Download Structure and life processes in Plants

Learning objective
• Plant structure of the main parts of a
typical flowering plant
• Describe the function of roots and stem
• Label the parts of a flower on a
diagram, and describe the functions of
each part
• What is the difference between
pollination and fertilization?
The Shoot System is
found
ABOVE
ground and the Root System
is found
BELOW or UNDER
ground.
Plant Body Organization
A plant consists of:
1. Root system, which is underground
-Anchors the plant, is used to absorb water
and minerals, conduction and storage
2. Shoot system, which is above ground
-Consists of supporting stems,
photosynthetic leaves and reproductive
flowers
Each has an apex that extends growth
Both systems depend on the
other.
– Lacking chloroplasts and living in the dark,
roots would starve without the sugar and
other organic nutrients imported from the
photosynthetic tissues of the shoot
system.
– Conversely, the shoot system (and its
reproductive tissues, flowers) depends on
water and minerals absorbed from the soil
by the roots.
AXILLARY
BUD
TERMINAL BUD
FLOWER
FRUIT
NODE
SHOOT
SYSTEM
NODE
INTERNODE
STEM
MAIN ROOT
NODE
LEAF
LATERAL
OR SIDE
ROOT
ROOT
SYSTEM
The Root
Structure of root
Types of Root Systems
Functions of the Root System
Structure of root
Roots have several structures, such as
root caps and root hairs that stems
lack.
Root cap
• Each root tip is covered by a root cap.
• The function of the root cap is to cover
and protect the delicate growing tip
from injury and damage as the root
pushes its way through the soil.
Root hairs
• Root hairs are tiny projections and
outgrowths on the outermost layer of
the root epidermis.
• The root hairs increase absorption of
water and minerals near the root tip.
Looks like a
tangled mass
of roots
Examples of plants
With this root
system are
 Rice
 Corn
 Sugar Cane
Fibrous root
• A fibrous root system - to many roots
of the same size developing from the
end of the stem, with smaller lateral
roots branching off these roots.
• Fibrous root systems, which are located
relatively close to the surface of the
soil, are adapted to obtain rainwater
from a larger area as it drains into the
soil.
• Monocots most often have fibrous
roots.
Have a large main
central root
Have many branching
roots
Go deep in the soil
Examples of plants :
 Large trees e.g.
mango, avocado
 Shrubs e.g. tomato,
peppers
• A taproot system - one main root with
many smaller lateral roots. Lateral roots
often initially occur in regular rows
along the length of the main root.
• Taproot systems often extend down
into the soil to obtain water located
deep underground
Roots :
- anchor plants firmly in the ground
- absorb water and minerals
from the soil
- Storage - some plants,
can store starch
- of some plants can
be used to grow
a new plant
Question
• Name the two organ systems and
three basic organs found in all
plants.
• What are root hairs and what is the
function of root hairs?
• Briefly explain the fibrous root.
• Describe the functions of roots.
Summary
• The root system is generally underground
and obtains water and dissolved nutrient
minerals for the plant.
• Root also anchor the plant firmly in place.
• A tap root system has one main root from
which many smaller lateral roots extend.
• A fibrous root system has several to many
oots of the same size developing from the
end of the stem.
The shoot system above – ground portion
The shoot system consists
of stems, leaves, flowers
and fruits that contain
seeds.
And the growth occurs at
apex.
Some stems grow
underground – Bulbs and
rhizomes etc. They may
be swollen to store food
e.g. potatoes.
Woody Plant Stem
The stems
support the
leaves and
flowers. In the
case of a tree,
the stems are
the trunk and all
the branches,
including the
smallest twigs.
External stem structure
• Stems all have buds,
which are undeveloped
embryonic shoots.
• A terminal bud (apical)
is the embryonic shoot
located at the tip of a
stem.
• Axillary buds, also
called lateral buds, are
located in the axils of a
plant’s leaves.
External stem structure
• When terminal and
Axillary buds grow,
they form stems that
bear leaves and/or
flowers.
• The area on a stem
where each leaf is
attached is called a
node, and the region
between two successive
nodes is an internode.
