title: Role of leaf hydraulic conductance in the regulation of stomatal conductance in almond and olive in response to water stress.
abstract: The decrease of stomatal conductance (gs) is one of the prime responses to water shortage and the main determinant of yield limitation in fruit trees. Understanding the mechanisms related to stomatal closure in response to imposed water stress is crucial for correct irrigation management. The loss of leaf hydraulic functioning is considered as one of the major factors triggering stomatal closure. Thus, we conducted an experiment to quantify the dehydration response of leaf hydraulic conductance (Kleaf) and its impact on gs in two Mediterranean fruit tree species, one deciduous (almond) and one evergreen (olive). Our hypothesis was that a higher Kleaf would be associated with a higher gs and that the reduction in Kleaf would predict the reduction in gs in both species. We measured Kleaf in olive and almond during a cycle of irrigation withholding. We also compared the results of two methods to measure Kleaf: dynamic rehydration kinetics and evaporative flux methods. In addition, determined gs, leaf water potential (Ψleaf), vein density, photosynthetic capacity and turgor loss point. Results showed that gs was higher in almond than in olive and so was Kleaf (Kmax = 4.70 and 3.42 mmol s(-1) MPa(-1) m(-2), in almond and olive, respectively) for Ψleaf > -1.2 MPa. At greater water stress levels than -1.2 MPa, however, Kleaf decreased exponentially, being similar for both species, while gs was still higher in almond than in olive. We conclude that although the Kleaf decrease with increasing water stress does not drive unequivocally the gs response to water stress, Kleaf is the variable most strongly related to the gs response to water stress, especially in olive. Other variables such as the increase in abscisic acid (ABA) may be playing an important role in gs regulation, although in our study the gs-ABA relationship did not show a clear pattern.
authors: Irrigation and Crop Ecophysiology Group, Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS, CSIC), Avenida Reina Mercedes, no. 10, 41012 Sevilla, Spain virginiahsa@gmail.com.
authors: Virginia
authors: V
authors: Hernandez-Santana
authors: Irrigation and Crop Ecophysiology Group, Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS, CSIC), Avenida Reina Mercedes, no. 10, 41012 Sevilla, Spain.
authors: Celia M
authors: CM
authors: Rodriguez-Dominguez
authors: Irrigation and Crop Ecophysiology Group, Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS, CSIC), Avenida Reina Mercedes, no. 10, 41012 Sevilla, Spain.
authors: J Enrique
authors: JE
authors: Fernández
authors: Irrigation and Crop Ecophysiology Group, Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS, CSIC), Avenida Reina Mercedes, no. 10, 41012 Sevilla, Spain.
authors: Antonio
authors: A
authors: Diaz-Espejo
mesh_terms: D031658:Olea / Q000378:metabolism* / Q000502:physiology; D018515:Plant Leaves / Q000378:metabolism*; D018526:Plant Transpiration / Q000502:physiology*; D000068181:Prunus dulcis / Q000378:metabolism; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water
keywords: Olea europaea; Prunus dulcis; deficit irrigation; drought; dynamic rehydration kinetics method; evaporative flux method; fruit crops