Flowering plants reproduce sexually through pollination, fertilization, and seed dispersal, which relies on interactions with pollinators and a response to environmental cues like photoperiod. Success in reproduction depends on transferring pollen from the anthers to the stigma via vectors like wind or animals, fertilization fusing gametes, and seeds dispersing from the parent plant. Flowering involves changes in gene expression and plant hormones in response to daylight that causes the shoot apex to develop reproductive structures instead of vegetative ones.

1. 9.4 Reproduction in plants
Essential idea: Reproduction in flowering plants is influenced by the biotic and abiotic
http://www.people.fas.harvard.edu/~ccdavis/weblinks/El_Pais_fil
es/Imagen_Rafflesiaceae_alcanza_metro_diametro_kilos_peso.jp
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Rafflesia keithii Meijer

2. Understandings
Statement Guidance
9.4.U1 Flowering involves a change in gene expression
in the shoot apex
9.4.U2 The switch to flowering is a response to the
length of light and dark periods in many plants.
9.4.U3 Success in plant reproduction depends on
pollination, fertilization and seed dispersal.
9.4.U4 Most flowering plants use mutualistic
relationships with pollinators in sexual
reproduction.

3. Applications and Skills
Statement Guidance
9.4.A1 Methods used to induce short-day plants to
flower out of season.
9.4 S.1 Draw internal structure of seeds.
9.4.S.2 Drawing of half-views of animal-pollinated
flowers.
9.4 S.3 Design of experiments to test hypothesis about
factors affecting germination.

4. 9.4 U.1 Flowering involves a change in gene expression in the shoot
apex
• Production of plant hormones
which when exposed to the
proper amount of photo-
inductive daylight convert
vegetative structure in
reproductive structure.
• The hormone is then transport
from the leaf to the shoot apex
cause genes to switch on
causing transcription of
proteins to begin.
• An increase in morphological
and molecular changes at the
shoot apex, especially involving
floral organ identity genes.

5. The mechanism of flowering
• mRNA moves from leaf to
flower meristem.
• This mRNA provides a link
between the phytochrome
system (the receptor), its
activation of genes in the
leaf (mRNA synthesis)
• Differentiation of the
meristem into the flower
structure comes about due
to the construction of
protein from protein
synthesis.
http://eatbetea.com/wpcontent/uploa
ds/2014/04/IMG_1211.jpg
9.4 U.1 Flowering involves a change in gene expression in the shoot
apex

6. 9.4 U.2 The switch to flowering is a response to the length of light and
dark periods in many plants.
Phytochrome and the control of
flowering
Flowering Cues:
• Plant have to coordinate the production of
flowers to coincide with the best reproductive
opportunities. There are many environmental
cues that affect flowering however the
photoperiod is the most reliable indicator on
'time' of year.
• The photoperiod the period of day light in
relation to dark (night). In northerly and
southern regions this photoperiod is a reliable
indication of the time of year and therefore
one of the most reliable indicators of the
seasonal changes.
Short and Long day Plants:
• Short day plants (SDP) typically flower in the
spring or autumn when the length of day is
short.
• Long day plants (LDP) typically flower during
the summer months of longer photoperiod

7. 9.4 U.2 The switch to flowering is a response to the length of light and
dark periods in many plants.
Critical Night Length
•Experiments have shown that
the important factor determining
flowering is the length of night
rather than the length of day.
•SDP have a critical long night.
That the length of night has to
exceed a particular length before
there will be flowering.
•LDP have a critical short night.
That the length of night must be
shorter than a critical length
before there will be flowering.

8. 9.4 U.2 The switch to flowering is a response to the length of light and
dark periods in many plants.
Phytochrome System:
•The receptor of photoperiod is located within the leaf.
•The cellular location of the receptor is unclear.
•The chemical nature of the receptor is a the molecule PHYTOCHROME.
•Phytochrome can be converted from one form to another by different
types of light.
http://www.putso.com.ne.kr/lecture/img/pfr.gif

11. 9.4 U.2 The switch to flowering is a response to the length of light and
dark periods in many plants.
www.click4biology.com

12. 9.4 U.2 The switch to flowering is a response to the length of light and
dark periods in many plants.
Flowering in Short day plant (SDP)
•Short day plants flower when the night
period is long.
*Night length is critical
Steps
 In day light or red light, Phytochrome
Red (Pr) is converted to Phytochrome
Far Red (Pfr). The conversion actually
only requires a brief exposure to
white or red light
 In the dark, Pfr is slowly converted
back to Pr. A long night means that
there is a long time for the
conversion.
 Under short day conditions (long
night) at the end of the night period
the concentration of Pfr is low.
 In SDP, low Pfr concentration is the
trigger for flowering.
http://cnx.org/resources/da0cef9ea401465d69b8142665006a50/Figure_30_06_01.jpg

