We tested the hypothesis that greater cavitation resistance correlates with less total inter-vessel pit area per vessel (the pit area hypothesis) and evaluated a trade-off between cavitation safety and transport efficiency. Fourteen species of diverse growth form (vine, ring- and diffuse-porous tree, shrub) and family affinity were added to published data predominately from the Rosaceae (29 species total). Two types of vulnerability-to-cavitation curves were found. Ring-porous trees and vines showed an abrupt drop in hydraulic conductivity with increasing negative pressure, whereas hydraulic conductivity in diffuse-porous species generally decreased gradually. The ring-porous type curve was not an artifact of the centrifuge method because it was obtained also with the air-injection technique. A safety versus efficiency trade-off was evident when curves were compared across species: for a given pressure, there was a limited range of optimal vulnerability curves. The pit area hypothesis was supported by a strong relationship (r2 = 0.77) between increasing cavitation resistance and diminishing pit membrane area per vessel (A(P)). Small A(P) was associated with small vessel surface area and hence narrow vessel diameter (D) and short vessel length (L)--consistent with an increase in vessel flow resistance with cavitation resistance. This trade-off was amplified at the tissue level by an increase in xylem/vessel area ratio with cavitation resistance. Ring-porous species were more efficient than diffuse-porous species on a vessel basis but not on a xylem basis owing to higher xylem/vessel area ratios in ring-porous anatomy. Across four orders of magnitude, lumen and end-wall resistivities maintained a relatively tight proportionality with a near-optimal mean of 56% of the total vessel resistivity residing in the end-wall. This was consistent with an underlying scaling of L to D(3/2) across species. Pit flow resistance did not increase with cavitation safety, suggesting that cavitation pressure was not related to mean pit membrane porosity.
Populations of cork oak (Quercus suber L.) were assessed for seasonal and inter-population variability in, and temperature responses of, the ratio between light-induced variable and maximum fluorescence of chlorophyll, Fv/Fm, considered a surrogate for the maximum photochemical efficiency of photosystem II (PSII). Seedlings from 10 populations throughout the distribution range of Q. suber in the Mediterranean basin were grown in a common garden in central Spain. The Fv/Fm ratio of dark-adapted leaves was measured at dawn every month for 2 years. Air temperature was recorded at a nearby climatic station. During the summer, when maximum air temperatures reached 40 degrees C, there were no significant differences in Fv/Fm among populations, but significant differences were seen during the winter. In colder months, Fv/Fm ranged in all populations between 0.5-0.6 and 0.2-0.3 in 2001 and 2002, respectively. The variance explained by the population effect was greatest during winter months, especially in 2002, reaching a peak value of 10% when minimum air temperature was below -10 degrees C. Populations originating from warmer sites showed the largest decline in Fv/Fm between the end of 2001 and the beginning of 2002. Thus, a negative linear relationship was established between mean annual temperature at the population source and population mean Fv/Fm recorded in the coldest month in 2002 and normalized by the Fv/Fm spring measurement.
Introducción: En los tiempos actuales los tintes naturales cobran importancia por su inocuidad, durabilidad y conservación ambiental. Otorgan identidad regional a todo proyecto de índole artesanal donde se empleen vegetales para teñir. El presente trabajo estudia el potencial tintóreo sobre fibra lana merino de las plantas autóctonas de la estepa patagónica. M&M: El área de recolección del material vegetal tintóreo se circunscribió a la zona sureste del Chubut, Argentina, correspondiendo al Distrito Florístico del Golfo San Jorge. Se aplicó la receta madre para la obtención del tinte y se desarrollaron tres tipos de procedimientos, pre-mordentado, mordentado directo y post-mordentado, dependiendo del momento de aplicación del alumbre. Se emplearon modificadores de color bicarbonato de sodio y sulfato de hierro. Mediante el uso de la tabla universal del sistema Munsell (Color, 2009) se estudió el tono, la luminosidad y saturación. Resultados: Se estudiaron 50 especies nativas de la Región Patagónica. En su totalidad se obtuvo la siguiente proporción: marrones 37%, amarillo 35 %, olivas 14%, grises 10% rosados 2 % y verdes 2%. Se destacan 9 especies de mayor saturación cromática. Los colores con mayor saturación se obtienen durante el proceso pre-mordentado. Las familias mejor representadas son Fabaceae y Asteraceae. Conclusiones: Del análisis de la literatura de plantas empleadas para tintes naturales en Argentina, surge que numerosas especies estudiadas en la presente investigación no registran antecedentes y resultan ser prometedoras brindando colores intensos de saturaciones elevadas. Podemos considerarlas verdaderos hallazgos y sugerirlas con alto potencial tintóreo para la fibra de lana merino.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.