MODULE: CROP

PHYSIOLOGY
GAMBIA COLLEGE
SCHOOL OF AGRICULTURE
Lecturer: Mr. H. Touray
 INTRDUCTION
• Definition -A plant:
• is multicellular;
• is non-motile
• has eukaryotic cells
• has cell walls comprised of cellulose
• is autotrophic i.e. produces its own food; and
• exhibits alternation of generations - has a
distinctive diploid (saprophyte) and haploid
(gametophyte) phase.
 INTRDUCTION CON’T
• PHYSIOLOGY: study of the function of cells,
tissues, organs of living things.
• It also shows how body parts come together to
function and keep the organism alive.
 INTRDUCTION CON’T
What is plant physiology?
• Plant physiology encompasses the study of plant
form and function of its parts.

• Plant physiology looks at the structure and

function of leaves, stems and roots, water and
sugar conductivity, and the reproductive organs of
plants.
 INTRDUCTION CON’T

IMPORTANCE OF WATER TO THE PLANT

• Water helps in the germination of seeds
• Water help in the process of photosynthesis process by
which green plant prepare their food.
• Water help in the transport of nutrients and minerals
from the soil to the plant
• Water helps in the maintenance of the plant structure
by providing the appropriate pressure to the plant
tissues
• Water provide habitat in the form of ponds, rivers, and
sea for a number of plant
 INTRDUCTION CON’T
• ANATOMY: study of the structure and
relationship between body parts.
• Plant Anatomy
• Cells
• Tissues
• Organs
THE STRUCTURE OF THE PLANT
CELL
 TYPES OF PLANT CELLS
a. Parenchyma cell • Characteristics: Living
at maturity; usually
spherical and elongated
in shape; usually have
only primary cell wall.
• Location: Cortex and
pith of root and stem,
mesophyll of leaves,
Xylem and phloem
• Function: Site for basic
metabolic cell functions
 TYPES OF PLANT CELLS
b. Collenchyma cell Characteristics: Living at
maturity; Elongated
with plastic cell wall.
Locations: Leaf petioles
and young leaves,
vascular bundles or on
the corners of angular
stems.
Function: Support plant
growth.
 TYPES OF PLANT CELLS
c. Scelerenchyma cell Characteristics: They are
characterized by
thickenings in their
secondary walls. They
are dead at maturity.
Location: In all plant
roots
Function: Offer protection
and support to other
plant tissues
TYPES OF SCELERENCHYMA
i. Sclereid Characteristics: Dead at
maturity; Elongated star
shaped or stone shaped
with lignified secondary
cell wall.
Location: Cortex, pith ,
mesophyll
Functions: offer
mechanical support and
protection
TYPES OF SCELERENCHYMA CELLS

