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Plant growth and developmentg p
GrowthGrowthIrreversible increase in size, results from cell division and cell enlargement
MorphogenesisDevelopment of formp
DevelopmentSum of all of the changes that PROGRESSIVELY elaborate an organism’s body
Nutritional requirements q
CO2CO2Mineral nutrients- essential chemical elements absorbed from the soil in the form of inorganic ionsabsorbed from the soil in the form of inorganic ions
H20*mineralsminerals
Essential nutrients
Required for a plant to grow from a seed and Required for a plant to grow from a seed and complete the life cycleNo other elem can replace itNo other elem can replace itIt has a direct or indirect action in plt metab17 essential nutrients17 essential nutrients
Macronutrients - 9Micronutrients – 8Micronutrients – 8
e
Macronutrients
Required in large amountsProduces the body of the plantCarrying out essential physiological processes9 macronutrients (CHONPSKCaMg)9 macronutrients (CHONPSKCaMg)1. CARBON 2. HYDROGEN 3. OXYGEN 4. NITROGEN5. PHOSPHORUS6. SULFUR7. POTASSIUM8. CALCIUM9. MAGNESIUM
1 CARBON - CO21. CARBON CO2
2. HYDROGEN - H2O3 OXYGEN CO3. OXYGEN - CO2
CHOj f l ’ i d-major component of plant’s organic compounds
ELEMENT FORM AVAILABLE IN PLANTS
MAJOR FUNCTIONS
Nitrogen NO3- , NH4
+ Component of nucleic acids, proteins, hormones, and coenzymes
Sulfur SO4-2 Component of proteins, coenzymes
Phosphorus H2PO4-, HPO4
2- Component of nucleic acid, phospholipids, ATP, Phosphorus H2PO4 , HPO4 Component of nucleic acid, phospholipids, ATP, several coenzymes
Potassium K+ Cofactor that functions in protein synthesis; major Potassium K Cofactor that functions in protein synthesis; major solute in water balance; operation of stomata
Calcium Ca2+ Stability of cell walls, maintaining membrane Calcium Ca Stability of cell walls, maintaining membrane structure and permeability; enzyme cofactor, regulating stimulus response
Magnesium Mg2+ Enzyme activator; component chlorophyllMagnesium Mg Enzyme activator; component chlorophyll
Micronutrients
Required in very small amountsUsually cofactors for enzymes; can be recycled 8 micronutrients
I1. Iron2. Chlorine3. Copper4. Manganese5. Zinc6 Molybdenum6. Molybdenum7. Boron 8. Nickel
ELEMENT AVAILABLE FORM IN PLANTS
MAJOR FUNCTIONS
Chlorine Cl- Essential in water splitting; water balanceC o e C sse a wa e sp g; wa e ba a ce
Iron Fe 3+; Fe 2+ Activator of some enzymes; form parts of h d f hl h ll cytochromes and nitrogenase; for chlorophyll
synthesis
Boron H2BO3- For chlorophyll synthesis; may be involved in nucleic acid synthesis CHO transport and membrane acid synthesis, CHO transport and membrane integrity
Manganese Mn2+ Activator of some enzymes; active in the formation of amino acids’ required in water splitting; integrity of amino acids required in water splitting; integrity of chloroplast membrane
Zinc Zn2+ Activator of some enzymes; formation of chlorophyll
Copper Cu2+, Cu+ Activator of some enzymes involved in redoxreactions; component of lignin-biosynthetic enzymes
Molybdenum MoO 2- Nitrogen fixation and nitrate reductionMolybdenum MoO42 Nitrogen fixation and nitrate reduction
Nickel Ni2+ Cofactor for an enzyme that functions in nitrogen metabolism
Mineral Deficiencyy
1. Function1. FunctionChlorosis- yellowing of leaves
Deficiency in Mg or FeDeficiency in Mg or Fe
2. MobilityMg highly mobileMg- highly mobile
Symptoms of deficiency show up 1st in older organs
F i bilFe- immobileSymptoms of deficiency show up in younger organs
Assignment g
Make a list of deficiency symptoms of essential Make a list of deficiency symptoms of essential elements
The role of soil bacteria in nitrogen t itinutrition
Plant hormones coordinate growth, development and responses to stimuliresponses to stimuli
HormoneHormoneGreek word “to excite”A small molecule that carries information from the A small molecule that carries information from the cell where it was produced to a particular target cells, causing a change in response to internal needs cells, causing a change in response to internal needs or external stimuliMinute concentrations are requiredMinute concentrations are requiredReaction to hormone: not on amounts but on relative concentration compared to other hormonesconcentration compared to other hormones
Signal-transduction pathwayg p y
Auxin
Major site: shoot apical meristemCan be found also in embryo of seed young leavesCan be found also in embryo of seed, young leavesMovement: Polar transport: unidirectionalNatural auxin: Indoleacetic acid (IAA)Na u a au : do eace c ac d ( )Higher conc inhibit cell elongation (due to synthesis of ethylene- inhibitor of plant growth)Synthetic auxins:
Naphthaleneacetic acid (NAA)2 4 di hl h ti id (2 4 D) h bi id2,4-dichlorophenoxyacetic acid (2,4 D)- herbicide
