Download What is a tree?

What is a plant?
Kingdom Plantae - technically plants are green
photosynthetic organisms
- Include 250,000 species
- autotrophs
- Produce organic sugar from CO2, water vapor and
light
- Base of many food chains/webs
- Nonmotile - spend most of their lives anchored to
one spot.
- multicellular
- Have a sex life – flowers possess male and female
structures
Three basic organs
A. Roots
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Anchors a plant
Absorbs minerals and water
Store nutrients
Three basic organs
B. Stems
Support the leaves and help orient the leaves
to the sun.
Conduct photosynthates from the leaves to
other organs of the plant.
Stems – transport water from the roots up to the leaves.
Many different types of stems.
Three basic organs
C. Leaves – most are responsible for
photosynthesis
bracts
spines
What is a tree?
A large, woody thing that produces shade
Self-supporting, perennial woody stem
To a horticulturalist a tree has a woody stem
that is more than 20 ft (6 m) tall which
branches at some distance above the ground.
To botanists trees cover the sprawling small
shrubs to the large giants that are over 100 m
tall.
A shrub has multiple stems and is less than 20
ft (6 m) tall.
Horsechestnut tree
Aesculus hippocastanum
Valued as a landscape tree
in Europe. It grows 50-70 feet
high and has a 40 feet wide
spread
Not trees
Lianas and other climbers
Woody stems that die back to the
ground each year like asparagus.
Bananas – lack wood (the trunk is made
from leaf stalks squeezed together.
Bamboos – hardened grasses although
they can reach 25 m tall and 25 cm
thick.
Asparagus shoot
Virginia creeper
-A woody vine/liana
with five leaflets
common bamboo
(Bambusa vulgaris)
golden stems marked
with dark green
longitudinal stripes.
Wide range of plants that have a tree
habit
Conifers and their allies
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Redwoods, pines, spruces, hemlocks, firs, yews
Cycads, Gnetales, Ginkgo
Angiosperms – flowering plants
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Dicotyledons – main group of trees: oaks, maples, beeches,
hickories, magnolias)
Monocotyledons
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Palms (mostly tropical)
Agavaceae (dragon trees)
Liliaceae (aloes, yuccas)
Xanthorrhoeaceae (grass trees that grow in Australia)
Loblolly pine
Pinus taeda L
Leaves of Ginkgo
When trees evolved
Plants arose more than 400 million years ago
(Silurian)
First trees arose in the Devonian (390 million
years ago)
Coal producing swamps of the Carboniferous
(360-290 million years ago are the result of
lush forests – giant horsetails, clubmosses, and
primitive conifers
250 million years ago there were cycads,
Ginkgos, and monkey puzzle pines (fossils are
found in the Arizona petrified forest).
Pines evolved around 180 – 135 million years
ago.
Living fossils
Trees that were once thought to be extinct but have
been found in remote areas
 Ginkgo – silver apricot or maidenhair tree was
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rediscovered in Japan by Europeans in 1690.
Dawn redwood (Metasequoia glyptostroboides) was
found in China in 1945.
Value of trees
Sacred to people
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Oaks sacred to European Druids
Baobabs to African tribes
Monkey puzzles to the Pehuenche people of Chile
Writing tablets were made from slivers of beech wood
(Fagus sylvatica) Beech is the Anglo-Saxon word for book.
Romans crowned athletes with branches from the bay
laurel (Laurus nobilis) which was extended to scholars and
poets.
Roman students were designated as bachelors from the
laurel berry (baccalaureus) leaving us with the bachelors
degree (baccalaureate).
Value of trees
Timber – 2300 million m3/yr is consumed worldwide
 Paper making
 Housing
 Synthetic rubber
 Matchsticks (get about 1 million from an average
Canadian aspen)
Cloth made from bark by the Polynesians and Africans
 Rayon can be made from wood
Keystone species – many other plants and animals
depend on trees.
Spices: nutmeg Myristica fragrans), cinnamon
(Cinnamomum verum), cloves (Eugenia caryophyllus),
coffee (Coffea arabica), tea (Camellia sinensis), and
carob (Ceratonia siliqua) – from the old world
Value of trees
Papaya, avocado, cocoa, brazil nut – new world
Olive oil and palm oil (used for margarine, candles, and
soap)
Artificial flavor of vanilla for cheap ice- cream is a
chemical derivative of wood.
Medicinal
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Extracts from Ginkgo are used to improve blood flow
Quinine (Cinchoma spp.)’Jesuit’s bark from Peru is used to fight
malaria.
Brake linings in cars – made from lignin
Trap and absorb pollutants
Reduce stress and improve healing in urban areas
Produce oxygen – a single mature beech tree can produce
enough oxygen for 10 people per year.
