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Advisor(s)
Abstract(s)
Drought is a major environmental constrain affecting plant performance and survival,
particularly in Mediterranean ecosystems. Terpenoids may play a protective role under
these conditions, however, observations of drought effects on plant terpenoid emissions
are controversial ranging from decreased emissions to unaffected or increased release
of terpenoids. In the present study we investigated terpenoid emissions of cork
oak (Quercus suber) and gum rockrose (Cistus ladanifer) in response to summer
drought stress in 2017. Pre-dawn leaf water potential (9PD) decreased from 0.64
to 1.72 MPa in Q. suber and from 1.69 to 4.05 MPa in C. ladanifer, indicating
a transition from mild to severe drought along summer. Total terpenoid emissions
decreased with drought, but differed significantly between species (p < 0.001) and
in response to 9PD, air temperature and assimilation rates. C. ladanifer emitted a
large variety of >75 compounds comprising monoterpenes, sesquiterpenes and even
diterpenes, which strongly decreased from 1.37 0.23 mg g1 h1 to 0.40 0.08 mg
g1 h1 (p < 0.001) in response to drought. Total emission rates were positively
correlated to air temperature (p < 0.001). C. ladanifer behavior points toward terpenoid
leaf storage depletion and reduced substrate availability for terpenoid synthesis with
increasing drought, most likely accelerated by high air temperatures. Q. suber emitted
mainly monoterpenes and emissions declined significantly from June (0.50 0.08 mg
g1 h1) to August (0.29 0.02 mg g1 h1) (p < 0.01). Emission rates were weakly
correlated with net assimilation rates (R2 = 0.19, p < 0.001), but did not respond strongly
to 9PD and air temperature. Early onset of drought in 2017 most likely reduced plant
metabolism in Q. suber, resulting in diminished, but stable terpenoid fluxes. Calculation
of standard emission factors (at 30 C) revealed contrasting emission patterns of
decreasing, unaffected, or increasing fluxes of single terpenoid compounds. Unaffected
or drought-enhanced emissions of compounds such as a-pinene, camphene or manoyl
oxide may point toward a specific role of these terpenoids in abiotic stress adaptation.
In conclusion, these results suggest a strong negative, but species- and compoundspecific
effect of severe drought on terpenoid fluxes in Mediterranean ecosystems
Description
Keywords
BVOC drought stress adaptation Mediterranean ecosystems Quercus suber Cistus ladanifer
Pedagogical Context
Citation
Haberstroh S, Kreuzwieser J, Lobo-do-Vale R, Caldeira MC, Dubbert M and Werner C (2018) Terpenoid Emissions of Two Mediterranean Woody Species in Response to Drought Stress. Front. Plant Sci. 9:1071
Publisher
Jairo A. Palta