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Advisor(s)
Abstract(s)
We tested the hypothesis that Eucalyptus
globulus Labill. genotypes that are more resistant to dry
environments might also exhibit higher cold tolerances
than drought-sensitive plants. The effect of low temperatures
was evaluated in acclimated and unacclimated
ramets of a drought-resistant clone (CN5) and a
drought-sensitive clone (ST51) of E. globulus. We
studied the plants’ response via leaf gas exchanges, leaf
water and osmotic potentials, concentrations of soluble
sugars, several antioxidant enzymes and leaf electrolyte
leakage. Progressively lowering air temperatures (from
24/16 to 10/ 2 C, day/night) led to acclimation of both
clones. Acclimated ramets exhibited higher photosynthetic
rates, stomatal conductances and lower membrane
relative injuries when compared to unacclimated ramets.
Moreover, low temperatures led to significant increases
of soluble sugars and antioxidant enzymes activity
(glutathione reductase, ascorbate peroxidase and superoxide
dismutases) of both clones in comparison to plants
grown at control temperature (24/16 C). On the other
hand, none of the clones, either acclimated or not,
exhibited signs of photoinhibition under low temperatures
and moderate light. The main differences in the
responses to low temperatures between the two clones
resulted mainly from differences in carbon metabolism,
including a higher accumulation of soluble sugars in the
drought-resistant clone CN5 as well as a higher capacity
for osmotic regulation, as compared to the droughtsensitive
clone ST51. Although membrane injury data
suggested that both clones had the same inherent
freezing tolerance before and after cold acclimation,
the results also support the hypothesis that the droughtresistant
clone had a greater cold tolerance at intermediate
levels of acclimation than the drought-sensitive
clone. A higher capacity to acclimate in a short period
can allow a clone to maintain an undamaged leaf surface
area along sudden frost events, increasing growth
Description
Keywords
antioxidant capacity chilling dehydration tolerance freezing solute accumulation
Pedagogical Context
Citation
"Tree Physiology". ISSN 0829-318X. 29 (2009) 77-86
Publisher
Oxford University Press