Thursday, July 26, 2012

Plant Reproduction (Pollination)

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I had an earlier version of this post where a few things were wrong, so I have corrected them. All of my corrections are written in blue, so if you read the earlier version without the blue words, you might want to check it out.

Plant Reproduction. One of the extremely important parts of PSLE. There are actually two parts to plant reproduction, one which is pollination, and the other called dispersal. In this post we will only be going through pollination and fertilization.

So what is the point of pollination ? Well, as we know, only plants can do this. The whole point of this is to make baby plants, called seeds. The whole point of pollination is to make seeds. You might think that making seeds are quite simple, but as you will soon see, it can get quite complicated.

Alright, starting off, I will talk about gender. That means whether you are a boy or a girl. Everyone is either a boy or a girl. (You probably know this already) Well, plants also have gender. They can be a boy plant or a girl plant. Actually, with plants, it can get a little confusing, because some plants are both boy and girl. (But that’s not important, so you can ignore that)

To make a seed, you need both a boy AND a girl flower. (There are such a thing as boy flowers.)

First, let us look at what a boy flower looks like…

Male Plant

As you can see, a male flower isn't anything special, except that it has these little things poking out. (You should be able to see what I am talking about from the diagram.) As you might also notice, the ANTHER, which is the little ball at the end of the thingy, (Again, you should know what I am talking about.) is important. Why is it so important? Well, the ANTHER makes POLLEN.

What is pollen? Well, pollen is one half of a seed. Together with something else, it can turn into a seed. (I will tell you what it is later.)

Pollen is created in the ANTHER. (That’s why I said that it was important. It is very important that you remember what it looks like. In fact, you should go back and look at what it looks like if you have forgotten. Try to remember ANTHER IS THE FATHER. ANTHER IS THE FATHER. I don’t know if this works for everyone, but this is how I remember it.) Pollen is small and sticky, and it sticks onto the anther. There are many pollen grains on one plant. Pollen

Now, let’s look at the girl plant.

Female Plant

This time, the girl plant has this huge fat swelled up thing in the middle of the flower. The important part of the girl plant is the OVARY. The ovary is that big swelled-up part at the bottom of the plant. As you may have guessed, the OVARY creates and makes the other half of the seed, the OVULES! That’s right. OVULES ARE MADE IN THE OVARY. Ovules are the other half of the seed, and together with the pollen, they can make a seed.

Of course, this is also very important to remember. Just remember, ovules are made in the ovary. This is easier to remember because they sound the same. OVULES. OVARY. OVULES ARE MADE IN THE OVARY. Ovules are found INSIDE the ovary. There are many ovules inside a girl plant.

Ovules

 

Stigmastigma

A fake and real picture of the stigma.

What is so important about the stigma? Well, you see, the pollen will land on top of the stigma. (I will explain how it lands on top of the stigma later.) It will always land on top of the stigma. So, as you can imagine, the stigma is very important.

Well, actually, I posted a wrong version of this post a while ago. Some of you might have read the wrong version of this. In the WRONG version, I said that Pollen grains fall into the ovary. I am SO sorry for any misunderstandings that might have been caused. Let me clarify. Pollen grains DON’T fall into the OVARY. They fall on the STIGMA. I repeat: The STIGMA.

Alright, so once the pollen lands on the the stigma, the stigma sprays a bit of this strange sugary liquid. For some reason, this liquid will cause the pollen to grow a POLLEN TUBE down into the ovary. (This is also important. Remember, POLLEN grows POLLEN TUBE!)

This pollen tube WILL connect to one of the OVULES inside the ovary. This means that the pollen is connected to a ovule through the pollen tube. (refer to the diagram below) The pollen will then PUMP all of the important stuff inside of it INTO THE OVULE. THE OVULE THEN BECOMES A SEED. The pollen dosen’t actually touch the ovule, but it can still turn the ovule into a seed.

Pollen Tubes 

If you are wondering what the important stuff is, it is basically just some cells. These cells make up half of a seed by themselves.  Combined with the ovules, which are the other half of the seed, the can make a whole seed.

Recap: Anther makes pollen, which is one half of a seed. Ovary makes ovules, which are the other half of the seed. When the pollen lands on the stigma, the pollen will grow a pollen tube down into the ovules. The pollen will then pump all of the important stuff into the ovules, and they will turn into a seed.

Simple enough to understand, right? Well, there is also a problem. How is the pollen going to get to the ovules? If they are on different plants, how are they going to get together? Plants can’t move. They can’t go to each other and put their pollen and ovules together. Does that mean that they can’t make seeds? Does that mean that all plants are going to die?  Well, plants have been clever enough to find out a way to put their pollen and ovules together. Well, actually, there are two ways.

  • The first way is using the wind. The pollen is blown off the anther by the wind. The wind will blow the pollen around, and if the pollen is lucky, it will fall on a Stigma of a girl plant. Then, the stigma will spray the strange sugary liquid on the pollen, causing the pollen to grow a pollen tube down into an ovule. The pollen will pump all of its important stuff through the tube into the ovule, and the ovule will become a seed.

. People call these kind of plants wind-pollinated plants. Only some plants can be pollinated this way.  These plants are usually quite ugly, so they have to depend on the wind to blow their pollen. Also, these kind of plants have to make A LOT of pollen. Why? Well, when the wind blows the pollen away, most of the pollen will not land on a girl plant. It might land on the ground, on the wall, in a volcano, in a toilet bowl but most of it won’t land on a girl plant. So, they must make a lot of pollen to make sure that at least a few of the pollen land on a girl plant. They also need to be light and small so that the wind can blow them off the plant easily.

Repro

  • There is also another way using insects. These are called insect-pollinated plants. Basically, some insect lands on the plant. Let’s say it is a bee. The bee comes down to take nectar from the plant. (By the way, mostly on insect-pollinated plants have nectar, and the bees use it to make honey. But that’s not important.) While drinking some nectar up, the bee brushes against the anther, and some of the pollen sticks to the bee. The bee will then fly away to collect nectar from other flowers. After a while, the pollen will eventually unstick itself from the bee and if it is lucky, it will fall onto a girl plant’s stigma. Then, the stigma will spray its sugary liquid, and the pollen will grow a pollen tube down into an ovule. The pollen will pump all of its important stuff into the ovule, and the ovule will become a seed.

Bees

Like wind-pollinated plants, only SOME plants are insect-pollinated. These plants are usually very big and brightly coloured, so that insects will be attracted to them. Of course, they also have nectar, so that insects will be attracted to collect nectar. Some of them also have special smells, that attracts insects to them. Basically, they want insects to be able to see them clearly and be attracted to them.

And surprisingly, that’s all to say about pollination. Yeah, that was quick. But that is basically how seeds are made. And that is the aim of pollination, to MAKE SEEDS. Also, take note that more than one pollen grain can enter the ovary. This means that there can be more than one seed created in each plant. Here’s a plant with 6 seeds:

Seeds

And yeah, that is basically what pollination is about. However, this is only the main concept, and I want to explore more on pollination in a later post, maybe in a bonus post. In that post, I will be talking about plants who are both boy and girl, Remember to check back soon. (Actually, you can check back a few weeks later, I’m probably going to be to busy with my PSLE Revision anyway.)

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