5.4 Homeostasis and Response (plant hormones) Flashcards
What is a tropism?
The response of a plant to a specific stimulus
What is phototropism?
The response of a plant’s shoot or root to light
What is a shoot?
The tip of a plant
What is gravitropism or geotropism?
The response of a plant’s shoot or root to gravity
What is auxin?
A hormone which controls the growth of a plant’s shoots and roots.
What happens 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, causing the shoot to bend 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 the shoot grow more, causing the shoot to bend away from the direction of gravity
- As a result, more light is usually available for photosynthesis
What is positive phototropism?
when the shoot bends towards the light
What is negative phototropism?
when the shoot bends away from the the light, towards gravity
What is positive gravitropism?
when the shoot bends towards gravity
What is negative gravitropism?
when the shoot goes upwards against gravity
How are phototropism and gravitropism linked?
+ phototropism = - gravitropism
- phototropism = + gravitropism
How do plants 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?
A type of plant hormone involved in seed germination
What is ethene?
A type of plant hormone involved in cell division and ripening
What is seed germination?
when a seed turns into a flower
What are the uses of auxins?
- weedkillers
- rooting powder
- tissue culture
Why can auxin be used for weedkillers?
auxin causes cells to grow at a rapid rate, causing plant death
Why can auxin be used for rooting powders?
auxin causes a new plant to grow very quickly
Why can auxin be used for tissue culture?
auxin promotes the growth of roots and shoots
What is tissue culture?
the growth of tissues or cells in an artificial medium, separate from the parent organism
What are the uses of ethene?
- control of fruit ripening in the food industry, allows fruit to be ripened just before they are sold
What are the uses of gibberlins?
- termination of seed dormancy
- promotion of flowering
- increase of fruit size
