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 Balancing Act Major Challenge
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. Shared Primitive Characters: Shared Derived Characters: Table 29.1 (578)
Over all transport in Plants: Major Balancing Act Major Challenge 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!
Regulation of transpiration occurs at the stomata, thanks to… Structure and Function Are correlated Regulation of Stomatal Opening: K+ Transport & Turgor Pressure *Light *CO2 *Circadian Rhythms
Transpiration on a cellular level How does water move up to the leaves? It can be pushed… It can be pulled… How powerful is transpiration? Fig. 36.12 Page 747
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 Balancing Act Major Challenge 3 “transport regions”: xm: ctc: wp:
Transmembrane (xm) Transport: mediated by transport proteinsand “set up” by chemiosmosis (proton pumps) Membrane Potential
All Hail The Mighty Flower! • Beauty • Ingenuity • Dominance • Support • Evolution/Classification
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)
Ingenuity 3: Double Fertilization What is a seed? What is a fruit?
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.)
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 kinasesthat 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 730 nm Shoot elongation
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
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.
So What? • So what happens when light is absorbed? photosystem
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)?