PUMPA - SMART LEARNING

எங்கள் ஆசிரியர்களுடன் 1-ஆன்-1 ஆலோசனை நேரத்தைப் பெறுங்கள். டாப்பர் ஆவதற்கு நாங்கள் பயிற்சி அளிப்போம்

Book Free Demo
These are the group of plants that produce seeds which are not enclosed within the ovary.
Life cycle and reproduction in gymnosperms:
Similar to the bryophytes and pteridophytes, gymnosperms also have two phases in their life cycle, such as
  • Gametophytic
  • Sporophytic
Sporophytic generation:
  
The sporophytic generation is the dominant one that contains the reduced gametophytes. The sporophytic plant body is differentiated into root, stem and leaf. They have well developed vascular tissues. In these plants, water is conducted by the tracheids of the xylem, and food is conducted by the sieve cell of the phloem. The sporophytes also have a cone in which sporangia and spores are produced.
Other characteristics of gymnosperms:
  • They are found in colder regions.
  • Gymnosperms have needle-like leaves.
  • They are woody terrestrial plants.
  • Xylem does not have vessels, and the phloem has no companion cells and sieve tubes.
  • The male gametophyte produces two gametes, but only one of them is functional.
Classification of gymnosperms:
Gymnosperms are classified into four different classes as follows:
  1. Cycadales
  2. Ginkgoales
  3. Coniferales
  4. Gnetales
1. Cycadales:
 
These are palm-like plants that are erect and unbranched. They are usually found in the  tropics and subtropics. The leaves of these plants are pinnately compound and form a crown. They have tap and coralloid.
Example:
cycadales.jpg
Cycas sp. and  Zamiaceae sp.
 
2. Ginkgoales:
  
These plants are characterised by their large appearance and fan-shaped leaves. Ginkgo biloba is the only living species in the group. All the others are extinct. These plants produce an unpleasant smell.
Example:
450px-Ginkgo_biloba_001.jpg
Ginkgo biloba
3. Coniferales:
  
These are the most commonly known species of gymnosperms. They are evergreen trees with a cone-like appearance. Hence, they do not shed in the winters. Their leaves are needle-like or scale-like. The seeds of these plants are winged and produced in female cones.
Example:
800px-Pinus_pinea_male_cones.jpg
Pinus sp.
4. Gnetales:
  
These are a small group of plants that possess advanced characters like angiosperms. They are generally characterised by their flowery leaves that have a soft coating. Similar to the others, their ovules are naked but are developed on a flower-like shoot.
Example:
6241001749_f88c9a3c49_o.jpg
Gnetum sp.
Economic importance of gymnosperms:
1. As food:
These plants are good sources of food materials. The seeds of Pinus gerardiana is edible. Some of the gymnosperm species are a good source of starch and also used in the production of sago.
 
2. As timber and paper:
Conifers are good sources of softwood. These are used for construction, packing and in the plywood industry.
Example: Cedrus, Agathis.
The woods of conifers are also used in paper industries.
Example: Pinus, Agathis
  
3. As paints:
The resin of pinus is used in the extraction of Terpentine, an essential oil. This oil is used in the preparation of paints.
 
4. Medicinal uses:
Turpentine is also used medicinally to get relief from pain, bronchitis etc. The alkaloid extracted from Ephedra is known as Ephedrine. It is used to cure asthma and respiratory problems.
 
5. As ornamental plants:
Araucaria bidwillii is an ornamental plant.
Reference:
https://commons.wikimedia.org/wiki/File:Big_Cycas.jpg
https://commons.wikimedia.org/wiki/File:Encephalartos_ferox_03.jpg
https://commons.wikimedia.org/wiki/File:Ginkgo_biloba_001.JPG
https://commons.wikimedia.org/wiki/File:Pinus_pinea_male_cones.jpg
https://www.flickr.com/photos/adaduitokla/6241001749