Lesson 3: The Plant Cell... Teacher: Sven Beer סוון בר 054-6411449, svenb@ex.tau.ac.il

For this lesson read: Biology of Plants – 6th ed. pp. 40-68 7th ed. pp. 35-58 8th ed. pp. 38-62 Only text on: Plastids (chloroplast), vacuole, cell wall and plasmodesmata! For next lesson read: Biology of Plants – 6th ed. pp. 133-139 7th ed. pp. 115-121 8th ed. pp. 122-129

The Plant Cell Plasmodesmata

The (Plant) Cell… The Prokaryotic “Plant” Cell

Endosymbiosis Cyanobacteria 28.2

1: Chloroplasts (plastid)

DEMO !!! Chloroplast 1.mov

Ulva chloroplasts

Chloroplast: The Site of Photosynthesis

The Structure of the Chloroplast Stroma Granum / Grana = Thylakoid stack / stacks

The Chlorophyll Structure Hydrophilic Hydrophobic

Chlorophyll MW ~ 950 Hydrophilic Hydrophobic

CO2 + H2O >>> CH2O + O2 photo - synthesis Light Reactions Carbon Fixation and Reduction Reactions (Dark reactions) stroma grana CO2 Fixation

Chloroplasts are one form of plastids Cold Prolamellar bodies Etioplast Light

Chloroplasts contain chlorophyll and carotenoids, in cold: chloroplast can not form chlorophyll and carotenoids bereak down slowly; chromoplast are formed from chloroplasts

Plasmodesmata

2: Vacuoles Vacuoles a) contain waste products; b) keep turgor

Waste products, antocyanins salts

Up to 90% of cell volume!

Autumn Colors: Chlorophyll is not formed in the cold – carotenoids break down slowly >> chromoplasts (yellow / orange) Sugars (and other organic compounds) form antocyanins (red) in the vacuoles

red orange

Vascular bundle! Vascular bundle! Cell Growth = vacuole expansion / A land plant will wilt in seawater!

3) Cell walls

Secretory Vehicles contain: Cellulose, Hemicellulose, Pectin and Glucoproteins

Primary wall Secondary wall Middle Lamella

Macrofibirls>>Microfibrils>>Micelles>>Cellulose

Cellulose (more in secondary walls) cross-linked by Hemicellulose(s) = xyloglucans (glucose + xylose) Pectins (in primary cell walls only) = hydrophilic polysaccharides Glycoproteins (in primary walls) Lignins (make for stiffness, more in secondary walls) Cutins, Suberins (cork) and Waxes Primary wall (while the cell enlarges) Secondary wall (when the cell has reached its final size)

Microfibrils, macrofibrils, lignin, glucoproteins

Plasmodesmata

Plasmodesmata Pit

Marine Botany Lesson 3 (cont): The physical and chemical environment relevant to marine plant growth in the oceans…

Abiotic = Physical / Chemical Conditions affecting Plant Growth Light – Irradiance Temperature Salinity Pressure Currents pH?

Light ? Photons Quanta

Light, both electromagnetic waves and particles (quanta), “that trigger nerve impulses from the retina” Quanta Photons

Leaves are green! Eye

Why are leaves green? Tomatoes (and Red Algae) red?

Visible radiation (= “light”) Quanta Photons Photosynthetically Active Radiation - PAR (400-700 nm)

Light, both electromagnetic waves and particles (quanta), “that trigger nerve impulses from the retina” Photons Quanta λ Quantum E = h*c / λ Photon(s) = quanta (380-750 nm)

Chlorophylls absorb light at ~450 and ~670 nm… but how do we know that THIS light drives photosynthesis???

Engelmann ~ (1890)

Absorption and Action Spectra Absorption Spectra Action Spectrum Engelman -1883 Filament of the alga Spirogyra

Red algae and Cyanobacteria Chlorophyll Chlorophyll Phycobilins

Red algae: Complementary chromatic adaptation (?) Phycobilins

Measuring Light (Ft. Candles) (Energy) Photon Flux (mol photons m-2 s-1); [mol photons = Einstein (E)] Sunny day: ~ 2000 mmol photons m-2 s-1 Demo

Quantum Yield Absorption vs. Quantum Yield….