Chapter 3: Plants Flashcards
What is phytochrome?
a pigment found in the leaves of flowering plants
What is a long day plant?
species flower only if day length exceeds minimum critical length
What is a short day plant?
species that only flower of day length is shorter than critical length and night is a continuous period of darkness that exceeds critical length
Name the two inter convertible forms of phytochrome
P660 & P730
Role of P660
absorbs red light with wavelength of 660 nm
Role of P730
absorbs far red light with wavelength of 730 nm
If day is short and night is long what type of plant will flower?
Short day Plant, P660 is rapidly converted to P730 but night is long enough to slowly convert P730 back to P660 thus inhibitory effect is removed
If day is long and night is short which type of plant will flower?
Long day Plant, P660 is rapidly converted to P730 and night is too short to slowly convert P730 back to P660 allows P730 to accumulate and reach critical level to stimulate flowering
Why is it assumed a hormone is involved in the photoperiod response?
the phytochrome system operates in the leaves whilst the flowers develop in the terminal which is a distance apart therefore has to be come form of communication between where light is stimulated and flowering occurs
Where in plants is most growth localised?
apical meristems
Where does cell division take place?
apical meristems
Stems and roots have clearly identified zones. What are they?
zones of division & zones of elongation
Where can additional growth take place?
internodal regions
Auxin
Produced: tip of shoot, diffuses down the stem
Function: increase cell elongation below stem tip
Cytokinins
Produced: meristematic tissues in zone of division
Function: increase cell division in apical meristems
