Biomechanics of Plant Cell Growth

Abstract

Plant cell growth is an irreversible yielding of the cell wall to the internal turgor pressure of the cell. Plant cells can control their expansion by modulating the structure and material properties of their wall. One major level of control is the distribution and orientation of the stiff cellulose microfibrils within the wall. When aligned, the microfibrils impart the wall with mechanical anisotropy which allows cells to expand preferentially along one direction. Moreover, growth is possible only when the stress in the wall exceeds a critical yield stress, also under cellular control. This article summarizes the key models that have been put forward to account for these aspects of cell growth. We begin with the now classic model by James Lockhart which reconciles the mechanical and hydraulic aspects of cell expansion. We then give an overview of newer modelling efforts to account for the complexity of cell wall mechanics.

Key Concepts:

  • Plant cell growth is an irreversible change in cell size involving stretching of the cell wall driven by the internal turgor pressure of the cell.

  • Growth is measured as the relative elemental growth rate (REGR).

  • The two main modes of cell morphogenesis are tip growth and diffuse growth.

  • For a cell to grow the cell surface must expand and water must enter the cell. The Lockhart equation encapsulates the balance between these two processes.

  • Under most circumstances, the rate of cell growth is limited by the extensibility of the cell, wall whereas the resistance to the influx of water is comparatively low (plant cell growth is said to be extensibility limited).

  • Cellulose microfibrils provide the cell wall with anisotropic mechanical properties which allow cells to expand along a preferred direction.

Keywords: cell wall; turgor pressure; Lockhart equation; cell growth; anisotropy; biomechanics

Figure 1.

Mode of morphogenesis in walled cells. (a) Tip growth as observed in pollen tubes and root hairs. (b) Diffuse growth in the Nitella internodal cell. Four successive internodal cells of increasing lengths are shown. (c) Intercalary growth in the Phycomyces sporangiophore. The relative growth rate is shown as shades of green (light green, slow growth and dark green, fast growth).

Figure 2.

Surface extension in a diffusely growing cell. (a) Typical displacement of material points on the surface of a cylindrical cell. Note that the cell elongates, widens and twists as it grows. (b) The deformation of a circumferential strip of wall material. The axial and transverse strain rates, and the shear rate are respectively: ɛ̇A=ln(H/h)/Δt, ɛ̇θ=ln(R/r)/Δt and ɛ̇=tanα/Δt.

Figure 3.

Force equilibrium in a cylindrical cell.

Figure 4.

Framework for the analysis of the cellular morphogenesis. Boxes delimit the three main aspects of cellular morphogenesis.

Figure 5.

Relationship between turgor pressure and cell elongation as observed in Chara and Nitella. (a) Increases or decreases in turgor pressure lead to an abrupt (elastic) change in cell length followed by a gradual transition to a new elongation rate. (b) The elongation rate depends strongly on the cell's pressure and shows a marked yield pressure (approximately 50% of normal pressure) below which growth is not possible (based on data published in Proseus et al., ).

close

References

Ahlquist CN, Iverson SC and Jahsman WE (1975) Cell wall structure and mechanical properties of Phycomyces. Journal of Biomechanics 8: 357–362.

Baskin TI (2005) Anisotropic expansion of the plant cell wall. Annual Reviews of Cell and Developmental Biology 21: 203–222.

Bingham EC (1922) Fluidity and Plasticity. New York: McGraw‐Hill.

Boyer JS (2009) Cell wall biosynthesis and the molecular mechanism of plant enlargement. Functional Plant Biology 36: 383–394.

Carpita NC and Gibeaut DM (1993) Structural models of primary cell walls in flowering plants: consistency of molecular structure with the physical properties of the walls during growth. Plant Journal 3: 1–30.

Cave ID (1968) The anisotropic elasticity of the plant cell wall. Wood Science and Technology 2: 268–278.

