Rhizosphere Carboxylate Concentrations of Chickpea are Affected by Soil Bulk Density

Abstract

We investigated whether carboxylate exudation by chickpea (Cicer arietinum L.) was affected by soil bulk density and if this effect was local or systemic. We hypothesised that concentrations of carboxylates would increase with distance from the root apex due to continuous and constitutive accumulation of carboxylates, and that exudate accumulation would be greater in a compacted soil than in a loose soil. Plants were grown in split-root or single cylinders containing loose (1400 kg m^-3) or compacted (1800 kg m^-3) soil. Rhizosphere carboxylate concentrations were measured of whole root systems as well as of sections along the root. The root diameter was greatest of plants grown in the compacted soil; however, root diameters were the same for both root halves in the split-root design, whether they grew in loose soil or in compacted soil. Similarly, carboxylate concentrations tended to be lower for the whole root system in the compacted soil, but were the same for both root halves in the split-root design, irrespective of whether the roots were in loose soil or in compacted soil. These results indicate that both root diameter and carboxylate exudation by roots in chickpea is regulated systemically via a signal from the shoot rather than by local signals in the roots. There was no accumulation of carboxylates with increasing distance from the apex, probably because microbial degradation occurred at similar rates as carboxylate exudation. Malonate, previously suggested as deterrent to microorganisms, is likely only a selective deterrent.

Key words

Carboxylates - chickpea - soil bulk density - split-root - rhizosphere - root diameter.

