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Phytoremediation Plant products Biofuels Effects of seed spacing on seed germination Effects of nutrient deprivation Effects of stresses Climate/CO2 change Non-coding RNAs Biotechnology Plant movements: flytraps, mimosa, soybeans Carnivorous plants Stress responses/stress avoidance Plant signaling (including neurobiology) Flowering? Hormones? Plant pathology? Plant tropisms and nastic movements Root growth responses Metal toxicity? Circadian rhythms? Effects of magnetic fields? Effects of different colors of light on plant growth?
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Plant Development Cell division = growth Determination = what cell can become Differentiation = cells become specific types Pattern formation Morphogenesis: organization into tissues & organs
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Plant Development umbrella term for many processes Embryogenesis Seed dormancy and germination Seedling Morphogenesis Transition to flowering, fruit and seed formation Many responses to environment
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Unique features of plant development
Meristems: plants have perpetually embryonic regions, and can form new ones No germ line! Cells at apical meristem become flowers: allows Lamarckian evolution! Different parts of the same 2000 year old tree have different DNA & form different gametes
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Cell walls Carbohydrate barrier surrounding cell Protects & gives cell shape 1˚ wall made first mainly cellulose Can stretch! 2˚ wall made after growth stops Inside 1˚ wall
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Endomembrane system Organelles derived from the ER 1) ER 2) Golgi 3) Vacuoles 4) Plasma Membrane 5) Nuclear Envelope 6) Endosome 7) Oleosomes
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VACUOLES Vacuoles are subdivided: lytic vacuoles are distinct from storage vacuoles!
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Endomembrane System Oleosomes: oil storage bodies derived from SER Surrounded by lipid monolayer! filled with lipids: no internal hydrophobic effect!
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Peroxisomes Fn: destroy H2O2, other O2-related poisons change fat to CH2O (glyoxysomes) Detoxify & recycle photorespiration products Destroy EtOH (made in anaerobic roots)
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Mitochondria matrix contains DNA, RNA and ribosomes Genomes vary from 100,000 to 2,500,000 bp, but only genes Sometimes mutate to cause cytoplasmic male sterility Reproduce by fission
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Mitochondria matrix contains DNA, RNA and ribosomes Genomes vary from 100,000 to 2,500,000 bp, but only genes Sometimes mutate to cause cytoplasmic male sterility Reproduce by fission IM is 25% cardiolipin, a bacterial phospholipid
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Mitochondria matrix contains DNA, RNA and ribosomes Genomes vary from 100,000 to 2,500,000 bp, but only genes Sometimes mutate to cause cytoplasmic male sterility Reproduce by fission IM is 25% cardiolipin, a bacterial phospholipid Genes most related to Rhodobacteria
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Mitochondria Fn : cellular respiration -> oxidizing food & supplying energy to cell Also make many important biochemicals
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Mitochondria Fn : cellular respiration -> oxidizing food & supplying energy to cell Also make important biochemicals & help recycle PR products
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Mitochondria Fn : cellular respiration -> oxidizing food & supplying energy to cell Also make important biochems & help recycle PR prods Have extra oxidases: burn off excess NADH or NADPH? Can’t kill plants with cyanide because of alternative oxidase!
