Plant Structure And Growth - Mt. San Antonio College

Plant Structure And Growth - Mt. San Antonio College

Control Systems in Plants Plant Hormones Coordinates growth Coordinates development Coordinates responses to environmental stimuli Plant Hormones

Auxin (IAA) Cytokinins Gibberllins Abscisic Acid

Ethylene Oligogaccharins Brassinosteroids Auxins

Stimulates stem elongation Stimulates root growth Stimulates differentiation and branching Stimulates development of fruit Stimulates apical dominance Stimulates phototropism and gravitropism Auxin Control

Auxin stimulates growth Auxin block on right causes cells to elongate and the plant bends left Auxin block on left

causes cells to elongate the the plant bends right Polar Transport Auxin is transported from apex to shoot Cell wall is acidic

auxin ion picks up H+ diffuses across plasma membrane Cytosol is neutral

auxon loses H+ uses energy to pump out H+ to maintain pH leaves cell through carrier proteins Acid Growth Hypothesis

Proton pump stimulated by auxin which lower pH of wall Hydrogen Ion activates Enzyme Enzyme breaks hydrogen bonds in cellulose Wall takes up water and elongates Auxin Others

Promotes secondary growth by encouraging vascular cambium and secondary xylem Promotes adventitious root at the base of a cut stem Promotes fruit growth without pollination (seedless tomatoes) Cytokinins

Stimulates root growth Stimulates cell division and differentiation (with auxins) more cytokinin - shoot buds develop more auxin - roots develop

Stimulates germination Delays Senescence Gibberellins Promotes seed and bud germination Promotes stem elongation

Promotes leaf growth Stimulates flowering and fruits (with auxin) Abscisic Acid Inhibits growth (with gibberellins)

Closes stomata under water stress Permits dormancy Ethylene Promotes fruit ripening Controls Abscission (with auxin)

Oligosaccharins Triggers defense responses against pathogens Regulates growth Brassinosteroids

Required for normal growth and development Signal-Transduction Pathways A hormone binds to receptor and stimulates secondary messengers which Activates cell responses Plant Movements

Phototropism Gravitropism Thigmotropism Plant Movement Rapid Leaf Movement

drop in turgor pressure within pulvini (at joints of the leaf) sent by action potentials Sleep Movements

cells on opposite sides of pulvinus control the movement Daily and Seasonal Responses Circadian Rhythm Photoperiodism

controls flowering (short-day vs. long-day) critical night length Photoperiodic Control Flowering Hormones Experiment indicates the presence of some

type of flowering hormone Phytochromes Function as photoreceptors / red (660nm) to far red (730nm) Activates kinases (regulatory proteins) Red vs. Far Red Response

Plant Responses to Environmental Stress Water Deficit Oxygen Deprivation Salt Stress

Heat Stress Cold Stress Herbivores Water Deficit Slows Transpiration

stomata close release of abscisic acid Inhibits growth of young leaves Change leaf shape Deeper root growth Oxygen Deprivation

Aerial roots Production of air tubes Salt Stress Salt glands Compatible solutes

Heat Stress Heat-shock proteins Cold Stress Altering the lipid composition of their membranes

Changes in the solute composition of the cytosol Responses to Herbivores Produce Canavanine Recruitment of predatory

animals Defense Against Pathogens Gene-for-gene recognition Defense Against Pathogens

Hypersensitive response (HR) phytoalexins are released PR proteins are released Seal off infected area Systemic acquired resistance (SAR)

Salicylic acid released due to death of cell Activates a Signal Transduction Pathway Activates SAR

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