Water uptake Path starts at root hairs Must take water from soil Ease depends on availability & how tightly it is bound Binding depends on particle size & chem Water uptake Availability depends on amount in soil pores Saturation: completely full Field capacity: amount left after gravity has drained excess Permanent wilting point: amount where soil water potential is too negative for plants to take it up Plant Stress Water? Nutrients? Environment? Temp? Pollution? Ozone, other gases? Herbicides, eg Round-Up, Atrazine? Insects and other herbivores? Pathogens = bacteria, viruses, fungi Salinity Plant Stress Next assignment: presenting a plant stressor, what is known about it, and why it might affect plant 2 compounds in an ~ 10 minute presentation? Alternative: presenting another good plant/stressor response to study and why we should choose it over the ones already presented. Mineral Nutrition Nutrients in soil Plants alter roots to aid uptake Also use symbionts Mycorrhizal fungi help: especially with P Some plants form symbioses with N-fixing prok. Nutrient uptake Most nutrients are dissolved in water Enter root through apoplast until hit endodermis Then must cross plasma membrane Nutrient uptake Then must cross plasma membrane Gases, small uncharged & non-polar molecules diffuse down their [ ] Important for CO2, auxin & NH3 transport Selective Transport 1) Channels integral membrane proteins with pore that specific ions diffuse through Selective Transport 1) Channels 2) Facilitated Diffusion (carriers) Carrier binds molecule 4 classes of Active transport ATPase proteins
1) P-type ATPases (P = phosphorylation) 2) V-type ATPases (V = vacuole) 3)F-type ATPases (F = factor) 4) ABC ATPases (ABC = ATP Binding Cassette) multidrug resistance proteins Secondary active transport
Uses [ ] created by active transport to pump something else across a membrane against its [ ] Nutrient uptake Gases enter/exit by diffusion down their [ ] Ions vary dramatically! Nutrient uptake Gases enter/exit by diffusion down their [ ] Ions vary dramatically! H+ is actively pumped out of cell by P-type H+ -ATPase Nutrient uptake Ions vary dramatically! H+ is actively pumped out of cell by P-type H+ -ATPase and into vacuole by V-type ATPase & PPase Nutrient uptake H+ is actively pumped out of cell by P-type H+ -ATPase and into vacuole by V-type ATPase & PPase Main way plants make membrane potential (Em)! Nutrient uptake H+ is actively pumped out of cell by P-type H+ -ATPase and into vacuole by V-type ATPase & PPase Main way plants make membrane potential (Em)! Used for many kinds of transport! Nutrient uptake Many ions are imported by multiple transporters with varying affinities Nutrient uptake Many ions are imported by multiple transporters with varying affinities K+ diffuses through channels down Em: low affinity Nutrient uptake Many ions are imported by multiple transporters with varying affinities K+ diffuses through channels down Em: low affinity Also taken up by H+ symporters : high affinity Nutrient uptake Many ions are imported by multiple transporters with varying affinities K+ diffuses through channels down Em: low affinity Also taken up by H+ symporters : high affinity Low affinity is cheaper but less effective Nutrient uptake K+ diffuses through channels down Em: low affinity Also taken up by H+ symporters : high affinity Low affinity is cheaper but less effective some channels also transport Na+ Nutrient uptake K+ diffuses through channels down Em: low affinity Also taken up by H+ symporters : high affinity Low affinity is cheaper but less effective some channels also transport Na+ why Na+ slows K+ uptake? Nutrient uptake K+ diffuses through channels down Em: low affinity Also taken up by H+ symporters : high affinity Low affinity is cheaper but less effective some channels also transport Na+ why Na+ slows K+ uptake? Na+ is also expelled by H+ antiport Nutrient uptake Na+ is also expelled by H+ antiport Enters through channels Ca2+ is expelled by P-type ATPases in PM Nutrient uptake Ca2+ is expelled by P-type ATPases in PM & pumped into vacuole & ER by H+ antiport & P-type Nutrient uptake Ca2+ is expelled by P-type ATPases in PM pumped into vacuole & ER by H+ antiport & P-type enters cytosol via gated channels Nutrient uptake PO43-, SO42-, Cl- & NO3- enter by H+ symport Nutrient uptake PO43-, SO42-, Cl- & NO3- enter by H+ symport also have anion transporters of ABC type Nutrient uptake PO43-, SO42-, Cl- & NO3- enter by H+ symport also have anion transporters of ABC type and anion channels Nutrient uptake PO43-, SO42-, Cl- & NO3- enter by H+ symport also have anion transporters of ABC type and