Abstract
Because both abscisic acid (ABA) and auxin (IAA) have been suggested as possible chemical mediators of differential growth during root gravitropism, we compared with redistribution of label from applied 3H-IAA and 3H-ABA during maize root gravitropism and examined the relative basipetal movement of 3H-IAA and 3H-ABA applied to the caps of vertical roots. Lateral movement of 3H-ABA across the tips of vertical roots was non-polar and about 2-fold greater than lateral movement of 3H-IAA (also non-polar). The greater movement of ABA was not due to enhanced uptake since the uptake of 3H-IAA was greater than that of 3H-ABA. Basipetal movement of label from 3H-IAA or 3H-ABA applied to the root cap was determined by measuring radioactivity in successive 1 mm sections behind the tip 90 minutes after application. ABA remained largely in the first mm (point of application) whereas IAA was concentrated in the region 2–4 mm from the tip with substantial levels found 7–8 mm from the tip. Pretreatment with inhibitors of polar auxin transport decreased both gravicurvature and the basipetal movement of IAA. When roots were placed horizontally, the movement of 3H-IAA from top to bottom across the cap was enhanced relative to movement from bottom to top whereas the pattern of movement of label from 3H-ABA was unaffected. These results are consistent with the hypothesis that IAA plays a role in root gravitropism but contrary to the idea that gravi-induced asymmetric distribution of ABA contributes to the response.
Similar content being viewed by others
References
Aberg B (1957) Auxin relations in roots. Annu Rev Plant Physiol 8: 152–180
Chanson A and Pilet E (1982) Transport and metabolism of [214-C] abscisic acid in maize root. Planta 154: 556–561
Davies PJ and Mitchell EK (1972) Transport of indoleacetic acid in intact roots of Phaseolus coccineus. Planta 105: 139–154
Davies PJ, Doro JA and Tarbox AW (1976) The movement and physiological effect of indoleacetic acid following point applications to root tips of Zea mays. Physiol Plant 36: 333–337
Gougler JA and Evans ML (1981) Adaptation of corn roots to exogenously applied auxin. Physiol Plant 51: 394–398
Hasenstein KH and Evans ML (1988) Effects of cations on hormone transport in primary roots of Zea mays. Plant Physiol 86: 890–894
Ishikawa H and Evans ML (1995) Specialized zones of development in roots. Plant Physiol 109: 725–727
Ishikawa H and Evans ML (1993) The role of the distal elongation zone in the response of maize roots to auxin and gravity. Plant Physiol 102: 1203–1210
Ishikawa H and Evans ML (1991) Computer-based video digitizer analysis of surface extension in maize roots: Kinetics of growth rate changes during gravitropism. Planta 183: 381–390
Katekar GF and Geissler AE (1981) Phytotropins: Conformational requirements for the abolition of the root geotropic response. Phytochemistry 20: 2465–2469
Katekar GF and Geissler AE (1992) On the role of the NPA receptor in the root gravitropic response mechanism. In: Karssen CM, van Loon LC and Vreugdenhil D (eds) Progress in Plant Growth Regulation, pp 921–927.
Konings H (1967) On the mechanism of the transverse distribution of auxin in geometrically exposed pea roots. Acta Bot Neerl 16: 161–176
Konings H (1968) The significance of the root cap for geotropism. Acta Bot B Neerl 17: 203–211
Konings H (1995) Gravitropism in roots: an evaluation of progress during the last three decades. Acta Bot Neerl 44: 195–223
Kundu KK and Audus LJ (1974) Root growth inhibitors from root cap and root meristem of Zea mays. J Exp Bot 25: 479–489
Lee JS, Mulkey TJ and Evans ML (1984) Inhibition of polar calcium movement and gravitropism in roots treated with auxin-transport inhibitors. Planta 160: 536–543
Moore R and Smith JD (1985) Graviresponsiveness and abscisic-acid content of roots of carotenoid-deficient mutants of Zea mays L. Planta 164: 126–128
Pilet PE (1973) Growth inhibitor from the root cap of Zea mays. Planta 111: 275–278
Pilet PE (1980) Hormonal control of root georeaction: Some light effects. In: Skoog F (ed) Plant Growth Substances 1979, pp 450–461. Berlin, Germany: Springer-Verlag
Pilet PE and Barlow PW (1987) The role of abscisic acid in root growth and gravireaction: A critical review. Plant Growth Regul 6: 217–265
Shaw S and WIlkins MB (1973) The source and lateral transport of growth inhibitors in geotropically stimulated roots of Zea mays and Pisum sativum. Planta 109: 11–26
Sussman MR and Goldsmith MHM (1981) Auxin uptake and action of N-1-naphthylphthalamic acid in corn coleoptiles. Planta 150: 15–25
Went FW and Thimann KV (1937) Phytohormones. New York, USA: Macmillan
Young LM, Evans ML and Hertel R (1990) Correlations between gravitropic curvature and auxin movement across gravistimulated roots of Zea mays. Plant Physiol 92: 792–796
Young LM and Evans ML (1994) Calcium-dependent asymmetric movement of 3H-indole-3-acetic acid across gravistimulated isolated root caps of maize. Plant Growth Regul 14: 235–242
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Young, L.M., Evans, M.L. Patterns of auxin and abscisic acid movement in the tips of gravistimulated primary roots of maize. Plant Growth Regul 20, 253–258 (1996). https://doi.org/10.1007/BF00043315
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00043315