A carregar...
Publicação
Limitations to leaf photosynthesis in field-grown grapevine under drought - metabolic and modelling approaches
| Nome: | Descrição: | Tamanho: | Formato: | |
|---|---|---|---|---|
| 200.94 KB | Adobe PDF |
Orientador(es)
Resumo(s)
The effects of a slowly-imposed drought stress on gas-exchange, chlorophyll a fluorescence,
biochemical and physiological parameters of Vitis vinifera L. leaves (cv. Aragonez, syn. Tempranillo) growing in a
commercial vineyard (South Portugal) were evaluated. Relative to well-watered plants (predawn water potential,
ΨPD = –0.13 ± 0.01 MPa), drought-stressed plants (ΨPD = –0.97 ± 0.01 MPa) had lower photosynthetic rates
(ca 70%), stomatal conductance, and PSII activity (associated with a higher reduction of the quinone A pool and
lower efficiency of PSII open centres). Stomatal limitation to photosynthesis was increased in drought-stressed
plants relative to well-watered plants by ca 44%. Modelled responses of net photosynthesis to internal CO2
indicated that drought-stressed plants had significant reductions in maximum Rubisco carboxylation activity
(ca 32%), ribulose-1,5-bisphosphate regeneration (ca 27%), and triose phosphate (triose-P) utilization rates
(ca 37%) relative to well-watered plants. There was good agreement between the effects of drought on modelled
biochemical parameters, and in vitro activities of key enzymes of carbon metabolism, namely Rubisco,
glyceraldehyde-3-phosphate dehydrogenase, ribulose-5-phosphate kinase and fructose-1,6-bisphosphate
phosphatase. Quantum yields measured under both ambient (35 Pa) and saturating CO2 (100 Pa) for
drought-stressed plants were decreased relative to well-watered plants, as well as maximum photosynthetic rates
measured at light and CO2 saturating conditions (three times ambient CO2 levels). Although stomatal closure was
a strong limitation to CO2 assimilation under drought, comparable reductions in electron transport, CO2
carboxylation, and utilization of triose-P capacities were also adaptations of the photosynthetic machinery to
dehydration that slowly developed under field conditions. Results presented in this study confirm that modelling
photosynthetic responses based on gas-exchange data can be successfully used to predict metabolic limitations to
photosynthesis.
Descrição
Palavras-chave
Drought Enzymes of carbon metabolism Gas exchange Modelling Photosynthesis Vitis vinifera
Contexto Educativo
Citação
Functional Plant Biology, 29, 451-459