What Are Non-Seed Producing Vascular Plants?
Before flowering plants and conifers arrived in the natural world, plant reproduction was carried out by spores. Instead of forming a seed with a protected embryo inside, plants would release many small spores into the environment, which when favorable conditions were found would germinate and grow into a new plant.
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Specialized Stem Tissue
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Vascular plants are those organisms, which have developed to a point where they have specialized tissue that forms a stem so the plant can stand upright. Within the stem are located the vascular bundles, which are tubular structures that transport water and nutrients throughout the plant.
The Vascular Bundles
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The vascular bundles are differentiated into the xylem and phloem. These are the tubes that transport fluids throughout the plant. The xylem carries water and nutrients from the roots to the green part of the plant, while the phloem is the pathway for sugars and starches that are created in the leaves during photosynthesis.
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Plants That Produce Spores
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Vascular plants that reproduce by spores include ferns, horsetails, liverworts and the club mosses. The spores form on the bottom of the leaves in little enclosed sacks called sori, or spore cases. When conditions are right the spores are released into the environment, where they may grow into new plants.
How Spores Grow
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Reproductive growth in spore-producing plants does not occur until the spore has been released from the parent plant and so that it can find a suitable habitat, in order that it can grow and differentiate into male and female parts. Then reproduction occurs and a new plant can start from the small gamete (this is similar to an embryo) that is created.
Evolutionary History
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The earliest vascular plants occurred about 400 million years ago during the Devonian era. This was about 150 million years before the emergence of the dinosaurs. During this era some of the ferns and other spore producing plants became quite large.
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References
- Photo Credit Image by Flickr.com, courtesy of Nicholas
