Flowering Flashcards
Why do flowers which are open during the day
close at night?
- they can lose water so close up
- frost damage
- no pollinators
- loss of heat
What controls the time when plants close?
- The plants’ biological clock is set to a 21-27 hour cycle. Photosynthesis, auxin production and cell division also rise & fall with the circadian rhythm.
What is the phytochrome?
important and conversions and interactions
A pigment called phytochrome detects the amount of
daylight in each diurnal (day/night) cycle.
What are the two forms of phytochrome?
Pr (biologically inactive)
Pfr (biologically active)
Pr - Pfr by red light (650-670nm)
Pfr - Pr by far red light (705-740nm)
Why is the phytochrome involved in seed germination and what does it do?
It is involved in seed germination, leaf growth,
flowering and dormancy.
Inhibits flowering in short day plants
Induces flowering in long day plants
What causes the leaves to change color in autumn?
- phytochrome levels change
- plant responds by producing abscisic acid at the petiole
- chlorophyll is moved from the leaf into the stem
- petiole cells softens until the leaf falls
What must occur to flower?
A plant must pass through several stages of development with several changes in gene expression occurring at the shoot meristem.
The plant must first pass from an immature to a sexually mature stage.
The apical meristem must change from a vegetative meristem to a floral meristem,
The organs of the flower must grow and develop.
What genes are responsible for flowering?
Leafy and flowering locus
Why do plants orientate their leaves perpendicular to the sun’s rays?
To maximise their absorption of sunlight and photosynthesis
Why do plants in desert climates orientate their leaves parallel to the sun’s rays?
To decrease leaf temperature and water loss through transpiration.
