8.1 Flashcards
What are plant responses to stimuli known as?
Tropisms
What is the definition of growth?
A permanent increase in the size of an organism or some part of it
What are the three stages of growth in plants?
Division, assimilation and elongation
What occurs during elongation?
Vacuoles develop, the cell wall stretches and a large central vacuole is produced, elongating the cell
What does chlorophyll formation depend on?
Light and day length
What type of light is most effective at stimulating germination?
Red light
What type of light inhibits germination?
Far red light
If seeds are exposed to a flash of red light, what will occur?
They will germinate
What is the class of pigments that cause the reaction to types of light know as?
Phytochromes
What is the wave length of Pr?
P680
What is the wavelength of Pfr?
P730
What is the factor that determines how long it takes for one pigment to be converted into another?
Light intensity
Does the conversion of Pfr to Pr take place fast or slow in the dark
Slow
Which pigment is more stable?
Pr
What is it called when plants grow rapidly in dark conditions to find light?
Etiolation
Without Pfr in dark conditions what happens to the plant?
The internodes grow but the leaves do not and chlorophyll does not form
What is the current hypothesis on Pfr ?
That it inhibits flowering
In long day plants what stimulates flowering?
The build up of Pfr
What pigment detects the photoperiod?
Florigen
What do auxins or IAA cause?
Positive phototropism
What occurs when molecules of IAA move to the site d elongation?
They bind to the receptor sites activating hydrogen pumps in the cytoplasm, leading an increased flexibility of cell walls
What six stimuli are plants sensitive to?
Light gravity water temp touch chemicals