ii. Fiber Characteristics: Dead at

maturity; long ,thin,
cells with thick lignified
secondary cell wall
Location: Xylem, phloem
and cortex
Functions: strengthening
and supportive cell type
 TYPES OF PLANT CELLS
d. Xylem cell Characteristics: Are dead
at maturity
Location: found in the
vascular tissues of
plants.
Functions: Transport
water and soluble
nutrients, minerals and
inorganic ions upwardly
from the roots of the
plants and its parts.
COMPNENTS OF THE XYLEM
i. Tracheid Characteristics: Dead at
maturity; similar to
vessel members except
with narrower diameter
and close pitted end
and do not form vessel.
Location: Xylem tissue
Function : Transport
water
COMPNENTS OF THE XYLEM
ii. Vessel member Characteristics: Dead at
maturity, lignified
secondary cell walls that
may be spiral, ringed or
pitted, perforation plates
in open end walls;
member connected
together to form vessels.
Location: Xylem
Function: Transport water
and dissolve minerals
 TYPES OF PLANT CELLS
e. Phloem cell Characteristics: alive at
maturity because they need
the energy to move
materials. They also have a
flaccid cell wall hence they
lack tensile strength that
allows them to move
materials at high pressure.
Location: Vascular tissues
Function: Transport food from
the plant leaves to other
parts of the plant.
 COMPNENTS OF THE PHOLEM
i. Sieve-tube member Characteristics: Living at
maturity but does not
contain nuclues elongate
cell with aggregates of
pores (sieve plates) on
the end walls and side
walls; Cells join end to
end to form sieve tubes.
Location: Phloem tissue
Function: transport sugar
 COMPNENTS OF THE PHOLEM
ii. Sieve cell Characteristics: Living at
maturity; structurally long
with tapered overlapping
ends. They have pores all
over their cell wall that is
surrounded by callose (a
carbohydrate that repairs the
pores after an injury).
Location: Phloem tissues
Function: Transport dissolved
food flows eg sucrose.
 COMPNENTS OF THE PHOLEM
iii. Companion cell Characteristics: Living at
maturity, Connected to sieve
tube
Location: Phloem tissues
Function: Help in moving
materials into and out of the
sieve tube members.
Characteristically, the sieve
tubes have Phloem (P)-
proteins at the cell wall and
callose and together they heal
injuries caused on the sieve
tubes.
 TYPES OF PLANT CELLS
f. Epidermal cell Characteristics: Living at
maturity; They are placed
closely together with no
intracellular spaces and are
covered with a waxy cuticle
layer to reduce water loss.
Location: plant stems, leaves,
roots and plant seed
Function: protect the plant from
environmental factors such as
high temperatures, pathogens,
chemical exposures
 TYPES OF EPIDERMAL CELLS
i. Guard cell Characteristics: Are bean-
shaped cells covering the
stomata opening, Living at
maturity
Location: Leaves; stem
Function: Regulate water
vapor loss, exchange of
oxygen and carbon dioxide
through the stoma.
 TYPES OF EPIDERMAL CELLS
iii. Pavement cells Characteristics: Most common
epidermal cells covering all plants.
They lack a defined shape, cells
are closely packed together
Function: prevent excessive loss of
water, protect other underlying
cells, maintain the plants’ internal
temperature and act as a physical
barrier from pathogens and
external damages from chemicals
such as radiations
 TYPES OF EPIDERMAL CELLS
Characteristics:T hey have a large
iii. Trichomes or size of about 300um in diameter.
epidermal hairs They do not multiply by cell
division instead they undergo
endo-replication for expanding
their cell population

Location: found on the epidermal

tissue. They are a specialized group
of cells with a well-defined shape.
Function: protect the plants from
predators and pathogens, by acting
as trappers and poisoners to animal
predators
 TYPES OF EPIDERMAL CELLS
iv. Subsidiary cell Characteristics: Living at
maturity; type of epidermal
cell , in contact with the
guard cell.
Location: Epidermis
Function: Regulate guard cell
opening .
 TYPES OF PLANT CELLS
g. Meristematic cell Characteristics: They divide
or continuously throughout the
life of a plant and rise to the
meristems Parenchyma, Collenchyma and
Sclerenchyma cells .They have
a self-renewal ability and high
metabolisms to control the cell.
Location: Tip of root and stem
Function: play a major role in
plant growth in width and
length
 TYPES OF MERISTEM
i. Apical meristems – they are found at the tips
of roots and stems that have started growing
and they contribute to the length of the plant
ii. Lateral meristems – They are found in the
radial part of the stem and roots and they
contribute to the plant thickness
iii. Intercalary meristems – they are found at
the base of the leaves and the contribution to
the size variance of the leaves.
 PLANT TISSUES
 Plants tissue systems is made of various cell
types that carry out specific functions.
 Plant tissue systems are divided into two goups:
 meristematic tissue
 permanent (or non-meristematic) tissue.
 MERISTEMATIC TISSUES
 A meristem is a site in the plant body where new
cells form (cell division) and the complex processes
of growth and differentiation are initiated.

 Growth means the irreversible increase in size that

comes from both cell division and cell enlargement.

 Cell differentiation refers to the changes that a cell

undergoes structurally and biochemically so that it
can perform a specialized function.
 PERMANENT TISSUES
 Permanent tissue consists of plant cells that are no longer
actively dividing.

 Meristems produce cells that quickly differentiate, or

specialize, and become permanent tissue.

 Such cells take on specific roles and lose their ability to

divide further.

 Permanent tissues are divided into three groups: Dermal,

Vascular, and Ground tissue.
 PERMANENT TISSUES CON’T
 Dermal tissue – this tissue lies on the surface of plants and its
made up of epidermal cells that protect the plants from losing
water.

