Influence of Transplanting Practices on Growth and Embolism Levels For Urban Tree Species
Abstract
Changes in xylem embolism levels due to drought stress or
freezing have been documented for a wide variety of
plants. High degrees of tissue water stress which lead to
increased levels of embolism are also often cited as factors
negatively influencing plant establishment. Embolized xylem
elements can potentially lead to restriction of stem water
flow, thereby reducing growth. Therefore, this dissertation
(5 experiments) was undertaken to determine if certain
transplanting practices affect embolism dynamics and plant
growth of selected urban tree species. Embolism was
estimated based on reductions in hydraulic conductance of
harvested stem segments. An initial experiment determined
the length of time from tissue harvest to embolism
measurement that stem samples may be held in cold
storage. Results varied between Fraxinus americana L.
(white ash) and Acer rubrum L. x saccharinum L. (hybrid
red maple), but data suggested white ash stem samples
should not be stored more than one day, especially for
between-species comparisons. A greenhouse experiment
investigated the growth and embolism levels for
container-grown Corylus colurna L. (Turkish hazelnut)
seedlings in response to root pruning. Increasing levels of
root pruning from 25 to 50% increased embolism, although
plant height also increased. There was no fertilizer level x
root pruning interaction for embolism. A field-harvest and
greenhouse growth experiment investigated the influence of
cold storage duration on plant growth and pre- and
post-transplant embolism levels. Embolism levels increased
with duration of cold storage for Acer rubrum L. (red
maple), but not for Crataegus phaenopyrum (L.f.) Medic.
(Washington hawthorn). After 15 weeks of growth,
however, embolism levels were similar for both species.
Growth increased with increased cold storage duration for
both species. A field experiment investigated the influence
of transplant season and root pruning on plant growth and
embolism of Turkish hazelnut and Syringa reticulata
(Blume) Hara (tree lilac). Embolism levels just prior to
budbreak and days to budbreak were highest for
fall-transplanted Turkish hazelnut. Embolism level was
unaffected by treatments. No clear relationship between
embolism and growth could be determined for either
species the first season after transplanting. Other
fall-transplanted Turkish hazelnuts, however, had growth
reductions that corresponded to increasing embolism levels
two years after transplanting. An additional transplanting
experiment examined the influence of root severance at
transplanting on water relations of red maple. Stem sap
flow (in vivo) was reduced within 2 h of harvest, and leaf
stomatal conductance was reduced 4 h after harvest.
Percent embolism (in vitro) was increased within 24 hr of
harvest. Results of these experiments indicate that root
pruning, and choice of transplant season can reduce plant
growth and increase embolism levels. No clear relationship
between embolism and growth reduction was evident.
Although embolism dynamics are clearly impacted by
transplanting, the implications for transplant success are
inconclusive. The role of embolism in transplant success
was not clear.
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- Doctoral Dissertations [14904]