26. Describe the mechanism of gaseous exchange in plants.
Answer:
a)Leaves
-Gaseous exchange in leaves take place in the spongy mesophyll where there are large air spaces and across the stomata; during the day photosynthesis take place using carbon (IV) oxide and releasing oxygen; the concentration of carbon (IV) oxide in the intercellular air spaces decreases as compared to outside/ atmosphere; hence carbon (IV) oxide diffuses through the stomata; in solution form into the intercellular air spaces; oxygen released during photosynthesis increases its concentration inside the intercellular spaces than outside/ atmosphere; hence it diffuses out of the leaf/ intercellular air spaces into the atmosphere through the stomata; and some oxygen is used for respiration.
-During the night photosynthesis does not take place but respiration continues using oxygen and releasing carbon (IV) oxide; this lowers the concentration of oxygen in the intercellular air spaces than the atmosphere; hence oxygen diffuses through the stomata into the intercellular spaces; carbon (IV) oxide released during respiration increases in concentration in the intercellular spaces than the atmosphere; hence diffuses through the stomata into the atmosphere;
b)Stem and roots of woody plants
-Gaseous exchange takes place through the lenticels; which are openings made up of loosely packed cork cells; the cells respire using oxygen thus lowering its concentration inside the lenticels than outside; hence it diffuses from the atmosphere through the lenticels; carbon (IV) oxide released during respiration increases its concentration inside the lenticels than the atmosphere; hence it diffuses out of the lenticels into the atmosphere;
c)Roots
-Gaseous exchange takes place across the epidermis and cuticle, pneumatophores; Oxygen is in higher concentration in the soil particles than inside the roots; hence diffuses into the cells/roots through the cuticle/ epidermis/ pneumatophores; Carbon (IV) oxide is in higher concentration in the roots than in the soil; hence diffuses out of the cells/roots through the cuticle/ epidermis/ pneumatophores;
d)Submerged hydrophytes.
-Gaseous exchange takes place through aerenchyma tissue; Oxygen concentration is higher in the water than in aerenchyma tissue; hence it diffuses into the aerenchyma tissue; Carbon (IV) oxide concentration is higher inside the aerenchyma tissue than water; hence it diffuses out of aerenchyma tissue into water.
-Gaseous exchange in leaves take place in the spongy mesophyll where there are large air spaces and across the stomata; during the day photosynthesis take place using carbon (IV) oxide and releasing oxygen; the concentration of carbon (IV) oxide in the intercellular air spaces decreases as compared to outside/ atmosphere; hence carbon (IV) oxide diffuses through the stomata; in solution form into the intercellular air spaces; oxygen released during photosynthesis increases its concentration inside the intercellular spaces than outside/ atmosphere; hence it diffuses out of the leaf/ intercellular air spaces into the atmosphere through the stomata; and some oxygen is used for respiration.
-During the night photosynthesis does not take place but respiration continues using oxygen and releasing carbon (IV) oxide; this lowers the concentration of oxygen in the intercellular air spaces than the atmosphere; hence oxygen diffuses through the stomata into the intercellular spaces; carbon (IV) oxide released during respiration increases in concentration in the intercellular spaces than the atmosphere; hence diffuses through the stomata into the atmosphere;
b)Stem and roots of woody plants
-Gaseous exchange takes place through the lenticels; which are openings made up of loosely packed cork cells; the cells respire using oxygen thus lowering its concentration inside the lenticels than outside; hence it diffuses from the atmosphere through the lenticels; carbon (IV) oxide released during respiration increases its concentration inside the lenticels than the atmosphere; hence it diffuses out of the lenticels into the atmosphere;
c)Roots
-Gaseous exchange takes place across the epidermis and cuticle, pneumatophores; Oxygen is in higher concentration in the soil particles than inside the roots; hence diffuses into the cells/roots through the cuticle/ epidermis/ pneumatophores; Carbon (IV) oxide is in higher concentration in the roots than in the soil; hence diffuses out of the cells/roots through the cuticle/ epidermis/ pneumatophores;
d)Submerged hydrophytes.
-Gaseous exchange takes place through aerenchyma tissue; Oxygen concentration is higher in the water than in aerenchyma tissue; hence it diffuses into the aerenchyma tissue; Carbon (IV) oxide concentration is higher inside the aerenchyma tissue than water; hence it diffuses out of aerenchyma tissue into water.
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Explain what would happen to red blood cells if they are placed in a concentrated salt solution. 
