1. 9.3 Reproduction in Angiospermophytes

3. Dicotyledonous Flower Parts
FUNCTION
Sepals
Protect the developing flower white in the bud
Petals
Modified leaves; often colourful to attract pollinators
Stamen
The “male” reproductive structure; made of anther and filament
Anther
Produces and releases pollen
Filament
Stalk of stamen that holds up anther
Carpel
The “female” reproductive structure; made of ovary, style, and stigma

4. Pistil
Can refer to a single carpel or a group of fused carpels
Stigma
Sticky top of carpel which pollen lands on
Style
Supports and holds up the style; gives the stigma exposure to pollen
ovary
Base of carpel in which the female sex cells develop; if fertilization occurs, it will turn into a protective fruit
Ovules
Found in the ovary; contain female sex cells, eggs
Pollen
Contain male sex cells (sperm)

5. Flowers occur in various colours, shapes and types – reflective of their pollinator
Complete flowers – contain all four basic flower parts (sepals, petals, stamen, and carpel)
Incomplete flowers – lack at least one of these parts
Staminate flowers – have only stamens
Carpellate flowers – have only carpets

6. Pollination
the process in which pollen (which contains the male sex cells –sperm) is placed on the female stigma.
Can occur via a variety of vectors
Wind
water
Insects
Birds
Bats

7. Angiosperms and their pollinators have coevolved (supported by fossil evidence)
The flowers colours, patterns, odours, shapes and even the time of day it blooms are designed to attract a specific pollinator
Often, the flower provides the gift of food to the pollinator in exchange for the pollinator unintentionally transporting pollen to the stigma

8. Examples Red flowers – pollinated by birds
Yellow and orange flowers – bees
Heavily scented flowers – nocturnal animals
Inconspicuous, odourless flowers – wind

11. Cross Pollination – pollen lands on the stigma of a different plant.
Self Pollination – when pollen from the anther of a plant falls on its own stigma
A form of inbreeding – thus less genetic variation
Cross Pollination – pollen lands on the stigma of a different plant.
Increases variation and offspring with different fitness

12. Fertilization
When the male and female sex cells unite to form a diploid zygote.
The female sex cells are in the ovules. The sperm from the pollen that has attached itself to the stigma must make its way to the ovules in the ovary.

13. Pollen attaches to stigma and begins to grow a pollen tube through the style
Within the growing pollen tube is the nucleus that will produce the sperm.
The pollen tube completes growing by entering an opening at the bottom of the ovary
The sperm moves from the tube to combine with the egg of ovule to form a zygote.

16. The Seed and Seed Dispersal
Once the zygote is formed, it develops with the surrounding tissue into the seed
As the seed is developing, the ovary around the ovule mature into a fruit
Seed dispersal can be aided by water, wind, animals

18. SEED
Is the means by which an embryo can be dispersed into to distant locations.
It is a protective structure for the embryo

20. Seed Part
Function
testa
Tough, protective outer coat
cotyledons
Seed leaves that function as nutrient storage structures
microphyle
Scar of the opening where the pollen tube entered the ovule
Embryo root and embryo shoot
Become the new plant when germination occurs

21. Pre-Germination Once seeds are formed, a maturation process follows.
The seed dehydrates until the water content of the seeds is about % of its weight.
At this point, the seed goes into a dormant period where there is low metabolism and no growth or development.
Duration is variable for different types of seed
It is an adaptation to environmental conditions

22. FUN FACT In 1995, a team of biologists found some seeds in a dried-up
lakebed. The seeds were from a type of lotus
plant. After germinating some of the seeds,
the biologists found them to be nearly 1300
years old!!! (They used radiometric dating to
determine this age.)

23. Fun Fact
In 2005, a 2000 year old Judean Date palm (found in the ruins of Herod the Great’s palace)was germinated

24. Germination Conditions
If conditions become favourable, the seed will germinated.
GERMINATION – is the development of the seed into a functional plant.
There are several conditions that must be fulfilled for a seed to germinate.

25. WATER Required to rehydrate the dried seed tissues
Makes the seed swell
As a result the seed coat will crack and hydrolytic enzymes are activated- they will start to catabolize large molecules (storage polysaccharides such as starch is converted into maltose) for cellular respiration.

26. OXYGEN
Required for the break down of those sugars in cellular respiration

27. TEMPERATURE
Appropriate temperature is required, that is varied among plants depending on their natural environment.
Ex. Period of low temperature followed by high temps – ensures that the seed does not geminate until the winter has passed.
Temperature is important for enzyme activity

28. Many plants have specific conditions other than these that must be met in order to germinate.
Ex:Lodgepole Pine

29. The emerging seedling is fragile and will be exposed to hard weather, parasites, predators, and other hazards.
Many seeds will not produce a functional plant because of these threats
To compensate, plants produce a large number of seeds

30. Metabolic Processes during Germination of a Starchy Seed
Seed absorbs water (which leads to many metabolic changes)
Gibberellin is released after the uptake of water
Gibberellin – plant growth hormone

31. Gibberellin triggers the release of the enzyme amylase
Amylase causes the hydrolysis of the starch into maltose
Maltose is hydrolysed into glucose which can be used for cellular respiration or converted into cellulose to build cell walls for new cells

32. Stored proteins and lipids will also be hydrolyzed to make proteins/enzymes and phospholipids and energy metabolism.
Germination uses the food stored in cotyledons to grown until it reaches light when it starts to photosynthesize

34. Control of Flowering Light important factor for growth and development
Plants are able to detect the presence of light, its direction, wavelength, intensity
PHOTOPERIODISM – the plant’s response to light involving the relative lengths of day and night.

35. *To ensure continued existence in an area, a plant must flower when pollinators are available and when necessary resources are plentiful

36. PLANT TYPE
FLOWERING AND LIGHT
EXAMPLES
LONG-DAY PLANTS
Bloom when days are longest and nights the shortest (midsummer)
- Require Pfr
Radishes, spinach, lettuce
SHORT-DAY PLANTS
Bloom in spring, late summer, and autumn when days are shorter
- Inhibited by Pfr
Poinsettias, chrysanthemums, asters
DAY-NEUTRAL PLANTS
Flower without regard to day length
Roses, dandelions, tomatoes

37. It is actually the length of night that controls the flowering process.
The control is brought about by a special blue-green pigment called phytochrome.

38. Phytochrome Phytochrome is a photoreceptor and a pigment
It absorbs light
There are 2 forms of phytochrome
Pr – absorbs red light
Pfr – absorbs far-red light/darkness

39. Far-Red Light Wavelengths between 700-800nm
At the far end of the visible light spectrum
(Between red light and infrared light)

40. During the day, when there is light, red light (wavelength of 660nm) is present
Pr absorbs red light and is rapidly converted into Pfr
At the end of the day, after many hours of light, plants will have most of their phytochrome in the form of Pfr

41. During the night, when there isn’t light (therefore no red light), Pfr is slowly converted back into Pr
By morning, most of the phytochrome will be Pr again
If there is even a flash of light interrupting the darkness during the night, it will disrupt the process of Pfr turning into Pr

42. Pr Pfr _____________________________________________________________ Pfr Pr

43. Long-day plants, require Pfr to flower
Long day = short night!
At the end of a short night, there will still be lots of Pfr remaining.
The remaining Pfr at the end of a short night stimulates the plant to flower.

44. In short-day plants, the Pfr acts as an inhibitor for flowering.
So after a short night, the remaining Pfr will prevent the plant from flowering.
If it was a long night, all the phytochrome will be in the form of Pr (there will be no Pfr) so flowering CAN occur.