Life 103 Week 8
Life 103 Week 8 LIFE 103
Popular in Biology of Organisms-Animals and Plants
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This 2 page Class Notes was uploaded by Caroline Hurlbut on Friday March 11, 2016. The Class Notes belongs to LIFE 103 at Colorado State University taught by Jennifer L Neuwald; Tanya Anne Dewey in Fall 2016. Since its upload, it has received 24 views. For similar materials see Biology of Organisms-Animals and Plants in Biology at Colorado State University.
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Date Created: 03/11/16
Plant Responses to Signals • stages of cell signal processing —reception: internal/external signals detected by receptors —transduction: second messengers transfer and amplify signals from receptors to proteins, changing their shape —response: signal transduction pathway—>regulation of cellular activities • plant hormones - chemical signals that modify or control physiological processes —help coordinate growth, development, and responses to stimuli —produced in low concentrations —can alter gene expression, enzyme activity, and membrane properties • examples of plant hormones —auxins: promote elongation of shoots —cytokinins: stimulate cytokinesis, control of cell division and apical dominance (if apical bud is removed, plants become bushier) —gibberellins: stem elongation (bolting) and seed germination —ethylene: gas produced in response to mechanical stress (triple response), involved in fruit ripening A. fruit producers can control ripening by controlling ethylene levels in green fruit • responses to light are critical for plant success —light can provide info about growth opportunity and time of day/year —phytochromes: pigments that regulate responses to light A. seed germination B. shade avoidance - shaded plant induced to grow vertically • circadian rhythms - 24 hour cycles governed by internal clock and set by day/night cycle photoperiodism • —short day plants: plants that ﬂower when day is shorter than critical length —long day plants: plants that ﬂower when a day is longer than critical length —responses to photoperiod controlled by night length • plants respond to different stimuli —gravitropism: response to gravity, can be positive (roots grow down) or negative (shoots grow up) —thigmotropism: growth in response to touch • environmental stresses —drought: plants reduce water loss by closing stomata —ﬂooding: air tubes to survive oxygen deprivation —heat: synthesis of heat shock proteins —cold: synthesis of antifreeze proteins and adjustment of membrane ﬂuidity • responses to pathogens —epidermis and periderm barrier is ﬁrst line of defense —pathogens can enter through wounds or stomata • immune responses of plants —effector triggered immunity results from the action of hundreds of disease resistant (R) genes —these defenses include hypersensitive response and systemic acquired resistance —hypersensitive response causes cell and tissue death (changes in cell wall conﬁne pathogen) —systemic acquired resistance causes expression of defense genes and is a long lasting response • defenses against herbivores —physical: thorns and trichomes —chemical: distasteful or toxic compounds
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