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Adaptations 1
Adaptations for Protection
Evolutionary Changes Over Time
• Ice Ages At least five major ice ages have occurred
throughout Earth's history: the earliest was over 2 billion
years ago, and the most recent one began approximately 3
million years ago and continues today (yes, we live in an ice
age!). Currently, we are in a warm interglacial that began
about 11,000 years ago.
• Continental drift – Mountains, Deserts, New bodies of
water
• Catastrophic events – Asteroids, Volcanic eruptions
• Geographic isolation - “Speciation”: Galapagos Islands
• Mutations – Ultra violet light, Chromosomal rearrangement
• Natural Hybridizations
Humidity
Light
Water
Temperature
Wind
Environmental
Conditions that
affect plants
Soil
Terms – Adaptations for Protection
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Dormancy
Avoidance strategy
Ephemerals
Thorns
Spines
Marginal Spines
Prickles
Recurved
Pilose
Pubescent
Stinging hairs
Cryptic coloration
Symbiosis with ants
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Callus
Leaf abscission
Resins
Pitch
Latex
Tannins
Alkaloids
Protection From the Environment
• Dormancy
• Ephemerals
• Alpine perennials
Dormancy
• Dormancy is a plants adaptation mechanism
to live through periods of time when climatic
conditions are too severe to carryout normal
plant functions.
Avoidance Strategies
• Plants that undergo avoidance strategies
spend the most severe times of the year
climatically in seed form; the main plant dying
back.
• The main downside of this strategy is a small
time window to grow up from that seed to
maturity vegetatively, then flower and
produce seed as an annual plant.
Ephemerals
• Ephemerals are plants that wait until climatic
conditions are right then produce a small plant,
flower and seed all in many cases in 3-4 months.
The dormant
seeds produced by
ephemerals often
have to wait for
years and are
responsible for
tremendous
desert blooms
Gorman, CA
Death Valley, CA
Goldfields (Lasthenia gracilis)
Ephemerals - Annuals
This normally bare desert in Namaqualand, Goegap Nature Reserve in South
Africa has a proliferation of flowers and desert ephemerals during the brief
spring wet season.
Protection from Animals
OR
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Protection from Animals
• Thorns, Spines, Prickles – obvious to us
• Camouflage – Rare in plants
• Symbiosis for Protection – Using Ants as
protectors
• Wound Healing - Protection from infection
• Chemical protection – Tannins and alkaloids.
• Other Methods - accumulation of materials from
the soil, manufacturing of internal antagonistic
particles
Thorns, Spines or Prickles
In common language the terms are used more or less interchangeably, but in
botanical terms, thorns are derived from shoots (so they can be branched
or not, they can have leaves or not, and they arise from a bud)
spines are derived from leaves (the entire leaf or some part of the leaf
that has vascular bundles inside, like the petiole or a stipule
Prickles are derived from the epidermis (so they can be found anywhere
on the plant, and do not have vascular bundles inside so they can be
removed more easily and cleanly than thorns and spines).
Thorns vs. Spines
Thorn of Pyracantha. B. Spine of barberry (Berberis). The thorn
is technically a modified, sharp-pointed stem. It occurs in the axil
of a leaf where a branch would normally develop. The spine is
technically a modified, sharp-pointed leaf. Since it has a bud in
its axil, the spine occurs in the relative position of a leaf.
Plants with Thorns
Thorns are
modified
stems
Hawthorn and Blackthorn Trees
Prunus spinosa
Crataegus spp.
Thorns of Fouquieria splendens
Thorns on Citrus
Pyracantha – “Firethorn”
Spines
Spines - Pereska grandiflora
Spines – Modified leaves
The Multiple Roles of Cactus Spines
Morning dew
may be the
only form of
rainfall for
several months
in the desert
showing
another use
for spines
collecting and
directing dew
down to the
roots.
Cephalocereus senilis – Old Man
cactus uses hair as camouflage
hiding spines beneath and to
protect from hot desert sun
Marginal Leaf Spines
Prickles - Roses
Recurved - facing down the stem in
order to fend off animals crawling up
the stem
Prickles – Ceiba speciosa
Pilose hair – Leaves
Pilose Hair - Stems
Pubescent Hairs on Leaves
The thick fuzzy covering
of hairs on many plants
help the plant to
conserve water during
transpiration keeping
the water around the
plant longer before
being pulled away by
the wind or evaporated
off too quickly by the
sun
Stachys byzantina – Lambs ears
Stinging Hairs on Stinging Nettle
The miserable sting felt from the many hollow
stinging hairs called trichomes on the leaves and
stems, which act like hypodermic needles,
injecting histamine and other chemicals that
produce a stinging sensation when contacted by
humans and other animals
Stinging nettles are also
attributed with helping with
the symptoms of some
forms of arthritis, some
allergies, urinary tract
infections, and hair and skin
conditions as well as bring a
digestive aid
Camouflage – Lythops “Living Stones”
Cryptic (hidden from view) Coloration
Only the tops of the fleshy leaves of the
Lythops protrude above the soil line where
it acts like a window focusing the light
further down chloroplasts deep below.
It is thought to protect the plant from
animals seeking succulent leaves for
moisture in the rocky deserts of South
Africa
Symbiosis With Ants
https://www.youtube.com/watch?v=IkTs0Q3JUls
2 species of acacia have developed a symbiotic relationship
with and colonies offering both a nutrient source and
housing in exchange for a rapid response “all hands on
deck” defense from browsing herbivores like elephants.
