All of us have read in our Science classes that plants grow from seeds. This is not true of all the plants that are found on Earth. Yes, you would be surprised to know that there are many plants that do not grow from the seeds.
Evolution of seedless plants
Scientists believe that the seedless plants first appeared on Earth about 400 million years ago. Such seedless plants include ferns, mosses, horsetails and liverworts. These plants have stems, roots, and leaves like other plants, but since they do not produce flowers, they have no seeds.
These plants, however, have specialized tissues for conducting water and food. Seedless plants lack a system of retaining and transporting water.
Reproduction in seedless plants
Now the question is, how do the seedless plants reproduce? Well, the seedless plants reproduce via seed-like objects, known as spores, or they produce through asexual reproduction.
What are spores?
Spores are usually unicellular or single-celled structures, having only one set of chromosomes. Spores lay dormant until conditions are favorable. Once conditions are favorable, cell division takes place in them and they grow into full-fledged plants. Spores are produced in bulk in a seedless plant and since they are very small and light, they are dispersed by the wind to new areas where they can grow.
What is asexual reproduction in seedless plants?
Some seedless plants reproduce asexually. This method of reproduction occurs when a part of the plant falls off on the ground and grows into a new plant on its own.
What are vascular and non-vascular plants?
Vascular plants are the plants which have a series of tubes that can transport water. All seed plants are vascular, whereas seedless plants can be vascular or non-vascular. Seedless vascular plants include ferns and horsetails. Such plants have proper roots, stems, and leaves. Non-vascular plants include mosses, liverworts, and hornworts. These plants do not have well-differentiated root, shoots and stems or water transport system so they thrive only in moist places.
Examples of seedless vascular plants
A. Fern
Ferns are one of the most common plants found in our homes. You would have seen these plants at the florist and even being used for landscaping in big hotels, malls and airports. Ferns produce spores on the underside of their leaves. The leaves of ferns are called fronds and have small brown spots down below. These small brown spots are nothing else but spores and you can feel them with your hands too. It is believed that the ferns were the first plant species to develop a water transportation system that helped them in growing larger.
B. Horsetails
Horsetails and ferns are closest living relatives to seed plants, because they have a vascular system. Most of these plants are extinct so the chances of you seeing them are rare.
Examples of non-vascular seedless plants
A. Mosses
Mosses are small, soft and spongy plants that grow only a few inches tall. They grow in clumps and form a sort of a carpet on the ground. Mosses anchor themselves to rocks and soil with short growths called rhizoids.
B. Liverworts
The worts are considered to be the simplest of all plants and believed to be one of the first plants to have colonized the Earth. They are small, flat and along the ground in large leaf-like structures. Instead of roots, they have little hair called rhizoids to absorb moisture. Like mosses, they also thrive in moist areas, and some species even spend their whole lives in water.
6 Interesting facts about the seedless plants
- In a hostile environment, such as the tundra where the soil remains frozen for almost the whole year, mosses provide food and shelter to many species, from small insects to musk oxen and reindeer.
- Mosses absorb pollutants from the air and hence the level of pollution at a particular place can be determined by the existing number of mosses there.
- Dried peat moss is a renewable resource for energy.
- Ferns promote the weathering of rock and help in soil formation.
- Ferns harbor nitrogen fixing bacteria in their roots and thereby enrich the soil in nutrients.
- Coal is primarily made of seedless vascular plants.