Question

Explain the main characteristics of Gymnosperm.
 

Answer 1

1. Gymnosperms are mostly perennials, xerophytic, evergreen, arboreal and woody.
2. They grow as woody trees, bushy shrubs or rarely as climbers (e.g., Gnetales).
3. None of them are herbs or annuals.
4. The main plant body is diploid sporophyte which is well differentiated into root, stem and leaves.
5. They possess well developed tap root system. In some cases the roots are symbiotically associated with aglae (eg. coralloid roots of Cycas) or with fungus (eg.Ectotrophic mycorrhizal roots oil Pinus) The coralloid roots contain symbiotic cyanobacteria. (blue-green algae such as Nostoc and Anabaena), which fix nitrogen and, in association with root tissues, produce such beneficial amino acids as asparagine and citrulline. The symbiotic association of the my celium of a fungus with the roots of plants. The majority of vascular plants have mycorrhizae. The fungus assists in the absorption of minerals and water from the soil and defends the roots from other fungi and nematodes, while the plant provides carbohydrates to the fungus.
6. The stem is erect, aerial, solid, and woody and branched (unbranched in Cycas).
7. Leaves are dimorphic. They possess two types of leaves brown: coloured, membranous, minute, deciduousscaly leaves and green coloured, simple, needle like or pinnately compound foliage leaves.
8. The leaves may be simple or compound. In Cycas the pinnate leaves persist for a few years. The leaves in gymnosperms are well-adapted to withstand extremes of temperature, humidity and wind. In conifers, the needle-like leaves reduce the surface area. Their thick cuticle and sunken stomata also help to reduce water loss.
9. Presence of leaf scar on stem after shading off leaves is peculiar characteristics of gymnosperms.
10. World’s tallest tree – Sequoia sempervirens(the giant red wood) is about 125 metres in height and 30 metres in girth. This plant is about 4000 years old and found in red wood park of California.
11. Smallest gymnosperm is Zamiapygmia is only up to 25 cm. in height.