Planta

, Volume 177, Issue 1, pp 121–130

Characterization of long-term extension of isolated cell walls from growing cucumber hypocotyls

  • Daniel J. Cosgrove
Article

DOI: 10.1007/BF00392162

Cite this article as:
Cosgrove, D.J. Planta (1989) 177: 121. doi:10.1007/BF00392162

Abstract

Walls from frozen-thawed cucumber (Cucumis sativus L.) hypocotyls extend for many hours when placed in tension under acidic conditions. This study examined whether such “creep” is a purely physical process dependent on wall viscoelasticity alone or whether enzymatic activities are needed to maintain wall extension. Chemical denaturants inhibited wall creep, some acting reversibly and others irreversibly. Brief (15 s) boiling in water irreversibly inhibited creep, as did pre-incubation with proteases. Creep exhibited a high Q10 (3.8) between 20° and 30°C, with slow inactivation at higher temperatures, whereas the viscous flow of pectin solutions exhibited a much lower Q10 (1.35). On the basis of its temperature sensitivity, involvement of pectic gel-sol transitions was judged to be of little importance in creep. Pre-incubation of walls in neutral pH irreversibly inactivated their ability to creep, with a half-time of about 40 min. At 1 mM, Cu2+, Hg2+ and Al3+ were strongly inhibitory whereas most other cations, including Ca2+, had little effect. Sulfhydryl-reducing agents strongly stimulated creep, apparently by stabilizing wall enzyme(s). The physical effects of these treatments on polymer interactions were examined by Instron and stress-relaxation analyses. Some treatments, such as pH and Cu2+, had significant effects on wall viscoelasticity, but others had little or no apparent effect, thus implicating an enzymatic creep mechanism. The results indicate that creep depends on relatively rugged enzymes that are firmly attached to or entangled in the wall. The sensitivity of creep to SH-reducing agents indicates that thiol reduction of wall enzymes might provide a control mechanism for endogenous cell growth.

Key words

Cell wall (viscoelastic properties)Cell wall enzymesCell wall extensionCreep of cell wallsCucumisHypocotyl (growth)

Abbreviations

DTT

dithiothreitol

EDTA

ethylenediaminetetraacetic acid

EGTA

ethyleneglycol-bis-(β-aminoethylether)-N,N,N′,N′-tetraacetic acid

Hepes

N-2-hydroxyethylpiperazine-N′-2-ethansulfonic acid

Copyright information

© Springer-Verlag 1989

Authors and Affiliations

  • Daniel J. Cosgrove
    • 1
  1. 1.Department of BiologyPennsylvania State UniversityUniversity ParkUSA