External Stem Structure
• Terminal bud = Extends the shoot system
during the growing season
• Axillary bud = Develops into branches
with leaves or may form flowers
• Node = Point of attachment of leaf to
stem
• Internode = Area of stem between two
nodes
Functions of plant stems
• Support
• Conduction
• Production
• Annual –complete their life cycle in a
single year or less (grains, legumes)
• Biennials - (such as carrot, cabbage)
take two years to complete their life
cycles before dying. In the first
season they produce extra
carbohydrates, which they store and
use during their second year when they
typically form flowers and reproduce.
• Perennials – plants that live and
reproduce for more than two years.
They include trees, shrubs, but herbs
can also be perennial.
Leaves
 External
Anatomy
 Leaf Types
 Function
Leaves
Tendrils
Mayapple
Leaves may be round, needle-like, scale like,
heart-shaped, fan-shaped, or thin and
narrow. They vary in size, colour, texture.
EXTERNAL ANATOMY
• Leaves possess a blade or lamina, an edge
called the margin of the leaf, the veins
(vascular bundles), a petiole, and two
appendages at the base of the petiole called
the stipules.
margin
Structure
The petiole, which joins
the leaf to a stem
node.
Some leaf blades are
attached directly to
the stem and lack a
petiole or stipules.
These are termed
sessile leaves.
Structure
• In the absence of
petioles in grasses
and many other
monocots, the base
of the leaf forms a
sheath that
envelops the stem.
Some monocots,
including palm trees,
do have petioles.
Structure
• The arrangement of
veins, differ in
monocots and dicots.
• Most monocots have
parallel major veins
that run the length of
the blade, while dicot
leaves have a multibranched network of
major veins.
veins
Structure: Leaf Types
Structure: Leaf Arrangement
Function of leaves
• Photosynthesis
• Transpiration - 99% of water absorbed
by plant is lost by transpiration
• Exchange of gases –
oxygen and carbon dioxide
What is the difference between
deciduous and evergreen?
• Deciduous - they shed all their leaves at
the same time and produce new leaves
the following rainy season.
• Evergreen - shed their leaves over a
long time period, so that some leaves
are always present.
Summary
• The shoot system is generally aerial and
obtains sunlight and exchanges gases such
as carbon dioxide and oxygen
– The shoot system consists of a vertical stem
that bears leaves (the main organs of
photosynthesis) and reproductive structures
(in flowering plants, flowers and fruits).
– Buds (undeveloped embryonic shoots) develop
on stems.
Summary
• Buds are undeveloped embryonic shoots. A
terminal bud is located at the tip of a
stem, whereas axillary buds (lateral buds)
are located in leaf axils.
• The area on a stem where each leaf is
attached is called a node, and the region
of a stem between two successive nodes is
an internode.
Summary
• Leaves exhibit variation in shape and form.
• Leaves typically consist of a broad, flat
blade and a stalk-like petiole. Some leaves
also possess small, leaf like outgrowths from
the base called stipules.
• Leaves may be simple or compound
• Leaf arrangement on a stem may be
alternate, opposite or whorled
• Leaves may have parallel or netted (either
pinnately netted or palmately netted)
venation.
Summary
• Monocot and dicot leaves can be
distinguished based on their external
structure.
• Monocot leaves have parallel venation,
whereas dicot leaves have netted
venation.
• The main function of stems is support,
conduction and production of new living
tissues.
Basic Flower Structure
The Parts of a Flower
Most flowers have four parts:
• sepals,
• petals,
• stamens,
• Pistil or carpel.
Complete flowers
• Complete flowers usually have four
parts-sepals, petals, stamens and pistilwhich are usually borne on a receptacle.
Incomplete flower
• Incomplete flowers lack one or more of
the four part: sepals, petals, stamens,
or pistil.
The parts of a flower
• Sepals protect the
bud until it opens.
• Petals attract
insects.
• Stamens make
pollen.
• Carpels grow into
fruits which contain
the seeds.
Parts of the Flower
• Sepals
– Outer covering of
the flower bud.
– Protects the
stamens and pistils
when flower is in
bud stage.
– Collectively known
as the calyx.
