :

CO2 :

• lots of air space

5) Stomata :

CO2 :

• mechanism controling gaseous exchange and water loss

Water :

• mechanism controling gaseous exchange and water loss
• located mainly at lower site

6) Vein :

• act as skeleton
• remove photosynthetic product

 

* think the structure of a leaf first

Gaseous exchange in plant

A) Guard cell:

sausage in shape : allow change of turgidity cause bending thich inner wall : allow bend in side substomatal space : allow gaseous diffusion chloroplast : allow photosynthetic product relay to change in shape

 

B) lenticel:

-layers of dead cells with lots of air space, air diffuse in through the air space to reach the living tissue.

special surface connected to inner system simple diffusion of gaseous smaller the pole, more efficient of gaseous exchange no control mechanism

 

C) root:

1. no cuticule, oxygen are free to diffuse
2. large surface area
3. intercellular spare in cortex, rapid diffusion of oxygen to inner system