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Table of Contents
Plant hormones
- There are five general classes of hormones: auxins, cytokinins, gibberellins, ethylene, and abscisic acid.
Phototropism
- movement in response to light.
- shoots grow toward light and are positively phototropic; roots grow away from light and are negatively phototropic.
- IAA increase in shaded side → plant curve toward light
- wavelengths less than 500μm—is most effective in producing a growth response.
Gravitropism
- response to gravity
Thigmotropism
- reaction to a solid object
- eg. tendrils of climbing plants wrapping around a support
- IAA (lengthening) and ethylene (contracting) are probably involved