Botany Overview
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Transcript of Botany Overview
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Botany Overview
• 1st Remarks:
• “Plants Can’t Run”• Plants have covered
the globe.• The basic
information is usually the most important.
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What’s here?
• Overview of plant evolution and plant clades
• Overview of plant growth and development
• Overview of Plant Transport• Overview of Photosynthesis• Overview of Plant Response to the
Environment
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What if you can’t run and you can’t eat?
Major Challenge
MajorBalancingAct
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Who are the Land Plants?
Table 29.1 (578)
Shared Primitive Characters:
Shared Derived Characters:
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Commonality: Alteration of Generations
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Sporophyte changes as plants become more derived.
Table 29.1 (578)
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Bryophyte Life Cycle
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Modern Pterophytes are usually found in moist places…why?
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Alteration of Generations: Pterophytes
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"a vast forest of the most stately pine trees that can be imagined, planted by nature at a moderate distance. . .
enameled with a variety of flowering shrubs." Fire defined where the longleaf pine forest was found and fostered an ecosystem diverse in plants and animals.
SOUTHERN COASTS
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Gymnosperm Lifecycle
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All Hail The Mighty Flower!
• Beauty• Ingenuity• Dominance • Support• Evolution/Classification
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What is a seed?
What is a fruit?
Ingenuity 3: Double Fertilization
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Meristems: Apical & Lateral
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Meristems: Apical & Lateral
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Secondary Growth
Initials!
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One more look @ 2ndary
Growth
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Over all transport in Plants:
Major Challenge
MajorBalancingAct
3 “transport regions”: xm: ctc: wp:
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Transmembrane (xm) Transport: mediated by transport proteins
and “set up” by chemiosmosis (proton pumps)
Membrane Potential
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Results of a chemo-electrical gradient…good stuff for the plant
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Apoplastic, symplatic, so what?
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These cellular processes lead to whole plant transport(aka Bulk Flow)
• Hydrostatic pressure pulls sap down
• Tension pulls sap (water) up• Facilitated by changes in
water potential between neighboring cells– Diffusion/Osmosis– Active Transport
• Vessel structure leads to increased transport efficiency– Xylem:
• Dead…– Phloem:
• So what…
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Accent of Xylem Sap: Differences in Water Potential!
• Facilitated by the physical properties of water– Adhesion/Cohesion
• Water molecules on the march!
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Plant Transport HO 1: Overview of Xylem Transport
?
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Phloem Loading: Source-Sink
Phloem Sap: 30% sugar (sucrose) by volume!Sugar Source: …Sugar Sink: …
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Transpiration on a cellular level
Fig. 36.12
Page 747
How does water move up to the leaves?
It can be pushed…
It can be pulled…
How powerful is transpiration?
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Regulation of transpiration occurs at the stomata, thanks to…
1. Structure and FunctionAre correlated
Regulation of Stomatal Opening:
K+ Transport & Turgor Pressure
*Light
*CO2
*Circadian Rhythms
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Bioenergetics: Background Info
• Producers
• Consumers
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Across four levels of organization
• Plants • Leaves
• Mesophyll Cells
• Chloroplasts
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PS: 2 Reactions in 1 organelle
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Food for thought:
How are cellular respiration and photosynthesis similar? How are they
different? Think about it on an organismal level, on an organelle level, and on a
biochemical level.
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More Food…Check out Figure 10.16
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So What? • So what happens when
light is absorbed?
photosystem
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If we could get down on the thylakoid membrane…
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No, really, so what?
• Where does the electron from water go once it replaces the electron in the chlorophyll molecule in the center of PSII (PS 680)?
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What happens? Well, chemiosmosis happens.
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What do the Light Reactions produce?
• Light Reactions…
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But chloroplasts still needs a little more ATP
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Light Reaction Review…
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Gimmie Some Sugar!
