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Results for “Droughts”

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PubMed2002

A rate equation model of stomatal responses to vapour pressure deficit and drought.

BACKGROUND: Stomata respond to vapour pressure deficit (D) - when D increases, stomata begin to close. Closure is the result of a decline in guard cell turgor, but the link between D and turgor is poorly understood. We describe a model for stomatal responses to increasing D based upon cellular water relations. The model also incorporates impacts of increasing levels of water stress upon stomatal responses to increasing D. RESULTS: The model successfully mimics the three phases of stomatal responses to D and also reproduces the impact of increasing plant water deficit upon stomatal responses to increasing D. As water stress developed, stomata regulated transpiration at ever decreasing values of D. Thus, stomatal sensitivity to D increased with increasing water stress. Predictions from the model concerning the impact of changes in cuticular transpiration upon stomatal responses to increasing D are shown to conform to experimental data. Sensitivity analyses of stomatal responses to various parameters of the model show that leaf thickness, the fraction of leaf volume that is air-space, and the fraction of mesophyll cell wall in contact with air have little impact upon behaviour of the model. In contrast, changes in cuticular conductance and membrane hydraulic conductivity have significant impacts upon model behaviour. CONCLUSION: Cuticular transpiration is an important feature of stomatal responses to D and is the cause of the 3 phase response to D. Feed-forward behaviour of stomata does not explain stomatal responses to D as feedback, involving water loss from guard cells, can explain these responses.

Adaptation, Physiological↗
PubMed2005

Mycorrhiza formation enhances adaptive response of hybrid poplar to drought.

Mycorrhized and nonmycorrhized plants of hybrid poplar (Populus tremula L. x Populus tremuloides Mich) were cultivated in petri dishes until the amount of water became limiting (detected by a decrease of photosynthetic yield). RNA was isolated from both main and fine roots and used for analysis of water channel (aquaporin) gene expression by semiquantitative RT-PCR. For three of five investigated aquaporin genes, expression did not differ between mycorrhized and nonmycorrhized plants. However, expression of the two other aquaporin genes was more pronounced in fine roots of mycorrhized plants, indicating that the root-fungus symbiosis may improve the water transport capacity under conditions of reduced water availability.

Adaptation, Physiological↗