role of mesophyll conductance during water stress and recovery in tobacco (Nicotiana sylvestris): acclimation or limitation?

While the responses of photosynthesis to water stress have been widely studied, acclimation to sustained water stress and recovery after re-watering is poorly understood. In particular, the factors limiting photosynthesis under these conditions, and their possible interactions with other environment...

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Bibliographic Details
Published in:Journal of experimental botany 2009-05, Vol.60 (8), p.2379-2390
Main Authors: Galle, Alexander, Florez-Sarasa, Igor, Tomas, Magdalena, Pou, Alicia, Medrano, Hipolito, Ribas-Carbo, Miquel, Flexas, Jaume
Format: Article
Language:English
Subjects:
Acclimatization
Carbon Dioxide - metabolism
Dehydration
Drought
Kinetics
Leaves
Mesophyll
mesophyll conductance
Natural springs
Nicotiana - chemistry
Nicotiana - physiology
Nicotiana sylvestris
Photosynthesis
photosynthetic limitation
Phytotrons
Plant Leaves - chemistry
Plant Leaves - physiology
Plants
recovery
Responses of g m to Interacting Environmental Factors
stomatal conductance
Stress, Physiological
Summer
Water - metabolism
water stress
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Summary:While the responses of photosynthesis to water stress have been widely studied, acclimation to sustained water stress and recovery after re-watering is poorly understood. In particular, the factors limiting photosynthesis under these conditions, and their possible interactions with other environmental conditions, are unknown. To assess these issues, changes of photosynthetic CO₂ assimilation (AN) and its underlying limitations were followed during prolonged water stress and subsequent re-watering in tobacco (Nicotiana sylvestris) plants growing under three different climatic conditions: outdoors in summer, outdoors in spring, and indoors in a growth chamber. In particular, the regulation of stomatal conductance (gs), mesophyll conductance to CO₂ (gm), leaf photochemistry (chlorophyll fluorescence), and biochemistry (Vc,max) were assessed. Leaf gas exchange and chlorophyll fluorescence data revealed that water stress induced a similar degree of stomatal closure and decreased AN under all three conditions, while Vc,max was unaffected. However, the behaviour of gm differed depending on the climatic conditions. In outdoor plants, gm strongly declined with water stress, but it recovered rapidly (1-2 d) after re-watering in spring while it remained low many days after re-watering in summer. In indoor plants, gm initially declined with water stress, but then recovered to control values during the acclimation period. These differences were reflected in different velocities of recovery of AN after re-watering, being the slowest in outdoor summer plants and the fastest in indoor plants. It is suggested that these differences among the experiments are related to the prevailing climatic conditions, i.e. to the fact that stress factors other than water stress have been superimposed (e.g. excessive light and elevated temperature). In conclusion, besides gs, gm contributes greatly to the limitation of photosynthesis during water stress and during recovery from water stress, but its role is strongly dependent on the impact of additional environmental factors.
ISSN:0022-0957
1460-2431
DOI:10.1093/jxb/erp071