 Ground tissue – This makes up the root vascular and epidermal

system majorly made up of parenchyma, collenchyma and
sclerenchyma cells responsible for plant photosynthesis, storage of
water and food and the plant support system.

 Vascular Tissue – this tissue is made up of xylem, phloem,

parenchyma and cambium cells, with its functions including
transportation of water (xylem), transportation of food (phloem),
minerals, hormones in the plant cells.
 PLANT ORGANS
 Plants have two distinct organ systems: a shoot system and a root
system.

 The shoot system consists of two portions:

i. the vegetative parts of the plant, such as the leaves and the stems
ii. the reproductive parts of the plant, which include flowers and
fruits.

 The shoot system generally grows above ground, where it absorbs

the light needed for photosynthesis.

 The root system, which supports the plants and absorbs water and
minerals, is usually underground
 PLANT ORGANS CON’T
 Root systems are mainly of two types:
 A tap root system has a main root that grows down
vertically, and from which many smaller lateral roots arise. A
tap root system penetrates deep into the soil.

 A fibrous root system is located closer to the soil surface,

and forms a dense network of roots that also helps prevent
soil erosion (lawn grasses are a good example, as are wheat,
rice, and corn). Some plants have a combination of tap roots
and fibrous roots. Plants that grow in dry areas often have
deep root systems, whereas plants growing in areas with
abundant water are likely to have shallower root systems.
 FUNCTIONS OF THE ROOT
 The roots of plants have three major
functions:
(i) anchoring the plant to the soil
(ii) absorbing water and minerals and
transporting them upwards
(iii) storing the products of photosynthesis.
 Some roots are modified to absorb moisture
and exchange gases.
 TYPES OF ROOTS
Tap root system Fibrous root system
 ROOT MODIFICATION
 Prop and stilt roots are Prop roots Example Banyan tree Stilt roots Example Maize
adventitious roots that
provide support to plants
and tree.

 The main difference is

that prop roots arise
from branches of trees
while stilt roots arise
from the base of the
stems.
 ANATOMY OF THE ROOT
Longitudinal section Transverse section
 PARTS OF THE ROOT AND THEIR
FUNCTIONS
 The root cap protects the fragile root tip.
 The zone of cell division is closest to the root tip; it is
made up of the actively dividing cells of the root
meristem.
 The zone of elongation is where the newly formed
cells increase in length, thereby lengthening the root.
 The zone of cell maturation where the root cells begin
to differentiate into special cell types.
 The Root hairs is an extensions of root epidermal cells,
which increases the surface area of the root, greatly
contributing to the absorption of water and minerals.
THE TRANSVERSE SECTION OF
MONOCOT AND DICOT ROOT
 PARTS OF THE ROOT AND THEIR
FUNCTIONS CON’T
 Epidermis is outer layer of the root which
surrounds a ground tissue and vascular tissue.
 It provide protection and helps in absorption.
 Cortex is between the epidermis and the
vascular tissue
 Pith lies between the vascular tissue and the
center of the root
 Both cortex and pith stores photosynthetic
products.
 PARTS OF THE ROOT AND THEIR
FUNCTIONS CON’T
 Endodermis separates the stele (arranged vascular
tissues in the inner root) from the ground tissue.

 Casparian strip ( waxy on the walls of the

endodermal cells) forces water and solutes to cross
the plasma membranes of endodermal cells instead
of slipping between the cells.

 Pericycle is the outermost layer of the root’s

vascular tissue which give rise to lateral roots
 THE STEM
 Stems are a part of the shoot system of a plant.

 A stems may be herbaceous (soft) or woody in

nature.
PARTS OF THE STEM
 Nodes points of attachment for
leaves, aerial roots, and flowers.
 Internode is the stem region
between two nodes.
 Petiole or stalk is an extension
from the stem to the base of the
leaf is the
 Axillary bud is the area
between the base of a leaf and
the stem which give rise to a
branch or a flower.
 Apex (tip) of the shoot contains
the apical meristem within the
apical or terminal bud.
INTERNAL TRANSVERSE SECTION
OF THE STEM
STRUCTURE OF THE APICAL BUD
 FUNCTIONS OF THE STEM

(i) The main function of the stem is to provide support to

the plant, holding leaves, flowers, fruits and buds;

(ii) In some cases, stems also store food for the plant.

