Write the general characteristic features of Gymnosperms.

Explanation

Gymnosperms are naked seed bearing plants.
1. Most of the Gymnosperms are evergreen woody trees or shrubs. Some are lianas (Gnetum ).
2. The plant body is sporophyte and is differentiated into root, stem and leaves.
3. A well developed tap root system is present. Coralloid roots of cycas have symbiotic association with blue green algae. In pinus the roots have mycorrhizae.
4. The stem is aerial, erect and branched or unbranched (Cycas) with leaf scars.
5. In conifers, two types of branches namely branches of limited growth (Dwarf shoot) and Branches of unlimited growth (Long shoot) is present.
6. Leaves are dimorphic ,foliage and scale leaves are present . foliage leaves are green , photosynthetic and borne on branches of limited growth . they show xerophytic features.
7. The xylem consists of tracheids but in Gnetum and Ephedra vassels are present.
8. Secondary growth is present. The wood may be manoxylic (Porous, soft more parenchyma with wide medullary ray -cycas) or pycnoxylic (compact with narrow medullary ray - pinus).
9. They are heterosporous. the plant may be monoecious (pinus) or dioecious (Cyca).
10. Microsporangia and megasporangia are produced on microsporophyll and megasporophyll respectively.
11. Male and female cones are produced.
12. Anemophilous pollination is present .
13. Fertilization is siphonogamous and pollen tube helps in the transfer of male nuclei.
14. Polyembryony (presence of many embryo ) is present . The naked ovule develop into seed. The endosperm is haploid and develop before fertilization.
15. The life cycle shows alternation of generation . the sporophytic phase is dominant and gametophytic phase is highly reduced.