Download In plants which portion occurs transpiration?

Chapter nine
Plant Physiology
Plants have plenty of tiny pores to occurs some physiological process.
Excess of water is lost from this pores.
 define the transpiration;
 described the structure of stomata & its
mechanism;
 analysis the important of stomata.
Transpiration
The physiological process by which the loss of excess
water in the form of water vapour through aerial parts
of the plant is called transpiration.
Types of transpiration
Stomatal transpiration: through the stomata. about 90-95% of
transpiration occurs by this way.
Cuticular transpiration: through the cuticle. About 5% occurs by
this way.
Lenticular transpiration: through the lenticel. About 1% occurs
by this way.
Stomatal transpiration process
The water absorbed by
root hairs rises up to the
xylem vessels
Translocated up to the
spongy and palisade
parenchyma
Its form a vapour
When stomata open the
water vapour comes out
Soil water
Absorption
xylem vessels
air cavity of leaves outside the leaf
Significance of transpiration in plant life
Absorption water
Upward conduction of water & sap
Salt absorption
Photosynthesis
Regulation of leaf temperature
Rainfall
Cell division
Physical growth
Prevent from germ infection
Osmosis
Stomata
Stomata are plenty of tiny pores found in leaves. It stands at
aerial parts of plants & help to gas exchanges.
Position
 Floating aquatic plants upper surface
 Submerged leaves lack stomata entirely
 Xerophytes plants have sunken stomata
 Dicotyledons plants have more stomata on the lower epidermis
than upper portion
 Monocotydons plants have same number of stomata on both
epidermis
Structure
subsidiary cells
Guard cell
outer thin wall
inner thick wall
a nucleus
plenty of chloroplast
Mechanism of opening & closing stomata
Endosmosis
enters H2O in guard cell
open stomata
Exosmosis
closed stomata
out of H2O in guard cell
turgid guard cell
flaccid guard cell
Lloyd’s theory
Lloyd (1908) introduced this theory. He proved that opening
& closing stomata depend on the variation of osmotic
pressure and interchange of starch & sugar is the cause of
that.
Insoluble starch in guard cell
Exosmosis of water
Soluble sugar
Endosmosis of water
Decrease osmotic pressure
Flaccid guard cell
Increase osmotic pressure
Turgid guard cell
Closed stomata
Open stomata
Sayre’s theory
Sayre (1926) introduced this theory. He proved that opening
& closing stomata depend on the inter change between sugar
& starch and PH is the cause of that.
In day time
Starch converted glucose-1phosphate
Increase osmotic pressure
At night
Turgid guard cell
glucose-1phosphate converted Starch
Decrease osmotic pressure
Flaccid guard cell
PH
goes up to 7.5
Open stomata
PH falls to 5
Closed stomata
Modern theory
Lexitt (1974) introduced this theory. He proved that K+ is
the cause of opening & closing stomata.
Night , K+ & H2O out of, osmotic pressure decrease
Open stomata
Closed stomata
Light , K+ & H2O enters, osmotic pressure increase
Individual Work:
According to Sayre’s theory what is causes for
opening & closing stomata?
Write down the importance of tomata in plants.
 In plants which portion occurs transpiration?
 By which process the transpiration take place?
 On basis of transpiration way how many types of transpiration
?
 Which type of chemical substances made a cuticle?
 In where the plants give out about 90-95% water in form of
vapour?
 In which process about 5-10% water given out in the form of
vapour?
 Which part of plant is the main organ of transpiration?
 How many guard cell adjacent the stomata?
 Which layer of guard cell is thick?
 How many nucleus contains each guard cell?