(iii) The stem of the plant connects the roots to the leaves,
helping to transport absorbed water and minerals to
different parts of the plant.

(iv) It also helps to transport the products of photosynthesis,

namely sugars, from the leaves to the rest of the plant.
 MODIFIED UNDERGROUND STEM
 Underground stem acts as
an organ of perennation.

 The plants store the food

synthesized in these
underground stems.
 UNDERGROUND MODIFIED STEMS
 Rhizomes are underground stem consisting of nodes and internodes.
 There are two types rhizome:
i. Rootstock types are a vertical rhizome, examples are banana
ii. Straggling type is a horizontal rhizome and is branched. Example
ginger.
 Tubers are terminal underground stem which gets swollen due to the
accumulation or storage of food. Examples potato
 Bulb are disc-shaped reduced form of stem. On its upper side, the bud
is surrounded by concentric leaves, which are fleshy and edible.
 Corm are short, unbranched, and thick underground stem. It shows
vertical growth and is covered by a thin sheathing leaf base of dead
leaves known as scales. Examples are amorphophallus, colocasia.
 Suckers are developed from the axillary bud of the underground stem,
the branches creep below the soil and grow upwards obliquely to form
new shoots. Examples Pineapple.
 SUBAERIAL MODIFIED STEMS
RUNNER
 Sub aerial stem are found
in plants with weak stem
in which branches lie
horizontally on the ground.

 These are meant for STOLON

vegetative propagation.

 They may be sub aerial or

partially sub terranean
 SUBAERIAL MODIFIED STEMS
Runners are slender, prostrate branch creeping on
the ground and rooting at the nodes. Example: lawn
grass (Cynodon dactylon).

Stolon are also a slender, lateral branch originating

from the base of the stem. But it first grows obliquely
above the ground, produces a loop and bends down
towards the ground. When touches the ground it
produces roots and becomes an independent plantlet.
Example: wild strawberry (Fragaria indica ).
 AERIAL MODIFIED STEMS
 The shoots trail or spread horizontally along the ground without rooting
at intervals.

 Stem climbers or Twiners weak, long and slender stem that climb other
plants or objects by twining round them. Climb­ing Plants are classified
into:

 Twiners
 Tendril climbers
 Root climbers
 Scramblers
 Adhesive climbers
 Lianas.
 CLIMBING STEM
ROOT CLIMBERS TENDRIL CLIMBERS

TWINNERS CLIMBERS
 THE LEAF
 Leaves are the main sites for photosynthesis.
 The thickness, shape, and size of leaves are
adapted to the environment.
 Each variation helps a plant species maximize
its chances of survival in their habitat.
 MODIFIED LEAVES
Pseudostem of banana Cladodes of cactus Thorns

Bracts of bougainvillea Storage leaves of aloe Fleshy leaves of onion

vera

Meristematic leaves of katakataka Phyllodes of acacia Carnivorous leaf Eg

pitcher plants
EXTERNAL STRUCTURE OF THE
LEAF
 lamina or leaf blade is the widest part
of the leaf.
 Petiole is the part that attached leaf to
the plant stem .
 Leaves that do not have a petiole and
are directly attached to the plant stem
are called sessile leaves.
 Stipules are Small green appendages
usually found at the base of the petiole.
 Most leaves have a midrib, which
travels the length of the leaf and
branches to each side to produce veins
of vascular tissue.
 The edge of the leaf is called the
margin.
INTERNAL STRUCTURE OF THE
LEAF
 INTERNAL STRUCTURE OF THE
LEAF CON’T
 Cuticle a waxy layer that covers the leaves of all plant
species. The cuticle reduces the rate of water loss from the
leaf surface.

 Epidermis the outermost layer of the leaf and is present on

both sides of the leaf. The epidermis helps in the regulation
of gas exchange and contains stomata an openings through
which the exchange of gases takes place.

