Submitted to: Annual Penn State Symposium in Plant Physiology
Publication Type: Abstract Only
Publication Acceptance Date: 7/28/1997
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Phosphorus (P)-deficient conditions enhance the development of proteoid root morphology in white lupin (Lupinus albus L.). Proteoid roots are short, densely clustered lateral root segments that arise from the pericycle. Previous work has demonstrated many metabolic changes in proteoid regions including: increased organic acid exudation, higher phosphoenolpyruvate carboxylase (PEPC) and malic dehydrogenase (MDH) activities, and higher acid phosphatase activities within the roots and in root exudates. The mechanisms by which proteoid roots are initiated are unknown, but it has been suggested that proteoid root formation may be regulated by hormones. Evidence from many different plants suggests that lateral root formation is regulated at least in part by auxin. To investigate the relation between auxin and proteoid root induction in white lupin, attempts were made to modify auxin transport at the early stages of lateral root development. Application of N-(1-napthyl)phthalamic acid (NPA and 2,3,5-triiodobenzoic acid (TIBA) dramatically reduced proteoid root formation in -P plants but had no significant effect on +P proteoid root formation or shoot morphology. Application of exogenous auxin (NAA) to the leaves increased proteoid root formation in +P plants by 3 fold as compared to +P control plants. NPA and TIBA applications significantly reduced PEPC and MDH activities in proteoid segments of -P roots, as compared to control roots. No significant differences in PEPC and MDH activities were observed between +P control roots and +P treated roots. No increased enzyme activities were observed in proteoid regions of NAA +P roots. This suggests that increased auxin levels may initiate proteoid root formation but do not cause the metabolic changes characteristic of -P proteoid regions.