Transcript Seed - SCIS Teachers

TOPIC 9 PLANT SCIENCE
HL 9.1-9.2-9.3
Page 294 in the Biology book
9.1Plants structure and growth
Parts of the plant:
Root
Shoot
Leaf
Flower
Bud
Comparison of moncotyledon and
dicotyledon plants
Cross section of a dicot leaf
Cross section of a dicot stem
Cross section of a dicot room
Modifications of stems, leaves,
Modifications of stems, leaves
• Runner, tuber, rhizome
PLANTS TISSUES
1- Meristem tissue
a. Apical meristem
b. lateral meristem
2-Dermal tissue
a. Epidermis:
b. Periderm:
3- Mesophyll:
4- Vascular tissue:
5- Supporting tissue
Apical meristem
Provides longitudinal
growth
Lateral meristem
Provides lateral growth
Lateral meristem
Apical and lateral growth pp308
Occurs at the tip of stems and root
Occurs laterally, between primary
phloem and xylem
Product of embryonic cells
Cambium- meristematic cells left over
from primary growth
Produces initial tissues of actively
growing plant from the outset
Functions in older stems (and roots) and
in woody plants from the outset
Forms epidermis, ground tissues, and
primary phloem and xylem
Forms mainly secondary phloem and
xylem
Produces growth in length and height of
plant
Produces growth in girth of stem, plus
strengthening of stem
The role of auxin in phototropism
Growth of plant towards light source
Darwin’s experiment
WENT’S EXPERIMENT
9.2 Transport in angiospermophytes
• Explain the process of mineral ion absorption
from the soil into roots by active transport.
• State that terrestrial plants support themselves
by means of thickened cellulose, cell turgor and
lignified xylem.
• Define transpiration.
• Explain how water is carried by
the transpiration stream, including the structure
of xylem vessels, transpiration pull, cohesion,
adhesion and evaporation.
• State that guard cells can regulate
transpiration by opening and closing stomata.
• State that the plant hormone abscisic acid
causes the closing of stomata.
• Explain how the abiotic factors light,
temperature, wind and humidity, affect the
rate of transpiration in a typical terrestrial
plant.
Outline how the root system
provides a large surface area for
mineral, ion and water uptake by
means of branching and root
hairs.
There are two pathways of water uptake. Apoplast and symplast ways.
Apoplast route: through space in the cellulose
Symplast route: through living cytoplasm
Water uptake by roots
Mass flow (Apoplas route.) The space between cells are filled
by water
Diffusion (sypmlast route): through the cytoplas of cells and
via the cytoplasmic connections between cells. (this is not the
major one)
Osmosis: from vacuole to vacuole driven by osmotic pressure
difference
Ion uptake
Active transport: Ions are absorbed against concentration
gradient. Nitrate and Calcium
Active uptake is a highly selective process: Some ions are
more absorbed than others. (Na+ and NO3 present in the soil
NO3 can be absorbed more than Na)
Membrane protein pumps involve active transport.
Transportation of water in the
stem
Water is transported by xylem tissue. Xylem is long hollow
capillary tube. They are made of dead cells.
Root:
When water molecules are absorbed by apoplast or symplast
way, water molecules reach to a waxy layer between cells
called (casparian strip) and edodermis cell layer.
Leaves
Meanwhile in the leaves transpiration occur.
Transpiration in the leaves
Transpiration: is the evaporation of of water vopour through
stomata of green plant leaves and stems.
Transpiration can pull xylem sap up a tree because of two
special properties of water:
1. Cohesion is the sticking together of molecules of the
same kind.
2. Adhesion is the sticking together of molecules of
different kinds.
OPENING AND CLOSING OF STOMATA
Stomata are openings on the surface of the leaves
(usually in the lower side). They are made of two guard
cells.
-
can open and close and
help plants to adjust their transpiration rates
according to changes in the environment
-
They are open during day light closed in dark (there
are exceptions)
-
They open and close due to change in turgor pressure
of the guard cells.
Stoma opening
Stoma closing
Transpiration
Apparatus to
measure
transpiration
rate.
Transport in phloem
Mass flow
hypothesis
High sugar
concentration
High water pressure
Outline the role of
phloem in active
translocation of
sugars (sucrose) and
amino acids from
source
(photosynthetic
Low sugar
tissue and storage concentration
organs) to sink
(fruits, seeds, roots).
Low water pressure
Adaptations of Xerophytes
-
Thick cuticle
Layers of hairs on the epidermis
Reduction on the number of stomata
Stomata in pits or groves
Leaf rolled or folded when short of water
Superficial roots (collects condensed water at soil
surface at night)
- Deep and extensive roots (exploit deep water
sources in the soil)
- C4 photosynthesis
- CAM metabolism
• C4 photosynthesis: They fix CO2 in day light
while stomata open- allowing stomata to be
closed in dry conditions.
• CAM metabolism: open their stomata at night,
retain CO2 in an organic acid then they CO2
are release when stomata are closed during
the day.
