GROWTH-REGULATORS IN DEVELOPING EFFECTIVE ROOT-NODULES OF THE GARDEN PEA (PISUM-SATIVUM-L)

Levels of auxins and abscisic acid (ABA) in developing pea root nodules and uninfected roots of the gradens pea (Pisum sativum L.) were determined by gas liquid chromatography of methanol extracts. Higher levels of ABA and two auxins, indole-3-acetic acid (IAA) and indole-3-propionic acid (IPA), were detected in root nodules than in uninfected roots. In roots higher levels of ABA and phenylacetic acid (PAA) were found in the terminal 5 mm segment which included the root apical meristem but the reverse was true for IPA. Between the 2nd and 5th weeks of development the levels of IAA and PAA in nodules increased. ABA and IPA concentrations appear to increase at the onset of nodule senescence. Higher levels of ABA were associated with the nodule meristem than with the pink-colored region of infected cells, the site of symbiotic nitrogen fixation.