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Short-term nitrogen dynamics are impacted by defoliation and drought in Fagus sylvatica L. branches

Abstract : The predicted recurrence of adverse climatic events such as droughts, which disrupt nutrient accessibility for trees, could jeopardize the nitrogen (N) metabolism in forest trees. Internal tree N cycling capacities are crucial to ensuring tree survival but how the N metabolism of forest trees responds to intense, repeated environmental stress is not well known. For 2 years, we submitted 9-year-old beech (Fagus sylvatica L.) trees to either a moderate or a severe prolonged drought or a yearly removal of 75% of the foliage to induce internal N cycling changes. During the second year of stress, in spring and summer, we sprayed N-15-urea on the leaves (one branch per tree). Then, for 14 days, we traced the N-15 dynamics through the leaves, into foliar proteins and into the branch compartments (leaves and stems segments), as well as its long-distance transfer from the labeled branches to the tree apical twigs. Defoliation caused a short- and mid-term N increase in the leaves, which remained the main sink for N. Whatever the treatment and the date, most of the leaf N-15 stayed in the leaves and was invested in soluble proteins (60-68% of total leaf N). N-15 stayed more in the proximal part of the branch in response to drought compared with other treatments. The long-distance transport of N was maintained even under harsh drought, highlighting efficient internal N recycling in beech trees. Under extreme constraints creating an N and water imbalance, compensation mechanisms operated at the branch level in beech trees and allowed them (i) to maintain leaf N metabolism and protein synthesis and (ii) to ensure the seasonal short- and long-distance transfer of recycled leaf N even under drastic water shortage conditions.
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https://hal.inrae.fr/hal-02624191
Contributor : Migration Prodinra <>
Submitted on : Tuesday, May 26, 2020 - 10:52:22 AM
Last modification on : Tuesday, June 15, 2021 - 2:57:29 PM

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Pierre-Antoine Chuste, Catherine Massonnet, Dominique Gerant, Bernhard Zeller, Joseph Levillain, et al.. Short-term nitrogen dynamics are impacted by defoliation and drought in Fagus sylvatica L. branches. Tree Physiology, Oxford University Press (OUP): Policy B - Oxford Open Option B, 2019, 39 (5), pp.792-804. ⟨10.1093/treephys/tpz002⟩. ⟨hal-02624191⟩

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