C depletion and tree dieback in young peach trees: a possible consequence of N shortage?

Key message Bud burst disruption, carbon depletion and tree dieback in spring were experimentally linked to N shortage the previous autumn. Dieback occurred despite tree N concentrations were compatible with plant survival: their N stores being blocked in the roots and woody axes. Context Tree dieback is generally linked to hydraulic failure or carbon (C) starvation but seldom to poor nitrogen (N) resources. Aim We provide here an experimental evidence linking autumn N shortage, C depletion and tree dieback in spring. Methods Young peach trees were either N deprived or fertilised in autumn, and then fed in excess in spring. Spring supplies were 15 N-labelled. The effects of the deprivation on tree development, N uptake and C status were then assessed by coupling in situ measurements of shoot development with organ biochemical and isotopic determinations. Results All deprived trees died within 3 months after burst. Bud burst was severely disrupted, and vegetative growth lim ited to the expansion of a few leaves. The dead trees absorbed between 39 and 117mg 15N in spring, and their roots and axes contained 758 mg more nitrogen than the fertilised trees, suggesting that they did not mobilise their N reserves in spring. They also had lower non-structural carbohydrate concentrations (15.4 % DW), which were below the threshold accepted for plant survival. Conclusion Two possible causes of total non-structural carbon (or TNC) depletion are discussed: insufficient storage due to advanced leaf senescence or increase in the C costs regarding winter embolism recover