Does long-term drought or repeated defoliation affect seasonal leaf N cycling in young beech trees?

Forest trees adopt effective strategies to optimize nitrogen (N) use through internal N recycling. In the context of more recurrent environmental stresses due to climate change, the question remains of whether increased frequency of drought or defoliation threatens this internal N recycling strategy. We submitted 8-year-old beech trees to 2 years of either severe drought (Dro) or manual defoliation (Def) to create a state of N starvation.

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

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.

The impact of prolonged drought on phloem anatomy and phloem transport in young beech trees.

Phloem failure has recently been recognized as one of the mechanisms causing tree mortality under drought, though direct evidence is still lacking. We combined 13C pulse-labelling of 8-year-old beech trees (Fagus sylvatica L.) growing outdoors in a nursery with an anatomical study of the phloem tissue in their stems to examine how drought alters carbon transport and phloem transport capacity.

Diurnal inhibition of NMDA-EPSCs at rat hippocampal mossy fibre synapses through orexin-2 receptors.

Diurnal release of the orexin neuropeptides orexin-A (Ox-A, hypocretin-1) and orexin-B (Ox-B, hypocretin-2) stabilises arousal, regulates energy homeostasis and contributes to cognition and learning. However, whether cellular correlates of brain plasticity are regulated through orexins, and whether they do so in a time-of-day-dependent manner, has never been assessed. Immunohistochemically we found sparse but widespread innervation of hippocampal subfields through Ox-A- and Ox-B-containing fibres in young adult rats.

Buffering growth variations against water deficits through timely carbon usage.

Water stresses reduce plant growth but there is no consensus on whether carbon metabolism has any role in this reduction. Sugar starvation resulting from stomatal closure is often proposed as a cause of growth impairment under long-term or severe water deficits. However, growth decreases faster than photosynthesis in response to drought, leading to increased carbohydrate stores under short-term or moderate water deficits.