© 2001 Heron Publishing—Victoria, Canada
Daily time course of whole-shoot gas exchange rates in two drought-exposed Mediterranean shrubs
Salvador Nogués (1), Sergi Munné-Bosch (1), Jaume Casadesús (2), Marta López-Carbonell (1) and Leonor Alegre (1, 3)
1. Departament de Biologia Vegetal, Universitat de Barcelona, Av. Diagonal 645, E-08028 Barcelona, Spain / 2. Servei de Camps Experimentals, Universitat de Barcelona, Av. Diagonal 645, E-08028 Barcelona, Spain / 3. Author to whom correspondence should be addressed (leonor@porthas.bio.ub.es) / Received March 8, 2000
Summary
Effects of drought on water relations, whole-shoot gas-exchange characteristics, and pigment and zeatin concentrations were
investigated in the Mediterranean shrubs rosemary (Rosmarinus officinalis L.) and lavender (Lavandula stoechas L.). Two-year-old, greenhouse-grown plants were placed in a whole-shoot gas-exchange measurement system and subjected to
10 days of drought, resulting in severe water stress, and then re-watered for 5 days in order to study their recovery. Water
stress resulted in a significant decline in maximum whole-shoot net CO2 assimilation rates (An) for both species that was associated with reductions in leaf area and stomatal conductance. Because shoot dark respiration
rate (Rd) was less sensitive to water stress than An, shoot Rd/An ratio increased from about 15 to 95% during water stress. No major changes in chlorophyll and carotenoid concentrations of
rosemary leaves were observed during the experiments, but chlorophyll and carotenoid concentrations fell significantly in
water-stressed lavender leaves. Zeatin concentrations were higher in rosemary leaves than in lavender leaves during water
stress. After re-watering, whole-shoot An and Rd rapidly recovered to their pre-drought rates.
Keywords:
dark respiration, drought, Lavandula stoechas, photosynthesis, Rosmarinus officinalis, zeatin.
