Transcript Ncumisa_Mnotoza

How Conifers succeed in the
North
Ncumisa Mnotoza
[email protected]
Available at http://planet.uwc.ac.za/nisl/Eco_people/Presentations/
Conifers
 All conifers are seed plants with vascular tissue that
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bear cones.
They contain more trees than shrubs.
They have monopodial growth form, that is a tall
straight trunk and narrow branches.
They are usually found in cool or cold climatic regions.
Most have evergreen leaves that are needle-like.
They are all wind pollinated.
Conifers make up 30% of the world’s forest and are a
group that consists of the tallest, largest, thickest and
oldest living thing.
Tallest: 112.83m Coast
Redwood
Largest: base trunk
31.5m volume 1486.9cm3
Giant sequoia
Thickest: trunk diameter
11.42m Montezuma cypress
Oldest: 4.7 million years
old
SCIENTIFIC CLASSIFICATION
Kingdom:
Division :
Class :
Order :
Family :
Genus :
Plantae
Pinophyta
Pinopsida
Pinales
Pinaceae
Pinus L.
GYMNOSPERMS
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Gymnosperms are plants that produce seeds not
spores, the seeds are naked meaning that they are
not covered by an ovary. These are non flowering
plants. Usually, the seed is produced inside pine cone
hence the name "conifer." In essence the name word
conifer means cone bearing.
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Conifer are trees and shrubs that have cones and
characteristically have needle-like, scale-like or awllike leaves.
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Approximately 600 species are counted as conifers,
and some fall under the family CONIFERACEAE.
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Gymnosperms have been
distributed among four
groups that have been
given equal ranks in the
Kingdom Plantae.
Namely:
 Division: Pinophyta –
Conifers
 Division: Ginkgophta –
Ginkgo
 Division: Cycadophta –
Cycads
 Division : Gnetophyta Gnetum, Ephedra
Coast Douglas-fir Cone
 Gymnosperms are not the same thing as
conifers but merely a division within that
group.
 In very cold climatic regions conifers are
the only group within the
gymnosperms that will be found
common
Pinophyta
Pinophyta it has one class, Pinopsida that includes
both the living and fossil taxa. Conifers have 6 to 8
families that contains 65 to 70 genera and 600-650
species. A phylogenic diagram relates the
seven most distinct families.
Phlogeny of molecular data based on cladistic
analysis of molecular data
Coniferales
There are six families within this order:
 Pinaceae
 Taxodiaceae
 Cupressaceae
 Araucariaceae
 Podocarpaceae
 Cephalotaxaceae
Pinaceae
Leaves are linear, flat or needle-like
and spirally arranged in two or more
rows
Monoecious
Cones are mostly woody and spirally
arranged scales
The bracts are separate from scales
except at the base. The bracts are
small and narrow sometimes longer
than scales. The bract and ovuliferous
scale are distinct
Two pollen sacs and pollen has two
air bladders. Sporophyll are spirally
arranged. Pollen grains are winged
Juvenile (left) and adult
foliage of Stone Pine
(Pinus pinea). The adult
shoot has dark brown
scale leaves and needles.
Pinophyte needle-like
leaves (close- up) Picea
Abies
Taxodiaceace
Parts are spirally arranged
Leaves are opposite or spirally arranged,
narrow, linear or awl- shaped
Monoecious
Cones have a globose scale that is
spirally arranged, leathery and woody. The
bract and ovuliferous scale are free when
young then they fuse in the mature cone
Each ovuliferous scale has 2 to 9 ovules.
Pollen sacs 2 to 9 on each microsporophyll
Pollen grains without air bladders, pollen
is wingless or winged
Cupressaceae
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Parts are oppositely or whorled in
arrangement
Monoecious or dioecious
Small adult leaves, scale-like
arranged in opposite pairs or
three
Cones are small, the scales are
confluent with bracts and are
woody when ripe and contains
numerous ovules. Ovules are
erect and can be any number
from 3 to 20 per scale.
FEATURES OF CYPERACEAE
Microsporophylls have 3 to 6 microsporangia and the
pollen sacs range between 3 and 6
Cones may overlap e.g Thunja
valvate e.g Cupressus
fleshy e.g Junipersus
. cones are fleshy
The
and berry-like, the
seeds are bird
dispersed
Pollen grains lack air bladders and
have a good drop mechanism
Araucariacaeae
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Spiral arranged leaves that are
(Monkey Puzzle Family)
narrow or broad with parallel veins,
the buds are not scaled
Dioecious or monoecious
Cones have a large woody one
seeded scales and no distinct bracts.
