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Stalk Formation in Dictyostelium

Kenneth B. Raper and Dorothy I. Fennell
Bulletin of the Torrey Botanical Club
Vol. 79, No. 1 (Jan. - Feb., 1952), pp. 25-51
Published by: Torrey Botanical Society
DOI: 10.2307/2482103
Stable URL: http://www.jstor.org/stable/2482103
Page Count: 27
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Stalk Formation in Dictyostelium
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Abstract

1. Sorocarps, or fruiting structures, in Dictyostelium are formed by the orderly differentiation of large numbers of separate but clearly coordinated amoeboid cells, or myxamoebae. 2. The sorophore, or stalk, consists of an outer sheath of cellulose surrounding a column of closely compacted, strongly vacuolated, pith-like cells. The sheath appears in advance of obvious cell differentiation and is formed by the extracellular deposition of cellulose in a critical circular zone, the dimensions of which are proportional to the mass of cooperating myxamoebae. 3. The principal force responsible for lifting the sorogen, or sporogenous mass, into the air results from the swelling of stalk cells entrapped in the elongating sorophore sheath; a second and progressively diminishing force results from the coordinated pseudopodial movements of the myxamoebae that comprise the sorogen. Tests which indicate that the sorophore sheath (of extracellular origin) is cellulosic in character include: staining reactions, solubilities, birefringence in polarized light, X-ray diffracton pattern, paper chromatography of hydrolysis products, and decomposition by cellulose- destroying bacteria.

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