Heliotropium europaeum is a toxic annual weed that has been found with increasing frequency in the Mediterranean agro-environment. We investigated, both in laboratory and in field, the ecological aspects of this species in order to verify a possible connection between cropping systems and population increase. Its germination, characterized by a high thermal optimum (about 35°C) is markedly reduced by burial. Strong depth-mediated germination inhibition was observed with over 2 cm of burial. Nongerminated seeds undergo a secondary dormancy highlighting their ability to form a persistent seed bank. Indeed the seed bank analysis carried out in an agroecosystem based on minimum tillage cropping systems showed a seed accumulation in the shallowest soil layers. The hypothesis that poor seed burial plays a crucial role in the population dynamics of this species was confirmed by the drastic reduction in seedling emergence after only 1 year of plowing. A strongly reduced emergence percentage was shown which causes not only a lower seedling density but also a lower inflorescence density and respective seed ripening. In conclusion, there is a clear relationship between an increase in this species and cultivation systems based on minimum tillage.

中文翻译：

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有毒杂草 Heliotropium europaeum L.：多样化种植系统中的萌发生态学、土壤种子库和出苗动态

天芥菜是一种有毒的一年生杂草，在地中海农业环境中发现的频率越来越高。我们在实验室和野外调查了该物种的生态方面，以验证种植系统与人口增长之间可能存在的联系。它的发芽，其特点是高温最适温度（约 35°C），因掩埋而显着减少。埋葬超过 2 厘米时观察到强烈的深度介导的发芽抑制。未发芽的种子经历二次休眠，突出了它们形成持久种子库的能力。事实上，在基于最少耕作系统的农业生态系统中进行的种子库分析表明，种子在最浅的土壤层中积累。种子埋藏不当在该物种的种群动态中起关键作用的假设被仅耕种一年后幼苗出现的急剧减少所证实。显示出苗率大大降低，这不仅导致幼苗密度降低，而且导致花序密度和相应的种子成熟度降低。总之，该物种的增加与基于最小耕作的耕作系统之间存在明显的关系。