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Morphological synergism in root hair length, density, initiation and geometry for phosphorus acquisition in Arabidopsis thaliana: A modeling approach

Abstract

Low phosphorus availability regulates root hair growth in Arabidopsis by (1) increasing root hair length, (2) increasing root hair density, (3) decreasing the distance between the root tip and the point at which root hairs begin to emerge, and (4) increasing the number of epidermal cell files that bear hairs (trichoblasts). The coordinated regulation of these traits by phosphorus availability prompted us to speculate that they are synergistic, that is, that they have greater adaptive value in combination than they do in isolation. In this study, we explored this concept using a geometric model to evaluate the effect of varying root hair length (short, medium, and long), density (0, 24, 48, 72, 96, and 120 root hairs per mm of root length), tip to first root hair distance (0.5, 1, 2, and 4 mm), and number of trichoblast files (8 vs. 12) on phosphorus acquisition efficiency (PAE) in Arabidopsis. SimRoot, a dynamic three-dimensional geometric model of root growth and architecture, was used to simulate the growth of Arabidopsis roots with contrasting root hair parameters at three values of phosphorus diffusion coefficient (D e=1×10−7, 1×10−8, and 1×10−9 cm2 s−1) over time (20, 40, and 60 h). Depzone, a program that dynamically models nutrient diffusion to roots, was employed to estimate PAE and competition among root hairs. As D e decreased from 1×10−7 to 1×10−9 cm2 s−1, roots with longer root hairs and higher root hair densities had greater PAE than those with shorter and less dense root hairs. At D e=1×10−9 cm2 s−1, the PAE of root hairs at any given density was in the order of long hairs > medium length hairs > short hairs, and the maximum PAE occurred at density = 96 hairs mm−1 for both long and medium length hairs. This was due to greater competition among root hairs when they were short and dense. Competition over time decreased differences in PAE due to density, but the effect of length was maintained, as there was less competition among long hairs than short hairs. At high D e(1×10−7 cm2 s−1), competition among root hairs was greatest among long hairs and lowest among short hairs, and competition increased with increasing root hair densities. This led to a decrease in PAE as root hair length and density increased. PAE was also affected by the tip to first root hair distance. At low D e values, decreasing tip to first root hair distance increased PAE of long hairs more than that of short hairs, whereas at high D e values, decreasing tip to first root hair distance increased PAE of root hairs at low density but decreased PAE of long hairs at very high density. Our models confirmed the benefits of increasing root hair density by increasing the number of trichoblast files rather than decreasing the trichoblast length. The combined effects of all four root hair traits on phosphorus acquisition was 371% greater than their additive effects, demonstrating substantial morphological synergy. In conclusion, our data support the hypothesis that the responses of root hairs to low phosphorus availability are synergistic, which may account for their coordinated regulation.

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References

  • Barber S A 1995 Soil Nutrient Bioavailability: A Mechanistic Approach. Wiley-Interscience. New York.

    Google Scholar 

  • Bates T R and Lynch J P 1996 Stimulation of root hair elongation in Arabidopsis thaliana by low phosphorus availability. Plant, Cell Environ. 19, 529–538.

    Google Scholar 

  • Bates T R and Lynch J P 2000a Plant growth and phosphorus accumulation of wild-type and two root hair mutants of Arabidopsis thaliana. Am. J. Bot. 87,958–963.

    Google Scholar 

  • Bates T R and Lynch J P 2000b The efficiency of Arabidopsis thaliana root hairs in phosphorus acquisition.Am. J. Bot.87, 964–970.

    Google Scholar 

  • Bhat K K S and Nye P H 1974 Diffusion of phosphate to plant roots in soil. III. Depletion around onion roots without root hairs. Plant Soil 41,383–394.

    Google Scholar 

  • Clausnitzer W and Hopmans J W 1994 Simultaneous modeling of transient three-dimensional root growth and soil water flow.Plant Soil 164, 229–314.

    Google Scholar 

  • Doussan C, Pages L and Vercambre G 1998 Modeling of the hydraulic architecture of root systems: An integrated approach to water absorption-model description.Ann. Bot.81, 213–223.

    Google Scholar 

  • Fitter A H, Stickland T R, Harvey M L and Wilson G W 1991 Architectural analysis of plant root systems I: Architectural correlates of exploitation efficiency.New Phytol.118, 375–382.

    Google Scholar 

  • Fohse D and Jungk A 1983 Influence of phosphate and nitrate supply on root hair formation of rape, spinach and tomato plants. Plant Soil74, 359–368.

    Google Scholar 

  • Fohse D, Claassen N and Jungk A 1991 Phosphorus efficiency of plants II. Significance of root radius, root hairs and cation-anion balance for phosphorus influx in seven plant species.Plant Soil 132,261–272.

    Google Scholar 

  • Gahoonia T S and Nielsen N E 1997 Variation in root hairs of barley cultivars doubled soil phosphorus uptake.Euphytica98,177–182.

    Google Scholar 

  • Gahoonia T S, Care D and Nielsen N E 1997 Root hairs and phosphorus acquisition of wheat and barley cultivars.Plant Soil191, 181–188.

    Google Scholar 

  • Ge Z, Rubio G and Lynch J P 2000 The importance of root gravitropism for inter-root competition and phosphorus acquisition efficiency: results from a geometric simulation model.Plant Soil 218,159–171.

    Google Scholar 

  • Lewis D G and Quirk J P 1967 Phosphate diffusion in soil and uptake by plants.Plant Soil26,445–453.

    Google Scholar 

  • Lynch J P, Nielsen K L, Davis R D and Jablokow A G 1997 Sim-Root: modeling and visualization of botanical root systems. Plant Soil18, 139–151.

    Google Scholar 

  • Ma Z, Bielenberg D G, Brown K M and Lynch J P 2001 Regulation of root hair density by phosphorus availability in Arabidopsis thaliana.Plant, Cell Environ.24,459–467.

    Google Scholar 

  • Nielsen K L, Lynch J P, Jablokow A G and Curtis P S 1994 Carbon cost of root systems: an architectural approach.Plant Soil165, 161–169.

    Google Scholar 

  • Nye P H and Tinker P B 1977 Solute movement in the soil-root system. University of California Press, Berkeley. pp 342.

    Google Scholar 

  • Schenk M K and Barber S A 1979 Phosphate uptake by corn as affected by soil characteristics and root morphology.J. Soil Sci. Soc. Am. 43, 880–883.

    Google Scholar 

  • Somma F, Hopmann J W and Clausnitzer V 1998 Transient threedimensional modeling of soil water and solute transport with simultaneous root growth, root water and nutrient uptake. Plant Soil 202,281–293.

    Google Scholar 

  • Statistical Analysis Systems Institute 1982 SAS User's Guide: Statistics.SAS Institute, Cary, NC.

    Google Scholar 

  • Tinker P B and Nye P H 2000 Solute movement in the rhizosphere. New York: Oxford University Press. Section editor: B. Sattelmacher

    Google Scholar 

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Ma, Z., Walk, T.C., Marcus, A. et al. Morphological synergism in root hair length, density, initiation and geometry for phosphorus acquisition in Arabidopsis thaliana: A modeling approach. Plant and Soil 236, 221–235 (2001). https://doi.org/10.1023/A:1012728819326

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  • DOI: https://doi.org/10.1023/A:1012728819326

  • Arabidopsis thaliana
  • competition
  • modeling
  • phosphorus acquisition efficiency
  • root hair length
  • root hair density