Gymnosperms (gymnos = naked; spermos
= seed) represent a primitive group of seed-bearing plants (spermatophytes)
in which the seeds are naked (i.e., without the covering
of a fruit wall) . This is because in gymnosperms, a closed carpel (ovary)
is not formed. The ovules are directly borne on open carpellary leaves
(megasporophylls) and hence they are "naked". These develop
into naked seeds after fertilization. The term ’gymnosperms’ was first
used by Theophrastus in 300 B.C. in his book, Enquiry into Plants.
Gymnosperms were most abundant and widely distributed
during the mesozoic era. However, they form only a small part of the present
day vegetation. There are about 70 genera and 725 species of gymnosperms
distributed in tropical and temperate regions. Most of these are the conifers,
which are comparatively better-represented today. Others include the cycads
and the Ginkgo tree.On the Indian sub-continent, these are found in the
form of the coniferous forests in the Himalayas.
(a) Distinguishing features of gymnosperms
The life cycle shows heteromorphic alternation of
Gymnosperm plants are more advanced than pteridophytes but are more
primitive than angiosperms.
A diploid plant body (sporophyte) is mostly a tree
with well developed roots, stem and leaves.
Two types of reproductive leaves are present: microsporophylls
that produce microspores and megasporophylls that produce
The gametophytes are greatly reduced, microscopic
and dependent on sporophyte plant body.