Jaume Flexas1, Josefina Bota2, José M. Escalona2, Bartolomé Sampol2, H. Medrano2
1Laboratori de Fisiologia Vegetal, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa, km 7.5. 07071 Palma de Mallorca, Balears, Spain.Corresponding author; email: [email protected]. 2Laboratori de Fisiologia Vegetal, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa, km 7.5. 07071 Palma de Mallorca, Balears, Spain.
Tóm tắt
The effect of diffusional and photochemical limitations to photosynthesis was
assessed in field-grown water-stressed grapevines
(Vitis vinifera L.) by combined measurements of gas
exchange and chlorophyll fluorescence. Drought was slowly induced, and the
progressive decline of photosynthesis was examined in different grapevine
cultivars along a continuous gradient of maximum mid-morning values of
stomatal conductance (g), which were used as an
integrative indicator of the water-stress conditions endured by the leaves.
Initial decreases of g were accompanied by decreases of
substomatal CO2 concentration (Ci), the estimated
chloroplastic CO2 concentration (Cc) and net
photosynthesis (AN), while
electron transport rate (ETR) remained unaffected. With increasing drought,
g, AN, Ci
and Cc further decreased, accompanied by slight decreases of ETR and of the
estimated mesophyll conductance
(gmes). Severe drought led to
strong reductions of both g and
gmes, as well as of ETR. The
apparent carboxylation efficiency and the compensation point for
CO2 remained unchanged under severe drought when
analysed on a Cc, rather than a Ci, basis, suggesting that previously reported
metabolic impairment was probably due to decreased
gmes.
