Influence of Summer Drought on Resprouting and Leaf Senescence in a Common Garden of Prunus spinosa L.

Understanding how woody plants cope with severe water shortages is critical, espe-cially for regions where droughts are becoming more frequent and intense. We studied the effects of drought intensity, focusing on post-drought resprouting, autumn leaf se-nescence and the subsequent spring bud burst. Furthermore, we aimed to study popu-lation differentiation in the drought and post-drought responses. We performed a summer dry-out experiment in a common garden of potted Prunus spinosa L. (Rosaceae) saplings. We looked at the responses in different visual stress symptom categories and at provenance differentiation between a local (Western Europe), a more southern and a more northern provenance. The chance on post-drought resprouting was larger for the more severely affected plants, and the timing of resprouting was earlier than for the less severely affected ones. The plants that displayed wilting of the leaves during the drought had a leaf senescence 2.7 days earlier than the controls, whereas plants with 25 to 75% and more than 75% of desiccated leaves were 7 and 15 days later, respectively. During the drought, the local provenance was the first to de-velop visual symptoms. Still, for the plants with no to mild symptoms due to the drought, this provenance displayed a larger chance for post-drought resprouting. Among the control plants, the northern provenance was earlier, and the southern was later in leaf senescence compared to the local provenance. This differentiation disap-peared for the plants with more than 25% of desiccated leaves due to the drought. Whereas leaf senescence could be earlier or later depending on the developed drought symptoms, the timing of bud burst was only delayed. Results indicate that resprouting and timing of leaf senescence are responsive to the severity of the experienced drought in a provenance dependent way.