Transpiration Flashcards
What is transpiration?
Transpiration is defined as the loss of water from plants in the form of water vapor through aerial parts of the plant.
What is cobalt chloride paper used for? What does its different colors indicate?
Cobalt chloride paper is an indicator for moisture.
BLUE- absence of moisture; dry
PINK- presence of moisture; wet
What are the two methods by which we can measure transpiration?
- Weighing method
- Potometer method
What are some precautions in the use of a potometer?
- potometer should be made water-tight.
- twig of the plant should be cut obliquely.
State the imitations in the use of potometer;
- The air bubble is difficult to introduce
- Twig may not remain fully alive for a long time
- Any changes in the outside air temp may affect the position of the air bubble
Name the three kinds of transpiration and give a brief description:
-
Stomata transpiration
- water escapes through leaves from minute pores called stoma
- most abundant form of transpiration; 90% -
Cuticular transpiration
- cuticle is a waxy layer secreted by the epidermis on the two surfaces of the leaf.
- The thickness of the cuticle varies from plant to plant, desert plants have thicker cuticles
- Greater thickness of cuticle lesser the transpiration rate -
Lenticular Transpiration
- present on old stems or barks . They allow Diffusion of gases for respiration & photosynthesis.
-they never close and remain open all time
Name the external factors that affect transpiration.
- Sunlight- More sunlight=more transpiration. Transpiration is less on cloudy days.
- Temperature- Increase in temp= more evaporation/transpiration
- Velocity of wind- more wind=more transpiration du to water being carried away from the surface of leaf and concentration of vapor in atmosphere reduces
- Humidity- Transpiration is less=more humid atmosphere.
- CO2- More CO2 over normal 0.03% causes stomata closure.
- Atmospheric pressure- decrease in AP=more transpiration
What is the internal factor that affects transpiration?
Water content of the leaves: Less water in/absorbed by plants-results in closure of stomata which ultimately means less transpiration.
What are the advantages in plants to reduce transpiration?
- Sunken stomata- In nerium it is covered b hairs
- Fewer stomata-
- Narrow leaves- nerium
- Loss of leaves-cacti has spines
- Thick cuticle- banyan
- Reduced expose surfaces - leaves may get rolled,wavy o folded
What is the significance of transpiration?
- Cooling effect
- Suction force
- Distribution of water and minerals
How does transpiration contribute in bringing rainfall?
Due to transpiration water vapor is released into the atmosphere and forms clouds. The water vapor condenses and falls as rain hence proving that transpiration brings rainfall.
Give three differences between evaporation and transpiration
Evaporation;
1. It is a fast process
2. It is loss of water in the form of water vapor from water bodies
1. Its a physical process and it depends on humidity and temperature
Transpiration;
1. It is a slow process
2. It is loss of water from aerial parts of a plant in the form of water vapor
3. It is vital and partly a physical process controlled by both by internal and external factors.
Define Guttation
Guttation is the loss of water from the margins of certain leaves through special pores known as Hydathodes, in the form of droplets. This phenomena is found in plants such as banana. This most occurs in plants that grow in areas with warm and humid conditions.
Define Bleeding
Bleeding is direct flowing out of plant sap from any cut surfaces in case of injury of plant.
State the differences between Guttation and bleeding
Guttation:
1. It occurs from the edges of leaves by hydathodes in uninjured plants
2. The exudate is mainly water with some dissolved mineral salts.
3. It occurs during early mornings or late nights.
4. Plants like banana, strawberry and nasturtium
Bleeding:
1. it occurs from any cut or injured part of plant.
2. the exudes is mainly plant sap and sugars
3. Occurs at any time of the day
4. Occurs in all plants that have been cut or injured.
