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Bouche P.S.,University of Ulm | Bouche P.S.,French National Institute for Agricultural Research | Bouche P.S.,University of Bordeaux 1 | Delzon S.,French National Institute for Agricultural Research | And 17 more authors.
Plant, Cell and Environment

Plants can be highly segmented organisms with an independently redundant design of organs. In the context of plant hydraulics, leaves may be less embolism resistant than stems, allowing hydraulic failure to be restricted to distal organs that can be readily replaced. We quantified drought-induced embolism in needles and stems of Pinus pinaster using high-resolution computed tomography (HRCT). HRCT observations of needles were compared with the rehydration kinetics method to estimate the contribution of extra-xylary pathways to declining hydraulic conductance. High-resolution computed tomography images indicated that the pressure inducing 50% of embolized tracheids was similar between needle and stem xylem (P50 needle xylem=-3.62MPa, P50 stem xylem=-3.88MPa). Tracheids in both organs showed no difference in torus overlap of bordered pits. However, estimations of the pressure inducing 50% loss of hydraulic conductance at the whole needle level by the rehydration kinetics method were significantly higher (P50 needle=-1.71MPa) than P50 needle xylem derived from HRCT. The vulnerability segmentation hypothesis appears to be valid only when considering hydraulic failure at the entire needle level, including extra-xylary pathways. Our findings suggest that native embolism in needles is limited and highlight the importance of imaging techniques for vulnerability curves. © 2016 John Wiley & Sons Ltd. Source

Zufferey V.,Institute des science en Production Vegetale IPV
Vitis - Journal of Grapevine Research

The leaf respiration (RD) of grapevine (Vitis vinifera 'Chasselas') was measured under field conditions during the growing season in leaves of different physiological ages in relation to the temperature and plant water status. RD increased with the temperature and was particularly high in young growing leaves on primary and lateral shoots. The RD response to the temperature evolved over the season according to the type and age of the leaves and their phenology. Leaf aging (senescence) induced a decrease in RD at the end of the season. At constant temperatures (20 °C), the highest RD rates were measured during the rapid plant growth phase (the Q10 values were also the highest), and they progressively decreased to reach their lowest rates at the end of the growing season. The lowest RD values were measured on leaves that were inserted opposite the clusters of primary shoots at any period during the season. Water stress led to a reduction in RD, especially when the leaf temperature was above 20 °C. The nocturnal RD evolution showed that the RD rates were greatest at nightfall when the nocturnal temperatures were still high and leaf carbohydrate availability was at its highest; the rates gradually decreased to reach the lowest RD values just before dawn. © The author(s). Source

Zufferey V.,Institute des science en Production Vegetale IPV | Murisier F.,Institute des science en Production Vegetale IPV | Belcher S.,Institute des science en Denrees Alimentaires IDA | Lorenzini F.,Institute des science en Denrees Alimentaires IDA | And 3 more authors.
Vitis - Journal of Grapevine Research

Seasonal patterns of total organic nitrogen (N) and total non-structural carbohydrate (TNC) concentrations in relation to the leaf-fruit ratio (source-sink) were measured over three years at different grapevine phenological stages in one- and two-year-old canes, trunks and roots of the cultivar 'Chasselas' (Vitis vinifera L.). The highest N and TNC concentrations were observed during the period from dormancy until budbreak. A decrease in the N and TNC reserves was measured in the different organs (canes, trunks and roots) from budbreak, reaching minimum values around flowering, except for the N concentration in the roots, which was lowest during the period between bunch closure and veraison. N storage was highest in the roots and occurred from veraison until leaf fall. The N concentration in the trunks and canes represented approximately half of that measured in the roots. TNCs accumulated preferentially in the roots and also in the trunks and canes during the growing season. The leaf area per vine (or canopy height) and yield both influenced the N concentration in the roots. High yield and low leaf area per vine decreased the N concentration in the roots. The leaf-fruit ratio, expressed as the "light-exposed leaf area per kg fruit", substantially influenced the N and TNC concentrations in the roots at harvest. The highest N and TNC concentrations in the roots were obtained when the leaf-fruit ratio approached 2.0 m2 of light-exposed leaf area per kg fruit. © The author(s). Source

Hofstetter V.,Institute des science en Production Vegetale IPV | Redhead S.A.,Eastern Cereal and Oilseed Research Center | Kauff F.,University of Kaiserslautern | Moncalvo J.-M.,Royal Ontario Museum | Vilgalys R.,University of Tennessee at Knoxville
Cryptogamie, Mycologie

We explored evolutionary relationships within the Lyophyllaceae by combining sequence data from six loci. The most likely phylogram led us to reconsider the Lyophyllaceae classification with the recognition of two new genera (Myochromella and Sagaranella) based on ecological and/or morphological distinctiveness. Lyophyllaceae are ecologically highly diversified and our phylogeny suggests that four to five ecological transitions from free-living to parasitic or mutualistic lifestyles have occurred within the family. Due to moderate phylogenetic support recovered for several relationships within that clade and due to the uncertainty about the ecological strategy adopted by five of the sampled species, three out of these transitions could be unequivocally reconstructed suggesting that saprotrophy is plesiomorphic for Lyophyllaceae. Significant differences in rates of molecular evolution were detected among taxa. These differences are not associated with ecological transitions throughout the Lyophyllaceae, however, within each of the major clades identified in the family, taxa of different ecological strategies show an overall tendency to evolve at different speeds at the molecular level. © 2014 Adac. Tous droits réservés. Source

Marti G.,University of Geneva | Marti G.,Toulouse 1 University Capitole | Schnee S.,Institute des science en Production Vegetale IPV | Andrey Y.,University of Geneva | And 4 more authors.

UV-C radiation is known to induce metabolic modifications in plants, particularly to secondary metabolite biosynthesis. To assess these modifications from a global and untargeted perspective, the effects of the UV-C radiation of the leaves of three different model plant species, Cissus antarctica Vent. (Vitaceae), Vitis vinifera L. (Vitaceae) and Cannabis sativa L. (Cannabaceae), were evaluated by an LC-HRMS-based metabolomic approach. The approach enabled the detection of significant metabolite modifications in the three species studied. For all species, clear modifications of phenylpropanoid metabolism were detected that led to an increased level of stilbene derivatives. Interestingly, resveratrol and piceid levels were strongly induced by the UV-C treatment of C. antarctica leaves. In contrast, both flavonoids and stilbene polymers were upregulated in UV-C-treated Vitis leaves. In Cannabis, important changes in cinnamic acid amides and stilbene-related compounds were also detected. Overall, our results highlighted phytoalexin induction upon UV-C radiation. To evaluate whether UV-C stress radiation could enhance the biosynthesis of bioactive compounds, the antioxidant activity of extracts from control and UV-C-treated leaves was measured. The results showed increased antioxidant activity in UV-C-treated V. vinifera extracts. © Molecules 2014. Source

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