4.5.4.1 Control and coordination Flashcards
What is a tropism?
A tropism is the response of a plant to a
specific stimulus.
What is phototropism?
Phototropism is the response of a plant’s
shoot or root to light.
What is gravitropism?
Gravitropism is the response of a plant’s
shoot or root to gravity.
What is auxin?
Auxin is a hormone which controls the
growth of a plant’s shoots and roots. When
auxin is unevenly distributed in a growing
plant, the rate of growth will also be unequal.
How do plant shoots show positive
phototropism?
● One side of the shoot is in the light, causing auxin to move to the shaded side.
● At the shaded side, the cells are stimulated to grow - the shoot bends towards the light.
● As a result, photosynthesis can occur at a faster rate.
How do plant shoots show negative
gravitropism?
● In a horizontal shoot, auxin accumulates in the
lower side due to gravity.
● Cells on the lower side of shoot grow more, causing the shoot to bend away from the direction of gravity.
● As a result, more light is usually available for
photosynthesis.
How do plant roots show positive
gravitropism?
● In a horizontal root, auxin accumulates in the
lower side, causing cells to grow less.
● The root bends in the direction of gravity
● As a result, more water and nutrients are
available to the plant roots
What are gibberellins?
Gibberellins are a type of plant hormone
involved in seed germination.
What is ethene?
Ethene is a type of plant hormone
involved in cell division and ripening
What are the uses of auxins?
● Weedkillers - auxin causes cells to grow at a
rapid rate, causing plant death.
● Rooting powder - auxin causes new plant to
grow very quickly.
● Tissue culture - auxin promotes growth of
roots and shoots.
What are the uses of ethene?
● Control of food ripening in the food industry -
allows fruit to be ripened just before they are
sold.
