1. Plants and People
Flowers

2. Why a Flower?

3. The Reproductive Structure of Flowering Plants:
Perianth
Petal: Corolla
Sepal:Calyx

4. Flower Anatomy
Calyx: the outer whorl of sepals; typically these are green, but are petal-like in some species.

5. Flower Anatomy
Corolla: the whorl of petals, which are usually thin, soft and colored to attract animals that help the process of pollination. .

6. Flower Anatomy
Androecium (from Greek andros oikia: man's house): one or more stamens, each with a filament topped by an anther where pollen is produced.
Pollen contains the male gametes.

7. Flower Anatomy
Gynoecium (from Greek gynaikos oikia: woman's house): all the female parts—the pistil(s) with ovule(s) inside.

8. Flower Anatomy
The basic unit of the female reproductive structure is the carpel. Each physcial body is called a pistil.
A flower may have a single carpel, which is a simple pistil (unicarpellate), or several carpels united in one compound pistil (syncarpous), or a cluster of un-united carpels/pistils (apocarpous)
The sticky tip of the pistil, the stigma, is the receptor of pollen.
The supportive stalk, the style, becomes the pathway for pollen tubes to grow from pollen grains adhering to the stigma, to the ovules, containing the gametes, housed inside the ovary.

9. Flower Anatomy carpel
fertilization
carpel structure

10. Evolution of the Carpel
See figures 3.1 and 3.2 in your book

11. Fruit and Seed Formation
A fruit develops from an ovary. A seed develops from an ovule.

12. Flower Structure Variation
perfect
imperfect
imperfect

13. Flower Structure Variation Ovary Position
A. ovary superior, floral parts hypogynous
B. ovary inferior, floral parts epigynous
C. ovary half-inferior
D. ovary superior, floral parts perigynous, hypanthium cup shaped

14. Flower Structure Variation
A flower having sepals, petals, stamens, and pistils is complete; if a flower is lacking one or more of these whorls, it is said to be incomplete.
complete
incomplete
no stamens present = incomplete

15. Inflorescences
An inflorescence is a group or cluster of flowers. It may be branched or unbranched. Modifications can involve the length, variations in the proportions, compressions, and swellings, and the order in which the flowers open.
Usually the modifications have been evolved to optimize the plant’s method of pollen dispersal.

16. Inflorescences
raceme
spike
corymb
umbel

17. Inflorescences
spadix
head
catkin

18. Pollen Dispersal
Bees, Beetles, Bats, Birds, Butterflies, etc…

19. Pollination Most species of flowering plants are hermaphroditic
Pollen from a flower could land on the stigma of the same flower or another flower on the same plant = self pollination
Pollen transferred from the anther on one flower to the stigma of another flower on a different plant = cross pollination
© 2008 Paul Billiet ODWS

20. Fertilisation Pollination ≠ Fertilisation
The male gamete (the male nucleus) has to get to the egg cell
The egg cell lies in an ovule in an ovary at the centre of the plant
The pollen grain germinates on the stigma
It grows a pollen tube down the style
It male nuclei travel down the pollen tube to the ovule
© 2008 Paul Billiet ODWS

21. Fertilisation Pollen grain Stigma Style Ovule Embryo sac Ovary
Pollen tube
Ovary
© 2008 Paul Billiet ODWS

22. Fertilisation Embryo sac Polar nuclei Egg cell Micropyle
© 2008 Paul Billiet ODWS

23. The double fertilisation
Pollen tube
Pollen tube entering micropyle
Male nucleus + egg cell
= zygote (2n)
Male nucleus + 2 polar nuclei = endosperm nucleus (3n)
Ovule
Nucellus
© 2008 Paul Billiet ODWS

24. Symmetry
Flowers that are actinomorphic have "radial symmetry", meaning they can be divided into symmetrical halves by more than one longitudinal plane passing through the axis, much as a pie can be cut into several equal and identical pieces.
Zygomorphic flowers are "yoke shaped” or have"bilateral” symmetry, where flowers can be divided by only a single plane into two mirror-image halves, much like a yoke or a person's face.

25. Dicot versus Monocot
Dicot
Monocot