Parts of the Flower
• Petals
– Brightly colored
– Protects stamen & pistils.
– Attracts pollinating
insects.
– Collectively called the
corolla.
– Collectively sepals (calyx)
and petals (corolla) are
called the perianth.
Parts of the Flower (Stamen)
• Male reproductive part
– Anther
• Produces pollen
– Filament
• Supports the
anther
– Collectively or a group
of stamens is the
androecium.
Pistil (female)
• Stigma
• Style
• Carpel (ovary)
• Ovules (eggs)
Collectively or a group of pistil or
carpel is known as Gynoecium
Parts of the Flower (Pistil)
• Female reproductive part
– Ovary
• Enlarged portion at base of pistil
• Produces ovules which develop
into seeds
– Stigma
• Holds the pollen grains
- Style
• Connects the stigma with the ovary.
• Where pollen tube grows down to
female sex cells.
• Supports the stigma so that it can
be pollinated.
Ovules (eggs)
• The stamens and pistils are considered
the essential parts of the complete
flower for sexual reproduction.
• The sepal (calyx) and the petals (corolla)
are accessory flower parts.
• A flower with both stamen and pistil
(carpel) are considered as perfect
flower.
• Imperfect flower has either one but not
both.
Carpel
female
parts
Stigma
Petals
Stamen
male
parts
Style
Ovary
Ovules
Sepals
Anther
Filament
Nectaries
Collect a cut-out flower, colour it in and put it together.
What do the parts do?
Sepalsprotect the
flower when
it is a bud
Stamen- anther
produces male sex
cells (pollen)
Petalscolourful to
attract the
insects
Style is where
pollen tube grows
down to female sex
cells.
Nectariesgive out
sugary liquid
to attract
insects
stigma traps pollen
ovary produces
female sex cells
(ovules)
Flowers
• Function
– Contain the sexual
organs for the plant.
– Produces fruit, which
protects, nourishes and
carries seeds.
– Attracts insects for
pollination.
Learn About Plants - Different Parts.flv
Quick Test
1. Name the parts of a flower that
attract insects.
2. Name the male part of a flower.
3. Which part of the flower contains
ovules?
4. Which part of the flower produces
pollen?
5. Which part of a flower catches
pollen grains?
Label the parts of a flower
SUMMARY
•A flower may contain sepals, petals,
stamens, and carpel (pistils).
•Sepals cover and protect the flower parts
when the flower is a bud.
•Petals play an important role in attracting
animal pollinators to the flower.
•Stamens produce pollen grains.
•Each pistil has three sections: a stigma, on
which the pollen grains land; a style, through
which the pollen tube grows; and an ovary
that contains one or more ovules.
Pollination and Fertilisation
Pollination
• Pollination involves the transfer
of pollen (male gamete) from
the anther to the stigma
(outermost female part)
• Plants are pollinated by insects
or the wind.
Pollination
Self-pollination
• Pollen from the
anther is
transferred to the
stigma in the same
flower or a
different flower on
the same plant
Cross Pollination
• Pollen from the anther of one plant is
transferred to the stigma of a
different plant of the same species
Learn About Plants - Life Cycle.flv
Mode of Pollination
1. Insect-pollinated flowers may have:
•
Brightly coloured petals- blue or
yellow petals.
