presentation 18 - plant hormones
DESCRIPTION
TRANSCRIPT
Plant hormones
HormonesHormones
• from Gr. to excite • natural chemical
messengers transported to target cells
• minute concentrations = substantial change
• growth regulators
Plants respond to stimuliPlants respond to stimuli
Plant hormones coordinate growth, Plant hormones coordinate growth, development and responses to stimulidevelopment and responses to stimuli
Tropisms
• growth responses
• organs curve towards (+) or away from (-) a stimulus
• ex. phototropism, thigmotropism, gravitropism
Studies on phototropismStudies on phototropism
• towards or away from light
• differential growth of cells on opposite sides of a shoot or coleoptile
• cells on darker side elongate faster than those on the light side
• experiments by Darwin and son and FW Went
• due to auxin distributions
Went experiment