Gas chromatography-mass spectrometry evidence for several endogenous auxins in pea seedling organs

Qualitative analysis by gas chromatography-mass spectrometry (GC-MS) of the auxins present in the root, cotyledons and epicotyl of 3-d-old etiolated pea (Pisum sativum L., cv. Alaska) seedlings has shown that all three organs contain phenylacetic acid (PAA), 3-indoleacetic acid (IAA) and 4-chloro-3-indoleacetic acid (4Cl-IAA). In addition, 3-indolepropionic acid (IPA) was present in the root and 3-indolebutyric acid (IBA) was detected in both root and epicotyl. Phenylacetic acid, IAA and IPA were measured quantitatively in the three organs by GC-MS-single ion monitoring, using deuterated internal standards. Levels of IAA were found to range from 13 to 115 pmol g-1 FW, while amounts of PAA were considerably higher (347—451 pmol g-1 FW) and the level of IPA was quite low (5 pmol g-1 FW). On a molar basis the PAA:IAA ratio in the whole seedling was approx. 15:1.