The gymnosperms are a distinct subdivision of the spermatophyta, the seed bearing plants. As the name indicates gymnosperms (gymnos =naked, sperma=seed) are naked seeded plants. The ovules or seeds are not enclosed in a ovary. Thus they occupy an intermediate position between pteridophytes and angiosperms. In the evolutionary point of view gymnosperms are the most primitive seed plants. Gymnosperms were the first seed plants and are relatively ancient groups that dominated the earth’s flora the same time when the dinosaurs dominated the animal world

The gymnosperms are characterized by the following features:
Sporophyte represents the dominant phase. The plants are generally woody trees, rarely shrubs, perennial. Sporophytes are large with true roots, stems and leaves.

Tap root system is present and it may be diarch to polyarchy with exarch xylem.

Stems are branched generally or may be unbranched (in Cycas). The vascular bundles in stem are conjoint, collateral and open. Xylem is generally made up of tracheids having bordered pits but vessels have been reported in Gnetum, Ephedra n and Welwitchia . phoem is composed of sieve cells and phloem parenchyma: but companion cells are ansent. Like angiosperm, secondary growth is present and annual rings are formed
The wood in gymnosperms is of two type:
(a) Manoxylic– Wood is soft and porous due to excess of parenchyma
e.g. Cycas
(b) Pycnoxylic– The wood is harder and compact e.g. Pinus.
Leaves are of two types-Scale leaves and green foliage leaves (evergreen) i.e.,leaves in gymnosperms are dimorphic. Leaves are in general spirally arranged. They are of two types-simple leaves and compound leaves with xerophytic characters (like sunken stomata and thick cuticle). Mesarch xylem and transfusion tissues are found in the leaves of most of the gymnosperms e.g. Cycas, Pinus

Leave a Reply

Your email address will not be published. Required fields are marked *