anion channels Plants take up N many ways Nutrient uptake Plants take up N many ways:NO3-& NH4+are main forms Nutrient uptake Plants take up N many other ways NO3- also by channels NH3 by diffusion NH4+ by carriers Nutrient uptake Plants take up N many other ways NO3- by channels NH3 by diffusion NH4+ by carriers NH4+ by channels Nutrient uptake Plants take up N many other ways 3 families of H+ symporters take up amino acids Nutrient uptake Plants take up N many other ways 3 families of H+ symporters take up amino acids Also have many peptide transporters some take up di- & tri- peptides by H+ symport Nutrient uptake Plants take up N many other ways 3 families of H+ symporters take up amino acids Also have many peptide transporters some take up di- & tri- peptides by H+ symport others take up tetra- & penta-peptides by H+ symport Nutrient uptake Plants take up N many other ways 3 families of H+ symporters take up amino acids Also have many peptide transporters some take up di- & tri- peptides by H+ symport others take up tetra- & penta-peptides by H+ symport Also have ABC transporters that import peptides Nutrient uptake Plants take up N many other ways 3 families of H+ symporters take up amino acids Also have many peptide transporters some take up di- & tri- peptides by H+ symport others take up tetra- & penta-peptides by H+ symport Also have ABC transporters that import peptides N is vital! NO3-& NH4+are main forms Nutrient uptake Metals are taken up by ZIP proteins & by ABC transporters same protein may import Fe, Zn & Mn! Nutrient uptake Much is coupled to pH gradient Nutrient transport in roots
Move from soil to endodermis in apoplast Nutrient transport in roots
Move from soil to endodermis in apoplast Move from endodermis to xylem in symplast Nutrient transport in roots
Move from endodermis to xylem in symplast Transported into xylem by H+ antiporters Nutrient transport in roots
Move from endodermis to xylem in symplast Transported into xylem by H+ antiporters, channels Nutrient transport in roots
Transported into xylem by H+ antiporters, channels,pumps Nutrient transport in roots
Transported into xylem by H+ antiporters, channels,pumps Lowers xylem water potential-> root pressure Water Transport Passes water & nutrients to xylem Ysof xylem makes root pressure Causes guttation: pumping water into shoot Transport to shoot Nutrients move up plant in xylem sap Nutrient transport in leaves
Xylem sap moves through apoplast Leaf cells take up what they want Nutrient assimilation
Assimilating N and S is very expensive! Reducing NO3- to NH4+ costs 8 e- (1 NADPH + 6 Fd) Nutrient assimilation
Assimilating N and S is very expensive! Reducing NO3- to NH4+ costs 8 e- (1 NADPH + 6 Fd) Assimilating NH4+ into amino acids also costs ATP + e- Nutrient assimilation
Assimilating N and S is very expensive! Reducing NO3- to NH4+ costs 8 e- (1 NADPH + 6 Fd) Assimilating NH4+ into amino acids also costs ATP + e- Nitrogen fixation costs 16 ATP + 8 e- Nutrient assimilation
Assimilating N and S is very expensive! Reducing NO3- to NH4+ costs 8 e- (1 NADPH + 6 Fd) Assimilating NH4+ into amino acids also costs ATP + e- Nitrogen fixation costs 16 ATP + 8 e- SO42- reduction to S2- costs 8 e- + 2ATP Nutrient assimilation
Assimilating N and S is very expensive! Reducing NO3- to NH4+ costs 8 e- (1 NADPH + 6 Fd) Assimilating NH4+ into amino acids also costs ATP + e- Nitrogen fixation costs 16 ATP + 8 e- SO42- reduction to S2- costs 8 e- + 2ATP S2-assimilation into Cysteine costs 2 more e- Most explosives are based on N or S! Nutrient assimilation
Most explosives are based on N or S! Most nutrient assimilation occurs in source leaves! N cycle Must convert N2 to a form that can be assimilated N2 -> NO3-occurs in atmosphere: lightning (8%) & Photochemistry (2%) of annual total fixed Remaining 90% comes from biological fixation to NH4+ N cycle Soil bacteria denitrify NO3-& NH4+back to N2 Plants must act fast! Take up NO3-& NH4+but generally prefer NO3- Main form available due to bacteria N assimilation by non-N fixers
Nitrate reductase in cytoplasm reduces NO3-to NO2- NO3-+ NADPH =NO2-+ NADP+ large enzyme with FAD & Mo cofactors NO2- is imported to plastids & reduced to NH4+ by nitrite reductase N assimilation by non-N fixers
NO2- is imported to plastids & reduced to NH4+ by nitrite reductase NO Fdred + 8 H+ = NH Fdox + 2 H2O 0.2% of NO2- is released as N2O : another reason rape & corn biofuels increase global warming N assimilation by non-N fixers