Agent Orange
Auxin
Major function: Major function: cell elongationroot growth (adventitious roots)root growth (adventitious roots)differentiation and branchingFruit development (seeds synthesize auxin)p ( y )Apical dominancePhototropism and gravitropismp g p
Acid growth hypothesisg yp
Cytokininy
Stimulate cytokinesis or cell divisionStimulate cytokinesis or cell divisionDiscovered from coconut milk
Cytokininy
Sites: growing tissues in roots, embryos and fruitsSites: growing tissues in roots, embryos and fruitsMajor functions
Cell division and differentiationCell division and differentiationCounteracting apical dominanceDelaying aging of leavesDelaying aging of leaves
Role of cytokinin and auxiny
Gibberellins
Cell elongation and seed germinationDerived its name from Gibberella, a fungusSite: apical meristems; young leaves and embryos
bolting
Gibberellins
Major functions:Stem elongation
GA – facilitate movement of expansins into correct position in cell wallin cell wall
Reverse dwarfismSeed germinationg
Stimulate production of alpha-amylaseJuvenility Promotes flowering
Biennials flower in their first yearF i f i i i f f iFruit formation -- increases size of fruits
Abscisic Acid
Terpenoid hormoneTerpenoid hormoneSites: leaves, stems, roots and green fruitSlows growthSlows growth
seed dormancyDormant buds inhibits cell division of vascular cambiumDormant buds, inhibits cell division of vascular cambium
Stress hormonesCloses stomataCloses stomataWater shortage can stress the root system production of ABA transported to leavesproduction of ABA transported to leaves
Ethyleney
Gaseous form Gaseous form Initiated by high concentrations of AUXINripening fruits nodes of stems senescent leaves and ripening fruits, nodes of stems, senescent leaves and flowers
Ethyleney
Major functionsMajor functionsRepresses growth in length while stimulating expansion in widthexpansion in widthEthylene production: stimulated by touch, wind or any damageany damageGrowth maneuver: triple response1 Slowing of stem or root elongation1. Slowing of stem or root elongation2. Thickening of root or stem3. Curving to grow horizontally3. Curving to grow horizontally
Ethyleney
Major functions:Major functions:Abscission of leavesSenescence/ agingSenescence/ aging
Progression of irreversible change that eventually leads to deathto deathRelated to fruit ripening and leaf abscission
Fruit ripeningFruit ripeningChlorophyll degradationSoftening of fruitSoftening of fruit
Brassinosteroids
Newly discoveredySteroid First discovered in Brassica, which includes cabbageBind to receptor protein the plasma membraneAct like auxin
Stimulate cell division and elongation in stemsCause differentiation of xylem cellsPollen tube growthPollen tube growth
Slow root growthDelay leaf abscissionDelay leaf abscission
Additional phytohormonesp y
PolyaminesyCell division and synthesis of DNA, RNA, and proteinsRoot initiation and tuber formationDevelopment of embryos, flowers and fruit
Jasmonic acidFatty acidInhibits growth of seeds, pollen and rootsP t l ti f t i i dPromotes accumulation of proteins in seedsStimulates formation of flower, fruit and seedPlant defensePlant defense
Growth responsesI T iI. Tropisms
Growth response that result in curvature of plant OWA AWA forgans TOWARD or AWAY from stimuli
Negative and positive tropismhA. Phototropism
B. Gravitropism Th C. Thigmotropism
D. HeliotropismH d iE. Hydrotropism
F. Chemotropism
A. Phototropism - light p g
Influenced by IAA Influenced by IAA Movement of auxin to darker sidedarker sideEnsures that leaves & stem will intercept light stem will intercept light for photosyn
B. Gravitropismitgravity
Controlled by Ca & yIAA Results in stems growing up while roots grow downEnsures that roots will encounter water & minerals
C. Thigmotropism – touch g p
Involves ethyleneyRelease of ethylene inhibits growth on gthe side that touches an objectAllows plts to climb obj. inc. plts chances of intercepting light for photosyn
Growth responsesII N ti tII. Nastic movements
direction of response independent of direction of direction of response independent of direction of stimulusSeismonasty – a nastic movement resulting fr contact Seismonasty a nastic movement resulting fr contact or mech disturbances such as shaking
Growth responsesII N ti tII. Nastic movements
SeismonastySeismonasty
Nyctinasty- sleeping movementsnastic response caused daily rhythms of light & dark
Growth responsesIII Ph t i diIII. Photoperiodism
Photoperiod- relative lengths of night and dayPhotoperiod relative lengths of night and dayResponse to changes in the photoperiodDetected by phytochrome and cryptochromesDetected by phytochrome and cryptochromes
Short day plants- poinsettiasLong day plants cloverLong day plants- cloverDay neutral plants- corn, impatiens