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