Humidity shapes reproductive development in Arabidopsis thaliana by modulating epidermal identity and cell wall dynamics

Plants have evolved mechanisms to cope with environmental fluctuations, yet climate change increasingly exposes them to prolonged and extreme conditions. Here, we show that sustained high humidity disrupts reproductive organ development in Arabidopsis thaliana at multiple stages. It impairs anther dehiscence and compromises pollen and stigma function, reducing seed set. In seedpods, high humidity inhibits de novo cuticle formation, allowing water infiltration and causing seed abortion. At the molecular level, high humidity reversibly downregulates the epidermal regulator ATML1 via ethylene signaling, disrupting epidermal specification in both seedpods and inflorescence meristems. This loss leads to meristem arrest and systemic changes in reproductive architecture, partly through altered cytokinin signaling. Together, these findings demonstrate atmospheric humidity acts not only as an environmental stressor but also as a reversible developmental cue, revealing humidity as an underappreciated regulatory layer in plant reproduction with implications for crop resilience under climate change.