 Two guard cells surround each stoma, regulating its

opening and closing
 INTERNAL STRUCTURE OF THE
LEAF CON’T
 The palisade parenchyma combined with spongy mesophyll cell
found below the layer of the epidermis.
 The palisade mesophyll has column-shaped, tightly packed cells,
and may be present in one, two, or three layers.
 The spongy mesophyll are loosely arranged cells of an irregular
shape.
 The air space found between the spongy mesophyll cells allows
gaseous exchange between the leaf and the outside atmosphere
through the stomata.
 Both tissue assists in light absorption used in photosynthesis.
 The Mesophyll cells are also found in good numbers within the
xylem and the phloem of vascular plants, helping in the
transportation of water and food materials in the plant
Flowers
 Parts of the flower and their functions

 Petals are brightly colored part of the flower which attract the agents of
polination during the day and it's scent during the night attract them.

 Flower petals are collectively called the corolla.

 In insect-pollinated flower contain nectaries which secrete sugary nectar. These

provide an incentive to insects to visit the flowers.

 Sepal are small leafy structures found under the flower.

 They form the flower bud which protects the flower during the initiation stage.
Collectively, all of the sepals form the calyx.

 The receptacle is the place on the stem where floral organs originate and attach.
 Parts of the plants’ reproductive
structures and their function
Male Parts/ Stamen Female parts/ carpel/ pistil
 Anther produces pollen  The ovary produces the ova and
forms the fruit.
grains.  The ova forms the seeds.
 Filament supports the  The style supports the stigma and and
connect the ovary and the stigma.
anther  Stigma receive pollen grains from the
anther during pollination.
 Transportation in Plants
 Transportation in plants is the process of transporting
water, minerals and food to all parts of the plant body.

 Transport in plants occurs at three levels:

 The uptake and release of water and solute by individual

cells.
 Short distance transport of substances from one cell to
another.
 Long distance transport of sap within xylem and phloem.
 Transportation in plants con’t

There are three means of transport in plants:

 Diffusion
 Facilitated diffusion
 Active Transport
 Transportation in plants con’t
 Diffusion – is the movement of substance from higher
concentration region to lower concentration region.
 It is a slow process and occurs most likely in liquid and
gases.
 In plants, diffusion is the only means of transport for
gases.
 The rate of diffusion depends on the gradient of
concentration, pressure, temperature and permeability of
membrane separating them.
 It is an important process in the life of a plant and the
process is passive ie. requires no energy
 Transportation in plants con’t
 Facilitated Diffusion – In this process, special
protein helps the substance move across the
membrane without the use of energy of ATP.

 It does not cause net transport of molecules and the

rate of transport is maximized when all the protein
transporters are being used.
 Transportation in plants con’t
 Active Transport – is the process in which
molecules are pump against the concentration
gradient using energy in the form of ATP.

 Through active transport mineral ions moved into

the root hair cells against concentration gradient.

 Once absorbed, mineral ions then diffuse through

the cortex cells and enter the xylem with water.
 Transportation in plants con’t
 Active Transport – is the process in which
molecules are pump against the concentration
gradient using energy in the form of ATP.
 Through active transport mineral ions moved
into the root hair cells against concentration
gradient.
 Once absorbed, mineral ions then diffuse
through the cortex cells and enter the xylem
with water.
 PLANT METABOLISM AND
NUTRITION
(a) Photosynthesis- is the process through which Plants produce their own
food.
 The chloroplast is the site of photosynthesis.
 Food production primarily is carried out in leaves.
 Water and minerals from the soil are absorbed by the root and transported
to the leaves through xylem.
 Carbon dioxide reaches leaves through stomata – which are small pores on
leaves surrounded by guard cells.
 Chlorophyll is a green pigment present in leaves which helps the leaves
capture energy from sunlight to prepare their food.
 During photosynthesis, water and carbon dioxide are used in the presence
of sunlight to produce carbohydrates and oxygen.
 Starch is released in the process, which is a carbohydrate.
 Photosynthesis provides food to all living beings
 PLANT METABOLISM AND
NUTRITION CON’T

Conditions necessary for photosynthesis:

 Sunlight
 Water
 Carbon dioxide
 Chlorophyll
 PLANT METABOLISM AND
NUTRITION CON’T
Equation of photosynthesis
6CO2 + 6 H2O + light energy C6H12O6 + 6O2
Carbon dioxide water glucose oxygen

 Carbon dioxide in the atmosphere reaches plant mesophyll via the stomata.

