Final Quiz Flashcards
Woody perennials of temperate zone, undergo every year a period of “rest” (__________) which marks the end of that year’s growing period
endo-dormancy
________ will grow in any climatic zone where growing season is long enough to allow them to mature
annuals
______ continuous active growth is impossible during an annual cycle
perennials
Dormancy is an _____ mechanism
evolved
define paradormancy
inhibition of bud growth due to factors
outside of the bud
give an example of paradormancy
“pinching” or “heading back” relieves apical dominance & enhances branching on
horticultural plants
define endodormancy
inhibition of bud growth due to internal
factors within the bud itself
give an example of endodormancy
true dormancy or rest
define ecodormancy
inhibition of growth due to non-conducive /
adverse environmenta
give an example of ecodormancy
lack of bud growth during an unseasonably cold spring
Trigger for ‘dormancy-breakage’ (2 reasons)
exposure of buds to cold temperatures
during the fall and winter or meeting the chilling requirement
define chilling requirements
An exposure of a minimum number of chill hours (0-7 °C) required to overcome dormancy
what is one chill unit?
1 hour at 32 - 45 F
Chilling requirement varies among
species and cultivars
Inadequate chilling results in what?
Poor flower bud-break, Poor / slow leaf development, Poor crop
_____ peaches are suitable for FL while relatively ______ peaches for SC and GA
low chill; high chill
Fruit producers and nursery professionals (temperate zone) may desire to _______ of those buds that are no longer endo-dormant
delay breaking
why would horticulutralists want to delay breaking?
to avoid cold damage to those buds that are already endo-dormant
how can delay breaking be done in the field
misting– evaporative cooling
do studies point to ABA inducing or deducing dormancy
inducing
_____ increases in buds at the onset of dormancy in several woody species
ABA
IAA/ABA balance favors ___ during mid-winter but shifts in the favor of ____ in the spring
ABA; IAA
Exogenous (external) application of ____ induces buddormancy
ABA
Exact role of ABA in bud-dormancy is _____
unclear
How is photoperiod signal perceived by plants?
phytochrome
- Photoperiod (short-days) signal is
perceived by ______
leaves
- This signal alters the ratio of
______ forms
phytochrome
- Altered phytochrome ratio serves
as a second-messenger to block
__________
GA biosynthesis
- Cell division and elongation are
_____ in the growth apices -
growth cessation
blocked
Using MRI (magnetic resonance imaging) technique, it was observed that endo-dormant apple buds had less “_____” water than the eco-dormant buds
free
Bound water increased in apple buds when exposed to
dormancy inducing treatments
Transition from active growth to the
suspension of growth (i.e. dormancy) and
then switch from dormancy to active
growth occurs in the
meristems
Therefore, researchers have focused on
stem apical meristem (SAM) to
investigate the physiological mechanism
of ______ induction and release
dormancy
Dormancy is _____ due to disruption
of cell-to-cell communication in the
stem apical meristem (SAM)
induced
Dormancy is ______ by
restoration of this cell-to-cell
communication leading to an active
apical mesristem
broken
SAM cells are united by
plasmodesmata network
define SAM
stem apical meristem
Cells can and do exchange signaling
______ and ______ through the plasmodesmata
molecules and other metabolites
Blockage of the plasmodesmatal connections is due to formation of a complex carbohydrate called what?
glucans
Glucan production is activated as the mersitems undergo _______
dormancy
Chilling enhances the production of enzymes called _______
glucanases
________ digest glucans and cell-to-cell connections are restored
Glucanases