Chafe SC and Wardrop AB (1972) Fine structural observations on the epidermis. I. The epidermal cell wall. Planta 107: 269–278.

Cleland R (1971) The mechanical behavior of isolated Avena coleoptile walls subjected to constant stress. Properties and relation to cell elongation. Plant Physiology 47: 805–811.

Cosgrove DJ (1985) Cell wall yield properties of growing tissue: evaluation by in vivo stress relaxation. Plant Physiology 78: 347–356.

Cosgrove DJ (1997) Assembly and enlargement of the primary cell wall in plants. Annual Review of Cell and Developmental Biology 13: 171–201.

Cosgrove DJ (2000) Loosening of plant cell walls by expansins. Nature 407: 321–326.

Cosgrove DJ (2005) Growth of the plant cell wall. Nature Reviews 6: 850–861.

Dumais J and Kwiatkowska D (2002) Analysis of surface growth in shoot apices. Plant Journal 31: 229–241.

Dumais J, Long SR and Shaw SL (2004) The mechanics of surface expansion anisotropy in Medicago truncatula root hairs. Plant Physiology 136: 3266–3275.

Dumais J Shaw SL Steele CR Long SR and Ray PM (2006) An anisotropic‐viscoplastic model of plant cell morphogenesis by tip growth. International Journal of Developmental Biology 50: 209–222.

Goriely A and Tabor M (2003) Biomechanical models of hyphal growth in actinomycetes. Journal of Theoretical Biology 222: 211–218.

Green PB (1954) The spiral growth pattern of the cell wall in Nitella axillaris. American Journal of Botany 41: 403–409.

Green PB, Erickson RO and Buggy J (1971) Metabolic and physical control of cell elongation rate. In vivo studies in Nitella. Plant Physiology 47: 423–430.

Hejnowicz Z, Heinemann B and Sievers A (1977) Tip growth: patterns of growth rate and stress in the Chara rhizoid. Zeitschrift für Pflanzenphysiologie 81: 409–424.

Hejnowicz Z and Sievers A (1995a) Tissue stresses in organs of herbaceous plants. I. Poisson ratios of tissues and their role in determination of the stresses. Journal of Experimental Botany 46: 1035–1043.

Hejnowicz Z and Sievers A (1995b) Tissue stresses in organs of herbaceous plants. II. Determination in three dimensions in the hypocotyl of sunflower. Journal of Experimental Botany 46: 1045–1053.

Hejnowicz Z and Sievers A (1996) Tissue stresses in organs of herbaceous plants. III. Elastic properties of the tissues of sunflower hypocotyl and origin of tissue stresses. Journal of Experimental Botany 47: 519–528.

Kamyia N, Tazawa M and Takata T (1963) The relation of turgor pressure to cell volume in Nitella with special reference to mechanical properties of the cell wall. Protoplasma 57: 501–521.

Kataoka H (1982) Colchicine‐induced expansion of Vaucheria cell apex. Alteration from isotropic to transversally anisotropic growth. Botanical Magazine 95: 317–330.

Lockhart JA (1965) An analysis of irreversible plant cell elongation. Journal of Theoretical Biology 8: 264–275.

Malvern LE (1969) Introduction to the Mechanics of a Continuous Medium. Englewood Cliffs: Prentice‐Hall.

Marga F, Grandbois M, Cosgrove DJ and Baskin TI (2005) Cell wall extension results in the coordinate separation of parallel microfibrils: evidence from scanning electron microscopy and atomic force microscopy. Plant Journal 43: 181–190.

McCoy EL (1989) The strain energy function in axial plant growth. Journal of Mathematical Biology 27: 575–594.

Métraux JP, Richmond PA and Taiz L (1980) Control of cell elongation in Nitella axillaris by endogenous cell wall pH gradients: multiaxial extensibility and growth studies. Plant Physiology 65: 204–210.

Ortega JKE (1990) Governing equations for plant cell growth. Physiologia Plantarum 79: 116–121.