 Water in the soil is absorbed by the root is used in photosynthesis, the
remainder is either transpired or incorporated into protoplasm, vacuoles or
other cell materials. The water utilized in photosynthesis is the source of
oxygen released as a photosynthetic by product.

 Chlorophyll a green pigment found in the stroma of the chloroplast trapped

or absorbed sunlight which serves as energy for photosynthesis.
THE STRUCTURE OF THE
CHLOROPLAST
(site for photosynthesis)
 PLANT METABOLISM AND NUTRITION

Steps in photosynthesis:
 Absorption of energy from sunlight
 Conversion of light energy into chemical
energy
 Hydrolysis of water into oxygen and hydrogen
 Carbon dioxide is reduced to form glucose by
utilizing chemical energy
STAGES OF PHOTOSYNTHESIS
 STAGES OF PHOTOSYNTHESIS
(a) Light requiring stage Occurs thylakoids of chloroplasts.
 At this some light energy is converted to chemical energy and
water molecules are split apart into hydrogen ions, electrons
and oxygen gas is released.

 In addition, ATP (adenosine triphosphate) molecules are created

and the hydrogen ions derived from the water molecules are in
the NADP which carries the hydrogen as NADPH.

 NADPH is integral in providing the hydrogen ions used in the

second series of major photosynthetic reactions: the carbon-
fixing reactions.
STAGES OF PHOTOSYNTHESIS
 STAGES OF PHOTOSYNTHESIS
CON’T
(b) Carbon-fixing reactions/ Calvin Cycle occurs in the stroma of the chloroplast.
 The carbon fixation process occurs in all types of plants (C3, C4, and CAM)
plants
 These reactions only occur if the end products of the light reactions are available
for use.
 The calvin cycle involve three (3) main stages:
1. Carboxylation: this is the stage in which the enzyme RuBP carboxylase
oxygenase or RuBisCO is used to combine atmospheric CO2 to the 5-carbon
sugar RuBP to produce PGA.
2. Reduction: In this stage, 2 ATP and 2 NADPH formed during light reactions are
used to form carbohydrate or glucose
3. Regeneration: In this stage, 1 ATP molecule is used for phosphorylation to
regenerate RuBP.

• In C3 plants, carbon fixation takes place in the light-independent or dark reaction stage
of photosynthesis.
CARBON FIXATION IN THE CALVIN
CYCLE
 PLANTS
 Plants can be categorized into C3, C4, and CAM plants based on
distinct pathways they used to fix carbon dioxide in the RUBP
during photosynthesis, leading to different adaptations for
various environments.
 C3 -normal conditions Eg (spinach, peanuts, cotton, wheat,
rice, barley, soya bean, oats and most trees and grasses)
 C4 - high temperature/high water/high light availability Eg
(corn, sugar cane, millet, sorghum, and cabbage)
 CAM -high temperature/low water availability Eg (cacti,
pineapple, orchids, aloe and agave)
 C3 plants are the most common, fixing carbon directly through
the Calvin cycle, while C4 and CAM plants have evolved to
minimize photorespiration and conserve water in hot and dry
environments
 PLANTS
 C3, C4 and CAM plants all have anatomy that helps them to
perform photosynthesis in their own unique way.

 C4 and CAM plants are specialists at avoiding the wasteful

process of photorespiration.

 Photorespiration is a process in plants where the enzyme

RuBisCO binds oxygen to RuBP instead of carbon dioxide,
leading to a loss of fixed carbon and energy.

 To avoid photorespiration, C4 plants perform part of

photosynthesis in their bundle sheath cells and CAM plants split
it into a daytime and nighttime process.
INTERNAL LEAF STRUCTURE OF
TYPES OF PHOTOSYNTHESIS IN
PLANTS:
 Comparisons of , and CAM plants

Separation of initial fixation Stomata

Type and Calvin cycle open Best adapted to
Cool, wet
No separation Day environments

Between mesophyll and bundle- Hot, sunny

sheath cells (in space) Day environments

Very hot, dry

CAM Between night and day (in time) Night environments
PHOTOSYNTHESIS IN PLANTS
 The enzyme phosphoenolpyruvate (PEPCase) in the
mesophyll cell is used to incorporate the
atmospheric in pyruvate () to form oxaloacetate
() which is converted to malate (aspartate) using
NAD-malate dehydrogenase.

