In this article we will discuss about the Characters and Economic Importance of Pteridophytes.
Characters of Pteridophytes:
They are characterised by the following features:
1. Plant body is a sporophyte (2n) and differentiated into true stem, leaves and roots.
2. Leaves can be microphyllous (small without forming leaf gaps in vascular supply of stem, e.g., Selaginella) or macrophyllous (megaphyllous or large forming leaf gaps in vascular supply of stem, e.g., most ferns).
3. Vascular tissues (xylem and phloem) are present. In xylem, true vessels are absent. In phloem, companion cells and sieve tube are absent. Instead, sieve cells are present.
4. Meiospores are formed inside sporangia by sporic meiosis. Leaves bearing sporangia are called sporophylls.
5. Spores may be similar (homosporous) as in majority of pteridophytes e.g., Pteris Adiantum. A few plants are heterosporous, i.e., with two types of spores, microspores and megaspores, e.g., Selaginella, Salvinia, Marsilea.
6. Gametophyte is small or inconspicuous. It is usually independent.
7. Sex organs are multicellular and jacketed. Antheridia are small and sessile. Archegonia are partially embedded. Archegonial neck is 4-rowed.
8. Sperms are bi or multi-flagellate. They require an external supply of water to reach archegonia.
9. Embryo stage is present.
10. Heteromorphic or heterologous alternation of generations is present in the life cycle.
11. Pteridophytes generally occur in cool, damp, shady places. Some extend to sandy soils. Azolla, Salvinia, Marsilea are aquatic.
Examples:
Selaginella, Adiantum, Dryopteris, Equisetum (Horse-tail) Salvinia.
Economic Importance of Pteridophytes:
(1) Food:
Like other plants, pteridophytes constitute a good source of food to animals. Sporocarps of Marsilea, a water fern, yield starch that is cooked and eaten by certain tribal.
(2) Soil Binding:
By their growth pteridophytes bind the soil even along hill slopes. The soil is protected from erosion.
(3) Scouring:
Equisetum stems have been used in scouring (cleaning of utensils) and polishing of metals. Equisetum species are, therefore, also called scouring rushes.
(4) Nitrogen Fixation:
Azolla (a water fern) has a symbiotic association with nitrogen fixing cyanobacterium Anabaena azollae. It is inoculated to paddy fields to function as biofertilizer.
(5) Medicines:
An anthelmintic drug is obtained from rhizomes of Dryopteris (Male Shield Fern).
(6) Ornamentals:
Ferns are grown as ornamental plants for their delicate and graceful leaves.