Used as a stable isotope-labeled internal standard in mass spectrometry for the quantification of indole-3-acetic acid (IAA) in plant and biological samples. Its deuterated structure allows for accurate differentiation from endogenous IAA during analytical testing, improving precision in hormone level measurements. Commonly applied in plant physiology research to study growth regulation, hormone metabolism, and stress responses. Also utilized in metabolic tracing experiments to monitor IAA biosynthesis and degradation pathways without altering biological activity.