This assignment is comprised of the dtails about the process of transpiration in plants, when was its study first conducted,who discovered the actual phenomenon at first, what's the actual process, its types, its importance for the plants. Studying this u will get almost all your points cleared.

1. Botany Assignment
ASSIGNMENT TOPIC : TRANSPIRATION
SUBMITTED BY : AREEBA BATOOL
SUBMITTED TO : SIR SALMAN SAEED
COURSE TITLE : PLANT PHYSIOLOGY
& ECOLOGY
DEPARTMENT : CHEMISTRY

2. Transpiration
 Transpiration is the biological process by which water is
lost in the form of water vapour from the aerial parts of
the plants.”
 Transpiration in Plants :
 V Like all living organism, plants also require an excretory
system to discharge excess water from their body.
 v This process of elimination of excess water from the plant
body is known as transpiration. It is generally the evaporation
of water from the surface of the leaves.
 V During the process of transpiration, water molecules in
the plant tissues are removed from the aerial parts of the
plants. Only a small amount of water absorbed by the plants
is utilized in growth and development. The rest is eliminated
in the form of transpiration.

3. diagram
 1

4. Discovery
details
 U Transpiration was first measured by Stephen Hales (1677–1761),
an English botanist and physiologist. He noticed that plants “imbibe”
and “perspire” significant amounts of water compared to animals and
created a novel method for measuring the emission of water vapour by
plants. He found that transpiration occurred from the leaves and that
this process encouraged a continuous upward flow of water and
dissolved nutrients from the roots. Modern research has shown that as
much as 99 percent of the water taken in by the roots of a plant is
released into the air as water vapour.
 U Excessive transpiration can be extremely injurious to a plant.
When water loss exceeds water intake, it can retard the plant’s growth
and ultimately lead to death by dehydration.

5. TYPES OF
TRANSPIRATION
 1.Stomatal Transpiration :
 On the epidermis of leaves, stomata are tiny pores. Stomata can also be observed on
the epidermis of green stems in herbaceous plants. They serve as a link between internal
tissue and the outer environment. As a result, they are the primary conduit for the escape
of water vapour. Stomatal transpiration is responsible for 80-90 percent of the plant’s total
water loss.
  Example :
 The evaporation of water from a plant’s stomata is known as stomatal transpiration. The
stomata are where most of the water transpired from a plant’s leaves departs; at least
90% of the water transpired from a plant’s leaves exits through the stomata.

6. Cuticular
Transpiration
 2. Cuticular Transpiration :
 •: The epidermis of leaves and stems is protected by a waxy coating of cutin
and cuticle. The presence of cuticles on the epidermis’s surface inhibits water
evaporation directly. If the cuticle is thin, it may be responsible for up to 20% of
total transpiration. However, as the thickness of the material grows, the amount
of water vapour loss decreases. Under normal conditions, cuticular transpiration
contributes for around 10% of the total amount of transpiration from leaf.
 •
 Example :
  The evaporation of water from a plant’s cuticle is referred to as cuticular
transpiration. A waxy film covers the surface of a plant’s leaves, and it’s known
as the cuticle. The cuticle loses roughly 5-10% of the water in the leaves, so this
method of transpiration does not account for much of a plant water loss.
 

7. Lenticular
Transpiration
 Lenticular transpiration:
 •
 • Small gaps in the cork of woody stems, branches, and fruits are known as lenticels. These
apertures allow water vapour to escape. Lenticular transpiration is the loss of water through
lenticels seen on woody stems and fruits. It accounts for about 1% of a plant’s overall water
loss. Lenticular transpiration can be significant in deciduous trees that drop their leaves in the
autumn.
 •
 Example :
  Evaporation of water from such a plant’s lenticels is known as lenticular transpiration. The
bark of branches and twigs has microscopic openings called lenticels. Lenticels are not found
in every plant. When compared to stomatal transpiration, the amount of water lost by this
method is relatively modest, although it can grow in a dry environment, just like cuticular
transpiration.
 

9. Leaf 🌿 Internal Structure

11. Factors Affecting on the Rate of
Transpiration in Plants

12. Environmental Factors
 The environmental factors rate of transpiration are affecting the rate :
 1.Humidity,
 2.Temperature,
 3.Atmospheric pressure,
 4.Wind speed or velocity.
 Relative Humidity :
 The amount of water vapour present in the air at a particular time and temperature is expressed as a
percentage of the amount required for saturation at the same temperature. The rate of transpiration is
inversely proportional to relative humidity. More the relative humidity less is the transpirate rate.
 Temperature :
 A high temperature lowers the relative humidity and opens the stomata even in darkness. As a result, the
rate of transpiration increases.

13. Factors
 Light
 The stomata open during the day and close in the dark. Presence of light is directly
proportional to the rate of transpiration.
 Air
 If the air is still, the transpiration rate is low. This is because the water vapour accumulates
around the transpiring organs and reduce the diffusion pressure deficit of the air.
 If the air is moving, the saturated air around the leaves is removed and the transpiration
rate increases.
 Water Availability
 The transpiration rate is directly proportional to the absorption of water by the roots from
the soil. A decrease in water absorption causes the closure of stomata and wilting, thereby
reducing the rate of transpiration.
 

14. 1. Students

15. JazakAllah