Protoplasma

, Volume 143, Issue 1, pp 1–10

Ultrastructural localization of ATPase activity in cotton fiber during elongation

  • P. A. Joshi
  • J. McD Stewart
  • E. T. Graham
Article

DOI: 10.1007/BF01282953

Cite this article as:
Joshi, P.A., Stewart, J.M. & Graham, E.T. Protoplasma (1988) 143: 1. doi:10.1007/BF01282953

Summary

The ultrastructural distribution of potassium chloride stimulated adenosine triphosphatase activity was investigated in the outer integument of a linted cultivar of cotton and a lintless (naked seed) mutant from one day preanthesis to eight days postanthesis by using a heavy metal simultaneous capture reaction technique. No enzyme activity other than in mitochondria was observed in the lintless mutant. In the linted cultivar no ATP-specific enzyme activity was seen in non-elongating epidermal cells, subepidermal cells of the outer integuments or any controls. As fiber initials started elongating, enzyme activity gradually appeared on the tonoplasts of enlarging vacuoles. Heavier lead phosphate deposits were observed on the membrane of small vacuoles compared to the tonoplast. This activity continued at least to eight days postanthesis. The enzyme inhibitor, N,N-dicyclohexylcarbodiimide inhibited, while KCl stimulated, tonoplast ATPase activity. The gradual increase of ATPase activity on the tonoplast of expanding fibers, but not on the tonoplasts of non-fiber cells, suggests the active transport of osmotically active compounds, presumably potassium and malate, into the vacuoles of expanding fibers. Fusion of smaller vacuoles with the large central vacuole indicates that these structures contribute additional membrane components along with their enzyme activity to the tonoplast of expanding fibers. The occurrence of ATPase activity, of ER-derived vesicular structures, and the organized pattern of deposition of these structures on the tonoplast indicate ER-originated ATPase activity. This study supports the theory of osmoregulation in cotton fiber where ATPase provides the energy for active accumulation of osmotically active compounds, (K+, malate) into the vacuoles, thereby generating and maintaining the turgor pressure required for fiber expansion.

Keywords

Cotton fiber Elongation Adenosine triphosphatase Localization Histochemistry 

Abbreviations

ATPase

Adenosine triphosphatase

DCCD

N,N-Di-cyclohexylcarbodiimide

EM

Electron microscope

ER

Endoplasmic reticulum

GP

β-Glycerophosphate

LC

Lead citrate

PEP-Case

Phosphoenolpyruvate carboxylase

UA

Uranyl acetate

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Copyright information

© Springer-Verlag 1988

Authors and Affiliations

  • P. A. Joshi
    • 1
    • 3
  • J. McD Stewart
    • 4
  • E. T. Graham
    • 2
  1. 1.Department of Plant and Soil ScienceUniversity of TennesseeKnoxville
  2. 2.Department Ornamental Horticulture and Landscape DesignUniversity of TennesseeKnoxville
  3. 3.Department of Pathobiology A-201, College of Veterinary MedicineUniversity of TennesseeKnoxvilleUSA
  4. 4.Department of AgronomyUniversity of ArkansasFayettevilleUSA

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