3/29/2011
3/26/2011
(2.81) Describe positive phototropism of stems
· Positive phototropism is towards the light
· A plant that receives uniformed light from above will grow upwards
· A plant will bend in the growth towards the light if it is a lateral light source
· Auxin (plant hormone) goes away from the light and therefore causes more growth on the area away from the light
(2.80) Describe the geotropic responses of roots and stems
· The embryonic roots in a seed grow downwards- positive geotropism
· The embryonic shoot will grow upwards- negative geotropism
· When the seed is turned the shoot grows upwards- negative geotropism
· The root still grows downwards- positive geotropism
(2.79) Understand that plants respond to stimuli
· Stimuli are changes in the environment (temperature, light changes)
· Plants receptors detect the stimuli and turn it into a response
· The responses take the form of growth
· Growth in response to stimuli is called tropism
o Tropism that involve light are called phototropism
o Tropism that involve gravity are called geotropism
· The connection between the receptor and the response usually takes the form of plant hormones sometimes know as plant growth regulators
3/20/2011
(2.54) Transpiration-
· Evaporation of water from surface of plant
o Heat is provided by sunlight as it is absorbed by the leaf structure
o Liquid is changed to gas right above the stomatal pore
o Evaporation is through the stomatal pores
o Gas diffuses through the pore (steep diffusion gradient)
3/15/2011
2.53- Uptake of water
·
· Water is absorbed by root hair cells
o Branching pattern helps absorb H2O
o increasing surface area for absorption of water
o There are hairs at the end of the branches in roots
o Water goes into the cell via osmosis
o Minerals go into the cell via active transport
o cell wall extends outward
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