Plant Responses/Behavior Cell division, germination, cell differentiation, flowering, fruit ripening, root growth, branching, etc

Tropisms Growth response toward (+) or away from (-) a stimulus Growth response toward (+) or away from (-) a stimulus

Phototropism Response to light Response to light Shoots (stems) + phototropism Shoots (stems) + phototropism Roots – phototropism Roots – phototropismGravitropism Response to gravity Response to gravity Shoots (stems) – gravitropism Shoots (stems) – gravitropism Roots + gravitropism Roots + gravitropismThigmotropism Response to touch Response to touch

Other Responses Apical dominance Apical bud/shoot represses lateral growth Apical bud/shoot represses lateral growth Photoperiodism Photoperiodism Plants detect & respond to periods of darkness Plants detect & respond to periods of darkness Abscission Abscission Aging of leaves Aging of leaves Circadian rhythms Circadian rhythms Cycles of daily behaviors Cycles of daily behaviors Controlled by endogenous clocks Controlled by endogenous clocks Sleep movements Sleep movements

Need specific amt of uninterrupted Darkness, MORE than critical night length (varies) Need specific amt of uninterrupted darkness SHORTER than critical night length

So what makes plants behave the way they do? HORMONES!!!! Chemical signals produced in one part of an organisms that influence another Chemical signals produced in one part of an organisms that influence another Triggers a response at the cellular level, relies on specific hormone receptor binding Triggers a response at the cellular level, relies on specific hormone receptor binding Effective at extremely small concentrations Effective at extremely small concentrations Overall behavior/growth is a result of a combo of all hormones Overall behavior/growth is a result of a combo of all hormones

Experimenting w/ Hormones Conclusions: Darwin-chemical in tip, light required Boysen-Jenson-signal is mobile,passed thru agar

Went Experiments: Chemical is produced in tip, Concentrates on dark side, Causes elongation of cells

The answer is….. AUXIN

Mechanism of Auxin

Stimulatory Hormones Auxins Auxins Elongation of cells in developing shoots Elongation of cells in developing shoots Induces cell division in vascular cambium Induces cell division in vascular cambium Promotes fruit growth Promotes fruit growth Responsible for photo & gravi tropisms Responsible for photo & gravi tropisms

Stimulatory cont…. Cytokinins Cytokinins Produced in actively dividing tissues(germinating seeds, fruits, roots) Produced in actively dividing tissues(germinating seeds, fruits, roots) Delay senescence Delay senescence Controls differentiation (w/ auxin) Controls differentiation (w/ auxin)

More stimulation… Gibberellins Produced in roots, stimulate stem & leaf growth Promote fruit development (W/ auxin) Stimulate germination (if environmental conditions are right)

Inhibitory Hormones Abscisic acid Abscisic acid Prepares for dormancy by inhibiting vascular cambium & slowing bud growth Prepares for dormancy by inhibiting vascular cambium & slowing bud growth Keeps seeds dormant Keeps seeds dormant Produced during water stress (causes guard cells to lose water, closing stomata) Produced during water stress (causes guard cells to lose water, closing stomata)

Inhibitory continued… Ethylene Ethylene Only gaseous hormone Only gaseous hormone Inhibits cell growth & elongation in all plant organs Inhibits cell growth & elongation in all plant organs Causes senescence Causes senescence Fruit ripening-degrades cell walls, reduces chlorophyll Fruit ripening-degrades cell walls, reduces chlorophyll Leaf abscission- degrades cell wall between stem & petiole Leaf abscission- degrades cell wall between stem & petiole

Even more plant behaviors (and you thought they were boring!) O2 deprivation O2 deprivation Release of ethylene from roots, holes form Release of ethylene from roots, holes form High salt High salt Produce extra solutes Produce extra solutes Heat Heat Heat shock proteins bind to enzymes & prevent denaturing Heat shock proteins bind to enzymes & prevent denaturing Cold Cold Synthesize more unsaturated FAs Synthesize more unsaturated FAs Herbivores Herbivores Pathogens Pathogens Anti-microbial compounds, alarm chemicals, PR genes Anti-microbial compounds, alarm chemicals, PR genes