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

Plants: an elegant system

Who Are The Land Plants?

Table 29.1 (578)

Who Are The Land Plants?

Table 29.1 (578)

Evolutionary Trend: reduction of the sporophyte, and liberation from water.

Table 29.1 (578)

Shared Primitive Characters:

Shared Derived Characters:

Commonality: Alteration of Generations

Overview of plant structure

Meristems: Apical & Lateral

A brief look at roots and leaves (easy points)

Over all transport in Plants:

Major Challenge

MajorBalancingAct

3 “transport regions”: xm: ctc: wp:

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

?

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

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?

How do abiotic variables effect transpiration rates?

Environmental Factor

Effect

light

humidity

wind

termperature

soil moisture

[CO2]

In the mean time…

Phloem Loading: Source-Sink

Phloem Sap: 30% sugar (sucrose) by volume!Sugar Source: …Sugar Sink: …

The IB wants you to understand this

It’s not just “phloem down” anymore.

“Plant cannot live by water alone”

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

Flowers and plant response to the environment.

All Hail The Mighty Flower!

• Beauty• Ingenuity• Dominance • Support• Evolution/Classification

The “ideal” flower

All in the family

(30.12)

An ideal seed

An ideal germination

Need flower diagram (1)

• (sim to Fig 9.15) • Also need 9.16 (seed anatomy) (3)

• Also need 9.17 (seed germination) (4)

• Also monocot and eudicot (2)

What is a seed?

What is a fruit?

Ingenuity 3: Double Fertilization

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

Auxin, auxin, auxin

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)

Essential overview of phytochromes

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?

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!

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]

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…