NO2- is imported to plastids & reduced to NH4+ by nitrite reductase NO Fdred + 8 H+ = NH Fdox + 2 H2O 0.2% of NO2- is released as N2O : another reason rape & corn biofuels increase global warming Regulated at NO3- reductase; always GOGAT Glutamate + NH4+ + ATP Glutamine + ADP +Pi Glutamine + a-ketoglutarate + NADH/2 Fdred 2 Glutamate + NAD+/ 2 Fdox 3. Fd GOGAT lives in source cp GS -> GOGAT Fd GOGAT lives in source cp NADH GOGAT lives in sinks GS -> GOGAT Glutamate + NH4+ + ATP Glutamine + ADP +Pi Glutamine + a-ketoglutarate + NADH/2 Fdred 2 Glutamate + NAD+/ 2 Fdox 3. Use glutamate to make other a.a. by transamination GS -> GOGAT 3. Use glutamate to make other a.a. by transamination Glutamate, aspartate & alanine can be converted to the other a.a. S assimilation SO42- comes from weathering or from rain: now an important source!Main thing that makes rain acid! S assimilation S is used in cysteine & methionine S assimilation S is used in cysteine & methionine Also used in CoA, S-adenosylmethionine S assimilation S is used in cysteine & methionine Also used in CoA, S-adenosylmethionine Also used in sulphoquinovosyl-diacylglycerol S assimilation S is used in cysteine & methionine Also used in CoA, S-adenosylmethionine Also used in sulphoquinovosyl-diacylglycerol And in many storage compounds: eg allicin (garlic) S assimilation SO42- comes from weathering or from rain: now an important source!Main thing that makes rain acid! Some bacteria use SO42-as e- acceptor -> H2S S assimilation SO42- comes from weathering or from rain: now an important source!Main thing that makes rain acid! Some bacteria use SO42-as e- acceptor -> H2S Some photosynthetic bacteria use reduced S as e- donor! S assimilation SO42- comes from weathering or from rain: now an important source!Main thing that makes rain acid! Some bacteria use SO42-as e- acceptor -> H2S Some photosynthetic bacteria use reduced S as e- donor! Now that acid rain has declined in N. Europe Brassica & wheat need S in many places S assimilation SO4 2- is taken up by roots & transported to leaves in xylem Most is reduced in cp S assimilation SO4 2- is taken up by roots & transported to leaves in xylem Most is reduced in cp 1.add SO4 2- to ATP -> APS S assimilation add SO4 2- to ATP -> APS Transfer S to Glutathione -> S-sulfoglutathione S assimilation add SO4 2- to ATP -> APS Transfer S to Glutathione -> S-sulfoglutathione S-sulfoglutathione + GSH -> SO32- + GSSG S assimilation add SO4 2- to ATP -> APS Transfer S to Glutathione -> S-sulfoglutathione S-sulfoglutathione + GSH -> SO32- + GSSG Sulfite + 6 Fd -> Sulfide S assimilation add SO4 2- to ATP -> APS Transfer S to Glutathione -> S-sulfoglutathione S-sulfoglutathione + GSH -> SO32- + GSSG Sulfite + 6 Fd -> Sulfide Sulfide + O-acetylserine -> cysteine + acetate O-acetylserine was made from serine + acetyl-CoA S assimilation Most cysteine is converted to glutathione or methionine S assimilation Most cysteine is converted to glutathione or methionine Glutathione is main form exported S assimilation Most cysteine is converted to glutathione or methionine Glutathione is main form exported Also used to make many other S-compounds S assimilation Most cysteine is converted to glutathione or methionine Glutathione is main form exported Also used to make many other S-compounds Methionine also has many uses besides protein synthesis S assimilation Most cysteine is converted to glutathione or methionine Cys + homoserine -> cystathione S assimilation Most cysteine is converted to glutathione or methionine Cys + homoserine -> cystathione Cystathione -> homocysteine + Pyruvate + NH4+ S assimilation Most cysteine is converted to glutathione or methionine Cys + homoserine -> cystathione Cystathione -> homocysteine + Pyruvate + NH4+ Homocysteine + CH2=THF -> Met + THF 80% of met is converted to S-adenosylmethionine & used for biosyntheses S assimilation Most cysteine is converted to glutathione or methionine Glutathione is made enzymatically! Glutamate + Cysteine -> g-glutamyl cysteine S assimilation Glutathione(GluCysGly) is made enzymatically! Glutamate + Cysteine -> g-glutamyl cysteine g-glutamyl cysteine + glycine -> glutathionine S assimilation Glutathione(GluCysGly) is made enzymatically! Glutamate + Cysteine -> g-glutamyl cysteine g-glutamyl cysteine + glycine -> glutathionine Glutathione is precursor for many chemicals, eg phytochelatins S assimilation Glutathione(GluCysGly) is made enzymatically! Glutamate + Cysteine -> g-glutamyl cysteine g-glutamyl cysteine + glycine -> glutathionine Glutathione is precursor for many chemicals, eg phytochelatins SAM & glutathione are also precursors for many cell wall components Assignment 1 Pick a secondary compound and figure out how to measure it Assignment 2 Design a way to see how plants are responding to the stress