 Malate or aspartate is exported to bundle sheath

cells where it is decarboxylated, releasing that is
refixed by RUBisCO via the Calvin cycle.
PHOTOSYNTHESIS IN CRASSULACEAN ACID
METABOLISM (CAM) PLANTS
 CAM plant is generally associated with anatomical features
that minimize water loss, such as thick cuticles, low surface-
to-volume ratios, large vacuoles, and stomata with small
apertures.
 In CAM plants, the uptake of atmospheric CO2 takes place
at night when stomata are open.
 The enzyme PEPCase to incorporate pyruvate into a four-
carbon acid (oxaloacetate), which inturn reduced to malate
using NAD-malate dehydrogenase enzyme.
 During the day, the Malate decarboxylase (NAD-malic
enzyme) acts on the malate to release CO2 which is by
RUBisCO via the Calvin cycle
 PLANT METABOLISM AND
NUTRITION CON’T
(b) Respiration in plants involves using the sugars produced
during photosynthesis plus oxygen to produce energy for plant
growth.
 Respiration in plant occurs in the mitochondria of the cells in
the leaves, stems and roots.
 Plants respire with the help of lenticel and stomata (exist in the
stem and leaves) which carry out function of gaseous exchange.
 Role of respiration in air temperature: Plant respiration
occurs 24 hours per day, but night respiration is more evident
since the photosynthesis process ceases.
 The respiration rate increases and consequently temperature
increases.
EQUATION OF RESPIRATION

C6H12O6 + 6O2 → 6CO2 + 6H2O + 32 ATP

(Glucose) ( Oxygen) (Carbon dioxide) (water ) ( Energy)
 Difference between photosynthesis and
respiration
Photosynthesis Respiration
 Energy stored in sugar  Carbon dioxide and water
molecules released
 Carbon dioxide and water  Decreases weight
used  Energy released from sugar
 Increases weight molecules
 Requires light  Can occur in light or darkness
 Occurs in chlorophyll  Occurs in all living cells
 In green organisms, produces  Uses oxygen (aerobic
oxygen respiration)
 With light energy, produces  With energy released from
ATP sugar, produces ATP.
 PLANT METABOLISM AND
NUTRITION CON’T
(c)Transportation in plant
 In plants, there are pipe-like vessels through
which water and minerals can enter the plants.
 These vessels are made up of elongated cells
and thick walls called conducting tissues.
 These conducting tissues are divided into two
types which are xylem and phloem.
 PLANT METABOLISM AND
NUTRITION CON’T
Transportation in plant
 PLANT METABOLISM AND
NUTRITION CON’T

Sugar translocation
 Sugars made in leaf mesophyll cells diffuse to the phloem cells in
the vascular bundles.
 Companion cells load dissolved sugars into the phloem Sieve-
Tube Members (STM) using energy (ATP). Water moves into cells
with high sugar concentration.
 Osmotic water flow generates a high hydraulic pressure that moves
dissolved sugars through the phloem to the rest of the plant (sink).
 Sugars made in the leaves are loaded into companion cells and
then into phloem STM.
 Water (from xylem) moves in by osmosis, creating pressure flow
down the phloem.
 PLANT METABOLISM AND
NUTRITION CON’T
How can water move from the ground all the way to the top of the plant?
 Water travels to the leaves via the stem. There are three processes
necessary for transport of water in plants, namely transpiration,
capillarity and root pressure. All these processes are passive and do not
require an input of energy.
 Transpiration : Loss of water in the form vapour via the stomata of the
leaf causes negative water pressure in the leaf. The negative pressure in
the leaf work like a suction force ,pulling the water up the stem.
 Capillary Action: moves water up the stem in response to the suction
forces. Water move by transpiration because of two forces: adhesion and
cohesion.
 Cohesion is the tendency for water molecules to stick together .
 Adhesion is the tendency for water molecules stick to other surfaces,
such as the inside of the xylem vessels. The stem xylem is structurally
adapted to capillary because of its narrow diameter.
 PLANT METABOLISM AND
NUTRITION CON’T
 Root Pressure: water moved up the stem via
a push force from the roots. Water is
constantly being absorbed by the
MMMM KCCCCCCCC due to the
negative water.
 Potential in the root cells. This movement of
water into the roots can cause water pressure
inside the roots high which pushes the water
up the xylem of the stem.
 PLANT METABOLISM AND
NUTRITION CON’T
(d) Plant hormones and their functions:
 Plant hormones are naturally occurring chemicals
messengers that influence plant development and
growth.
 Plants develop their hormones as one way of
assuring their survival.
 Since a plant cannot move away from a threatening
situation, it is important that it have an internal
messenger system that ensures that the entire plant
is able to react in a proper way to its environment.
 Types of plant hormones
1.Auxins - promotes cell growth and differentiation, especially on
the tips of plants. It controls plants' response to light.