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Phase 1: Carbon Fixation
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Phase 2: Reduction
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Phase 3: Regeneration of RuBP
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Photosynthesis: The Big Picture
Location
Energy conversions
Material inputs/outputs
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Photorespiration• A drain on Calvin Cycle Energy that produces no ATP,
it does produce CO2
• Why? Rubisco has an affinity for O2
• …and when [O2] build up in cells (and [CO2] drop)…
• Rubisco binds RuBP to O2 instead of CO2
• Why? Rubisco evolved before O2 concentrations were appreciable in atmosphere
• Can drain as much as 50% of photosynthetic energy away.
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Fighting Photorespiration the C4 way
• High Light, High heat (think Corn).
• What happens when it gets too hot, and transpiration increases?
• What happens to [CO2] and [O2]?• How do plants combat this?
• Fix CO2 into PEP Carboxylase• (4-C compound)• Deliver 4-C compound to Calvin Cycle in
Bundle Sheath (where [O2] are lower.• Perform Calvin Cycle in Bundle Sheath • Transport Sugars (Sucrose) to Phloem• Spatial Separation!
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Fighting Photorespiration the CAM way
• What are conditions like in the desert?
• What will the stomata do?• How will the plants get CO2?
• Open stomata at night!
• Fix CO2 into organic acids(Crussalean Acid Metabolism) at night, store in vaculoles
• During day, when light is available…
• Temporal Separation!
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Botany Overview
• 1st Remarks:
• “Plants Can’t Run”• Plants have covered
the globe.• The basic
information is usually the most important.
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Why Study Plant Hormones/Plant Responses to
the environment?• Ties into the theme: “Plants can’t run.”• Allows us to look at cellular (and sub-cellular
processes) and relate them to organism function.
• Gives us a glimpse of how organisms respond to stimuli and interact with an ecosystem (abiotic and biotic forces).
• In a sense, this is physiological ecology
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Basic Concepts related to plant hormones
• Small molecules that can pass through cell membrane and trigger receptor molecules.
• Hormones affect plant growth and development by affecting:– Cell division, Cell Elongation, Cell Differentiation
• Response to a hormone doesn’t depend so much on absolute amounts of a hormone, but depends on relative concentrations of certain hormones relative to other hormones.– Plants are under the influence of multiple hormones b/c they
respond to multiple stimuli (e.g. temperature, day length, osmotic balance). Certain hormone balance causes a specific response (e.g. phototropism, flowering, fruit ripening, etc.)
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General Signal Transduction
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Action Spectrum for plants control photomorphogenesis (plant growth and development)
• Two major classes of Photoreceptors:– Blue Light Receptors
• Phototropism (Photoropin)• AM opening of stomata• (Zeaxanthin)• Slowing of hypocotyl
elongation (cryptochrome)– Phytochromes
• Red Light/Far Red Light Receptors
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Because Plant Cells have Phytochromes• Phytochromes are
receptors for red light• Consists of two domains
– One receives the light– One has kinases that link
the reception of light with cellular response
• Revert between two isomers (Pr and Pfr)– Pr = Red light (660nm)– Pfr = Far Red light (730nm)
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Light & Phytochromes initiate a cell signal and Response
Shoot elongation
730 nm
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Phytochromes also set circadian rhythms
• Circa = approximately; dies = day• Cyclic variations based on 24 period• What changes?
– Humidity, temperature, light• How do plants respond?
– Plants respond by opening and closing stomata and synthesizing certain enzymes
• Caveat: this rhythm is internal, but it is set by an external stimulus: light
• Phytochromes also signal plants when to flower. This is called…phtoperiodism. – Why keyed to day length?
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Other stresses on plants• Gravity: gravitropism
– • Mechanical stimuli: wind, herbivory, touch
– thigmomorphogenesis:
• Drought–
• Flooding–
• Heat stress– “Heat-shock Proteins”
• Cold Stress/Freezing: membrane contents/[solute]