Ethylene as a Central Regulator of Seed Germination, Early Seedling Development, and Stress Adaptation.

Ethylene, a two carbon phytohormone is required for fine-tuning the seed dormancy release, germination, and early seedling development. It interacts with abscisic acid (ABA), and alleviates dormancy by increasing endosperm softening and radicle protrusion. It works in synergy with gibberellins and helps in rapid seed germination, whereas, its cross talk with reactive oxygen species (ROS) facilitates cell wall modification. After germination of seedling, ethylene affects hypocotyl elongation and apical hook formation, protecting the shoot tip during soil emergence. It also reshapes the root system architecture by coordinating auxin transport and brassinosteroid responses, thereby optimizing the plant's search for water and nutrients. Beyond development, ethylene confers tolerance to salinity, hypoxia, and extreme temperatures, by sustaining antioxidant defenses and metabolic adjustments that keep the embryo safe. In agricultural practices, well-timed ethylene treatments can break seed dormancy, tighten germination uniformity, and improve seedling establishment under harsh conditions. Experiments in sunflower and lettuce, demonstrate that this hormone boosts seed vigor and synchronizes germination. Despite the researchers made substantial progress, we still lack answers about species-specific regulation, epigenetic control, and interplay with other hormones. Because transcriptomics, genetics, and biotechnology now provide sharper tools we can better coordinate ethylene responses for crop improvement. Consequently, adopting these strategies, we can support sustainable agriculture and strengthen global food security. This chapter discusses the critical importance of ethylene in bridging basic plant biology with practical applications.