Table 1.

Levels of selected flavonoids from seed exudates.

Flavonoid	MRM transition	ng/seed	pmol/seed
Chrysoeriol†	301.05 > 286.00	5 ± 1	16 ± 4
Hyperoside	465.00 > 303.05	2,455 ± 32	4,963 ± 66
Luteolin†	287.15 > 153.05	38 ± 9	133 ± 31
Luteolin-7-glucoside	449.10 > 287.00	52 ± 43	117 ± 96
Quercetin*	303.15 > 153.15	<LOQ	<LOQ

Five flavonoids were quantified in alfalfa seed exudates using ultra-performance liquid chromatography-mass spectrometry in MRM, positive ion mode. Seed exudates were harvested by incubating surface-sterilized alfalfa seeds in water for 24 h and enriched for flavonoids by solid phase extraction. Values are the means and SDs from six independent replicates.

^†Indicates nod gene-inducing flavonoid in S. meliloti.

^*LOQ, limit of quantification (0.5 ng/seed).