Lodoicea maldivica

Litchi chinensis

Phoenix dactylifera

BOI 101/3 (SEEDS)

Plants and Animals Biodiversity

Prof Madya Dr. Rahmad Zakaria (rahmadz@usm.my)

Adapted from:
Dr. Rosazlina Rusly (rosazlinarusly@usm.my)
Entada rheedii
BOI101RR • A mature seed contains an embryonic plant and food stored in either the endosperm or the
cotyledons.
• Endosperm is the nutritive tissue that surrounds the embryonic plant in a seed.
• The seed, in turn, is surrounded by a tough, protective seed coat, derived from the
Seed •
outermost layers (the integuments) of the ovule, and enclosed within a fruit.
The mature embryo within the seed consists of a short embryonic root, or radicle; an
Development embryonic shoot; and one or two seed leaves, or cotyledons. Monocots have a single
cotyledon, and dicots have two.
• The short portion of the embryonic shoot connecting the radicle to one or two cotyledons
is the hypocotyl.
• The shoot apex above the point of attachment of the cotyledon(s) is the plumule (also
known as the epicotyl).
Seed dispersal
• Wind, animals, water, and explosive dehiscence disperse the
various seeds and fruits of flowering plants.
• Effective methods of seed dispersal have made it possible
for certain plants to expand their geographic range. In some
cases, the seed is the actual agent of dispersal, whereas in
others the fruit performs this role.
• Wind disperses the seeds of many plants. Plants such as
Dipterocarp Seed (Shorea sp.), maple trees have winged
fruits (Samara) adapted for wind dispersal. Light, feathery
plumes enable other seeds or fruits to be transported by
wind.

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Seed dispersal
• Some plants have special structures that
aid in the dispersal of their seeds and
fruits by animals.
• The hooked fruits often get caught in
animal fur and are dispersed as the animal
moves about.
• Fleshy, edible fruits are also adapted for
animal dispersal.
• As an animal eats these fruits, it either
discards or swallows the seeds. Many
seeds that are swallowed have thick seed
coats and are not digested.
• Some edible fruits apparently contain
chemicals that function as laxatives to
speed seeds movement through an
animal’s digestive tract.
KOPI LUWAK
Dispersal Methodology:
• A. FLOATING
• The coconut (Cocos nucifera) is
an example of a fruit adapted
for dispersal by water.
• The coconut has air spaces that
make it buoyant and capable of
being carried by ocean currents.
• When it washes ashore, the
seed may germinate and grow
into a coconut palm tree.

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Seed dispersal
(B: mechanical ejection)

• Such seeds are found in fruits that use

explosive dehiscence (mechanical
ejection), in which the fruit bursts open
suddenly, and quite often violently, to
forcibly discharge its seeds.
• Pressures due to differences in turgor or
to drying out cause these fruits to burst
open suddenly.

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 Seed dispersal
C: Animal
• Animals such as squirrels and many bird
species also help disperse acorns and other
fruits and seeds by burying them for winter
use.
• Many buried seeds are never used by the
animal and germinate the following spring.

Millions Of Trees Are Planted Every Year By

Squirrels Who Forgot Where They Buried
Their Nuts
https://nedhardy.com/2020/02/10/squirrels-
plant-trees/
 Germinations

• As they mature, seeds dehydrate and become dormant (low

metabolism, no growth & development)
• Germination is the resumption of growth, development and
metabolic rate is triggered by the environmental conditions: the
presence of water and oxygen, proper temperature, and sometimes
the presence of light penetrating the soil surface.
• When a seed germinates, its metabolic machinery is turned on, and
numerous materials are synthesized and degraded. Therefore, water
is an absolute requirement for germination.
• The absorption of water by a dry seed that precedes germination is
known as imbibition. As a seed imbibes water, it often swells to
several times its original, dry size. Cells imbibe water by osmosis,
which is the movement of water across a membrane from an area of
high concentration to an area of low concentration, and by
absorption of water onto and into materials such as cellulose, pectin,
and starches within the seed.