The shape of trees (growth habits)
Conical outline or excurrent – conifers, sweet
gum, yellow poplar
 Branches are produced in whorls around the main
central axis
 Usually one whorl per year
Deliquescent or decurrent – most deciduous
hardwoods
 Leading shoot of a young tree gives way to a
number of strong branches
Columnar – single, unbranched trunk; leaves in cluster
at top of trunk. Palms
weeping
fastigiate
columnar
The shape of trees (growth habits)
Fastigiate – columnar growth with very short
branches
Dwarf – smaller than normal
Weeping – branches lack hormones that maintain
geotropy (e.g., weeping willow).
The shape of trees (growth habits)
Flat –topped, umbrella shaped
 Mediterranean stone pine (Pinus pinea)
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Resists drying winds – leaves hide behind each
other out of the wind
The shape of trees (growth habits)
Trees grown in open areas have wide-spreading
branches
Trees grown in shade tend to be taller and narrower
with fewer side branches to help acquire light.
Leaf parts
1. leaf blade – portion of the leaf that is thin and
flattened
2. petiole – stalk of a leaf may or may not be present
3. stipules – pair of appendages occur at base
of leaf (occur in 25% of angiosperms)
- May be attached to the petiole or stem
- May form a ring around the stem
- Colors: green, yellow, brown, red, or purple
- Green stipules may be temporary or
persistent photosynthetic structures
- May be thin, and papery; hard and woody
or spine-like.
- Some plants loose their stipules after a leaf
develops  a scar may form.
Leaf complexity
Simple leaf – a leaf with
a single blade
Compound leaf
- a leaf with more than
one blade per petiole
or leaf base
Leaflet – one of the segments of a compound
leaf
Pinnately compound – a compound leaf;
leaflets attached along a central axis
Rachis – axis of a pinnately compound leaf
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A continuation of the petiole
It is above the point of attachment of the
lowermost leaflet
equivalent to a midrib on a simple leaf
has all leaflets attached to it
Pinna – the primary division of a pinnately
compound leaf
Palmately compound – a compound leaf with
leaflets radiating from a common point of attachment
resembles fingers
on a hand
no rachis
Leaf Arrangement
1. Opposite – two leaves
attached at each node
on opposite sides of a stem.
2. Alternate – only one leaf
attached at each node.
3. Whorled – three or more leaves
symmetrically distributed around the stem at
same node
Leaf Attachment
Sessile – a leaf blade
attached directly to a twig
Leaf venation
1. Pinnate venation –
one simple major vein
2. Palmate venation –
more than one major vein
ex: silver maple
3. Dichotomous venation
- the veins branch in two
over and over again
- occur in ferns, Ginkgo,
few angiosperms
4. Parallel venation
- veins are in parallel arrangement
- common to yucca, bananas, grasses, palms
- These plants commonly possess a leaf sheath
Stem features
1. Node – position on a stem where a leaf
branch or aerial root grows
2. Internode – part of stem axis between two
nodes
3. Axillary (side) bud – a bud born in the axis
of a leaf
4. Terminal bud - located at the tip of the stem
and it is the dominant bud
- can cause all the lateral buds below to remain
dormant
FRUITS
- Develop from the ovary of a flower and, often, other
tissues that surround it.
- Arise from fertilization
- A seed container
-Does not have to be sweet.
- It protects developing seeds
- May help disperse mature seeds
Large diversity of fruit types
Classified on the basis of the characteristics of
the mature ovary
Fruits can be fleshy or dry
Identification - the determination of a specimen
as being identical to or different from a
previously known plant.
- A previously known specimen is not always
available and the unknown specimen may
prove to be a new one.
i.e.: Three specimens A, B, and C.
- Specimen A is classified as Solanum nigrum.
- Specimen B is similar to A and is considered to
be S. nigrum.
- Specimen C is dissimilar so further study is
required
How to determine an unknown
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3.
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5.
Consult a flora monograph in a library
Look at herbarium specimens
Look at garden specimens
Ask an expert
Use a taxonomic key –dichotomous keys are the
most common. It consists of a series of two
contrasting statements.
- Each statement is a lead; the pair of leads
constitutes a couplet
- Select the best lead statement, then and then all
couplets under that lead are sequentially checked
for fit until identification is reached.
Money Taxonomic Key
1. Is it made of metal?
Yes ............................................... Go to 2
No ............................................... Go to 5
2. Is it a silver type color?
Yes ............................................... Go to 3
No ............................................... Penny
3. Is the outer edge smooth?
Yes ............................................... Nickel
No ............................................... Go to 4
4. Is there an Eagle on the back?
Yes ............................................... Quarter
No ............................................... Dime
5. Do the corners have a number 1 in them?
Yes ............................................... $1 Bill
No ............................................... $2 Bill