Antonio Gascó

Resistance to water flow through leaves of Coffea arabica is dominated by extra-vascular tissues

The leaf hydraulic conductance (Kleaf) of Coffea arabica L. was measured for shoots exposed to non-lethal temperature stress or to a freeze-thaw cycle, and compared with Kleaf of non-stressed samples (controls). Exposure to temperatures below 6°C for 1 h caused measurable damage to the functional integrity of cell membranes as shown by increased membrane leakiness to electrolytes. A 1 : 1 relationship was found to exist between relative electrolyte leakage and relative Kleaf suggesting that membrane damage caused Kleaf to increase. Low temperatures did not cause membrane disruption as shown by the comparison of chilled samples with frozen-thawed ones. In frozen leaves, membranes were extensively disrupted and both electrolyte leakiness and Kleaf increased 5-fold. Low temperatures did not induce alterations of the hydraulic properties of the leaf vascular system, as revealed by measurements of Kleaf after up to 500 cuttings of minor veins were made in the leaf blade of control and chilled leaves. Calculations showed that 62-75% of leaf hydraulic resistance resided in the extra-vascular water pathway. Results are discussed within the frame work of our current understanding of leaf hydraulic architecture as well as in terms of plant adaptation to extremes in temperature.

Variation in photosynthetic performance and hydraulic architecture across European beech (Fagus sylvatica L.) populations supports the case for local adaptation to water stress

The aim of this study was to provide new insights into how intraspecific variability in the response of key functional traits to drought dictates the interplay between gas-exchange parameters and the hydraulic architecture of European beech (Fagus sylvatica L.). Considering the relationships between hydraulic and leaf functional traits, we tested whether local adaptation to water stress occurs in this species. To address these objectives, we conducted a glasshouse experiment in which 2-year-old saplings from six beech populations were subjected to different watering treatments. These populations encompassed central and marginal areas of the range, with variation in macro- and microclimatic water availability. The results highlight subtle but significant differences among populations in their functional response to drought. Interpopulation differences in hydraulic traits suggest that vulnerability to cavitation is higher in populations with higher sensitivity to drought. However, there was no clear relationship between variables related to hydraulic efficiency, such as xylem-specific hydraulic conductivity or stomatal conductance, and those that reflect resistance to xylem cavitation (i.e., Ψ(12), the water potential corresponding to a 12% loss of stem hydraulic conductivity). The results suggest that while a trade-off between photosynthetic capacity at the leaf level and hydraulic function of xylem could be established across populations, it functions independently of the compromise between safety and efficiency of the hydraulic system with regard to water use at the interpopulation level.

Application of Multi-Barrier Membrane Filtration Technologies to Reclaim Municipal Wastewater for Industrial Use

The significant percentage of the world water consumption devoted to industrial use, along with an increasingly higher environmental concern of society, has awaken the interest of industry on using municipal reclaimed water for replacing fresh water use coming from utilities or natural resources. Depending on the type of industry and the specific application, water must meet certain quality requirements. Therefore, those water quality standards that are required for those most relevant industrial applications wherein the use of reclaimed water has noticeably been reported are herewith reviewed. Although the use of internal water treatments for recycling and reusing their own effluents has recently and widely been reported within many industrial sectors worldwide, the substitution of fresh water by reclaimed municipal wastewater has yet to be extended much. The increasing proportion of municipal wastewater reclamation plants that rely on membrane filtration technologies versus the total number of reclamation facilities that are distributed worldwide is also assessed within this review, including the discussion of their main related drawbacks.