Download - Botany Overview
Botany Overview
• 1st Remarks:
• “Plants Can’t Run”• Plants have covered
the globe.• The basic
information is usually the most important.
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
What if you can’t run and you can’t eat?
Major Challenge
MajorBalancingAct
Who are the Land Plants?
Table 29.1 (578)
Shared Primitive Characters:
Shared Derived Characters:
Commonality: Alteration of Generations
Sporophyte changes as plants become more derived.
Table 29.1 (578)
Bryophyte Life Cycle
Modern Pterophytes are usually found in moist places…why?
Alteration of Generations: Pterophytes
"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
Gymnosperm Lifecycle
All Hail The Mighty Flower!
• Beauty• Ingenuity• Dominance • Support• Evolution/Classification
What is a seed?
What is a fruit?
Ingenuity 3: Double Fertilization
Meristems: Apical & Lateral
Meristems: Apical & Lateral
Secondary Growth
Initials!
One more look @ 2ndary
Growth
Over all transport in Plants:
Major Challenge
MajorBalancingAct
3 “transport regions”: xm: ctc: wp:
Transmembrane (xm) Transport: mediated by transport proteins
and “set up” by chemiosmosis (proton pumps)
Membrane Potential
Results of a chemo-electrical gradient…good stuff for the plant
Apoplastic, symplatic, so what?
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…
Accent of Xylem Sap: Differences in Water Potential!
• Facilitated by the physical properties of water– Adhesion/Cohesion
• Water molecules on the march!
Plant Transport HO 1: Overview of Xylem Transport
?
Phloem Loading: Source-Sink
Phloem Sap: 30% sugar (sucrose) by volume!Sugar Source: …Sugar Sink: …
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?
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
Bioenergetics: Background Info
• Producers
• Consumers
Across four levels of organization
• Plants • Leaves
• Mesophyll Cells
• Chloroplasts
PS: 2 Reactions in 1 organelle
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.
More Food…Check out Figure 10.16
So What? • So what happens when
light is absorbed?
photosystem
If we could get down on the thylakoid membrane…
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)?
What happens? Well, chemiosmosis happens.
What do the Light Reactions produce?
• Light Reactions…
But chloroplasts still needs a little more ATP
Light Reaction Review…
Gimmie Some Sugar!
Phase 1: Carbon Fixation
Phase 2: Reduction
Phase 3: Regeneration of RuBP
Photosynthesis: The Big Picture
Location
Energy conversions
Material inputs/outputs
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.
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!
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!
Botany Overview
• 1st Remarks:
• “Plants Can’t Run”• Plants have covered
the globe.• The basic
information is usually the most important.
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
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.)
General Signal Transduction
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
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)
Light & Phytochromes initiate a cell signal and Response
Shoot elongation
730 nm
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?
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]