Name: Bisnan, Ysabel Mari M. Date: July 1, 2022
Activity 5
Rate of Transpiration
I. Introduction:
What is Transpiration?
Transpiration is the process of water movement through a plant and its
evaporation into the atmosphere from its aerial parts. In leaves and in
young shoots the epidermal layer contains minute microscopic pore like
structures called stomata. Transpiration occurs chiefly through the
stomata of the leaves. The stomata are mainly concerned with exchange
of gases during the process of photosynthesis and respiration. Each
stomata has a slit like opening called the stomatal pore, which is
surrounded by two special cells called the guard cells. These special cells
help to regulate the rate of transpiration by opening and closing the
stomata.
Importance of Transpiration
1. Transpiration helps in the absorption of water from the soil.
2. The absorbed water is transported from the roots to the leaves through the xylem vessels that a
transpiration pull.
3. Transpiration helps to cool down the plant surface during evaporation.
Environmental Factors that Affect the Rate of Transpiration
1. Light:Stomata are triggered to open in light so plants transpire more rapidly in the presence of
2. Temperature: Plants transpire more rapidly at higher temperatures because water evaporat
temperature rises.
3. Humidity:Humidity is expressed as the percentage of water vapour present in the atmosphere.
humidity of the outside atmosphere, the lower the rate of transpiration.
4. Wind:When there is no breeze, the air surrounding a leaf surface becomes increasingly humid,
of transpiration. The increase in the wind velocity increases the rate of transpiration by removin
leaf surface.
In different plants, distribution, number, size and type of stomata vary. Even within a plant, the uppe
the leaf may have different distributions. In some plants a greater number of stomata is present on t
than on the upper surface of the leaf. Therefore, the loss of water from the lower surface is greater than
We can study the rate of transpiration from the two surfaces of a leaf by comparing the loss of wat
surfaces of the leaf.
Rate of transpiration can be easily demonstrated by cobalt chloride paper test. Dry cobalt chloride pap
turns pink when it comes in contact with water. Using this property of cobalt chloride paper we can
during transpiration.
We can measure the rate of transpiration by using the time taken for the paper to change its colour fro
II. Objectives
• Students understand the concept of transpiration.
• Students understand the importance of transpiration.
Activity 5
Rate of Transpiration
I. Introduction:
What is Transpiration?
Transpiration is the process of water movement through a plant and its
evaporation into the atmosphere from its aerial parts. In leaves and in
young shoots the epidermal layer contains minute microscopic pore like
structures called stomata. Transpiration occurs chiefly through the
stomata of the leaves. The stomata are mainly concerned with exchange
of gases during the process of photosynthesis and respiration. Each
stomata has a slit like opening called the stomatal pore, which is
surrounded by two special cells called the guard cells. These special cells
help to regulate the rate of transpiration by opening and closing the
stomata.
Importance of Transpiration
1. Transpiration helps in the absorption of water from the soil.
2. The absorbed water is transported from the roots to the leaves through the xylem vessels that a
transpiration pull.
3. Transpiration helps to cool down the plant surface during evaporation.
Environmental Factors that Affect the Rate of Transpiration
1. Light:Stomata are triggered to open in light so plants transpire more rapidly in the presence of
2. Temperature: Plants transpire more rapidly at higher temperatures because water evaporat
temperature rises.
3. Humidity:Humidity is expressed as the percentage of water vapour present in the atmosphere.
humidity of the outside atmosphere, the lower the rate of transpiration.
4. Wind:When there is no breeze, the air surrounding a leaf surface becomes increasingly humid,
of transpiration. The increase in the wind velocity increases the rate of transpiration by removin
leaf surface.
In different plants, distribution, number, size and type of stomata vary. Even within a plant, the uppe
the leaf may have different distributions. In some plants a greater number of stomata is present on t
than on the upper surface of the leaf. Therefore, the loss of water from the lower surface is greater than
We can study the rate of transpiration from the two surfaces of a leaf by comparing the loss of wat
surfaces of the leaf.
Rate of transpiration can be easily demonstrated by cobalt chloride paper test. Dry cobalt chloride pap
turns pink when it comes in contact with water. Using this property of cobalt chloride paper we can
during transpiration.
We can measure the rate of transpiration by using the time taken for the paper to change its colour fro
II. Objectives
• Students understand the concept of transpiration.
• Students understand the importance of transpiration.
