Plant Reproduction Essay, Research Paper
Plants have two different ways to reproduce. The first one is vegetative reproduction. With this type all the plants that have the same parent have the same genetic make-up. This also lets plants pass adaptations on that they have abtained over the years. Plants with good genetic make-up usually spread quickly and take over an area. An example of this would be the dandelion. These plants can sprout from any part of the plant. An example of this is the potato, farmers will pick the potatoes and cut them into small pieces and then plant them again so they may grow again. Scientists have also placed a branch from one tree and place it on another one; it is now possible to buy an apple tree with six different branches and six different types of apples.
The more common way to reproduce is sexual reproduction. In order for this to happen gametes must be produced and fertilized. Seeds, fruits, and embryos must also be developed. The two main advantages of reproducing this way are new genetic combinations and seeds spread over a large area. The following are the reproductive parts in this process.
The first part is the flower, which has four types of modified leaves. The first one is the sepal, which protects the other parts of the plant. The second is the petal, which is located inside the sepal. These are normally bright in color to attract animal pollinators. The third is the stamen, which is the male or pollen producing substance. The stamen contains anthers, which is were pollen develops. The last part is the pistils and they are located in the center of the flower. This is the part that contains the female sex parts like the stigma, which traps the pollen. Many plants have both the male and female reproductive parts on the same plant like corn, others like spinach don’t.
Plants also have spores because of meiosis; these spores then grow into haploid gameophytes which produce gametes for fertilization. Plants produce to spores, one is the microspore, which is the male part, and the other is the megaspore, which is the female part. A pollen grain is young male gameophyte enclosed in a protective wall. When fertilization takes place the wall is destroyed and the pollen is transferred to the pistil. Cross-pollination is when a pollen grain is blown to another plant or carried by an animal.
Pollen maturation starts when the pollen lands on the stigma and a pollen tube grows toward the ovule. For this to work the proteins of the male and female must be compatible. Only on pollen tube can grow into each ovule but there is normally more than one of them.
The ovule must form inside of the megaspore and then develop into an embryo sac. The embryo sac contains eight haploid nuclei: three at the end of the micropyle, one is the egg nucleus, three at the opposite end, and two polar nuclei.
When fertilization takes place it may only take an hour after pollination. Some plants like barley however take about two months. Double fertilization also takes place, that is when one sperm fertilizes the egg, and the other forms an endosperm.
When the seed and fruit are being developed the wall of the ovule develops a protective seed coat. While this is going on the ovary has turned into a seed. To make sure the seed gets enough food the endosperm keeps dividing so it can keep bringing in food. A little FYI for you is that many fruits do not taste good, they are just for protection of the seed.
Once a seed is mature it is ready to be released. Most seeds try to grow away from their parents so they don’t have to battle over food and sunlight. Some seeds are blown in the wind and some are carried by animals. Animals don’t eat plants until they are ripe because they taste bad, thus giving the seed enough time to develop so it can make it through the animal. Some seeds are not even eaten they just attach themselves to animals.
When Germination starts the seed becomes dormant enabling it to survive for an extended period of time. Some plants like water lilies can survive this way for a thousand years; other plants like sugar maple trees can only last a week. In order for a plant to germinate it must have water, oxygen, and a particular temperature in some cases.