2. PLANT LIFE
ON EARTH
According to the research
conducted by Hedges, the
first plants on Earth had
evolved about 700 million
years ago much earlier than
previous estimates of around
430 million years ago, which
were based on the earliest
fossils.
3.
4. EARLY LAND
PLANTS
Bryophytes and seedless vascular plants
were the first groups to evolve on land.
Bryophytes – they lack true
stems, roots, or leaves.
Seedless vascular plants – they
have lignified vascular tissue that
allows the species to form trees
up to 100 feet tall.
8. AVASCULAR
PLANTS
PLANT CATEGORIES
These type of plants lacks in
vascular bundles. They possess
simpler structures for the
conduction of water and nutrients.
They do not have true roots,
stems, and leaves.
BRYOPHYTES
liverworts, hornworts and mosses
10. VASCULAR
PLANTS
PLANT CATEGORIES
hese type of plants have vessels to
ansfer water and nutrients from the
round parts to the aerial parts of the
lants.
Flowering plants
Trees
Ferns
TREE
FERNS
12. VASCULAR
PLANTS
STRUCTURES
They have specialized
structures on the leaves and
stems that captures CO2 and
light from above ground.
Chlorophyll captures the light
from the sun during
photosynthesis. Stomata
(leaves) and lenticels (stems)
are specialized structures for
13. LIGNIN
Lignin- hard material in the
cell walls of vascular plants
that allows plants and trees to
stand upright.
It provides structural support
for the plants.
This polymer supports the
vascular bundles (xylem and
phloem) in plants.
16. XYLEM
VASCULAR BUNDLES
Moves water from the roots
upward to the leaves or shoots to
be used in photosynthesis and
also delivers dissolved minerals
and growth factors through
apoplastic and symplastic
pathway.
This provides structural support
in stem and branches and is the
main component of wood.
XYLEM
PHLOEM
Cross-section of a leaf
18. WATER MOVEMENT THROUGH A PLANT
Absorption of
large
quantities of
water from
the soil
Translocation
of water
through the
plant
Loss of water
to the
atmosphere
as water
vapor
21. APOPLASTIC
PATHWAY
SYMPLASTIC
PATHWAY
Apoplast - the intercellular
space between the plasma
membrane and the cell wall.
In apoplastic pathway, water and
ions move through the apoplast
from the soil to the roots to the
vascular bundles (xylem).
The water and ions move from
apoplast of one cell to another to
reach the xylem.
Symplast- the interconnected
holes (plasmodesmata) between
plant cells where water and ions
move from cell to cell until it
reaches the vascular bundles
(xylem).
This movement of water and
ions is known as the symplastic
pathway.
22.
23. PLASMODESMATA
Plasmodesmata are
channels between plant cells
are interconnected to each
other for transport of water and
nutrients,cell-to-cell
communication, and signaling.
These channels are used in
symplastic pathway of the
roots.
25. COHESION-TENSION
THEORY
Cohesion tension theory
says that the movement of
water in the upwards direction
against gravity is guided by the
attractive forces between the
particles of water and other
charged molecule which
known as cohesion and
adhesion.
26. COHESION
PROPERTY OF WATER
Cohesion refers to the attraction
of molecules for other molecules
of the same kind, and water
molecules have strong cohesive
forces thanks to their ability to
form hydrogen bonds with one
another.
Water to water attraction
27. ADHESION
PROPERTY OF WATER
Adhesion is the attraction of
molecules of one kind for
molecules of a different kind, and
it can be quite strong for water,
especially with other molecules
bearing positive or negative
charges.
Attraction of water to other
surface
28. COHESION-TENSION
THEORY
Due to cohesion of water and the
adhesion of water to charged groups
on the surface of the tracheid and
vessel cells, water will rise in the
xylem through capillary action.
Capillary Action - the motion
where liquid flows through narrow
spaces without external forces, such
as gravity, the movement is aided by
intermolecular forces.
31. TRANSPIRATION
Transpiration is the loss of a
plant’s water to its environment
through evaporation (water
vapor).
As water molecules transpire
through the stomata of leaves the
cohesion of water will pull on
other water molecules that will
pull water up the xylem of the
entire plant.
33. LEAF ANATOMY
Cuticle: made up of cutin
embedded in a matrix of very
hydrophobic cuticular waxes.
• Highly resistant to diffusion of
both liquid water and water
vapor from the underlying
cells.
34. LEAF ANATOMY
• Mesophyll - photosynthetic
interior cells that create an
interconnected system of
intercellular air spaces
known as substomatal
space.
35. LEAF ANATOMY
Stomata: small pores
interrupting the epidermis and
the overlying cuticle.
• Guard cells: regulate the
closure and opening of
stomata
37. TRANSPIRATION PROCESS
1. Evaporation of water from
the moist mesophyll cell
walls (esp. those bordering
substomatal air spaces) into
substomatal air space.
39. TYPE OF TRANSPIRATION
Stomatal Transpiration:
diffusion of water vapor
through the stomatal
pores; 90-95% of water
loss from leaves
Cuticular Transpiration:
small quantities of water
vapor can still pass
through; 5-10%
Lenticular
Transpiration:
loss water lthrough
lenticels of stem; 0.1 %
42. FACTORS INFLUENCING
TRANSPIRATION RATE
actual water content of air
↓ RH = ↑ water vapor pressure = ↑ transpiration rate
HUMIDITY
↑ RH = ↓ water vapor pressure = ↓ transpiration rate
Relative Humidity/ RH
43. FACTORS INFLUENCING
TRANSPIRATION RATE
↑ atmospheric temp = ↑ leaf
temp = ↑ vapor pressure
gradient = ↑ transpiration rate
TEMPERATURE
Temperature greatly influences the
magnitude of the driving force for water
movement out of a plant rather than having
a direct effect on stomata. As temperature
increases, the water holding capacity of
that air increases sharply. The amount of
water does not change, just the ability of
that air to hold water.
44. FACTORS INFLUENCING
TRANSPIRATION RATE
A thick boundary layer is maintained
as it breaks up air movement over the
leaf = ↓ transpiration rate
WIND
↑ wind speed = ↓ boundary layer = ↓ diffusion path length = ↑ water vapor pressure
= ↑ transpiration rate
