Mediterranean woody plant specialized metabolites affect germination of Linum perenne at its dry and upper thermal limits

Abstract : 8 Aims: Soil temperature and moisture impact plants not only during growth and survival but also 9 during seed germination and interaction of seeds with the chemical environment. The quantitative 10 impacts of either temperature and moisture or plant specialized metabolites (PSM) on germination 11 are widely studied. However, the combined effect of PSM and moisture or temperature on 12 germination remains poorly understood. 13 Methods: We addressed this issue by studying the effect of PSM extracted from four Mediterranean 14 woody plants on germination speed and final percentages of a subordinate herbaceous plant, Linum 15 perenne. 16 Results: By using hydro-and thermal time threshold models, we show how PSM interact with 17 temperature and moisture levels to limit germination at dry and upper thermal limits, with the 18 magnitude of effects depending on the source plant. PSM effects on germination, also observed on 19 natural soils, persisted after their removal from the seed environment. 20 Conclusions: We conclude that the impact of climate change on reproduction of herbaceous plants 21 can be modulated by effects of PSM from woody plants, which might exacerbate the negative 22 impacts of global changes on biodiversity. 23