Orientation responses in plants Flashcards
(40 cards)
What is the difference between tropism and nastic responses?
Tropisms are directional responses to a directional external stimuli.
Nastic responses are non-directional responses to the intensity of a stimuli.
What is the difference between a positive and negative tropism?
If tropisms grow towards the stimuli it’s positive, if it grows away its negative.
What are the possible stimuli that plants respond to?
Light stimuli - Phototropism Chemical stimuli - Chemotropism Gravity stimuli - Gravitotropism Water stimuli - Hydrotropism Temperature stimuli - Thermotropism Touch stimuli - Thigmotropism
What is the definition of a hormone?
Hormones are molecules that are often produced in one location and do things in another.
What is auxin?
Auxin is a plant hormone which is produced in the tip of plant shoots and causes cells to grow larger than normal.
What is the role of auxin in phototropisms?
The auxin hormone causes the plant to bend and grow towards light stimuli. When the plant is exposed to light the auxin spreads to the darker side which therefore elongates the plant towards the light.
What is the role of auxin in gravitropisms?
The auxin moves to the lower sides of the roots due to gravity, the loss of this auxin at the higher end of the plant causes the roots to grow downwards.
What is Abscisic Acid?
A plant hormone. It functions in many plant development processes, particularly bud dormancy.
What is Abscission?
The process whereby a plant sheds parts, particularly leaves, fruit and seeds/pods when their loss is beneficial to the plant.
What is Autotroph?
An organism that is able to produce complex organic molecules from simpler molecules found in its environment, using an external energy source
What is cytokinin?
A group of hormones that promote cell division in plant roots and shoots and the growth of buds.
What is ethylene?
A plant hormone that promotes the ripening of fruit.
What are Gibberellins?
Plant hormones that regulate growth and influence various developmental processes, including germination, dormancy and flowering.
What is a Nyctinasty?
A circadian rhythmic movement of plants in response to the onset of darkness (Eg the closing of the petals of a flower at dusk)
What is the photoperiod?
The period of time each day in which an organism receives sunlight.
What is Photoperiodism?
The response of an organism to seasonal changes in the photoperiod.
What is Photosynthesis?
The process by which plants and some bacteria use the energy from sunlight to produce glucose from carbon dioxide and water.
What is the phytohormone
Any of a range of chemicals that regulate plant growth.
What are the 2 primary ways in which plants can respond to stimuli?
Growth movements (Tropisms = long term slow) and Turgor movements (Nastic responses = reversible more rapid)
Define the phrase “Primary plant growth”
Growth by cell division and elongation and the early stages of differentiation before tissues become woody (Lignified)
What are the cells in the tips of shoots and roots of the plant called?
Apical Meristematic cells.
How do the Apical Meristematic cells differ from other types of plant cells?
These cells are undifferentiated - They have no specific function, they are still generalised cells that can develop into one of many cell types
What happens in the zone of cell division?
Cells multiply by the process of mitosis.
What happens in the zone of cell elongation?
Cells grow in both width and length as water fills the vacuole and the elastic cell stretches.