Cones fall when seeds are ripe
Microsporophylls consist of 5 to 20
micropsporophylls. The scale of a
seed contains one ovule and is fused
with a sterile bract.
Ovules are solitary with
microsporangia hanging from a
peltate sporophyll. The male strobili is
dense, cylindrical with many
sporophylls
Pordocarparceae
leaves are evergreen, spirally
arranged, scale-like or needle-like,
linear or lanceolate, or
oblanceolate
Monoeciouis or dioecious
Ovule erect or reflexed
Commonly the the ovuliferous
scale is folded around the single
ovule to form an added envelop,
the epimatium, which is fused
completely or partially to the
integument or in some species it is
fused to the bract scale
Podocarparceae cones
Male cones have a number of microsporophylls each
with 2 pollen sacs. The pollen grains have 2 or 3 air
bladders. The pollen is winged
In some species the ovule are borne in cones. In
others the female cone is reduced to form a fleshy
receptacle with a single terminal ovule. The outer seed
coat is dry or fleshy, in reduced cones or supported by
a fleshy bract and stalk
Cephalotaxaceae
Spirally arranged linear leaves and
opposite or whorled branching
Dioecious
The ovules are borne on cones.
Ovules are in pairs at the base of each
opposite bracts. One ovule grows into
a big olive-like seed that has an outer
fleshy layer that surrounds a stony
layer
The male cone have spirally
arranged microsporophyll with 2 to 3
pollen sacs. The pollen bladders have
no air bladders. The pollen is wingless
Pollination is a drop mechanism
Reproductive Characteristics
Dioecious or monecious plants:
The microsporangiate stobili are pollen cones, that
makes pollen(microgametophyes. They consist of
sporophylls where the pollen sacs (microsporangia)
are borne on the lower surface
All species are wind-pollinated
Sperm are not flagellated they reach the egg via a
pollen tube.
Except for the Taxaceae, ovules are borne in
secondarily reduced microsporangiate stobili (seed
cones) with seed scales that have ovules. These are
subtended by a sterile bract, together they are called a
seed scale complex. They are arranged around the
central axis of the ovulate cone.
A GENERALIZED LIFE CYCLE OF PINES
The male cone releases pollen to fertilise the ovum. The
pollen is transported by wind to the female cone. When the
female gamete is fertilized it is called a zygote that grows into
an embryo.The embyro has integument cells that surround it
and altogether can be found in the seed. When the seed is
mature it drops onto the ground, and germinates. The
seedlings grow into a mature plant that produces cones…and
the cycle continues
SUCCESS OF CONIFERS
MORPHOLOGY:
A scale or a needle leaf is very small and thus has
minimal exposed surface area and they are also
lightweight.
This would make it impossible for trees and shrubs trap
any snow on their leaves because it would not be able to
support the weight of snow.The minimal surface area
exposure ensures that they do lose any water that it
retains.
The branches are thin, so they cannot trap much snow,
or this would result in the branches breaking off the trees.
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Photosynthesis still occurs in extremely low
temperatures due to the leaves being evergreen.
These trees take advantage of the short wet and
the short dry season which is characteristic of the
northern climates.
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This mechanism allows tress to ‘save’ nutrients,
because they do not have to form new leaves annualy.
This is advantageous in soils with low nutrients and
environments with a slow decomposition.
TRACHEIDS
They are long, narrow-diameter cells. Their narrowness
prevents bubbles forming during spring when stems
thaw. Air bubbles form as water freezes and air goes
out of solution forming a gas. Due to the tracheids being
narrow only small bubbles can form which end up
redissolving.
STOMATA
They help the trees in the case of water loss and to
aviod dessicatio form occuring,(as the air warms in
spring the soil is still frozen and water can't move into
tree freely to make up for the water loss from leave
ECONOMIC IMPORTANCE
Conifers are used to make softwood
timber.This wood is commonly used in
temperate regions for lumber constrution
making: polywoods, particleboards, and
chipboards; from processed softwood,
paper, plastics, tannins, turpentine.
 Conifers provide food: nuts and berries
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REFERENCES
Chamberlain Charles Joseph, 1966. ‘Gymnosperms:
Structure and Evolution’. General Publishing
Company, LTD, Canada.
Dallimore W. and Jackson A. B., 1966. ‘A Handbook
of Coniferaceae and Ginkgoaceae, 4th Edition. Edward
Arnold LTD, London
Sporne K. R., 1965. ‘The Morphology of
Gymnosperms’, Hutchinson & Co LTD, London
http://en.wikipedia.org/wiki/Pinophyta