Temperature during seed maturation influences timing of bud burst in seedlings and saplings of Prunus padus.

We tested whether temperature during seed maturation in a broadleaved woody perennial may influence the phenological performance of seedlings through an epigenetic memory. We performed two controlled crosses of Prunus padus in two subsequent years (2015 and 2016). Clonal mother shrubs were subjected to a cold and a warm condition during seed maturation. In the first year after germination the seedlings from the warm seed maturation condition burst their buds earlier compared to the cold condition seedlings, whereas in the second and third year, these seedlings burst their buds later. A temporary maternal effect may have advanced bud burst for the warm condition seedlings in the first year, whereas a delay of bud burst in the following years suggest a transgenerational epigentic memory, putatively expressing a stress reaction upon the suboptimal elevated temperature during seed maturation. In the spring of 2020, seedlings were divided in a cold and a warm treatment. The warm spring treatment enlarged the difference in timing of bud burst between the cold and warm seed maturation conditions in both crosses, suggesting that the epigenetic memory is more strongly expressed in a warmer spring environment. The timing of the autumnal leaf senescence in the seedlings was not influenced by the temperature during seed maturation in all observation years, suggesting that autumnal senescence is less (epi)genetically determined in comparison to bud burst, and more sensitive to ambient temperatures.