•
Strong sweet fragrance
•
Nectar producing glands
•
Guidelines to lead insects to Nectar
•
Stamen are inside
•
Stigma and pollen are sticky
2. Wind-pollinated flowers may
have:
•
Large stigmas outside the flower
•
Little or no fragrance
•
Light non-sticky pollen
•
Lack showy petals
Insect Pollinated Plants
Wind Pollinated Plants
Wind/Insect Pollination
Mode of Pollination (Continued)
3. Bird-pollinated flowers may have:
•
Long tube shaped flowers
•
Bright red and yellow flowers
•
No odour
4. Mammal-pollinated flowers may
have:
•
White flowers
•
Strong fruity odour
•
Flowers opening at night
5. Water-pollinated flowers may
have:
•
Pollen which floats on water
(this form of pollination is rare)
Wind Pollinated Flowers
Feature
Reason
small petals, often brown or dull
green
no need to attract insects
no scent
no need to attract insects
no nectar
no need to attract insects
pollen produced in great
quantities
because most does not reach
another flower
pollen very light and smooth
so it can be blown in the wind
anthers loosely attached and
dangle out
to release pollen into the
wind
stigma hangs outside the flower
to catch the drifting pollen
stigma feathery or net like
to catch the drifting pollen
Insect Pollinated Flowers
Feature
Reason
large, brightly coloured petals
to attract insects
often sweetly scented
to attract insects
usually contain nectar
to attract insects
moderate quantity of pollen
less wastage than with wind
pollination
pollen often sticky or spiky
to stick to insects
anthers firm and inside flower
to brush against insects
stigma inside the flower
so that the insect brushes against
it
pollen sticks to it
stigma has sticky coating
Pollination Summary
Structure
Wind
Pollinated
Insect
Pollinated
Petals
dull
bright colour
Pollen
light
sticky
Stamen
dangling
inside flower
Stigma
feathery
sticky
nectar
none
makes sugar
Fertilisation
• Fertilisation involves the fusion of the
nucleus of the male gamete (in the
pollen) with the nucleus of the female
gamete (in the ovules).
Fertilisation
• Pollen grains
germinate on the
stigma, growing down
the style to reach an
ovule.
• Fertilised ovules
develop into seeds.
• The ovary enlarges to
form the flesh of the
fruit and to protect
the ovary.
*The ovule forms the seed and the
ovary forms the fruit.
• A fruit is a ripened ovary
Pollination of flowers.flv
Seed dispersal
Seeds are dispersed in many different ways:
• Wind
• Explosion
• Water
• Animals
• Birds
• Scatter
Seed Dispersal- why?
Seeds must be carried away (dispersed /
scattered) from the parent plant to:
• Reduce overcrowding
• Reduce competition for:
- Water
- Light
- Nutrients
What is a benefit of a seed
being dispersed far away from
parent plant?
• This helps to raise the offsprings
chance of survival, at the same time
ensuring the parent plants survival.
• If the seeds land close to the parent
plant competition for resources such as
water, sunlight, and nutrients will take
place, weakening both the offspring
plants as well as the parent plant.
How birds and animals help
seed dispersal
• Some seeds are
hidden in the ground
as a winter store.
• Some fruits have
hooks on them and
cling to fur or
clothes.
How birds and animals help
seed dispersal
• Birds and animals
eat the fruits and
excrete the seeds
away from the
parent plant.
Seed Dispersal
Dispersal
method
Description
Wind
Seeds are designed to
travel as far as
possible.
May have extensions
which act as parachutes
or wings.
Fruits may be shaken
like a pepper pot.
Seeds/
Fruits
Learn About Plants - Seed Dispersal.flv
Quick Test-A
1. What term is used to describe male and
female gametes?
2. What is pollination?
3. Name the two types of pollination.
4. Describe the differences in the pollen
between insect and wind pollinated
plants.
5. Explain why the stigmas of wind
pollinated flowers hang outside the
flowers.
Quick test-B
1. Why do wind pollinated flowers not
produce nectar?
2. How does the male gamete reach the
female gamete?
3. What is a fruit?
4. Name three ways in which fruits and
seeds are dispersed.
5. Why is it important that fruits and
seeds are carried away from the
parent plant?
Parts Of A Flowering Plant.flv
Summary
• Pollination is the transfer of pollen grains from
anther to stigma.
• Flowers pollinated by insects are often yellow or
blue and possess a scent.
• Bird-pollinated flowers are often yellow, orange
or red and do not have a strong scent.
• Bat-pollinated flowers often have dusky white
petals and possess a scent.
• Plants pollinated by wind often have smaller petals
or lack petals altogether and do not produce a
scent or nectar; wind-pollinated flowers make
copious amounts of pollen.
Summary
• Fertilised ovules develop into seeds.
• Seeds are enclosed within fruits,
which are mature, ripened ovaries.
• Seeds and fruits are adapted for
various means of dispersal,
including animals, wind, water and
explosive dehiscence.