The effect of calcium antagonists and inhibitors of secretory processes on auxin induced elongation and fine structure of pisum sativum stem segments

Cunninghame, M.E.; Hall, J.L.

Protoplasma 133(2-3): 149-159

1986


ISSN/ISBN: 0033-183X
DOI: 10.1007/bf01304630
Accession: 006638814

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Abstract
The treatment of dark grown pea stem segments with chelators of divalent cations (EGTA, EDTA, CTC), various Ca2+ antagonists (LaCL3, A-23187, verapamil) and inhibitors of secretory processes (monensin, CB) reduced elongation in the presence of indole-3-acetic acid (IAA). Generally the inhibition increased with increasing concentrations of the substances. The timing of the responses can be correlated with maximum auxin-stimulated secretion of cell wall material. Examination of cell ultrastructure showed that changes in dictyosome activity could explain a reduced deposition of cell wall material and so cause inhibition of elongation. The inhibitors affected the morphology and vesiculation of the dictyosomes, and the appearance of the plasma membrane, ER and mitochondria in different ways. The most pronounced effects on ultrastructure resulted from monensin and LaCl3 treatments with the dictyosomes being most affected; large vesicles appeared in the cytoplasm. Less pronounced effects on cell structure were seen in EGTA, A-23187 and verapamil treated tissue. The effects on the dictyosomes are considered to be due to disturbances of Ca2+ and other ionic levels within the cells.

The effect of calcium antagonists and inhibitors of secretory processes on auxin induced elongation and fine structure of pisum sativum stem segments