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• Seed germination and

subsequent growth also
require a great deal of energy.
Germinations Because plants obtain this
energy by converting the
energy of fuel molecules
stored in the seed’s
endosperm or cotyledons to
ATP by aerobic respiration,
oxygen is usually needed
during germination.
• Some plants, such as rice, can
respire without oxygen during
the early stages of
germination and seedling
growth. This enables rice
plants to grow and become
established in flooded soil, an
environment that would
suffocate most young plants.
 • Temperature is another
environmental factor that affects
Germinations germination.
• Each plant species, has an optimal, or
ideal, temperature at which the
seeds germinates.
• For most plants, the optimal
germination temperature is between
250C and 300C.
• Some seeds, such as those of apples,
require prolonged exposure to cold
before they germinate at any
temperature.
• Some of the environmental factors
necessary for seed germination help
ensure the survival of the young
plant. The requirement of a
prolonged cold period ensures that
seeds germinate in the spring rather
than in the autumn.

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• Some plants—especially those

with tiny seeds, such as
Germinations lettuce—require light for
germination.
• A light requirement ensures
that a tiny seed germinates
only if it is close to the surface
of the soil.
• If such a seed germinates
several inches below the soil
surface, it may not have
enough food reserves to grow
to the surface.
• On the other hand, if this light-
dependent seed remains
dormant until the soil is
disturbed and it is brought to
the surface, it has a much
greater likelihood of survival.
 Germinations
• In certain seeds, internal factors, which are under genetic
control, prevent germination even when all external
conditions are favorable.
• Many seeds are dormant either because the embryo is
immature and must develop further or because certain
chemicals are present.
• The presence of such chemical inhibitors helps ensure
the survival of the plant.
• The seeds of many desert plants, for example, often
contain high levels of abscisic acid.
• Abscisic acid is washed out only when rainfall is sufficient
to support the plant’s growth after the seed germinates.

BOI101RR Gibberellic acid (GA)

 • Some seeds, such as those of
Germinations legumes, have extremely hard,
thick seed coats that prevent
water and oxygen from
entering, thereby inducing
dormancy.
• After these seeds are dispersed
into the natural environment,
exposure to the elements
gradually weakens their seed
coats so that germination
eventually occurs.
• Scarification, the process of
scratching or nicking the seed
coat (physically with a knife or
chemically with an acid) before
sowing it, induces germination
in these plants.

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• Once conditions are right for seed

germination, the first part of the plant to
emerge from the seed is the radicle, or
embryonic root.
The patterns of early growth • As the root grows and forces its way through
the soil, it encounters considerable friction
from soil particles.
• The delicate apical meristem of the root tip is
protected by a root cap.
• The plant shoot is next to emerge from the
seed.
• Stem tips are not protected by anything like a
root cap, but plants have ways to protect the
delicate stem tip as it grows up through the
soil to the surface.
• The stem of a bean seedling (dicot), for
instance, curves over to form a hook so that
the stem tip and cotyledons are actually
pulled up through the soil.
• Corn and other grasses (monocots) have a
special sheath of cells called a coleoptile that
surrounds the young shoot.
• First the coleoptile pushes up through the
soil, and then the leaves and stem grow up
through the middle of the coleoptile.
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• Certain parts of a plant grow

throughout its life.

The patterns of plant growth • This indeterminate growth—the

ability to grow indefinitely—is
characteristic of stems and roots,
both of which arise from apical
meristems. Theoretically, stems and
roots could continue to grow
forever.
• Other parts of a plant, such as
leaves and flowers, have
determinate growth; that is, they
stop growing after reaching a
certain size. The size of each of
these structures varies from species
to species and from individual to
individual depending on the plant’s
genetic programming and on
environmental conditions, such as
availability of sunlight, water, and
essential minerals.
WE JUMP BACK

HOW POLLEN GRAINS

TRAVEL FROM THE ANTHER
TO THE STIGMA?
(POLLINATION)

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 • Before fertilization occurs,
Pollination pollen grains must travel from
the anther (where they form)
to the stigma. The transfer of
pollen grains from anther to
stigma is known as
pollination.
• Plants are self-pollinated if
pollination occurs within the
same flower (autogamy) or
within a different flower on
the same individual plant
(geitonogamy).
• Cross-pollination occurs when
pollen grains are transferred
to a flower on another
individual of the same species
(allogamy).

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 Pollination
• Flowers pollinated by animals have
various features to attract them,
including showy petals (a visual
attractant) and scent (an olfactory
attractant).
• One reward for the animal pollinator
is food. Some flowers produce
nectar, a sugary solution, in special
floral glands called nectaries.
• Pollinators use nectar as an energy-
rich food. Pollen grains are also a
protein-rich food for many animals.
• As they move from flower to flower
searching for food, pollinators
inadvertently carry pollen grains on
their body parts, facilitating sexual
reproduction in plants.
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 Pollinators

• Botanists estimate that insects

pollinate about 70 percent of all
flowering plant species.
• Bees are particularly important
as pollinators of crop plants.
• Bee-pollinated crops provide
about 30 percent of human food.

