Gymnosperm Introduction


Gymnosperm Introduction

  • The word ‘gymnosperm’ was used in 300 B.C., by Theophrastus, a pupil of Aristotle, in his book “Enquiry into Plants”. 
  • Theophrastus used this term to embrace all those plants whose seeds are unprotected (Gymnos=naked; sperma=seeds). 
  • The seed plants (Spermatophyta) are grouped into two major groups on the basis of protection afforded to the ovule before and after fertilization. 
  • These groups are the gymnosperms and the angiosperms. 
  • The gymnosperms have their ovules freely exposed before and after fertilization. They are not enclosed by any ovary wall.


Vegetative Character:

Habit and habitat: 

  • The gymnosperms are the most ancient seed plants that originated during the late Paleozoic (ca 265 million year ago) era, but flourished well during the Mesozoic.
  • The living gymnosperms include middle-sized or tall trees and shrubs and number approximately 70 genera and 725 species. .
  • Plant body sporophytic which is differentiated into root, stem, and leaf.     


  • The roots are generally taproot, but mycorrhizae and coralloid roots are known in some genera. In root xylem is exarch and diarch to polyarch.


  • The stem is aerial, erect, unbranched or branched. 
  • In some genera branches may be of two types; 
  • (i) the long shoot 
  • (ii) the dwarf shoot. 
  • Collateral, conjoint, endarch and open vascular bundle present in young stem. 
  • In xylem vessels and in phloem companion cells are absent.


  • The leaves may be simple or compound and vary in size from a minute scale leaf to a large and more than six feet long. 
  • They show great variation in shape also. 
  • The venation may be reticulate, parallel or even dichotomous. 
  • Leaves are of two types: 
  • (i) Microphyllus leaf – These are small and scaly, 
  • (ii) Megaphyllus – these are large and well developed. 
  • The arrangement of leaves may be opposite and decussate [Gnetum, Ephedra], whorled[Cycas] or spirally arranged (Podocarpus, Taxus etc.).


  • The secondary wood in the gymnosperms may be:

(i) Manoxylic: 

  • This is porous, soft ,more parenchymatous in nature and found in cycadophyta It has wide medullary rays and is useless commercially.

(ii) Pycnoxylic: 

  • This wood is compact and has narrow medullary rays and characteristic of coniferophyta. 
  • It is of great commercially value.  

Reproductive Character:

  • The gymnosperms are heterosporous i.e., Microspore and Megaspore. 
  • But the two kind of spore produce two kind of gametophyte, i.e., the microspore or the pollen grains produce male gametophyte 
  • whereas the single megaspore enclosed within the megasporangium develops into the female gametophyte bears two or more archegonia.
  • The two types of cone or strobili may be borne on the same tree [pinus] or on different trees [Ginkgo, Cycas].
  • The microspores and megaspores are haploid due to result of meiosis in the respective spore mother cell they are pioneers of male and female gametophyte. 
  • The strobili or the cones are of varying sizes and shapes. 
  • Their position on the plant also varies.
  • Male cones are ephemeral. 
  • Microsporangia present at the abaxial surface of sporophyll. 
  • Number of sporangia in a sporophyll may be fixed or not fixed.
  • Microspore is the first cell of the male gametophyte.
  • Megasporangium are naked on sporophyll.
  • Ovule is orthotropous and unitegmic generally.
  • In female gametophytes the number of archegonia varies according to species. 
  • Archegonia consists of egg and one venter canal cell.
  • Pollination takes place by wind. 
  • Pollen grains are collected at ovule in specific structure known as pollen chamber.
  • Zygote is the mother cell of the next sporophytic generation.
  • Embryo development is of meroblastic type i.e.embryo develops from the basal part of zygote.
  • Endosperm development starts before fertilization so it is a haploid structure.
  •  Embryo development by free nuclear division at the initial stage.
  • Polyembryony is common in gymnosperm 
  • The alternation of generations is heterologous in all the gymnosperms. 
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