186,161 research outputs found
The challenge of the Mediterranean climate to plant hydraulics: responses and adaptations.
No full textMediterranean-type biomes characterized by warm summers with a distinct drought period lasting
from 2 up to 10 months occur in several world regions including the Mediterranean basin, S-California,
Chile, S-Africa and SW-Australia. All these areas are covered by a peculiar and hyper-diverse vegetation
dominated by evergreen trees and shrubs with small and coriaceous leaves. Drought adaptation of
Mediterranean plants relies on different mechanisms including deep rooting patterns, avoidance or resistance
of cavitation-induced embolism, compensation or repair of embolism-induced hydraulic damage.
The complementarity and/or co-occurrence of these physiological traits in different species inhabiting
Mediterranean biomes is probably the basis for high plant biodiversity in these fascinating habitats.
Ongoing climate changes, leading to enhanced frequency and intensity of drought episodes in Mediterranean
biomes, represent a major threat to future conservation of these fragile ecosystems, especially if
future harsher climate conditions will overcome the drought resistance limits of Mediterranean plants.
Current knowledge about drought resistance mechanisms as well as about processes leading to decline
and death of woody plants under extreme climatic conditions is revised and directions for future research
are suggested
Changes of xylem sap ionic content and stem hydraulics in response to irradiance in Laurus nobilis L.
No full textVein cavitation and stomatal behaviour of sunflower (Helianthus annuus L.) leaves under water limitation
No full textChanges in leaf hydraulics and stomatal conductance following drought stress and irrigation in Ceratonia siliqua L. (Carob tree)
No full textAxial-to-radial water permeability of leaf major veins: a possible determinant of the impact of vein embolism on leaf hydraulics?
No full textDiurnal changes in embolism rate in nine dry forest trees: relationships with species-specific xylem vulnerability, hydraulic strategy, and wood traits
No full textRecent studies have reported correlations between stem sapwood capacitance (Cwood) and xylem vulnerability to embolism, but it is unclear how Cwood relates to the eventual ability of plants to reverse embolism. We investigated possible functional links between embolism reversal efficiency, Cwood, wood density (WD), vulnerability to xylem embolism and hydraulic safety margins in nine woody species native to dry sclerophyllous forests with different degrees of iso versus anisohydry. Substantial inter-specific differences in terms of seasonal/diurnal changes of xylem and leaf water potential, maximum diurnal values of transpiration rate and xylem vulnerability to embolism formation were recorded. Significant diurnal changes in percentage loss of hydraulic conductivity (PLC) were recorded for five species. Significant correlations were recorded between diurnal PLC changes and P50 and P88 values (i.e., xylem pressure inducing 50 and 88% PLC, respectively) as well as between diurnal PLC changes and safety margins referenced to P50 and P88. WD was linearly correlated with minimum diurnal leaf water potential, diurnal PLC changes and wood capacitance across all species. In contrast, significant relationships between P50, safety margin values referenced to P50 and WD were recorded only for the isohydric species. Functional links between diurnal changes in PLC, hydraulic strategies and WD and Cwood are discussed
Relax and refill: xylem rehydration prior to hydraulic measurements favours embolism repair in stems and generates artificially low PLC values
No full textDiurnal changes in percentage loss of hydraulic conductivity (PLC), with recorded values being higher at midday than on the following morning, have been interpreted as evidence for the occurrence of cycles of xylem conduits' embolism and repair. Recent reports have suggested that diurnal PLC changes might arise as a consequence of an experimental artefact, that is, air entry into xylem conduits upon cutting stems, even if under water, while under substantial tension generated by transpiration. Rehydration procedures prior to hydraulic measurements have been recommended to avoid this artefact. In the present study, we show that xylem rehydration prior to hydraulic measurements might favour xylem refilling and embolism repair, thus leading to PLC values erroneously lower than those actually experienced by transpiring plants. When xylem tension relaxation procedures were performed on stems where refilling mechanisms had been previously inhibited by mechanical (girdling) or chemical (orthovanadate) treatment, PLC values measured in stems cut under native tension were the same as those measured after sample rehydration/relaxation. Our data call for renewed attention to the procedures of sample collection in the field and transport to the laboratory, and suggest that girdling might be a recommendable treatment prior to sample collection for PLC measurements
Coping with drought-induced xylem cavitation: coordination of embolism repair and ionic effects in three Mediterranean evergreens.
No full textEmbolism repair and ionic effects on xylem hydraulic conductance have been documented in different tree species. However, the diurnal and seasonal patterns of both phenomena and their actual role in plants’ responses to drought-induced xylem cavitation have not been thoroughly investigated. This study provides experimental evidence of the ability of three Mediterranean species to maintain hydraulic function under drought stress by coordinating the refilling of xylem conduits and ion-mediated enhancement of stem hydraulic conductance (Kstem). Vessel grouping indices and starch content in vessel associated parenchyma cells were quantified to verify eventual correlations with ionic effects and refilling, respectively. Experiments were performed on stems of Ceratonia siliqua L., Olea europaea L. and Laurus nobilis L. Seasonal, ion-mediated changes in Kstem (ΔKstem) and diurnal and/or seasonal embolism repair were recorded for all three species, although with different temporal patterns. Field measurements of leaf specific stem hydraulic conductivity showed that it remained quite constant during the year, despite changes in the levels of embolism. Starch content in vessel-associated parenchyma cells changed on diurnal and seasonal scales in L. nobilis and O. europaea but not in C. siliqua. Values of ΔKstem were significantly
correlated with vessel multiple fraction values (the ratio of grouped vessels to total number of vessels). Our data suggest that the regulation of xylem water transport in Mediterranean plants relies on a close integration between xylem refilling and ionic effects. These functional traits apparently play important roles in plants’ responses to drought-induced xylem cavitation
Hydraulic connections of leaves and fruits to the parent plant in Capsicum frutescens L. (Hot pepper) during fruit ripening.
No full textAuthor-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
