San Juan Bautista Valle Nacional, Mexico
San Juan Bautista Valle Nacional, Mexico

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Vasquez-Murrieta M.S.,Escuela Nacional | Patino-Siciliano A.,Laboratory of Plant Ecology | Dendooven L.,CINVESTAV
Bioresource Technology | Year: 2010

Metal concentrations were measured in plants growing on heavily contaminated tailings from a mine active since about 1800 in San Luis Potosí (Mexico). Viguiera dentata (Cav.) Spreng., Parthenium bipinnatifidum (Ort.) Rollins, Flaveria angustifolia (Cav.) Pers., F. trinervia (Spreng.) C. Mohr. and Sporobolus indicus (L.) R. Br. were tolerant to high As, Cu, Pb and Zn concentrations. Of those, S. indicus excluded heavy metals from its shoots, while P. bipinnatifidum and F. angustifolia accumulated them. V. dentata and P. bipinnatifidum were accumulators of As, but not hyperaccumulators. It was found that V. dentata, P. bipinnatifidum, F. angustifolia, F. trinervia and S. indicus, could be used to vegetate soils contaminated with As, Cu, Pb and Zn. Ambrosia artemisifolia could be used to remediate soils contaminated with Zn, S. amplexicaulis those with Cu and F. angustifolia and F. trinervia those with As, as they have a strong capacity to accumulate those metals. © 2010 Elsevier Ltd. All rights reserved.


Verbeeck H.,Laboratory of Plant Ecology | Betehndoh E.,Laboratory of Plant Ecology | Maes W.H.,Laboratory of Plant Ecology | Hubau W.,Ghent University | And 12 more authors.
Journal of Tropical Forest Science | Year: 2014

The Congo Basin has a large secondary forest area. Nevertheless, global plant trait databases lack substantial data from this biome and functional trait diversity is largely unknown. We analysed a unique leaf trait dataset (specific leaf area, nutrient and isotope concentrations) collected from 88 individual trees belonging to 10 different species in tropical lowland forest in the Democratic Republic of the Congo. The trait data were found to be consistent with global datasets. δ15N was the only trait significantly influenced by plot location. For all other leaf traits, shade tolerance was a significant factor. The species factor was significant within each shade tolerance class. This shows that shade tolerance is an important but not exclusive factor determining functional diversity. Tree height had significant influence on δ13C, specific leaf area and area-based nutrient concentrations. Higher individual trees had thicker sun-adapted leaves, regardless of the species. A principal component analysis (PCA) resulted in three significant ordination axes: leaf-thickness, N-content and P-content. By hierarchical clustering of the PCA scores, four functional groups were distinguished. This showed that species with diverse strategies coexisted in the ecosystem. © Forest Research Institute Malaysia.


De Schepper V.,Laboratory of Plant Ecology | Steppe K.,Laboratory of Plant Ecology | Van Labeke M.-C.,Laboratory of In Vitro Biotechnology and Horticulture | Lemeur R.,Laboratory of Plant Ecology
Environmental and Experimental Botany | Year: 2010

Stem diameter variations are not solely driven by the water status of a tree, but also by the carbon status in the phloem. We mechanically changed the carbon status in young oak trees (Quercus robur L.) by girdling the stem in order to investigate its effect on stem diameter variations. The stem was girdled at two heights by removing the bark which contains the carbon conducting phloem. The upper stem zone (U) still received new assimilates from the leaves, while the lowest stem zone (L) received only stored carbon from the roots. The middle stem zone (M) was completely isolated from crown and roots. As downward carbon transport was interrupted after girdling, the stem expansion and the roots. We argue that expedited growth in U was driven by both irreversible radial growth and reversible swelling. In contrast to U, stem expansion and carbohydrate content decreased in the two lower stem zones (M and L). Time lags were observed between the moments of morning shrinkage when comparing the three stem zones (U, M and L). Since these time lags correlated with the soluble carbohydrate content, it seems that daily dynamics in stem diameter variations were influenced by changes in carbon status. Furthermore, a decrease in xylem sap flow rate was observed, which could be attributed to an indirect effect of girdling. This decrease seems to be provoked by a feedback inhibition of net photosynthesis rate via stomatal closure. Such feedback inhibitions are often described in literature as a consequence of the reduced sink strength after girdling. This study, hence, demonstrates that a disturbance in tree carbon status not only changes carbon-related processes (i.e. radial stem growth, photosynthesis, carbon storage), but also water-related processes (i.e. stem swelling and shrinkage, transpiration and sap flow). © 2009 Elsevier B.V. All rights reserved.


De Swaef T.,Laboratory of Plant Ecology | Hanssens J.,Laboratory of Plant Ecology | Cornelis A.,Laboratory of Plant Ecology | Steppe K.,Laboratory of Plant Ecology
Annals of Botany | Year: 2013

Background Upward water movement in plants via the xylem is generally attributed to the cohesion-tension theory, as a response to transpiration. Under certain environmental conditions, root pressure can also contribute to upward xylem water flow. Although the occurrence of root pressure is widely recognized, ambiguity exists about the exact mechanism behind root pressure, the main influencing factors and the consequences of root pressure. In horticultural crops, such as tomato (Solanum lycopersicum), root pressure is thought to cause cells to burst, and to have an important impact on the marketable yield. Despite the challenges of root pressure research, progress in this area is limited, probably because of difficulties with direct measurement of root pressure, prompting the need for indirect and non-destructive measurement techniques. Methods A new approach to allow non-destructive and non-invasive estimation of root pressure is presented, using continuous measurements of sap flow and stem diameter variation in tomato combined with a mechanistic flow and storage model, based on cohesion-tension principles. Key Results Transpiration-driven sap flow rates are typically inversely related to stem diameter changes; however, this inverse relationship was no longer valid under conditions of low transpiration. This decoupling between sap flow rates and stem diameter variations was mathematically related to root pressure. Conclusions Root pressure can be estimated in a non-destructive, repeatable manner, using only external plant sensors and a mechanistic model. © The Author 2012.


De Schepper V.,Laboratory of Plant Ecology | Steppe K.,Laboratory of Plant Ecology
Journal of Experimental Botany | Year: 2010

In trees, water and sugars are transported by xylem and phloem conduits which are hydraulically linked. A simultaneous study of both flows is interesting, since they concurrently influence important processes such as stomatal regulation and growth. A few mathematical models have already been developed to investigate the influence of both hydraulically coupled flows. However, none of these models has so far been tested using real measured field data. In the present study, a comprehensive whole-tree model is developed that enables simulation of the stem diameter variations driven by both the water and sugar transport. Stem diameter variations are calculated as volume changes of both the xylem and the phloem tissue. These volume changes are dependent on: (i) water transport according to the cohesion-tension theory; (ii) sugar transport according to the Münch hypothesis; (iii) loading and unloading of sugars; and (iv) irreversible turgor-driven growth. The model considers three main compartments (crown, stem, and roots) and is verified by comparison with actual measured stem diameter variations and xylem sap flow rates. These measurements were performed on a young oak (Quercus robur L.) tree in controlled conditions and on an adult beech (Fagus sylvatica L.) tree in a natural forest. A good agreement was found between simulated and measured data. Hence, the model seemed to be a realistic representation of the processes observed in reality. Furthermore, the model is able to simulate several physiological variables which are relatively difficult to measure: phloem turgor, phloem osmotic pressure, and Münch's counterflow. Simulation of these variables revealed daily dynamics in their behaviour which were mainly induced by transpiration. Some of these dynamics are experimentally confirmed in the literature, while others are not. © 2010 The Author.

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