Plant and Soil

, Volume 166, Issue 2, pp 281–290 | Cite as

Assimilation of exogenous 2′-14C-indole-3-acetic acid and 3′-14C-tryptophan exposed to the roots of three wheat varieties

  • D. A. Martens
  • W. T. FrankenbergerJr.
Research Article


This study was conducted to determine if plants can assimilate indole-3-acetic acid (IAA) from rooting media and if exogenous L-tryptophan (L-TRP) can be assimilated and converted by plants into auxins. The addition of 2′-14C-IAA (3.7 kBq plant-1) to wheat (Triticum aestivum L.) seedlings of three varieties grown in nutrient solution resulted in the uptake (avg.=7.6%) of labelled IAA. Most of the label IAA was recovered in the shoot (avg.=7.2%) with little accumulation in the root (avg.=0.43%). A portion of the assimilated IAA-label in the plant was identified by co-chromatography and UV spectral confirmation as IAA-glycine and IAA-aspartic acid conjugates. Little of the assimilated IAA label was found as free IAA in the wheat plants. These same assimilation patterns were observed when 2′-14C-IAA was added to wheat plants grown in sterile and nonsterile soil. In contrast, the wheat varieties assimilated considerably less (avg.=1.3%) of the added microbial IAA precursor, 3′-14C-L-TRP (3.7 kBq plant-1) and thus much lower amounts of IAA conjugates were detected. Glasshouse soil experiments revealed that 2 out of 3 wheat varieties had increased growth rates and increased yields when L-TRP (10-5 and 10-7M) was added to the root zone. It is surmised that this positive response is a result of microbial auxin production within the rhizosphere upon the addition of the precursor, L-TRP. The amino acid composition of the root exudates plays a critical role in microbial production of auxins in the rhizosphere. This study showed that wheat roots can assimilate IAA from their rooting media, which will supplement the endogenous IAA levels in the shoot tissue and may positively influence plant growth and subsequent yield.