13. 9.4 U.2 The switch to flowering is a response to the length of light and
dark periods in many plants.
Flowering in Long day Plants
(LDP):
*Night length is critical
•Long day plants flower when the
night period is short.
Steps
In day light (white or red) the
Pr is converted to Pfr.
During periods when the day
light period is long but
critically the dark period is
short, Pfr does not have long
to breakdown in the dark.
Consequently there remains
a higher concentration of
Pfr.
In LDP, high Pfr
concentration is the trigger
to flowering. http://jordantimes.com/uploads/repository/a98b
24c425cded558dc267e1366e05003088e2d4.jpg

14. 9.4 A.1 Methods used to induce short-day plants to flower out of season
http://www.silversurfers.com/wp-
content/uploads/2012/09/red-white-parrot-tulip.jpg

15. 9.4 U.3 Success in plant reproduction depends on pollination,
fertilization and seed dispersal.
Pollination
•The process in which pollen is
transferred from the anther to
the stigma.
•Requires a vector e.g. insects
mammals, winds, birds, water.
•Cross fertilization involves pollen
from one plant landing on the
stigma of a different plant
•Self pollination involves the
transfer of the plants own pollen
to its own stigma
http://www.pollinator.ca/bestpractices/ima
ges/conifer%20pollen%20release.jpg

16. http://www.pollinis.org/wp-content/uploads/2014/05/Image-
Pollination_Bee_Dandelion_Zoom2.jpg

17. 9.4 U.3 Success in plant reproduction depends on pollination,
fertilization and seed dispersal.
Fertilization
• Fusion of the gamete nuclei
(in the pollen grain) with the
female gamete (in the ovule)
to form a zygote.
• Pollen grains often contain an
additional nuclei used in the
‘fertilization’ of the food
store cells.
Seed dispersal
• Fertilized ovules form seeds.
The seeds are moved away
from the parental plant
before germination to reduce
competition for limited
resources with parental
plant. There are variety of
seed dispersal mechanism
including fruits, winds, water
and animals
http://leavingbio.net/The%20Structure%20and
%20Functions%20of%20Flowers_files/image018.jpg
Fertilization

18. http://www.nature.nps.gov/biology/invasivespecies/Prevention.cfm
Seed dispersal: Sticky seeds hitching a ride on fur

19. 9.4 U.4 Most flowering plants use mutualistic relationships with
pollinators in sexual reproduction.
• Sexual reproduction in
flowering plants depends on
the movement of pollen from
stamen to a stigma
• Pollen is transferred by wind,
water (less common) and
animals known was
pollinators (more common)
• Pollinators: birds, bats &
insects (bees & butterflies)
• Mutualism – close association
between 2 organisms that
both benefit from the
relationship. Pollinators gain
food by nectar and plants
gains a means to transfer
pollen to another plan
http://upload.wikimedia.org/wikipedia/commons/d/db/Colibri-thalassinus-001-edit.jpg

20. 9.4 U.4 Most flowering plants use mutualistic relationships with
pollinators in sexual reproduction.
• Sexual reproduction in flowering plants depends on the movement of pollen from stamen to a stigma
• Pollinators: birds, bats & insects (bees & butterflies)

21. 9.4 S.1 Draw internal structure of seeds
Dicotyledonous seeds
• Testa protects the plant embryo and the cotyledon food stores
• Cotyledons contain food store for the seed
• Plumule is the embryonic stem
• Radicle is the embryonic root
• Micropyle is a hole in the testa ( from pollen tube fertilization)
through which water can enter the seed prior to germination
• Scar is where the ovule was attached to the carpel wall

22. The Children Pureed Red Meat Smoothies

23. 9.4 A.2 Drawing of half-views of animal-pollinated flowers.
• Sepals cover the flower structure while the
flower is developing. In some species these are
modified to ' petals'.
• Petals surround the male and female flower
parts. Function is to attract animal pollinators.
• Pistil (female reproductive part)
 Stigma is the surface on which pollen lands
and the pollen tube grows down to the
ovary.
 Style connects the stigma to the ovary.
 Ovary contains the ovules (contain single
egg nuclei).
• Stamen (male reproductive part)
 Filaments support the anthers
 Anther that contain the pollen. Together
they are called the stamen.

26. 9.4 A.3 Design of experiments to test hypothesis about factors affecting
germination.
The metabolic events of
seed germination:
a) Water absorbed and the activation of
cotyledon cells
b) Synthesis of gibberellin which is a plant
growth substance. (Hormone is no longer a
term used to describe such compounds).
c) The gibberellin brings about the synthesis of
the carbohydrase enzyme amylase
d) Starch is hydrolyzed to maltose before
being absorbed by the embryonic plant
e) The maltose can be further hydrolyzed to
glucose for respiration on polymerized to
cellulose for cell wall formation causing
growth.

27. Weird green aliens
smiled making a greeting

29. 9.4 A.3 Design of experiments to test hypothesis about factors affecting
germination.
Conditions for Germination
Seeds require a combination of:
Oxygen for aerobic respiration
Water to metabolically activate the cells
Temperature for optimal function of enzymes
All are need for successful germination. Each seed has its own particular
combination of the three factors.
http://www.emperorswithoutclothes.com/images/seed_growth.jpg

30. 9.4 A.3 Design of experiments to test hypothesis about factors affecting
germination.