More than Just a Shell: Indehiscent Fruits Drive Drought-Tolerant Germination in Invasive Lepidium Species

Abstract

This study aims to assess the drought stress tolerance of germinating seeds of the invasive indehiscent fruit-producing Lepidium species, specifically Lepidium appelianum, Lepidium draba, and the invasive dehiscent fruit-producing L. campestre. Drought stress tolerance experiments were conducted using various concentrations of polyethylene glycol (PEG) following standard protocols. The results revealed that seeds/fruits of L. appelianum and L. draba exhibited significantly higher drought stress tolerance compared to seeds of L. campestre. Fresh seeds and fruits of L. appelianum were capable of germinating under various drought stress treatments, while fresh and after-ripened seeds and fruits of L. draba germinated in every condition except for −0.8 MPa. Conversely, L. campestre fresh seeds did not germinate under the most severe drought stress conditions (−0.6 and −0.8 MPa). It is crucial to note that fresh fruits of L. draba displayed pericarp-mediated chemical dormancy, while fresh seeds of L. campestre demonstrated physiological dormancy. However, fresh seeds and fruits of L. appelianum did not exhibit any dormancy. This study suggests that germinating seeds and fruits of L. appelianum demonstrate the strongest tolerance to drought stress, while L. draba exhibits moderate tolerance. On the contrary, L. campestre seeds display the least tolerance to drought stress. The differences in drought stress tolerance among the studied Lepidium species reflect the climatic facets in their native distribution areas. Given the potential high invasiveness associated with the drought stress tolerance of L. appelianum and L. draba, it is imperative to develop special control strategies to manage these invasive species in the face of future climate change.