Key words

auxins exudates microbial metabolism Triticum 


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  1. Andreae W A and Good N E 1955 The formation of indoleacetylaspartic acid in pea seedlings. Plant Physiol. 30, 380–382.Google Scholar
  2. Andreae W A and vanYsselstein M W H 1956 Studies on 3-indoleacetic acid metabolism. III. The uptake of 3-indoleacetic acid by pea epicotyls and its conversion to 3-indoleacetylaspartic acid. Plant Physiol. 31, 235–240.Google Scholar
  3. Andreae W A and vanYsselstein M W H 1960 Studies on 3-indoleacetic acid metabolism: Effect of calcium ions on 3-indole-acetic acid uptake and metabolism by pea roots. Plant Physiol. 35, 220–224.Google Scholar
  4. Arshad M and Frankenberger W TJr 1992 Microbial production of plant growth regulators. In Soil Microbial Technologies. Ed. BMetting. pp 307–347. Marcel Dekker, New York.Google Scholar
  5. Bandurski R S and Schulze A 1977 Concentration of indole-3-acetic acid and its derivatives in plants. Plant Physiol. 60, 211–213.Google Scholar
  6. Barber D A and Martin J K 1976 The release of organic substances by cereal roots in soil. New Phytol. 76, 69–80.Google Scholar
  7. Beffa R, Martin H V and Pilet P E 1990 In vitro oxidation of indoleacetic acid by soluble auxin-oxidases and peroxidases from maize roots. Plant Physiol. 94, 485–491.Google Scholar
  8. Bialek K and Cohen J D 1989 Quantification of indoleacetic acid conjugates in bean seeds by direct tissue hydrolysis. Plant Physiol. 90, 398–400.Google Scholar
  9. Cohen J D and Bandurksi R S 1978 The bound auxins: Protection of indole-3-acetic acid from peroxidase-catalyzed oxidation. Planta 139, 203–208.Google Scholar
  10. Davies P J 1987 The plant hormones: Their nature, occurrence, and functions. In Plant Hormones and Their Role in Plant Growth and Development. Ed. PJDavies. pp 1–11. Martinus Nijhoff Publishers, Dordrecht, The Netherlands.Google Scholar
  11. Frankenberger WTJr and Brunner W 1983 Method of detection of auxin-indole-3-acetic acid in soils by high performance liquid chromatography. Soil Sci. Soc. Am. J. 47, 237–241.Google Scholar
  12. Frankenberger WTJr, Chang AC and Arshad M 1990 Response of Raphanus sativus to the auxin precursor, L-tryptophan applied to soil. Plant and Soil 129, 235–241.Google Scholar
  13. Frankenberger WTJr and Arshad M 1991a Yield response of watermelon and muskmelon to L-tryptophan applied to soil. Hort. Science 26, 35–37.Google Scholar
  14. Frankenberger WTJr and Arshad M 1991b Yield response of Capsicum annuum to the auxin precursor, L-tryptophan applied to soil. Plant Growth Regul. Soc. Am. 19, 231–240.Google Scholar
  15. Frankenberger WTJr and Poth M 1987 Determination of substituted indole derivatives by ion suppression-reverse phase high-performance liquid chromatography. Anal. Biochem. 165, 300–308.Google Scholar
  16. Frankenberger WTJr and Poth M 1988 L-Tryptophan transaminase of a bacterium isolated from the rhizosphere of Festuca octoflora (Graminae). Soil Biol. Biochem. 20, 299–304.Google Scholar
  17. Goldsmith MHM 1977 The polar transport of auxin. Annu. Rev. Plant Physiol. 28, 439–478.Google Scholar
  18. Goldsmith MHM 1982 A saturable site responsible for polar transport of indole-3-acetic acid in sections of maize coleoptiles. Planta 155, 68–75.Google Scholar
  19. Hitchcock AE and Zimmerman PW 1953 Adsorption and movement of synthetic growth substances from soil as indicated by the responses of aerial parts. Contrib. Boyce Thompson Inst. 7, 447–476.Google Scholar
  20. Jacobs W P 1979 Plant Hormones and Plant Development. Cambridge University Press.Google Scholar
  21. Kendall FH, Park CK and Mer CL 1971 Indole-3-acetic acid metabolism in pea seedlings. A comparative study using carboxyl- and ring-labelled isomers. Ann. Bot. 35, 565–579.Google Scholar
  22. Kutáček M 1985 Auxin biosynthesis and its regulation on the molecular level. Biol. Plant. 27, 145–153.Google Scholar
  23. Lynch JM and Whipps JM 1990 Substrate flow in the rhizosphere. Plant and Soil 129, 1–10.Google Scholar
  24. Martens DA and Frankenberger WTJr 1991 On-line solid-phase extraction of soil auxins produced from exogenously-applied tryptophan with ion-suppression reverse-phase HPLC analysis. Chromatographia 32, 417–422.Google Scholar
  25. Martens DA and Frankenberer WTJr 1992 Pulsed amperometric detection of amino acids separated by anion exchange chromatography. J. Liq. Chromatogr. 15, 423–439.Google Scholar
  26. Martens DA and Frankenberger WTJr 1993a Metabolism of L-tryptophan in soil. Soil Biol. Biochem. 25, 1679–1687.Google Scholar
  27. Martens DA and Frankenberger WTJr 1993b Stability of microbial-produced auxins derived from L-tryptophan added to soil. Soil Sci. 155, 263–271.Google Scholar
  28. Martin HJ and Pilet PE 1986 Saturable uptake of indol-3yl-acetic acid by maize roots. Plant Physiol. 81, 889–895.Google Scholar
  29. Meuwly P and Pilet PE 1991 Simultaneous gas chromatographymass spectrometry quantification of endogenous [12C]- and applied [13C]-indole-3yl-acetic acid levels in growing maize roots. Plant Physiol. 95, 179–183.Google Scholar
  30. Monteiro AM, Crozier A and Sandberg G 1988 The biosynthesis and conjugation of indole-3-acetic acid in germinating seed and seedling of Dalbergia dolichopetala. Planta 174, 561–568.Google Scholar
  31. Pernet J J and Pilet P E 1979 Importance of the tip on the (5-3H)-indole-3yl-acetic acid transport in maize root. Z. Pflanzenphysiol. Bd. 94, 273–279.Google Scholar
  32. Petzold U, Neuman St and Dahse I 1989 Amino acid and sucrose uptake into cotyledons and roots of Sinapis alba L. Biochem. Physiol. Pflanz. 185, 27–40.Google Scholar
  33. Sandberg G, Crozier A and Ernstsen A 1987 Indole-3-acetic acid and related compounds. In Principles and Practice of Plant Hormone Analysis. Vol. 2 Eds. LRivier and ACrozier. pp 169–301. Academic Press, London.Google Scholar
  34. Soldal T and Nissen P 1978 Multiphasic uptake of amino acid by barley root. Physiol. Plant. 43, 181–188.Google Scholar
  35. Thurman DA and Street HE 1962 Metabolism of some indole auxins in excised tomato roots. J. Exp. Bot. 13, 369–377.Google Scholar
  36. Venis MA 1972 Auxin-induced conjugation systems in peas. Plant Physiol. 49, 24–27.Google Scholar
  37. Whipps JM 1984 Environmental factors affecting the loss of carbon from the roots of wheat and barley seedlings. J. Exp. Bot. 35, 767–773.Google Scholar
  38. Whipps JM and Lynch JW 1983 Substrate flow and utilization in the rhizosphere of cereals. New Phytol. 95, 605–623.Google Scholar

Copyright information

© Kluwer Academic Publishers 1994

Authors and Affiliations

  • D. A. Martens
    • 1
  • W. T. FrankenbergerJr.
    • 1
  1. 1.Department of Soil and Environmental SciencesUniversity of CaliforniaRiversideUSA

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