1. HortBotany Lesson Plan #9
Flowers
HortBotany
Lesson Plan #9

2. Flowers: A Marvelous Innovation
Flowering plants first appeared around 140 million years ago (Upper Jurassic).
Oldest flower fossil is 125 million years old.
The dominant forms of plant life were gymnosperms, cycads, and ferns.

3. Today
Flowering plants (Angiosperms) are now the dominant form of plant life over most of the earth’s land surface. Ferns are rarely dominant and gymnosperms are dominant only in cold, or seasonally cold locations. Cycads are hanging on by a thread. Why have flowering plants been so successful?

4. Angiosperm Flowers
Ovaries protect ovules and developing seeds; mature into fruits that promote seed dispersal
Floral structure encourages pollinator fidelity; nectar and pollen to reward pollinators
Fast reproductive cycle compared to gymnosperms

5. Structure of flowers
Flowers are composed of four whorls. From the outside in, they are:
Calyx (sepals)
Corolla (petals)
Androecium (stamens)
Gynoecium (pistils)

6. Calyx Outermost whorl Usually green Protects developing flower
Made up of SEPALS
Sepals free or not

7. Sepals
Usually green; leaflike structures that protect the flower, as it forms and emerges.

8. Sometimes sepals are colorful

9. Calyx
The group of sepals on a flower

10. Corolla Is usually colorful and showy Attracts pollinators
Guides pollinators
Is composed of petals
Petals may be united or separate

11. Petals Located just inside the sepals
Leaf-like and often very colorful

12. The collection of petals on a flower
Corolla
The collection of petals on a flower

13. Perianth
The sepals and the petals of a flower. (Not the reproductive parts.)

14. HIPPEASTRUM 'MARMADUKE’
Tepals
When there is no clear distinction between the sepals and the petals...they are called “tepals”.
HIPPEASTRUM 'MARMADUKE’

15. Androecium Is composed of stamens Stamens have filaments and anthers
Pollen is produced in anthers
Stamens can be free or united

16. Stamens Male reproductive parts of a flower
Arranged around the female parts

17. Anther
Part of the stamen
Produces and holds pollen

18. Stalk that holds up the anther
Filament
Stalk that holds up the anther

19. Gynoecium Is composed of pistils
A pistil is composed of an ovary, style, and stigma.

20. Pistil = 1 or more carpels
Each theoretical leaf unit is termed a carpel
A pea pod is a mature pistil made up of 1 carpel
Pistils with 2 style branches and/or chambers in the ovary are said to have 2 carpels
Pistils with 3 style branches and/or chambers are said to have 3 carpels etc.

21. Stigma Found at the end of the pistil
Has a sticky surface to catch pollen

22. Style
The neck of the pistil

23. Ovary
Part of the pistil that contains the ovules

24. Ovule
The part of the flower in which the eggs are produced and seeds develop

25. Ovary Position I. Above the calyx and corolla (ovary superior)
II. Ovary partially inferior
III. Below the calyx and corolla (ovary inferior)
Ovary position: I superior II partially-inferior III inferior.
a androecium g gynoecium p petals s sepals r receptacle.

26. Hypanthium
If the corolla and calyx are attached to a cup or tube that is then attached to the receptacle, the cup or tube is called a hypanthium.

27. Receptacle
The top floral whorls are attached to the receptacle – the tissue where the stalk to the flower changes to being part of the flower

28. Pedicels Flowers are borne on pedicels
Think of a pedicel as the stalk to a flower

29. Attracting Pollinators
To survive, species must reproduce
Pollination is the first major step in the reproduction of seed plants like gymnosperms and angiosperms
Flowers persuade animals to serve as pollinators, preferably faithful pollinators
To get the right pollen, flowers need to be memorable so …

30. Start thinking like a pollinator
Is there a reward?
How can I find another like this one?
Symmetry
Color pattern
Odor
Will it be safe for me?
Corolla – united or separate petals
Corolla more important than calyx – why?
Can I reach the reward and is it adequate?
nectaries and androecium

31. insect pollination

32. hummingbird pollination

33. bat pollination

34. eastern cottonwood catkins
wind pollination;
eastern cottonwood catkins

35. Complete vs. Incomplete Flowers

36. Sepals, petals, stamens and pistil
Complete flowers
Have all 4 basic parts:
Sepals, petals, stamens and pistil

37. Incomplete Flowers
Flowers that are missing one of the four basic parts

38. Perfect vs. Imperfect Flowers

39. Flowers that have both male and female parts
Perfect Flowers
Flowers that have both male and female parts

40. Flowers that lack one of the sex structures
Imperfect flowers
Flowers that lack one of the sex structures

41. Monoecious vs. Dioecious

42. male catkins and female strobili
Monoecious = 1 House
refers to a species
separate male and female flowers on the same plant
Black Alder
male catkins and female strobili

43. Dioecious = 2 Houses refers to a species
separate male and female flowers on different plants

44. Common Winterberry male flowers Common Winterberry female flowers
Common Winterberry fruit

45. What about corn? Monoecious or dioecious?

46. Corn is monoecious

47. The End