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• Plants pollinated by insects often have blue or yellow petals. The insect eye does not see color the
same way the human eye does.
Pollinators • Most insects see well in the violet, blue, and yellow ranges of visible light but do not perceive red
as a distinct color.
• Insects see ultraviolet radiation as a color called bee’s purple. Many flowers have dramatic
ultraviolet markings called nectar guides that may or may not be visible to humans but that direct
insects to the center of the flower where the pollen grains and nectar are.
BOI101RR

Pollinators
• Insects have a well-developed sense of smell, and many insect-
pollinated flowers have strong scents that may be pleasant or foul to
humans.
• Amorphophallus titanum, the titan arum, is a flowering plant with the
largest unbranched inflorescence in the world (endemic to Sumatra).
• Due to its odor, like that of a rotting corpse, the titan arum is
characterized as a carrion flower, and is also known as the corpse
flower or corpse plant.
• The "fragrance" of the titan arum resembles rotting meat,
attracting carrion-eating beetles and flesh flies (family Sarcophagidae)
that pollinate it.
• The inflorescence's deep red color and texture contribute to the illusion
that the spathe is a piece of meat. During bloom, the tip of the spadix is
approximately human body temperature, which helps the perfume
volatilize; this heat is also believed to assist in the illusion that attracts
carcass-eating insects.
• As flies move from one reeking flower to another looking for a place to
lay their eggs, they transfer pollen grains. (Should a fly lay her eggs on
the carrion flower, the larvae will starve to death when they hatch.)
 Pollinators
• Birds such as hummingbirds are
important pollinators.
• Because birds do not have a strong
sense of smell, bird-pollinated
flowers usually lack a scent.
• Hummingbird-pollinated flowers
have a long, tubular corolla with
nectar glands at the bottom.
• The bird hovers beside a flower
and inserts its beak and long
tongue inside to lap up the nectar.
• Hummingbird pollinated flowers
produce more nectar than insect
pollinated flowers, because
hummingbirds are larger animals
than insects and therefore require
more food. BOI101RR
 Pollinators
• Bats, which feed at night and do not see
well, are important pollinators,
particularly in the tropics, where they
are most abundant.
• Bat-pollinated flowers are night
blooming and often have dull white
petals and a strong scent, usually of
fermented fruit.
• Nectar-feeding bats are attracted to the
flowers by their scent; they lap up the
nectar with their long, extensible
tongues.
• As they move from flower to flower, they
transfer pollen grains.

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Some flowering plants depend on wind to disperse pollen grains

• Some flowering plants, such as grasses,

ragweed, maples, and oaks, are pollinated by
wind.
• Wind-pollinated plants produce many small,
inconspicuous flowers.
• They do not produce large, colorful petals,
scent, or nectar. Some have large, feathery
stigmas, presumably to trap wind-borne
pollen grains.
• Because wind pollination is a hit-or-miss
affair, the likelihood of a pollen grain landing
on a stigma of the same species of flower is
slim.
• Wind-pollinated plants produce large
quantities of pollen grains, which increases
the likelihood that some pollen grains will
land on the appropriate stigma.
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 The Plant Life Cycle
• Sperm cells reach the archegonium in a variety
of ways, such as by water, animals, and wind.
They swim down the neck of the archegonium,
and one sperm cell fuses with the egg.
• This process, known as fertilization, results in a
fertilized egg, or zygote.
• The diploid zygote is the first stage in the
sporophyte generation. The zygote divides by
mitosis and develops into a multicellular
embryo, the young sporophyte plant.
• Embryo development takes place within the
archegonium; thus, the embryo is supported,
nurtured, and protected as it develops.
Eventually, the embryo grows into a mature
sporophyte plant. The mature sporophyte has
special spore-producing cells that are capable
of dividing by meiosis. Each of these spore
mother cells divides by meiosis to form four
haploid spores.
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Alternation of
Generations
 I’m the one who
disturbed my mummy
just now with my sexy
voice
meaw…meaw…hehe.

~~~Lemon

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