absolute 1 pure, unmixed; e.g. absolute alcohol. 2 not relative; e.g. absolute configuration. 3 describing a measurement defined in fundamental units of mass, length, and time that does not depend on the characteristics of the measuring apparatus; e.g. absolute temperature.

abscisic acid or (formerly) abscisin II or dormin or ABA; 5-(1- hydroxy-2,6,6-trimethyl-4-oxocyclohex-2-en-1-yl)-3-methylpenta- 2,4-dienoic acid; a chiral sesquiterpene. The naturally occurring form, the 2Z,4E,S isomer, also designated (S)-abscisic acid, is a phytohormone formed by the degradation of carotenoids. It controls abscission in flowers and fruit but probably not in leaves, and is also implicated in geotropism,

abrin a highly toxic ∼65 kDa glycoprotein obtained from the seeds of jequirity, or Indian liquorice (Abrus precatorius L.), a tropical Asian vine that also occurs in Florida. It consists of an ∼30 kDa acidic A chain, and an ∼35 kDa neutral B chain, held together by disulfide bonds. The A chain is a powerful