The ambiguous role of 2,4-dichlorophenoxyacetic acid in wheat tissue culture

The very basal, highly immature regions of dissected young leaves of Triticum aestivum L. cv. Kite formed adventitious roots on a nutrient medium supplemented with comparatively low concentrations (0.16 to 0.63 μM) of 2,4-dichlorophenoxyacetic acid (2,4-D). Higher concentrations (up to 640 μM) had to be applied to stimulate growth from more mature regions higher up the leaf. Yet, already at 2.5 μM roots were less distinct and more callus-like, and eventually (at 10 to 640 μM) only a subculturable callus of apparently suppressed, slowly proliferating root primordia developed. Furthermore, at the most basal, highly immature regions growth was significantly retarded when the auxin concentratio…