Topic 9.3
REPRODUCTION OF
FLOWERING PLANTS
© 2012 Pearson Education, Inc.
9.3 Reproduction in angiospermophytes
• Draw and label a diagram showing the
structure of a dicotyledonous animalpollinated flower.
• Distinguish between pollination, fertilization
and seed dispersal.
• Draw and label a diagram showing the
external and internal structure of a named
dicotyledonous seed.
• Explain the conditions needed for the
germination of a typical seed.
• Outline the metabolic processes during
germination of a starchy seed.
• Explain how flowering is controlled in long-day
and short-day plants, including the role of
phytochro
The flower is the organ of sexual reproduction in
angiosperms
• Flowers typically contain four types of highly
modified leaves called floral organs.
1. Sepals enclose and protect a flower bud.
2. Petals are showy and attract pollinators.
3. Stamens are male reproductive structures.
4. Carpels are female reproductive structures.
© 2012 Pearson Education, Inc.
The flower is the organ of sexual reproduction in
angiosperms
• A stamen has two parts.
1. An anther produces pollen,
2. A stalk (filament) elevates the anther.
• A carpel has three parts.
1. The stigma is the landing platform for pollen.
2. The ovary houses one or more ovules,
3. A slender neck (style) leads to an ovary.
© 2012 Pearson Education, Inc.
Figure 31.9A
Figure 31.9B
Stamen
Anther
Stigma
Carpel
Style
Ovary
Filament
Sepal
Petal
Ovule
Life Cycle of a flowering plant
• In the life cycle of a generalized angiosperm,
– fertilization occurs in an ovule,
– the ovary develops into a fruit,
– the ovule develops into the seed containing the
embryo,
– the seed germinates in a suitable habitat, and
– the embryo develops into a seedling and then mature
plant.
© 2012 Pearson Education, Inc.
Figure 31.9C_s5
Ovary, containing
ovule
Embryo
3 Seed
2 Fruit (mature ovary),
containing seed
1 Mature plant with
flowers, where
fertilization occurs
5 Seedling
4 Germinating seed
• Pollination is the transfer of pollen from anther to
stigma.
• Pollen may be carried by wind, water, and
animals.
• As a pollen grain germinates,
– the tube cell gives rise to the pollen tube, which
grows downward into the ovary, and
– the generative cell divides by mitosis, producing two
sperm.
© 2012 Pearson Education, Inc.
• At fertilization,
– one sperm fertilizes the haploid egg to produce a
diploid zygote, and
– another sperm fuses with the diploid central cell
nucleus to produce a triploid (3n) cell that will give
rise to the endosperm, which nourishes the
developing embryo.
 This formation of a diploid zygote and a triploid
nucleus is called double fertilization.
© 2012 Pearson Education, Inc.
Figure 31.10
Development of male
gametophyte
(pollen grain)
Development of female
gametophyte
(embryo sac)
Anther
Ovule
Ovary
Cell within
anther
Meiosis
Surviving
cell (haploid
spore)
Meiosis
Four haploid
spores
Single
spore
Pollination
Germinated
pollen grain
on stigma
Mitosis
Wall
Mitosis
(of each spore)
Nucleus of
tube cell
Generative cell
Embryo
sac
Pollen grain
released
from anther
Egg cell
Two sperm
in pollen
tube
Pollen
tube
enters
embryo sac
Two sperm
discharged
Double
fertilization
occurs
Triploid (3n)
endosperm
nucleus
Diploid (2n)
zygote
(egg plus
sperm)
Figure 31.10_1
Development of male
gametophyte
(pollen grain)
Development of female
gametophyte
(embryo sac)
Anther
Ovule
Cell within
anther
Meiosis
Four haploid
spores
Ovary
Meiosis
Surviving
cell (haploid
spore)
Figure 31.10_2
Surviving
cell (haploid
spore)
Four haploid
spores
Single
spore
Pollination
Germinated
pollen grain
on stigma
Mitosis
Wall
Mitosis
(of each spore)
Nucleus of
tube cell
Generative cell
Pollen grain
released
from anther
Embryo
sac
Egg cell
Two sperm
in pollen
tube
Development
of male
gametophyte
(pollen grain)
Development
of female
gametophyte
(embryo sac)
Figure 31.10_3
Pollen
tube
enters
embryo sac
Two sperm
discharged
Double
fertilization
occurs
Triploid (3n)
endosperm
nucleus
Diploid (2n)
zygote
(egg plus
sperm)
The ovule develops into a seed
• After fertilization, the ovule, containing the
triploid central cell and the diploid zygote, begins
developing into a seed.
• The seed contains proteins, oils, and starches.
• The zygote first divides by mitosis to produce two
cells.
– One cell becomes the embryo.
– The other cell divides to form a thread of cells that
pushes the embryo into the endosperm.
© 2012 Pearson Education, Inc.