2. Cytokinin - promotes cell division and lateral growth in plants. It

helps in the rapid division of seeds and fruits.

3. Gibberellins - helps in breaking dormancy in seeds and buds. It

can be used in the production of seedless fruits.

4. Abscisic acid - promotes dormancy in seeds and buds. It promotes

wilting and falling of leaves.

5. Ethylene - promotes fruit ripening.

 CROP DEVELOPMENT CYCLE
 A life cycle shows how a living thing grows and
changes.
 The major stages of the Plant life cycle are:
 Seed
 Germination
 Growth
 Reproduction
 Pollination
 Seed spreading stages.
 CROP LIFE CYCLE CON’T
SEEDS Seed Stage
 The plant life cycle
starts with a seed; every
seed has seed coat,
embryo and cotyledon.
 The cotyledons store
food for the young
plant.
 The seed coat protects
the embryo.
 CROP LIFE CYCLE CON’T
Parts of the Seed Events of Germination
 First water is absorbed by the seed
through the micropyle and the
testa.
 Enzymes in the soil digest the
foods stored in the seeds:These
foods now are absorbed by the
embryo and used it to
grow larger.
 The radicle grows larger and
breaks through the testa. It
becomes the roots of the new
plant.
 The plumule grows larger and
emerges above the ground.
CROP LIFE CYCLE CON’T
Growth stage
 At this stage , plants have to produce
their own food via a process is called
photosynthesis.
 The plants store the sugars in the roots
and stem. The root system continues to
develop, anchoring the plant into the
ground and growing root hairs which
help the plant to better absorb water and
nutrients.
 The stem grows longer towards the sun
and transports water and food between
the roots and leaves.
 Sugars and starches are changed into
energy used to make new plant growth.
 New leaves grow and flower buds from
the top of the stem, or meristem.
CROP LIFE CYCLE CON’T
Reproduction
 Inside the bud, a complete sexual
reproductive part of the plant Is
form (the flower)
 The bud opens and forms the
sepal of the mature flower.. The
petals of the flower are often very
noticeable, brightly colored, and
strongly scented in order to
attract pollinators.
 The fertilized eggs become seeds
in this stage of the flower life
cycle. In fruit producing plants,
the ovary ripens and becomes
fruit.
CROP LIFE CYCLE CON’T
Pollination
 Plants depend on insects, birds, animals,
wind, water, or other pollinators to carry
pollen from the male flowers or male parts
to the female flowers or female parts.
 Without pollinators, there would be no
seeds or new plants in these plant species.
 Brightly colored petals, strong smell,
nectar, and pollen attract pollinators.
Flowers are specially adapted to attract
their specific pollinators.
 Pollen sticks to the legs and wings of
insects that go from flower to flower for
nectar and pollen, which they use as a
food. Pollen sticks to the fur of animals
and even to the clothes of humans.
 Wind blows pollen which lands on other
flowers
 CROP LIFE CYCLE CON’T
Seed dispersed by wind Spreading Seeds
 Seed dispersal, is the final
stage of the flower life
cycle.
 Seeds are spread in many
ways: by wind Human,
animal and water.
 Once the seeds fall to the
ground, the plant life cycle
starts all over again.