Coniferophyta Cycadophyta Ginkgophyta Gnetophyta

LEAVES Needle-like

(small, long &

narrow)

Compound

leaves (resembles

palms or ferns)

Fan-shaped

leaves

Broad leaves

like

angiosperms

SEEDS Seeds in cones Seeds in

cones

Seeds are

completely

exposed

Seeds in cones

arranged in

clusters

XYLEM Tracheid Tracheid Tracheid

Tracheid &

vessel

elements

PHLOEM Sieve tubes Sieve tubes Sieve tubes

Sieve tubes &

companion

cells

TYPE OF

PLANTMonoecious Dioecious Dioecious Monoecious or

Dioecious

COMPARISON OF STRUCTURES IN GYMNOSPERMS

division Gnetophyta

subdivision Gnetophytina

class Gnetopsida

subclass Gnetidae

order Gnetales

DISTINGUISHING CHARACTERISTICS

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 disintegrates.

FEATURES (SOME ARE COMMON WITH

FLOWERING PLANTS)

Vessel elements in the vascular system not in

other gymnosperms

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 flower

Most are considered dioecious

Distribution, separated by genus:Green –WelwitschiaBlue –GnetumRed – EphedraPurple – 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 erosion.

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 meristematic tissue.

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 desert.

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 the fertilization.

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,

decongestant

2. @Southwestern UNITED STATES and MEXICO

(stem fragments)

Mormon tea, Mexican tea, squaw tea, and desert tea

3. Used for losing weight, obesity, enhances athletic performance.

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.

@ Nigeria

the leaf of G. africanum is used in the treatment of an enlarged spleen, sore throats and as a cathartic

@Ubangi

treatment of nausea and is considered to be an antidote to some forms of poison

@ Congo-Brazzaville

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

(GNETUM AFRICANUM AND G. BUCHHOLZIANUM)

IMPORTANCE CONTINUED..

The leaves are either eaten raw or are finely shredded and added to soups and stews.(protein, essential amino acids and mineral elements)

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.

FORM AND STRUCTURE WELWITSCHIA EPHEDRA GNETUM

LEAVES

presence of two large permanent leaves that are developedoutward

-reduced or scalelike

-have two primary veins, which are connected to two axial stem vascular bundles.

Two leaves at a node are broad and have a pinnate venation system (one midvein

with lateral secondary veins that run to the

leaf margin) and a meshwork of smaller veins.

STEM

stem at maturity is a short broad crown, often branched into three growing points and mostly hidden by the leaves

leaves are arranged in pairs on the stem or in whorls of three with their bases forming a sheath around the stem at a node

less remarkable, although one species produces its main leaves on short side branches (short shoots)

WHAT DO THEY LOOK LIKE?

HMMMM…

WELWITSCHIA

EPHEDRA

GNETUM

THANK YOU

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