CHEMICAL COORDINATION IN
PLANTS-page247-255
Objectives
●.
● DEFINE TROPISMS
● Explain how AUXINS control tropisms
● Discuss how shoots respond to gravity
Sensitivity – Responding to the
environment
WHAT IS TROPISM ?
It is a growth response by a plant,
toward or away from a stimulus.
TROPISMS
● The response to ___________ is called PHOTOTROPISM
● ______________ is the response to the earth’s gravity
● The response to _________________ is called HYDROTROPISM
COPY AND COMPLETE
● SHOOTS GROW TOWARDS
______________, SO THEY SHOW
POSITIVE __________________.
● SHOOTS GROW AWAY FROM ________________ SO THEY
SHOW__________________
AUXINS
● Are produced in stem tips and root tips● In special tissues called meristematic tissues
● How do auxins work?
AUXINS ARE
CONCENTRATED AT
THE TIP OF THE
SHOOT IN THE
APICAL BUD
WHEN LIGHT IS SHONE
FROM ONE DIRECTION
(UNILATERAL LIGHT)
AUXINS MOVE TO THE
SHADED/DARK SIDE
THIS UNEQUAL
DISTRIBUTION OF AUXINS
CAUSES THE CELLS ON THE
SHADED SIDE TO DIVIDE
RAPIDLY AND THE UNEVEN
GROWTH CAUSES THE TIP
TO BEND OVER