1. The Great War Project The Biology of the Flower It’s All About Sex!

2. Perfect Flowers Have both male and female parts
Note: ‘carpel’ in diagram may also be called the pistil

4. Monocot vs. Dicot
Flowering plants (Angiosperms) fall into two broad plant groups; the monocots and the dicots
Distinguishing the two groups is quite easy
Look at leaf veins; if veins are branching with a netted pattern the plant is a dicot; if leaf veins are parallel, then the plant is a monocot
Seeds of dicots can be split (eg. beans) while seeds of monocots cannot be split (eg. corn)

5. Flower Differences
Monocots have flower parts in multiples of 3 while dicots have flower parts in multiples of 4 or 5 (note: petals may be fused in some flowers)
Many monocots have sepals that look like petals giving the flowers the appearance that they have 6 petals. When petals and sepals look the same, they are called tepals.

8. Dicot flowers

9. Monocot flowers

10. Imperfect Flowers: Monecious vs. Dioecious
While most flowers are both male and female, some plants have separate male and female flowers
Mono = one ( monoecious plants have separate male and female flowers on the same plant)
Dio = two (dioecious plants have separate male and female flowers on separate plants)

11. Monoecious

12. Dioecious

13. Flower colour important
Certain colours attract certain pollinators
Moth pollinated flowers are generally white or highly fragrant, esp. at night
Bee flowers often pink, purple and blue
Butterfly flowers often yellow, orange, red
Bird-pollinated flowers often red, tubular with no fragrance

15. Human vs. Insect Vision

16. Flower Shape Flowers fall into two broad shape categories
Radial Symmetry (Actinomorphic)
Bilateral Symmetry (Zygomorphic)

17. A Special Case: Daisies
A ‘single’ daisy is actually a tight cluster of numerous, tiny, individual flowers
Collectively, they are referred to as a ‘head’ of flowers
Outer flowers have a single, large modified petal (called ray flower)
Inner flowers are called disc flowers

18. What is the purpose of this variability in flowers?
Ultimately, results in pollination
Mode of Pollination – Animal vs. Wind
Many monoecious and dioecious plants are wind pollinated
Actinomorphic (radial symmetry) flowers most popular with flies/butterflies
Zygomorphic (bilateral symmetry) flowers most popular with bees, hummingbirds

20. Outbreeders vs. Inbreeders
Can often tell by looking at the flower whether it is an inbreeder (self-pollinating) or outbreeder (cross-pollinator)
Inbreeder characteristics
Few flowers
Small flowers
No fragrance
Mono-coloured
No stripes (nectar-guides) on flowers
Anthers close to stigma
Stigma not obviously visible

21. Outbreeders vs. Inbreeders
Outbreeder characteristics
Large number of flowers
Large flowers
Fragrant
Brightly coloured
Stripes (nectar-guides) present
Anthers spaced from stigma
Stigma large and obvious

22. Advantages of cross-pollination
Increases genetic variability
Adaptation to changing conditions
Strong evolutionary potential
Successful colonization long-term
BUT: depends on effective mode of cross-pollination

23. Self-pollination
Advantage: reliable seed set regardless to pollinator activity and can allow a successful individual to rapidly colonize an area in the short-term
Disadvantage: less genetic variability thus cannot adapt to changing environment
Evolutionary dead-end

24. Orchids : the Ultimate Flowering Plant
Largest group of flowering plants – 20,000 species
Considered the most highly-evolved flower
Little wastage of pollen
Often use a specific group of pollinators, even a specific species of pollinator
Orchid use mimicry more than any other group of flowers
PROBLEM: VERY sensitive to environmental change and at risk for extinction

25. 1/3 of orchids use mimicry
Utilize pseudo-copulation
May produce fragrance that mimics the pheromones of a female insect
Part or all of the flower appears like the female insect
Males try to mate with the flower, bringing about pollination

27. MUN Botanical Garden For more information, please contact:
Todd Boland, Research Horticulturist MUN Botanical Garden Memorial University of Newfoundland St. John’s, NL, A1C 5S7