Vascular Vs. Non-vascular Plants

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Vascular plants use roots to absorb water and nutrients.
Vascular plants use roots to absorb water and nutrients.

Vascular plants, which scientists call tracheophytes, contain specialized lignified tissues to transport water and nutrients throughout the body of the plant. Non-vascular plants, in contrast, do not have a vascular system and instead rely generally upon capillary action to move water throughout their bodies. Non-vascular plants include mosses, liverworts and hornworts, which scientists collectively refer to as bryophytes.

  1. Evolution

    • The fossil record confirms that non-vascular plants are evolutionarily more primitive than vascular plants. Bryophytes first appear in the fossil record in the Ordovician period of the Paleozoic era, while the first known vascular plants appear in the fossil record during the more recent Silurian period of the same era. However, vascular plants did not evolve from non-vascular plants. Rather, both vascular and non-vascular plants evolved from a primal green algae, according to the Kenyon College Department of Biology.

    Structure

    • Bryophytes grow in clumps or swaths and generally reach only about 1 inch in height because of their lack of a vascular system to transport nutrients to disparate parts. Shallow bryophyte root-like rhizoids act only as a grasping mechanism rather than a vascular mechanism. Mosses have stem- and leaf-like structures and a spongy consistency to absorb water and develop spore capsules. Hornworts grow stem-like columns that split open to release spores. Liverworts have many deep lobes and develop spore-containing coils. Vascular plants contain roots to absorb water, a stem or stems with vascular xylem and phloem tissue, and porous leaves to perform photosynthesis and absorb carbon dioxide.

    Reproduction

    • Non-vascular bryophytes can reproduce asexually through growth of new plant material but most often reproduce sexually. Bryophytes produce gametangium, structures that contain male and female gametes. The female gametangium contains a single ovum, and the male gametangium contains many sperm. When the male gametangium opens, it releases the sperm, which then find their way to the ovum with the aid of moving water and wind. This fertilization results in the creation of spores, which spread and grow into new non-vascular plants. Vascular plants, by contrast, may reproduce by spores but more often reproduce by seed with or without a fruit covering. Vascular plants produce seeds through a female ovum and sperm pollen, which combine to produce a complete embryo.

    Habitat

    • Because non-vascular plants cannot transport water throughout their bodies, they require consistently moist environments. Some non-vascular plants, particularly mosses, can desiccate without death by lowering their metabolism. However, for most non-vascular plants, lack of water means certain death. Vascular plants, in contrast, can thrive in habitats of various moisture levels because they are able to transport and store water for later use. Vascular plants, therefore, adapt well to many different environments and exist in almost all habitats on Earth.

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References

  • Photo Credit roots image by cassiusjb from Fotolia.com

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