Micronutrient composition of xylem sap and needles as a result or P-fertilization in maritime pine

International audienc

Micronutrient composition of xylem sap and needles as a result or P-fertilization in maritime pine

International audienc

Do trees use reserve or newly assimilated carbon for their defense reactions ? A 13C labeling approach with young Scots pines inoculated with a bark-beetle-associated fungus (Ophiostoma brunneo ciliatum)

Three-year-old saplings of Pinus sylvestris L. were labeled with 13CO2 prior to inoculating the trunk with Ophiostoma brunneo ciliatum, a blue-staining fungus usually associated to Ips sexdentatus. During incubation, half the trees were submitted to a severe drought that decreased photosynthesis and natural 13C content in non-labeled saplings. A large 13C-excess was obtained in wood and phloem, especially in the fractions of soluble proteins, starch and soluble sugars of labeled saplings. Drought increased 13C-excess, due to reduced photosynthesis and smaller dilution of 13C by the addition of newly assimilated 12C. The induced-reaction zones in inoculated saplings displayed large total C (58 g 100 g−1) because of the accumulation of secondary metabolites. They also showed much larger 13C-excess than any other compartment: the contribution of stored C to the reaction zones was much higher than that of currently assimilated C. Moreover, drought lowered the contribution of the latter, as shown by the increase of 13C in the reaction zones. We conclude that stored C was readily mobilized for the construction of reaction tissues, and that the contribution of currently assimilated C was only minor.De jeunes pins sylvestres (Pinus sylvestris L.) âgés de trois ans ont été marqués avec du 13CO2 puis inoculés dans le tronc avec Ophiostoma brunneo ciliatum, un champignon habituellement associé au scolyte Ips sexdentatus. Pendant l’incubation, la moitié des arbres a été soumise à une sécheresse sévère qui a fortement réduit la photosynthèse et l’abondance naturelle en 13C des individus non marqués. Un fort excès en 13C a été détecté dans le bois et le phloème ainsi que dans les protéines solubles, l’amidon et les sucres solubles des individus marqués. La sécheresse a amplifié cet excès, du fait d’une photosynthèse réduite et donc d’une moindre dilution du 13C par du 12C récemment assimilé. Les zones de réaction induite autour des points d’inoculation présentaient de fortes teneurs en C (58 g 100 g−1), du fait de l’accumulation massive de métabolites secondaires. Elles présentaient également un excès de 13C plus marqué que n’importe quel autre tissu : ces zones de réaction étaient donc essentiellement constituées à partir de C provenant des réserves avec une faible contribution de C récemment assimilé. De plus, la sécheresse a augmenté la contribution du C de réserve, comme le montre l’augmentation de l’excès de 13C dans les zones de réactio

Influence d'un dessèchement du sol sur la nutrition minérale de jeunes plants de résineux

Deux expériences ont été menées en serre sur de jeunes plants, respectivement de sapins ( Abies alba, nordmanniana et numidica) et d’épicéa (Picea abies). Différentes durées et intensités de dessèchement du sol ont été appliquées. Cette année-là, la croissance aérienne ainsi que les différences de croissance et de biomasse foliaire entre traitements ont été faibles chez les sapins, importantes chez l’épicéa. En fin d’année, les concentrations des différents éléments dans les aiguilles des sapins étaient d’autant plus faibles que la sécheresse avait été plus marquée. Chez l’épicéa, les prélèvements foliaires effectués en cours de saison de végétation fournissent un résultat à peu près identique au précédent. Par contre, en fin d’année cela n’est plus valable que pour le potassium ; au contraire, le déficit hydrique a alors augmenté les teneurs foliaires en azote, manganèse et calcium. Il en découle, et pour cet élément cela concorde avec les renseignements bibliographiques, que l’analyse du potassium apparaît comme un test robuste de diagnostic de déficit hydrique sur de jeunes résineux, qui reste valable même après disparition du stress. Parallèlement, une fertilisation en potassium pourrait peut-être corriger en partie les conséquences de la sécheresse.Two experiments have been realized in a greenhouse on young plants of firs (Abies alba, nordmanniana et numidica) and spruce (Picea abies). Different durations and intensities of soil drying have been carried out. That year, the shoot increase as well as the differences of growth and new leaf area between treatments were small for firs and important for spruce. At the end of the year, the more important had been the soil desiccation, the smaller were the different elements contents in the firs needles. On spruce, the results are about the same with sampling during the growth period. On the other hand, at the end of the year, it is not the case any longer, except for potassium ; on the contrary, the water deficit had then increased the needles contents in nitrogen, manganese and calcium. Analysis of foliar potassium content appears therefore (ours results agree with litterature for this element) as a good test for water deficit diagnosis on young plants of conifers ; this test remains available even after the stress has disappeared. Concurrently, soil fertilization with potassium could perhaps reduce the effects of soil dessication on these plants

Description of the maturation stages of <i>T. melanosporum</i> ascocarps (modified from Giovanni Pacioni, personal communication).

<p>Description of the maturation stages of <i>T. melanosporum</i> ascocarps (modified from Giovanni Pacioni, personal communication).</p

Kinetics of δ¹³C (in ‰) in the fine roots and <i>T. melanosporum</i> mycorrhizas beneath hazel tree A11 in 2010–2011 after the pulse labelings of the leaves with ¹³CO₂.

<p>Two-way Anova has been performed using R; data have been raised to the power minus 2 prior to Anova as suggested by the Box-Cox method in order to ensure the normality of residuals. Anova showed a ‘date’ (p<0.01) and ‘organ’ (p<0.001) effects but no interaction. Standard errors of means are given (in brackets). Mean comparison has been made for simple effects (Tukey test): for d¹³C in fine roots and d¹³C in mycorrhizas respectively, means followed by a different letter are significantly different.</p

Kinetics of δ¹³C (in ‰) in leaves of the hazel tree A11 after pulse labeling and δ¹³C of buds and branches sampled during the winter following the pulses.

<p>One-way Anova has been performed using R; data have been raised to power minus 2 prior to Anova as suggested by the Box-Cox method in order to ensure the normality of residuals. Standard errors of means are given in brackets and mean values followed by a different letter are significantly different from the others at p<0.05 (Mean comparison Tukey’s test).</p

(A) Maturity, numbers and fresh weight of ascocarps harvested beneath the labeled tree A11; (B) δ¹³C (in ‰) in <i>T. melanosporum</i> ascocarps (peridium and gleba) beneath the labeled tree A11, and beneath non-labeled trees (natural abundance) at each sampling date from October 2010 to January 2011.

<p>n = 3 to 7 ascocarps harvested at each sampling date. Two-way Anova has been performed using R (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0064626#pone-0064626-t004" target="_blank">table 4B</a>); data have been log transformed prior to Anova as suggested by the Box-Cox method in order to ensure the normality of residuals. Anova showed a ‘date’ (p<0.05) and ‘organ’ (p<0.001) effects but no interaction. Standard errors of means are given (in brackets). Mean comparison has been made for simple effects (Tukey test): for δ¹³C in the peridium and δ¹³C in the gleba, means followed by a different letter are significantly different.</p