Acacia sphaerocephala Bull horn acacia
Whistling Thorn Acacia
Acacia drepanolobium
Another species of
acacia tree that
provides shelter and
food in exchange for
immediate defense of
the tree
Wound Healing
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Tannin
Callus
Resin
Gums
Wound wood
Latex
Branch Collar
Branch bark Ridge
Callus
Callus is a material (polysaccharide molecule) laid down at the
wound sites of many plants to resist the invasion of pathogens. It
also precedes the process of wound wood production in woody
trees.
Callus – Wound wood
Woundwood is a specialized
wood laid down by woody
plants and trees to close off and
compartmentalize damaged
areas of wood tissue and
protect it from disease and
pathogen.
Woody plants don’t “Heal
wounds but merely close them
off and protect all new wood
being formed.
A properly healing wound – First immediately
covered with Callus to corm a infection barrier and
then healing over the wound with wound wood
Knots in lumber are areas of old
broken or cut branches closed
off inside the wood.
Woundwood - 3 years
Year 1
Year 2
Year 3
Good tree pruning works with the trees
natural wound repair system
When removing a branch the rule is to make
the removal cut just outside the Branch
Collar to allow the tree full access to it’s
natural repair processes of callus and wound
wood
Wound wood
Leaf Abscission
Leaf scar with visible vascular bundles
The Development of a Leaf Abscission Layer
Resins
Plants secrete resins and
rosins for their protective
benefits. They confound a
wide range of herbivores,
insects, and pathogens;
while the volatile phenolic
compounds may attract
benefactors such as
parasitoids or predators of
the herbivores that attack
the plant.
The resin produced by most plants is a viscous liquid, composed
mainly of terpenes, with lesser components of dissolved nonvolatile solids, which make resin thick and sticky.
Wikipedia
Resin/Pitch
Trees often respond to invasion of
their bark layer by flooding the hole
with pitch pushing out the invader
and plugging the hole. The response
is normally almost immediate but
when the tree is stressed the
response time can be delayed
allowing more successful invasions
Latex - Ficus
Most Ficus in the Moraceae family produce a white
latex that seals wounds and acts as an antibacterial,
fungicidal and even an anti herbivore material.
Some people have latex allergies and must avoid
exposing their skin to Ficus latex
Latex - Euphorbia
Euphorbia like the Fig
Family Moraceae produces
a white latex that protects
wounds from infection.
The latex from Euphorbia
(depending on the species)
can be problematic when
coming in contact with the
skin or especially the eyes
of humans.
The latex of the poinsettia
which is a Euphorbia as
well has little to non of this
effect
Tannins
Tannin is an astringent, bitter plant polyphenolic compound that binds to and
precipitates proteins and various other organic compounds including amino
acids and alkaloids.
The term tannin (from tanna, an Old High German word for oak or fir tree, as
in Tannenbaum) refers to the use of wood tannins from oak in tanning animal
hides into leather; hence the words "tan" and "tanning" for the treatment of
leather
The tannin compounds are widely distributed in many species of plants,
where they play a role in protection from predation, and perhaps also as
pesticides, and in plant growth regulation. The asstringency from the
tannins is what causes the dry and puckery feeling in the mouth following
the consumption of unripened fruit or red wine. Likewise, the destruction or
modification of tannins with time plays an important role in the ripening of
fruit and the aging of wine.
Wikipedia
Gums
Gums are slightly different than
resins in their chemical
composition, but like resins dry
on exposure to air and form a
protective barrier to wounded
tissues
Cherry tree gum
The Chicle tree is
responsible for
chewing gum
manufacturing
Manilkara chicle
Alkaloids
Rhubarb leaves
contain a high
concentration of
Oxalic acid which
can make you sick
if you consume
large quanities
The prized sugary
stem of the rhubarb
is the part we often
eat
Alkaloids
• Extracts from plant alkaloids have played a
large role in pharmaceuticals: pain relievers,
cardiac and repertory stimulates, muscle
relaxants, blood vessel constrictors, cures for
malaria, and pupal dilators used in eye exams.
• Caffeine, nicotine, morphine, extracted from
plant products have addictive qualities
• Phytotoxins: Hemlock, Castor bean, Solanine
Chemical Protection - Secondary Products
• There are several chemicals produced by
plants that don’t help serve the primary
functions of the plant (Growth, Respiration,
Reproduction etc.) but fulfill a secondary roll
often unknown by us. Some of these
chemicals (Secondary Products) we have
learned do serve a purpose to the plant and
we as humans have also benefitted greatly
from some of these organic compounds in our
daily lives.
Protective Chemical Review
• Tannin – astringent taste (unripe fruit) bind with proteins
causing cellular death
• Resin – non water soluble, conifers, hardens in air
• Callus – Parenchyma cell rapid protective layer over
wounds
• Callous – Not to be confused with Callus this material is
used by the plant to plug damaged phloem tubes
• Latex – White bleeding, dries to protective coat
• Gums – water soluble, dry to a protective coat
• Alkaloids – one of the most diverse and heavily studied of
plant secondary compounds providing many medicinal uses
for us
Solanaceae - The Nightshade Family
Contains:
The Potato S. tuberosum
TheTomato S. lycopersicum
The Eggplant S. melongena
Chile peppers
Bell Peppers
Fruits/tubers of these plants highly prized but the
leaves contain Alkalloids that can be poisonous if
consumed