When dealing with the parts of a flower, we must keep in mind that every flower, no matter how beautiful or ugly, simple or complicated, has only one purpose: to make itself utterly irresistible to whatever type of pollinator it needs (if it needs one at all) to carry on the genetic code which makes it a flower and not a mouse. Flowers are used by plants for sexual reproduction. In fact, every single part of a flower is used only for reproduction.
All the different parts of a flower are there for no other purpose. You see, we think that flowers are the most beautiful things on earth, but all they care about is making themselves beautiful for one purpose - to attract a mate, to reproduce and carry on their genes to the next generation. It's a bit of a let down when you think about it. Have we been tricked? No more than any lover has ever been tricked by beautiful looks.
But with flowers, I think we can forgive them because they are, after all, totally innocent. That's where their true beauty secret lies. To humans, they are perfect and can do no wrong. But some of them sure can trick their pollinators .... The reproductive parts of a flower can be heavily disguised sometimes, so that visiting pollinators don't actually know they have anything to do with it.
Anything which carries pollen is called a Vector. This includes Insects (especially Bees), Birds, Wind and Water and nowadays Humans who deliberately mix and match this with that in their plant breeding programs.
We're all used to the typical flowers we see around us every day, but we are in for a few surprises if we look deeper. There are two types of flowers: Typical (perfect) and Non-typical (imperfect) - these are the basic types we need here.
The Female Parts of a Flower.
A typical (perfect) flower is Complete. It has a female part: the Pistil (also called the Carpel). This is made up of the stigma, the style and the ovary. The ovary contains the ovule (or ovules) where fertilization occurs. The stigma is where the pollen lands. The pollen then grows a tube which moves downwards through the style until it reaches the ovary. (In the maize plant, the pollen tube can grow to 12 inches!)
The Male Parts of a Flower.
Perfect flowers also have male parts which are made up of the Stamen which consists of the anther (which has the pollen) and the filament (the little stalk). This is easily seen in a lily.
Detailed diagram showing the Reproductive Parts of a Flower.
The simple standard flower in your backyard eg. the rose bush. It's Perfect and Complete. It has all it needs to ensure pollination. In the above diagram: The Pollen is found on the top of each Stamen (male). This is carried to the Stigma (female) where it then grows a pollen tube down to the Ovary where it fertilizes an Ovule and creates a Seed. And as in humans, once an ovule is fertilized it shuts off so that no other pollen can gain access.
Another interesting thing about flowers. So far, we've called them Perfect or Imperfect or Complete. But the Perfect Flowers are also Hermaphrodite. An Earthworm is Hermaphrodite. It would be most unusual for Humans to be Hermaphrodite, because Hermaphrodite means having both Male and Female parts. Perfect flowers can fertilize themselves. Or rather, a pollen vector can do it. But the correct Botanical term for a plant having both male and female parts is 'Bisexual'. The further you dig with Botany, the more 'TERMS'! you find.
If there are no other plants around to 'mate' with, then a visiting insect can fertilize the one flower there and then. And it doesn't even have to move very far. All it has to do is brush against the Anther as it sips the Nectar from the Stigma, thereby transferring minute pollen grains from the Male to the Female parts of the flower, and the job is done. The downside of this type of reproduction is that it doesn't encourage any diversity. All offspring plants would be much the same as the parent plant. That's where Evolution by Natural Selection comes in, giving us a wide diversity of living organisms.
The reason plants are so successful is that they have just so many different ways of being fertilized, giving us so many wonderful specimens to admire.
Can you label this diagram with the Parts of a Flower?
Petals. The colorful, often bright part of the flower. They attract pollinators and are usually the reason why we buy and enjoy flowers. And, wait for it, petals are 'only' modified leaves which have evolved beautiful colours and perfumes to attract pollinators! But does that mean we've been tricked? Not really, after all, a rose is beautiful no matter what its different parts are called. 'But not if it were called 'a thistle or a skunk cabbage'. Anne of Green Gables.
Sepals are the green parts of the calyx that cover the outside of a flower bud to protect the flower before it opens.
Tepals. Quite often a flower may be said to have tepals. These are added protection for the bud before it opens. A Lily is a perfect example:
The petals, sepals, tepals and nectaries are not directly involved in reproduction. But they are necessary to protect and show off to the world that the plant is, indeed, there. And where to get the nectar.
So, to answer the very common question : Are all the parts of a flower involved in reproduction, I think we can say 'Yes'. They are all necessary, but some are involved indirectly.
The beautiful pink Oriental Stargazer Lily shows three distinct Petals and three distinct Tepals (smaller and behind the Petals).
Nectaries are small glands which the plant uses to produce Nectar. And Nectar Guides are specific ways the plant has of leading the pollinators straight to where the pollen is. These may or may not be visible to humans.
Amazing photo of a Nectary producing Nectar.
How we see a flower. The red parts which make our flower special are there only as a guide to the nectar.
How 'they' see our garden flowers. In the Ultra Violet (UV) Light. Amazing! In the image on the right, the pollen is highlighted in white. The rest of the flower doesn't matter to the insect.
Other plants may have both male and female parts - but they are located in different parts of the plant or tree. eg. the Pine Tree has female cones at the top and male cones at the bottom. Scientifically, as you can imagine, there are different botanical names for this type of plant, but for our purposes, the Pine Tree is still Bisexual. Both its female and male parts are at least on the same plant. So it's reasonably normal.
This flower is a 'perfect' example of a Perfect, typical, Complete flower. You can see that it has petals, many stamens and a single pistil or carpel (which consists of a Stigma, a Style and below, out of sight - an Ovary). That's the dark bit poking up. It also has some buds.
Have some fun just like our kids do. Just drag and drop:
Plants which are Unisexual have only female parts or male parts, but not both, and therefore need another plant of the opposite sex to complete fertilization. eg. the Holly Bush. They are Incomplete or Imperfect. Some other examples are Fig Trees, Gingko, Mulberry Bush and Oak Trees. Vegetables which are Unisexual include Squash and Cucumber.
The Holly Tree is either male or female (an Incomplete plant). So if you want offspring you will need one of each. The Paw Paw Tree can be either Complete or Incomplete. If you have a Paw Paw Tree and it doesn't bear fruit, it's Incomplete. It's either male or female and it will need a mate. Just like us. But if you have a Paw Paw which bears fruit, it's probably Complete, having both sexes on board.
Pine trees have both male and female parts. The female cones form at the top and the males at the bottom. When the reproductive season arrives, the female cones open up and fall to the ground. The males then open up and release their pollen (sperm) which falls onto an open female cone. When this happens, the female cones close up again until the fertilized embryo is ready. Then it opens again to let the embryo out. The baby plant is in the form of a winged seed which can be carried a long way to an ideal location where it can send down its roots and grow into a new pine tree or conifer. Now that's amazing! And I think it's kind of romantic.
'The fact that I can plant a seed and it becomes a flower, share a bit of knowledge and it becomes another's, smile at someone and receive a smile in return, are to me continual spiritual exercises'.