References

• 1 Arvidsson J.. Nutrient uptake and growth of barley as affected by soil compaction.  Plant and Soil. (1999);  208 9-19
• 2 Cawthray G. R.. Improved reversed-phase liquid chromatography method for the analysis of low-molecular-mass organic acids in plant root exudates.  Journal of Chromatography A. (2003);  1011 233-240
• 3 Clark L. J., Whalley W. R., Barraclough P. B.. How do roots penetrate strong soil?.  Plant and Soil. (2003);  255 93-104
• 4 Dinkelaker B., Römheld V., Marschner H.. Citric acid excretion and precipitation of calcium citrate in the rhizosphere of white lupin (Lupinus albus L.).  Plant, Cell and Environment. (1989);  12 285-292
• 5 Gerke J.. Kinetics of soil phosphate desorption as affected by citric acid.  Zeitschrift für Pflanzenernährung und Bodenkunde. (1994);  157 17-22
• 6 Gilbert G. A., Knight J. D., Vance C. P., Allan D. L.. Proteoid root development of phosphorus deficient white lupin is mimicked by auxin and phosphonate.  Annals of Botany London. (2000);  85 921-928
• 7 Hagström J., James W. M., Skene K. R.. A comparison of structure, development and function in cluster roots of Lupinus albus L. under phosphate and iron stress.  Plant and Soil. (2001);  232 81-90
• 8 Hocking P. J., Keerthisinghe G., Smith F. W., Randall P. J.. Comparison of the ability of different crop species to access poorly-available soil phosphorus. Ando, T., Fujita, K., Mae, T., Matsumoto, H., Mori, S., and Sekiya, J., eds Plant Nutrition - For Sustainable Food Production and Environment. Dordrecht; Kluwer Academic Publishers (1997)
• 9 Hocking P. J., Jeffery S.. Cluster-root production and organic anion exudation in a group of old-world lupins and a new-world lupin.  Plant and Soil. (2004);  258 135-150
• 10 Jones D. L.. Organic acids in the rhizosphere - a critical review.  Plant Soil. (1998);  205 25-44
• 11 Jones D., Brassington D.. Sorption of organic acids in acid soils and its implications in the rhizosphere.  European Journal of Soil Science. (1998);  49 447-455
• 12 Khan T. N., Siddique K. H. M.. Registration of “Heera” chickpea.  Crop Science. (2000);  40 1501-1502
• 13 Keerthisinghe G., Hocking P. J., Ryan P. R., Delhaize E.. Effect of phosphorus supply on the formation and function of proteoid roots of white lupin (Lupinus albus L.).  Plant, Cell and Environment. (1998);  21 467-478
• 14 Kitson R. E., Mellon M. G.. Colorimetric determination of phosphorus as molybdo-vanado-phosphoric acid.  Industrial and Engineering Chemistry Analytical Edition. (1944);  16 379
• 15 Lambers H., Cramer M. D., Shane M. W., Wouterlood M., Poot P., Veneklaas E. J.. Structure and functioning of cluster roots and plant responses to phosphate deficiency.  Plant and Soil. (2003);  248 ix-xix
• 16 Li J., Copeland L.. Role of malonate in chickpeas.  Phytochemistry. (2000);  54 585-589
• 17 McCluskey J., Herdman L., Skene K. R.. Iron deficiency induces changes in metabolism of citrate in lateral roots and cluster roots of Lupinus albus.  Physiologia Plantarum. (2004);  121 586-694
• 34 Neumann G., Römheld V.. Root excretion of carboxylic acids and protons in phosphorus-deficient plants.  Plant and Soil. (1999);  211 121-130
• 18 Passioura J. B.. Soil structure and plant growth.  Australian Journal of Soil Research. (1991);  29 717-728
• 19 Peñaloza E., Corcuera L. J., Martinez J.. Spatial and temporal variation in citrate and malate exudation and tissue concentration as affected by P stress in roots of white lupin.  Plant and Soil. (2002);  241 209-221
• 20 Ryan P. R., Delhaize E., Jones D. L.. Function and mechanism of organic anion exudation from plant roots.  Annual Review of Plant Physiology and Plant Molecular Biology. (2001);  52 527-560
• 21 Shane M. W., De Vos M., De Roock S., Lambers H.. Shoot P status regulates cluster-root growth and citrate exudation in Lupinus albus grown with a divided root system.  Plant, Cell and Environment. (2003);  26 265-273
• 22 Shane M. W., Lambers H.. Cluster roots: a curiosity in context.  Plant and Soil. (2005);  274 101-125
• 23 Skene K. R., James W. M.. A comparison of the effects of auxin on cluster root initiation and development in Grevillea robusta Cunn. ex R. Br. (Proteaceae) and in the genus Lupinus (Leguminosae).  Plant and Soil. (2000);  219 221-229
• 24 Stirzaker R. J., Passioura J. B., Wilms Y.. Soil structure and plant growth: impact of bulk density and biopores.  Plant and Soil. (1996);  185 151-162
• 25 Veneklaas E. J., Stevens J., Cawthray G. R., Turner S., Grigg A. M., Lambers H.. Chickpea and white lupin rhizosphere carboxylates vary with soil properties and enhance phosphorus uptake.  Plant and Soil. (2003);  248 187-197
• 26 Watt M., Evans J. R.. Linking development and determinacy with organic acid efflux from proteoid roots of white lupin grown with low phosphorus and ambient or elevated atmospheric CO₂ concentration.  Plant Physiology. (1999);  120 705-716
• 27 Watt M., Evans J. R.. Proteoid roots: physiology and development.  Plant Physiology. (1999 b);  121 317-323
• 28 Watt M., McCully M. E., Kirkegaard J. A.. Soil strength and rate of root elongation alter the accumulation of Pseudomonas sp. and other bacteria in the rhizosphere of wheat.  Functional Plant Biology. (2003);  30 483-491
• 29 Weber E., George E., Beck D. P., Saxena M. C., Marschner H.. Vesicular-arbuscular mycorrhiza and phosphorus uptake of chickpea grown in northern Syria.  Experimental Agriculture. (1992);  28 433-442
• 30 Wouterlood M., Cawthray G. R., Turner S., Lambers H., Veneklaas E. J.. Rhizosphere carboxylate concentrations of chickpea are affected by genotype and soil type.  Plant and Soil. (2004 a);  161 1-10
• 31 Wouterlood M., Cawthray G. R., Scanlon T. T., Lambers H., Veneklaas E. J.. Carboxylate concentrations in the rhizosphere of lateral roots of chickpea (Cicer arietinum) increase during plant development, but are not correlated with phosphorus status of soil or plants.  New Phytologist. (2004 b);  162 745-753
• 32 Wouterlood M., Lambers H., Veneklaas E. J.. Plant phosphorus status has a limited influence on the concentration of phosphorus-mobilising carboxylates in the rhizosphere of chickpea.  Functional Plant Biology. (2004 c);  32 153-159
• 33 Zaidi A., Khan M. S., Amil M.. Interactive effect of rhizotrophic microorganisms on yield and nutrient uptake of chickpea.  European Journal of Agronomy. (2003);  19 15-21

Editor: H. Papen