The ovule develops into a seed
• The result of embryonic development in the
ovule is a mature seed, including
–
–
–
–
–
an endosperm,
one or two cotyledons,
a root,
a shoot, and
a tough seed coat.
© 2012 Pearson Education, Inc.
• Seed dormancy
– is a period when embryonic growth and
development are suspended and
– allows for germination when conditions are
favorable.
© 2012 Pearson Education, Inc.
Figure 31.11A
Triploid cell
Ovule
Zygote
Cotyledons
Endosperm
Two cells
Seed
coat
Shoot
Embryo
Root
Seed
Figure 31.11B
Embryonic
leaves
Embryonic
shoot
Embryonic
root
Seed coat
Cotyledons
Common bean (eudicot)
Fruit tissue
Cotyledon
Seed coat
Embryonic
leaf
Sheath
Corn (monocot)
Endosperm
Embryonic
shoot
Embryonic
root
• Hormonal changes induced by fertilization trigger
the ovary to develop into a fruit.
• Fruits
– house and protect seeds and
– aid in their dispersal. How?
© 2012 Pearson Education, Inc.
• After pollination, a pea plant flower
– drops its petals,
– the ovary starts to grow, expanding tremendously,
and its wall thickens, and
– a pod forms, holding the peas, or seeds.
© 2012 Pearson Education, Inc.
Figure 31.12A
1
2
3
Figure 31.UN04
Endosperm
nucleus (3n)
(2 polar nuclei
plus sperm)
Zygote (2n)
(egg plus
sperm nucleus)
• Mature fruits may
be fleshy or dry.
– Fleshy fruits
include oranges,
tomatoes, and
grapes.
– Dry fruits include
beans, nuts, and
grains.
© 2012 Pearson Education, Inc.
Seed germination continues the life cycle
• At germination, a seed
– takes up water.
What is the role of water in seed germination?
– Needs oxygen. Why?
© 2012 Pearson Education, Inc.
Figure 31.13A
Foliage leaves
Cotyledon
Embryonic Cotyledon
shoot
Embryonic
root
Seed
coat
Figure 31.13B
Foliage
leaves
Protective sheath
enclosing shoot
Embryonic
root
Cotyledon
Figure 31.UN03
Pollen (n)
Ovary
Embryo
sac (n)
Fertilization
within ovule
Ovule
Fruit (from ovary)
Mature
plant (2n)
Seed (from ovule)
Embryo (2n)
Germinating
seed (2n)
• Plants display rhythmic behavior including the
– opening and closing of stomata and
– folding and unfolding of leaves and flowers.
© 2012 Pearson Education, Inc.
Plants have internal clocks
• Circadian rhythms (daily) are controlled by
internal timekeepers known as biological clocks.
• Light/dark cycles keep biological clocks precisely
synchronized.
• For most organisms, including plants, we know
little about
– where the clocks are located or
– what kinds of cells are involved.
© 2012 Pearson Education, Inc.
Figure 33.10
Noon
Midnight
Plants mark the seasons by measuring photoperiod
• Biological clocks can influence seasonal events
including
– flowering,
– seed germination, and
– the onset of dormancy.
• The environmental stimulus plants most often use
to detect the time of year is called photoperiod,
the relative lengths of day and night.
© 2012 Pearson Education, Inc.
Plants mark the seasons by measuring photoperiod
• Plant flowering signals are determined by night
length.
• Short-day plants, such as chrysanthemums and
poinsettias
– generally flower in the late summer, fall, or winter
– when light periods shorten.
• Long-day plants, such as spinach, lettuce, and
many cereal grains
– generally flower in late spring or early summer
– when light periods lengthen.
© 2012 Pearson Education, Inc.
Figure 33.11
0
Time (hrs)
24
Plants bloom only
with a longer dark
period.
1
2
Flash of light
prevents flowering.
3
Light
Shortday
(longnight)
plants
Darkness
Flash of
light
Plants bloom
only with a
shorter dark
period.
4
5
Flash of light
induces
flowering.
6
Critical dark
period
Longday
(shortnight)
plants
Phytochromes are light detectors that may help set the
biological clock
• Phytochromes
– are proteins with a light-absorbing component and
– may help plants set their biological clock and monitor
photoperiod.
• Phytochromes detect light in the red and far-red
wavelengths.
– One form of phytochrome absorbs red light (Pr).
– One form detects far-red light (Pfr).
– When Pr absorbs light, it is converted into Pfr.
– When Pfr absorbs light, it is converted into Pr.
© 2012 Pearson Education, Inc.
Figure 33.12A
Red
light
Pr
Pfr
Far-red
light
Pr is naturally produced during dark hours, while Pfr is broken
down.
The relative amounts of Pr and Pfr present in a plant change as
day length changes.
Figure 33.12B
0
Time (hrs)
24
1
R
2
R FR
3
RFRR
4
RFRRFR
Critical dark
period
Short-day
(long-night)
plant
Long-day
(short-night)
plant