Structure of a flower: its four whorls and what each part does.
↔ Swipe the diagram sideways to see all of it
A flower is the reproductive part of a flowering plant. It sits on a stalk (pedicel) whose swollen tip is the receptacle (thalamus). Four whorls arise from it: calyx (sepals, usually green, protect the bud), corolla (petals, often coloured, attract insects), androecium (stamens, the male parts) and gynoecium or pistil (carpels, the female parts).
Name the four whorls of a flower from outside to inside.
Calyx, corolla, androecium, gynoecium.
What is the function of sepals? Of petals?
Sepals protect the bud. Petals attract insects for pollination.
Which whorls are the essential (reproductive) whorls?
Androecium and gynoecium. Calyx and corolla are accessory whorls.
A stamen has an anther (holds pollen sacs which make pollen grains) on a filament. A carpel has a stigma (receives pollen), a style (stalk) and an ovary (contains ovules; each ovule holds an embryo sac with the egg). A flower with both stamens and carpels is bisexual; with only one it is unisexual. Example: hibiscus has 5 sepals, 5 petals, many stamens joined into a tube around the style, and a five-lobed stigma.
Differentiate bisexual and unisexual flowers with an example of each.
Bisexual has both stamens and carpels, e.g. hibiscus, mustard. Unisexual has only one kind, e.g. papaya, cucumber.
What does an ovule become after fertilisation? What does the ovary become?
The ovule becomes the seed; the ovary becomes the fruit.
A flower has 5 sepals, 5 petals, 10 stamens and 1 carpel. How many parts does it have in each essential whorl?
Androecium: 10 stamens. Gynoecium: 1 carpel.
1. What is the stalk of a flower called?
2. What is the receptacle?
3. Name the male and female reproductive parts of a flower.
4. Name the parts of a stamen.
5. Name the parts of a carpel.
6. Where are pollen grains made?
7. What is the function of the stigma?
8. What does the ovary contain?
9. Why are the calyx and corolla called accessory whorls?
10. Draw a labelled longitudinal section of a flower (name five labels you would include).