SlideShare utilise les cookies pour améliorer les fonctionnalités et les performances, et également pour vous montrer des publicités pertinentes. Si vous continuez à naviguer sur ce site, vous acceptez l’utilisation de cookies. Consultez nos Conditions d’utilisation et notre Politique de confidentialité.
SlideShare utilise les cookies pour améliorer les fonctionnalités et les performances, et également pour vous montrer des publicités pertinentes. Si vous continuez à naviguer sur ce site, vous acceptez l’utilisation de cookies. Consultez notre Politique de confidentialité et nos Conditions d’utilisation pour en savoir plus.
I made this powerpoint as a requirement in our Botany class. I have also based my information from several sources. Please bare with the presentation if there are "bad" fonts. I don't know how it happened to change, maybe because of Slideshare's formatting and stuffs. Thank you!
COMPARISON OF STRUCTURES IN GYMNOSPERMS
Coniferophyta Cycadophyta Ginkgophyta Gnetophyta
(small, long &
palms or ferns)
SEEDS Seeds in cones Seeds in
Seeds in cones
XYLEM Tracheid Tracheid Tracheid
PHLOEM Sieve tubes Sieve tubes Sieve tubes
Sieve tubes &
Monoecious Dioecious Dioecious Monoecious or
presence of both tracheids and vessel elements in
their xylem tissue
a tube grows from the eggs to unite with the pollen
tubes in order for fertilization to take place between
the gametophytes. The sperm themselves are not
motile, like we see in the cycads and gingko.
undergoes double fertilization, however no
endosperm forms and the second egg fertilized
FEATURES (SOME ARE COMMON WITH
Vessel elements in the vascular system not in
Both Welwitschia and some Gnetum species are
pollinated by insects
Flower like structures on male cones of Welwitschia
Nectar-produced on the tip of the cones rather in
Most are considered dioecious
Distribution, separated by genus:
Blue – Gnetum
Red – Ephedra
Purple – Gnetum and Ephedra range overlap
Grows in the deserts of Namibia and Angola
(distribution coincides with the fog belt); This is
a plant of remarkably bizarre habits and
survives in very harsh localities.
The plant was discovered by Austrian
botanist Friedrich Welwitsch.
Welwitschia has just two strap like leaves that grow
continuously, but most leaves break up in the harsh desert
environment and become tatty and brown at the ends.. they are
evergreen, a single pair and generally broad and flat
Plant resembles a woody carrot. The stem is exceedingly
fibrous and has a prominent, thick, corrugated
periderm. Unequal growth causes the stems of these plants to
become weirdly distorted and there are only two strap-shaped
leaves, growing from a terminal groove in the photosynthetic
tissue of the stem.
Uses its millions of stomata on the surface of it's large
leaves. to absorb water from fog through millions of stomata -
from there the water moves to the rest of the plant.
GROWTH HABIT IS UNIQUE: The apical growth
point of the stem stops growing from an
early stage. This causes the stem to grow
upwards and outwards, away from the original
apex (which remains dead), resulting in the
characteristic obconical shape.
The female cones produce drops of nectar
to entice insects to pollinate them.
They have a single tap root grows deep into the
sandy desert soil in search of water. The roots of
Welwitschia can grow up to 30 meters deep, sponge
and lateral roots are also a part of the root system.
The leaves that lay on the sand surface also prevent wind
Antelope and rhino chew the leaves for their juice
during times of drought, and spit out the tough fibres. They
also eat the soft part near the groove. This luckily does not
damage the plant as they simply grow out again from the
The core, especially of the female plant, was used
as food for people in earlier times. It is said to be very
tasty either raw or baked in hot ashes, and this is how it got
its Herero name, onyanga, which means onion of the
The female plant has large cones while the
male plant has flowers. The male reproductive
structure has six stamens each with a anther and a
pistil. A female plant of average size may bear from
60 to 100 or even more cones. The Welwitschia
female plant can produce a lot of seeds: up to
10 000 or even more. Unlike other known plants
fertilization occur in the pollen tube rather
than in the embryo sac. It is known that wind plays
a major role in the fertilzation, but much has to be
learned about a little insect which also helps with
Most species of are branched shrubs (or rarely small trees) while
others are vine-like, often clambering over other vegetation.
They have slender stems with needle like leaves and small,
sometimes brightly colored, cones.
They grow in dry areas in the Northern hemisphere,
such as North Africa, Europe and North America.
Ephedra looks very much like a gigantic version of
psilotum and can grow up to 3m.
Some are monoecious.
Known as jointfirs.
1. @CHINA - known as ma-huang
ephedrine colds, fever, sweating,
2. @Southwestern UNITED STATES and MEXICO
Mormon tea, Mexican tea, squaw tea, and desert tea
3. Used for losing weight, obesity, enhances athletic
Have fruit-like juicy covering for the seeds, which, like
fruit, are edible to birds and aid in the spreading of seed.
Leaves have network of veins, something seen in
dicotyledonous flowering plants, but no earlier evolved plants.
All are dioecious, with the male plants producing catkins of
stamens and the females catkins of ovules barely protected by an
envelope. Majority of the species are lianas.
There are about thirty species in the genus, which occurs
throughout the tropics in Asia, South America
and in Central Africa.
(GNETUM AFRICANUM AND G. BUCHHOLZIANUM)
the leaf of G. africanum is used in the treatment of
an enlarged spleen, sore throats and as a cathartic
treatment of nausea and is considered to be an
antidote to some forms of poison
the leaves are used as a dressing for warts and
boils and a tisane of the cut-up stem is taken to reduce
the pain of childbirth
The leaves are either eaten raw or are finely
shredded and added to soups and
stews.(protein, essential amino acids and mineral
The leaves of
both Gnetum africanum and G. buchholzianum
are a very important article of trade in the
Central African region, particularly in Cameroon
where the leaves are harvested on a daily basis and
sold in local and regional markets.
STRUCTURE WELWITSCHIA EPHEDRA GNETUM
presence of two
leaves that are
-have two primary
veins, which are
connected to two
axial stem vascular
Two leaves at a
node are broad
and have a
system (one midvein
with lateral secondary
veins that run to the
leaf margin) and a
stem at maturity is
a short broad
points and mostly
hidden by the
arranged in pairs
on the stem or in
whorls of three
with their bases
forming a sheath
around the stem
at a node
its main leaves on