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Planta. 1969 Sep;85(3):284-98. doi: 10.1007/BF00389404.

P protein and microtubular systems in Nicotiana, callus phloem.

Author information

1
Agricultural Research Council Institute of Animal Physiology, Babraham, Cambridge.

Abstract

A study of the ultrastructure of cultured tobacco callus phloem shows that it is very similar to that found in the intact stem.Fibrils similar to the P protein, characteristic of angiosperm phloem, are found initially within the rough endoplasmic reticulum. This has not been shown previously.Preincubation of the callus at 0 or 50° C or in solutions of cholchicine prior to fixation have no effect on the relative proportions or the individual structures of the two forms of P protein found in tobacco callus phloem sieve elements. However 1% colchicine does reduce the number of microtubules found in callus cells by up to 80%.The morphological similarity between P 1 protein tubules and microtubules therefore appears coincidental and not due to a different arrangement of a common basic unit.The function of the P protein is considered and reasons for the comparative stability of plant microtubules compared with their animal equivalents are discussed.

PMID:
24515636
DOI:
10.1007/BF00389404

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