For 10 points, name this gaseous plant hormone.
The receptor for this molecule is complexed with the CTR1 protein in the ER of responsive cells, and that receptor's c-terminus is homologous to bacterial two-component systems and contains a histidine kinase domain. A rise in this molecule corresponds with the climacteric stage of a certain process. The synthesis of this molecule relies on MTA nucleosidase and an enzyme that synthesizes a cyclopropane derivative called ACC, which is cleaved from S-adenosyl methionine in the Yang cycle. Ein3 mutants are insensitive to this hormone. This molecule is responsible for causing the thickening, shortening and hooking of the hypocotyl in response to a barrier, known as the triple response. This hormone is responsible for leaf abscission and fruit ripening, and is the cause of one bad apple spoiling the bunch. For 10 points, name this gaseous plant hormone.
The receptor for this molecule is complexed with the CTR1 protein in the ER of responsive cells, and that receptor's c-terminus is homologous to bacterial two-component systems and contains a histidine kinase domain.
{Ethylene}