Paolillo DJ Jr (2000) Axis elongation can occur with net longitudinal orientation of wall microfibrils. New Phytologist 145: 449–455.

Passioura JB and Fry SC (1992) Turgor and cell expansion: beyond the Lockhart equation. Australian Journal of Plant Physiology 19: 565–576.

Peters WS and Bernstein N (1997) The determination of relative elemental growth rate profiles from segmental growth rates: a methodological evaluation. Plant Physiology 113: 1395–1404.

Peters WS and Tomos AD (2000) The mechanic state of “inner tissue” in the growing zone of sunflower hypocotyls and the regulation of its growth rate following excision. Plant Physiology 123: 605–612.

Peters WS, Hagemann W and Tomos AD (2000) What makes plants different? Principles of extracellular matrix function in ‘soft’ plant tissues. Comparative Biochemistry and Physiology A 125: 151–167.

Preston RD (1974) The Physical Biology of Plant Cell Walls, pp. 68–118. London: Chapman & Hall.

Probine MC and Preston RD (1961) Cell growth and the structure and mechanical properties of the wall in internodal cells of Nitella opaca. Journal of Experimental Botany 12: 261–282.

Proseus TE, Ortega JKE and Boyer JS (1999) Separating growth from elastic deformation during cell enlargement. Plant Physiology 119: 775–784.

Proseus TE, Zhu GL and Boyer JS (2000) Turgor, temperature and the growth of plant cells: using Chara corallina as a model system. Journal of Experimental Botany 51: 1481–1494.

Ray PM and Ruesink AW (1962) Kinetic experiments on the nature of the growth mechanism in oat coleoptile cells. Developmental Biology 4: 377–397.

Richmond PA, Métraux JP and Taiz L (1980) Cell expansion patterns and directionality of wall mechanical properties in Nitella axillaris. Plant Physiology 65: 211–217.

Roelofsen PA (1965) Ultrastructure of the wall in growing cells and its relation to the direction of the growth. Advances in Botanical Research 2: 69–149.

Sachs J (1887) Lectures on the Physiology of Plants. Oxford: Oxford University Press.

Sellen DB (1983) The response of mechanically anisotropic cylindrical cells to multiaxial stress. Journal of Experimental Botany 34: 681–687.

Shaw SL, Dumais J and Long SR (2000) Cell surface expansion in polarly growing root hairs of Medicago truncatula. Plant Physiology 124: 959–969.

Suslov D and Verbelen JP (2006) Cellulose orientation determines mechanical anisotropy in onion epidermis cell walls. Journal of Experimental Botany 57: 2183–2192.

Suslov D, Verbelen JP and Vissenberg K (2009) Onion epidermis as a new model to study the control of growth anisotropy in higher plants. Journal of Experimental Botany 60: 4175–4187.

de Vries H (1877) Untersuchungen über die mechanischen Ursachen der Zellstreckung. Engelmann: Leipzig.

Wold MP and Gamow RI (1992) Fiber composite model for helical growth in the Phycomyces cell wall. Journal of Theoretical Biology 159: 39–51.

Zhu GL and Boyer JS (1992) Enlargement in Chara studied with a turgor clamp: growth rate is not determined by turgor. Plant Physiology 100: 2071–2080.

Further Reading

Sellen DB (1980) The mechanical properties of cell walls. In: Vincent JFV and Currey JD (eds) The Mechanical Properties of Biological Materials, vol. 34, pp. 315–329. London: Cambridge University Press.

Silk WK and Erickson RO (1979) Kinematics of plant growth. Journal of Theoretical Biology 76: 481–502.

Taiz L (1984) Plant cell expansion. Regulation of cell wall mechanical properties. Annual Review of Plant Physiology 35: 585–658.

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite close
Jordan, Benjamin M, and Dumais, Jacques(Mar 2010) Biomechanics of Plant Cell Growth. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0022336]