Researchers identified ethylene-related mutants in Arabidopsis thaliana by analyzing changes in the "triple response" of dark-grown seedlings. The triple response includes inhibition of stem elongation, radial swelling of the stem, and absence of normal geotropic response. Three types of mutants were isolated: eto (constitutive triple response), hls (hookless), and ein (ethylene-insensitive). The eto mutants produced significantly more ethylene than wild-type plants, while hls mutants showed reduced ethylene production. Ein mutants were insensitive to ethylene and showed increased ethylene production. These mutants provided insights into ethylene biosynthesis and signaling pathways. The study also revealed that ethylene production is regulated by multiple mechanisms, and mutations in different loci can affect ethylene perception and signaling. The findings highlight the importance of ethylene in plant growth and development, and the mutants serve as valuable tools for studying ethylene-related processes. The research contributes to understanding the molecular basis of ethylene action in plants.Researchers identified ethylene-related mutants in Arabidopsis thaliana by analyzing changes in the "triple response" of dark-grown seedlings. The triple response includes inhibition of stem elongation, radial swelling of the stem, and absence of normal geotropic response. Three types of mutants were isolated: eto (constitutive triple response), hls (hookless), and ein (ethylene-insensitive). The eto mutants produced significantly more ethylene than wild-type plants, while hls mutants showed reduced ethylene production. Ein mutants were insensitive to ethylene and showed increased ethylene production. These mutants provided insights into ethylene biosynthesis and signaling pathways. The study also revealed that ethylene production is regulated by multiple mechanisms, and mutations in different loci can affect ethylene perception and signaling. The findings highlight the importance of ethylene in plant growth and development, and the mutants serve as valuable tools for studying ethylene-related processes. The research contributes to understanding the molecular basis of ethylene action in plants.