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Mitochondria Fn : cellular respiration -> oxidizing food & supplying energy to cell Also make important biochems & help recycle PR prods Have extra oxidases Do lots of extra biochemistry
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endosymbionts Peroxisomes Mitochondria Plastids
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Plastids Present in all plant cells, but take many forms Chloroplasts do photosynthesis Amyloplasts store starch Chromoplasts store pigments Leucoplasts are found in roots
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Chloroplasts Bounded by 2 membranes 1) outer envelope 2) inner envelope
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Chloroplasts Interior = stroma Contains thylakoids membranes where light rxns of photosynthesis occur mainly galactolipids
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Chloroplasts Interior = stroma Contains thylakoids membranes where light rxns of photosynthesis occur mainly galactolipids Contain DNA, RNA, ribosomes
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Chloroplasts Contain DNA, RNA, ribosomes 120, ,000 bp, ~ 100 genes
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Chloroplasts Contain DNA, RNA, ribosomes 120, ,000 bp, ~ 100 genes Closest relatives = cyanobacteria
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Chloroplasts Contain DNA, RNA, ribosomes 120, ,000 bp, ~ 100 genes Closest relatives = cyanobacteria Divide by fission
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Chloroplasts Contain DNA, RNA, ribosomes 120, ,000 bp, ~ 100 genes Closest relatives = cyanobacteria Divide by fission Fns: Photosynthesis
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Chloroplasts Fns: Photosynthesis & starch synth Photoassimilation of N & S
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Chloroplasts Fns: Photosynthesis & starch synth Photoassimilation of N & S Fatty acid & some lipid synth
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Chloroplasts Fns: Photosynthesis & starch synth Photoassimilation of N & S Fatty acid & some lipid synth Synth of ABA, GA, many other biochem
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Chloroplasts & Mitochondria
Contain eubacterial DNA, RNA, ribosomes Inner membranes have bacterial lipids Divide by fission Provide best support for endosymbiosis theory
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Endosymbiosis theory (Margulis)
Archaebacteria ate eubacteria & converted them to symbionts
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Endosymbiosis theory (Margulis)
Archaebacteria ate eubacteria & converted them to symbionts
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Endosymbiosis theory (Margulis)
Archaebacteria ate eubacteria & converted them to symbionts
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cytoskeleton network of proteins which give cells their shape also responsible for shape of plant cells because guide cell wall formation left intact by detergents that extract rest of cell
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Cytoskeleton Actin fibers (microfilaments) ~7 nm diameter Form 2 chains of polar actin subunits arranged in a double helix
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Actin fibers polar subunits arranged in a double helix Add to + end Fall off - end Fn = movement
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Actin fibers Very conserved in evolution
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Actin fibers Very conserved in evolution Fn = motility Often with myosin
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Actin fibers Very conserved in evolution Fn = motility Often with myosin: responsible for cytoplasmic streaming
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Actin fibers Very conserved in evolution Fn = motility Often with myosin: responsible for cytoplasmic streaming, Pollen tube growth & movement through plasmodesmata
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Actin fibers Often with myosin: responsible for cytoplasmic streaming, Pollen tube growth & movement through plasmodesmata
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Actin fibers Often with myosin: responsible for cytoplasmic streaming, Pollen tube growth & movement through plasmodesmata
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Intermediate filaments
Protein fibers 8-12 nm dia (between MFs & MTs) form similar looking filaments Conserved central, rod-shaped -helical domain
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Intermediate filaments
2 monomers form dimers with parallel subunits Dimers form tetramers aligned in opposite orientations & staggered
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Intermediate filaments
2 monomers form dimers with parallel subunits Dimers form tetramers Tetramers form IF
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Intermediate filaments
2 monomers form dimers with parallel subunits Dimers form tetramers Tetramers form IF Plants have several keratins: fn unclear
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Intermediate filaments
2 monomers form dimers with parallel subunits Dimers form tetramers Tetramers form IF Plants have several keratins: fn unclear No nuclear lamins! Have analogs that form similar structures
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Microtubules Hollow, cylindrical; found in most eukaryotes outer diameter - 24 nm wall thickness - ~ 5 nm Made of 13 longitudinal rows of protofilaments
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Microtubules Made of ab tubulin subunits polymerize to form protofilaments (PF) PF form sheets Sheets form microtubules
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Microtubules Protofilaments are polar - end + end all in single MT have same polarity
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Microtubules In constant flux polymerizing & depolymerizing Add to (+) Fall off (-)
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Microtubules Control growth by controlling rates of assembly & disassembly because these are distinct processes can be controlled independently! Colchicine makes MTs disassemble Taxol prevents disassembly
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Microtubules Control growth by controlling rates of assembly & disassembly Are constantly rearranging inside plant cells!
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Microtubules Control growth by controlling rates of assembly & disassembly Are constantly rearranging inside plant cells! during mitosis & cytokinesis
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Microtubules Control growth by controlling rates of assembly & disassembly Are constantly rearranging inside plant cells! during mitosis & cytokinesis Guide formation of cell plate & of walls in interphase
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µT Assembly µTs always emerge from Microtubule-Organizing Centers (MTOC)
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µT Assembly µTs always emerge from Microtubule-Organizing Centers (MTOC) patches of material at outer nuclear envelope
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Microtubules MAPs (Microtubule Associated Proteins) may: stabilize tubules alter rates of assembly/disassembly crosslink adjacent tubules link cargo
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2 classes of molecular motors
1) Kinesins move cargo to µT plus end 2) Dyneins move cargo to minus end “Walk” hand-over-hand towards chosen end
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µT functions Give cells shape by guiding cellulose synth
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µT functions Give cells shape by guiding cellulose synth Anchor organelles
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µT functions Give cells shape by guiding cellulose synth Anchor organelles Intracellular motility
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