gynosperms - defination , classification, similarities.
GYMNOSPERMS
This includes 1) Defination 2) characters, classification 3) similarities
with pteridophytes . 4) similarities with angiosperm.
The term gymnosperms
(gymnos = naked; sperma = seed) was introduced by Theophrastus .The phanerogams
or Spermatophyta (sperm = seed; phyton = plant) or seed plants are those plants
which reproduce by means of seeds, not spores. Gymnosperm does not have fruits
they are non-floweringIn these plants the ovules are borne naked or the surface
of the megasporophylls, which are often arranged in the cones or sori.They have
thick cuticle,
needle-like leaves, and sunken stomata on the leaves reduce the rate of water
loss.
Characteristics of
Gymnosperms-
·
They are non –
flowering.
·
They are not
fruit-bearing plants.
·
They are mostly
pollinated by the wind.
·
They have sporophytic
phase and have root , stem and leaves.
·
They form cones with
reproductive structures.
·
They develop
needle-like leaves and are usually found in dry places.
·
They are first true
plants.
Classification of
Gymnosperms
Gymnosperms are
classified into four types as given below –
a)Coniferophyta
b)Cycadophyta
c)Ginkgophyta
d)Gnetophyta
Resemblances or Similarities
with Pteridophytes:
1. Sporophytic, phase is independent .
2.It is differentiated into root, stem and leaves.
3. Presence of megaphyllous leaves.
4. Gymnosperm is heterosporus this ability bis shown by
some ptreridophytes also.
5.Present of archegonia
6.Motile gametes
7. occuring embryo
after fertilization.
8. Alternation of
generation.
Similarities of Gymnosperms with
Angiosperms:
1. Main plant body is sporophytic
2. Plants are trees or shrubs and may be erect or
climbing.
3. Root system is well developed and the roots may be
diarch, triarch, tetrach or polyarch.
5. Vascular bundles are conjoint, collateral, open and
endarch.
6.secondary growth
7. Wood may be pycnyoxylic
8.Anomophily (wind ) mode of pollination.
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