This paper reflects the research and thoughts of a student at the time the paper was written for a course at Bryn Mawr College. Like other materials on Serendip, it is not intended to be "authoritative" but rather to help others further develop their own explorations. Web links were active as of the time the paper was posted but are not updated.
2000 First Web Report
In the beginning of the moss cycle, the spore is released from the capsule with haploid sporophyte. The haploid spores germinate and turns into protonema. Male and female gametophytes develop gametophytes buds. The male gametophytes contain an antheridium's, which is where the sperm develop and mature. Eggs develop in the female archegonia. Raindrops are used to wash sperm from the antheridium's to the stationary, mature egg. The sperm fuses with the egg to produce a zygote. The zygote undergoes mitosis to form the sporophyte. The sporophyte is usually brown at maturity, which indicates its inability to photosynthesize or contain chlorophyll. Chlorophyll helps the plants make their own food. With the combination of the sunshine, air and chlorophyll, the mosses are able to make sugar, which is their basic food. Therefore, the sporophyte is totally dependent upon the haploid gametophytes for its sustenance. Within the capsule, sporogenous tissue undergoes reduction division to produce spores and then the spore is released. This creates an alternating generations of mosses(2).
By means of sexual reproduction, some species of mosses have both female and male on the plant and some have two different plants with male and female organs. The male and female organs, of sexual reproduction, are very distinctive in shape, structure and leaves. The male plants can be recognized by the modification of their leaves. The male plant also has a thin wall, which contains the male gametes. On the antheridia (male organs) are sterile hairs that are for protection, moisture conservation and for the discharge of the sperm. The male sperm has two thread-like tails that are used to swim to the archegonia (female organ). Mosses are considered as amphibians in relation to the other plants, for they have motile sperm. The sperm swims through water to the non-motile egg.
In asexual reproduction, plants are called vegetative reproduction. They produce offspring genetically identical to the parent plant. Any part of the moss plant can be regenerated. Fragments from the stem, whole leaves, leaf pieces and segments of the spores can be used for reproduction. A different means of asexual reproduction, are organs called brood bodies. The may be in the form of tubes, filaments, clusters of green cells, small leaves of leafy shoots that are produced in the leaves or stems.
There are a thousand different types of mosses. The two most common mosses look like hay or have spongy appearances. Moss can adapt to different climates. They can survive in the hottest summers and coldest winters. The moss cannot store water in their roots like oak trees, through harsh weather, to protect the chlorophyll from drying out. Therefore, in order to survive, the mosses stop making food and stops growing. In bright sunlight, they fold and curl their leaves up to protect them from the sun1. There does exist limitations of mosses. These things are: lack of vascular tissue, lack of water for sperm transfer, and vulnerable protonema stage(3).
Besides natural reasons, there has been chemical treatment done to limited the growth of moss. In high rainfall areas, mosses have tremendous capacity for reproduction. Mosses are established and colonized in weak grass areas, which they eventually take over the area. Mosses are unwanted in these areas because they include poor aeration, poor drainage, low fertility, high acidity and heavy shade(4). Chemical treatment is only used if growing conditions for grass are not improved. By means of chemical control, they use ammonium sulphate. Some cultural control is used by improving surface draining, removing building of dead organism matter, increasing aeration, reducing shade and adding lime if soil is acidic.
What if all organisms reproduced asexual and sexual? I believe that there will be some unwanted organisms in particular areas. Also, by these means, there may be a larger population of organism with no room capacity to contain them all. Why do just mosses and other land plants reproduce asexually and sexually? I think it is good for just a few organisms to have that ability because it simply can be controlled. Can any one imagine humans spreading spores in order to produce sporophytes? In mosses, there exist more sporophytes than male and female gametophytes. Humans, in this generation, are already having problems with birth control, which would make it even more impossible to keep control over spores released. When spores are released, I think that it is an involuntary organ that no one can control or is unaware of what's happening. As I watch talk shows on television, I notice that these teens are unaware of what they are doing and are subliminally "releasing" babies. It is good that this limited ability is not benefiting humans.
The benefits of asexual and sexual reproduction are what the bryologist hypothesized, that asexual reproduction prevails in colony maintenance and sexual reproduction is more effective in establishing new colonies. I agree that that can be applied to both mosses and humans. I see how well they both work together as a colony and can see the settled differences. The mosses reproduce close together to create a spongy unit. This contains water for the sperm to reach the archegonia. They also have the ability to create new colonies and again work together to build a tight unit. As for humans, I wish it were that easy. In our environments, people hardly work together. Most people are doing things for themselves. It is very important that everyone work together to help the community and together attain goals to build it up. This is one characteristic that we lack and that is the help of every individual to create a unit that overcomes trash, drugs, violence, and homelessness.
2) Moss Life Cycle , COMMENTS ABOUT IT
3) Mosses , COMMENTS ABOUT IT
4) Moss Reproduction , COMMENTS ABOUT IT
ETC (AS NECESSARY)
| Back to Biology 103 | Back to Biology | Back to Serendip |