Abstract:
Red-osier dogwood plants were grown outdoors in a lathhouse
and under two temperature regimes in growth chambers to determine
the time of vegetative maturity, the transition between summer and
winter dormancy. Xylem water potential (XWP), tissue moisture
content, ethylene and ethane production, and electrical impedance
were used to try to find a quantitative measure of vegetative maturity
that could be used by researchers and nurserymen to predict maturity.
XWP showed a significant correlation with tip dieback, but
the variability within samples precludes its use as an index of maturity.
The change in moisture content was too gradual to be of value
as a predictive index. Ethylene production of stem sections correlated
with tip dieback, and deserves future testing. Frozen stem
sections produced ethane and ethylene, both of which declined as
maturity progressed. Electrical impedance values showed promise
as the most accurate measure of maturity in red-osier dogwood.
A second objective was to relate vegetative maturity to the first
stage of cold acclimation in red-osier dogwood. Previous research
has suggested that the onset of cold acclimation occurred before rest
and about the time that the plants matured. Confirmation that vegetative
maturity and the onset of cold acclimation coincide is presented
in these studies.
