Impact of Erysiphe alphitoides on transpiration and photosynthesis in Quercus robur leaves

International audienceOak powdery mildew, (Erysiphe alphitoides) causes one of the most common diseases of oaks. We assessed the impact of this pathogen on photosynthesis and water relations of infected leaves using greenhouse grown oak seedlings. Transpiration of seedling infected by oak powdery mildew was also investigated. Altogether, E. alphitoides had a low impact on host gas exchange whether at leaf or whole plant scale. Maximal stomatal conductance of infected leaves was reduced by 20-30% as compared to healthy controls. Severely infected seedlings did not experience any detectable change of whole plant transpiration. The reduction in net CO 2 assimilation, A n , was less than proportional to the fraction infected leaf area. Powdery mildew reduced both the maximal light driven electron flux (J max) and the apparent maximal carboxylation velocity (Vc max) although Vc max was slightly more impacted than J max. No compensation of the infection occurred in healthy leaves of partly infected seedlings as the reduced photosynthesis in the infected leaves was not paralleled by increased A n levels in the healthy leaves of the seedlings. However, E. alphitoides had a strong impact on leaf lifespan of infected leaves. It is concluded that the moderate effect of E. alphitoides on oak might be related to the small impact on net CO 2 assimilation rates and on tree transpiration; nevertheless, the severe reduction in leaf lifespan of heavily infected leaves may lead to decreased carbon uptake over the growth season

Photochemical efficiency of photosystem II in rapidly dehydrating leaves of 11 temperate and tropical tree species differing in their tolerance to drought

Les diminutions d'efficience photochimique du PS II en réponse à une déshydratation rapide et sévère des feuilles ont été comparées sur 11 espèces d'arbres connues pour présenter des degrés variables de tolérance à la sécheresse. Des semis de Quercus robur, Q. petraea, Q. pubescens, Q. rubra, Q. cerris, Q. ilex, Dalbergia sissoo, Eucalyptus camaldulensis, Acacia holosericea, Azadirachta indica et Populus candicans ont été élevés en serre. Cinquante à soixante disques foliaires ont été prélevés sur des plants. Ils ont transpiré librement à l'obscurité pendant des temps variables pouvant aller jusqu'à 6 h. Leur degré de déshydratation a été estimé par leur teneur en eau relative et leurs cinétiques d'induction de fluorescence ont été enregistrées. Toutes les espèces ont présenté une remarquable stabilité de la fluorescence de base et de la fluorescence maximale, ainsi que de l'efficience photochimique du photosystème II. Les premiers signes de dysfonctionnement observés ont consisté en une baisse de l'efficience photochimique qui a débuté à des déficits de teneur en eau relative de l'ordre de 0,23 à 0,40 suivant l'espèc

Editorial: “Fifty years Annals of Forest Science”

International audienceKey MessageAnnals of Forest Scienceis publishing a series of review papers to celebrate 50 years of activities as a journal in forest and wood science. The reviews emphasize the extent to which forest and wood sciences changed and developed as a large array of disciplines devoted to complex objects with sometimes many conflicting issues

In vivo and in situ rhizosphere respiration in Acer saccharum and Betula alleghaniensis seedlings grown in contrasting light regimes

A perfusive method combined with an open-system carbon dioxide measurement system was used to assess rhizosphere respiration of Acer saccharum Marsh. (sugar maple) and Betula alleghaniensis Britton (yellow birch) seedlings grown in 8-1 pots filled with coarse sand. We compared in vivo and in situ rhizosphere respiration between species, among light regimes (40, 17 and 6% of full daylight) and at different times during the day. To compute specific rhizosphere respiration, temperature corrections were made with either species-specific coefficients (Q10) based on the observed change in respiration rate between 15 and 21°C or an arbitrarily assigned Q10 of 2. Estimated, species-specific Q10 values were 3.0 and 3.4 for A. saccharum and B. alleghaniensis, respectively, and did not vary with light regime. Using either method of temperature correction, specific rhizosphere respiration did not differ either between A. saccharum and B. alleghaniensis, or among light regimes except in A. saccharum at 6% of full daylight. At this irradiance, seedlings were smaller than in the other light treatments, with a larger fine root fraction of total root dry mass, resulting in higher respiration rates. Specific rhizosphere respiration was significantly higher during the afternoon than at other times of day when temperature-corrected on the basis of an arbitrary Q10 of 2, suggesting the possibility of diurnal variation in a temperature-independent component of rhizosphere respiration

Monitoring the regulation of gene expression in a growing organ using a fluid mechanics formalism

<p>Abstract</p> <p>Background</p> <p>Technological advances have enabled the accurate quantification of gene expression, even within single cell types. While transcriptome analyses are routinely performed, most experimental designs only provide snapshots of gene expression. Molecular mechanisms underlying cell fate or positional signalling have been revealed through these discontinuous datasets. However, in developing multicellular structures, temporal and spatial cues, known to directly influence transcriptional networks, get entangled as the cells are displaced and expand. Access to an unbiased view of the spatiotemporal regulation of gene expression occurring during development requires a specific framework that properly quantifies the rate of change of a property in a moving and expanding element, such as a cell or an organ segment.</p> <p>Results</p> <p>We show how the rate of change in gene expression can be quantified by combining kinematics and real-time polymerase chain reaction data in a mechanistic model which considers any organ as a continuum. This framework was applied in order to assess the developmental regulation of the two reference genes <it>Actin11 </it>and <it>Elongation Factor 1-β </it>in the apex of poplar root. The growth field was determined by time-lapse photography and transcript density was obtained at high spatial resolution. The net accumulation rates of the transcripts of the two genes were found to display highly contrasted developmental profiles. <it>Actin11 </it>showed pulses of up and down regulation in the accelerating and decelerating parts of the growth zone while the dynamic of <it>EF1β </it>were much slower. This framework provides key information about gene regulation in a developing organ, such as the location, the duration and the intensity of gene induction/repression.</p> <p>Conclusions</p> <p>We demonstrated that gene expression patterns can be monitored using the continuity equation without using mutants or reporter constructions. Given the rise of imaging technologies, this framework in our view opens a new way to dissect the molecular basis of growth regulation, even in non-model species or complex structures.</p

Is the management of forest soil fertility at a turning point? A brief conclusion

Is the management of forest soil fertility at a turning point? A brief conclusio

La gestion de la fertilité des sols forestiers est-elle à un tournant ? Une conclusion transitoire

La gestion de la fertilité des sols forestiers est-elle à un tournant ? Une conclusion transitoir

\u3ci\u3eAnnals of Forest Science\u3c/i\u3e Promotes Multidisciplinary Research on Forests and Wood in a Changing World and Is Now a Full Open Access Journal

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