Plant Form & Function - Ecology & Evolutionary Biology
Transcript of Plant Form & Function - Ecology & Evolutionary Biology
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Plant Form & FunctionChs 36 &37
05 March 2009ECOL 182R UofA
K. E. BonineVideo 35.2
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Focus on Angiosperms
Most (97%) angiosperms are in two clades:
• Monocots: one cotyledon• Eudicots: two cotyledons• Other clades include star
anise and relatives, water lilies, and magnoliids.
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Angiosperm Diversification
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Monocots
PalmsLilies
Grasses
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Eudicots
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Angiosperm Structure
• Shoot System– Leaves (petiole & blade), Photosynthesis– Stems, elevate and support
• Root System– Anchor– Root Hairs, take up Water and Minerals
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Morphological Adaptations
• Modified Leaves Spines
• Thick bark
• Waxy cuticle to retard water loss• Tall stem to avoid herbivory
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Prickly Pear in Galapagos
Tall; Waxy Cuticle
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Leaf Typessimple vs. compound
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Modified Leaves!
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Modified Stems!
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Modified Stems/Leaves
Stems:-Tuber-Runner-“Barrel” Leaves:
-Spines
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Root Types1. Taproots (w/ Lateral roots)
2. Fibrous Roots
3. Adventitious Roots – from above ground stem
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Mesquite
Roots to 50m !
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Mangroves• Live in salty habitat• Roots in water with low oxygen content
Pneumatophores
Salt Excretion
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Adaptive RadiationMorphological
Diversity
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Phenotypic Plasticity
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Phenotypic Plasticity
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Monocot vs. Eudicot
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Monocot vs. Eudicot
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Vascular Tissues• Xylem
– Distributes water and minerals from roots to rest of plant
• Phloem– Transports carbohydrates (product of
photosynthesis) from leaves to rest of plant
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Where does the carbon we eat in a salad come from?
A. The EarthB. The AirC. The WaterD. Fossil FuelsE. None of the above
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25Octotillo Boojum
same family
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more about leaves…
Epidermis is important outer layer of leaves and stems:
-may contain waxy cuticle layer-retard water loss
-specialized cells to allow for gasexchange (and water loss)
-guard cells of stomata
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guard cells of stomata
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guard cells of stomata
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C3 vs C4 & CAM (see Ch 10)
• Photosynthesis slightly different among different groups.
• Acted on by natural selection.• C3 do better in temperate climates.• C4 do better in hotter climates
– even with stomata closed can fix carbon.– CAM is a form of C4 wherein the initial
carbon is incorporated at night and the light reaction takes place the next day.
C4 and CAM help reduce water lossduring photosynthesis.
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C3 vs C4 & CAM
If you placed these plants side-by-side at noon in March and then took the temperatureof the leaf surface…
Rose Prickly Pear
A. they would be same tempB. rose would be coolerC. cactus would be coolerD. need more information
Why?Because with CAM photosynthesis, stomata closed during day and therefore much less evaporation to cool the leaf
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Meristems• Apical Meristems
– Sites of primary growth– Found in tips of roots and stems– Found in leaf buds
• Lateral Meristems- Generate secondary growth
at vascular cambium- Including wood (2º xylem)
and bark (2º phloem)
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Apical meristem
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Secondary Growth
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Tree rings are secondary xylem that arises annually
from vascular cambium
Secondary Growth
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Vascular Bundlesxylem, phloem, (& vascular cambium in eudicots)
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Vascular Cambium (for 2º growth)
• Meristem Cells Become…– 2º Phloem to the outside– 2º Xylem to the inside
Cork Cambium• Mostly produces cells to the outside,
comprises most of the BARK
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Vascular Cambium
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Cork Cambium
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What is a knot in wood?
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Plants:Transport of
Water & Sugar+
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Video 35.2
Recovery in a wilted plant
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Pressure Potential (Ψp)aka Turgor Pressure
Physical force of water either because of gravity or some other
push…
In plants, water into cells meetsresistance of cell wall, leading to
turgor pressure (opposite of wilt!).
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4337.1
Isotonic (same solutes)
Hypotonic(fewer solutes)
Hypertonic(more solutes)
COMPARATIVE!
Osmotic Potential
44Hill et al 2004
Solution B has more dissolved solutes
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If you put a cell in a hypertonicsolution it will
A.Remain unchanged
B.Tend to shrink
C.Tend to swell
D.Depends on the solution
Water follows solutes.
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from left to rightSequoia Redwood (oldest trees), Coast Redwood (tallest trees), Douglas Fir, Port Orford Cedar, Sitka Spruce
How do plants get water >300’ in the air?
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Moving Water and Solutes
Xylem and Phloem
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37.4
Water moves from high
potential to low potential
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4937.10
Tension, Cohesion, Adhesion
Result in Capillary Action
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The water only continues to move if being pulled by
TRANSPIRATION1. Root pressure can move
water short distance2.Capillary action can move
water short distance3.Cohesion-Tension can pull
water from ground to top of Coast Redwood (>300’)
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Water is a polarmolecule and
hydrogen bonds link water molecules
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Transpiration (water evaporating from leaf surface) Rates will be highest when
Stomates are open/closed
Humidity in atmosphere is high/low
Temperature around tree is high/low
Tree is in shade/sun
open
low
high
sun
What does this tell you about trees living in the desert?
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Why is water transpiring?
1. Stomata open to get CO2
2. Stomata open for leaf cooling
5437.11
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Cohesion-Tension relies on acontinuous column of water from soil to atmosphere at leaf surface
Theory only really accepted in 1990s! Relies on very strong surface tension that results from transpiration.
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Based on your understanding of cohesion-tension theory, why does a tree trunk become slightly narrower during each day?
37.13
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Adaptations to Desert Living
a.Small or no leavesb.Thick waxy cuticlec.Thick epidermisd.Stomata on underside
of leavese.Trichomes to increase
humidity at leaf surfacef.C4 or CAM photosynthesis
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Getting & moving water is “free”.
Getting nutrients and moving sugars around costs energy (ATP)
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Energy to get nutrients etc.
• Plants have a proton pump(instead of a NaK-ATPasepump) that creates electrochemical gradient to do work.
6037.17
During middle of growing
season,mature leaves
provide sugars to
rest of plant
Source vs. Sink
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What happens differently to movements of sugars in early spring, before there are any
leaves?
Source vs. SinkStorage cells in roots
Developing leaves
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Proton Pump (ATP) needed to move sugars from photosynthesizing leaf(source) into phloem and then also from phloem into storage cells or growing tissues (sinks).
37.22
Move sucrose into cell
AGAINST its concentration
gradient
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Why does ‘girdling’ kill a tree?
Active xylem and phloem are just
under the bark. If tree can’t
transport water and carbohydrates
then it will die.
Was this tree girdled in March or in July?