Two sets of receptors for this compound are named after its synthetic analog, pyrabactin. After its biosynthesis in the terpenoid pathway, this compound may be conjugated with a β-D-glucosyl ester for storage or oxidize into phaseic acid. This compound was first isolated in the 1960s from young cotton plants and sycamore leaves. Plant roots synthesize this compound to induce an increase in its (*) root-to-shoot ratio at low water potential. Guard cells influx calcium ions in the presence of this hormone, resulting in stomatal closure during drought stress. This hormone counteracts the “elongative” effects of (-5[1])gibberellins (-5[1])to (-5[1])prevent germination during seed dormancy. For 10 points, name this growth-inhibiting plant hormone named for its dubious involvement in leaf shedding. (10[3])■END■