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Structural and Mechanical Peculiarities of the Petioles of Giant Leaves of Amorphophallus (Araceae)

Zygmunt Hejnowicz and Wilhelm Barthlott
American Journal of Botany
Vol. 92, No. 3 (Mar., 2005), pp. 391-403
Stable URL: http://www.jstor.org/stable/4123886
Page Count: 13
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Structural and Mechanical Peculiarities of the Petioles of Giant Leaves of Amorphophallus (Araceae)
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Abstract

Petioles (up to 4 m tall) of huge solitary leaves of mature plants of Amorphophallus titanum and A. gigas resemble tree trunks supporting an umbrella-like crown. In a mechanical sense, the petiole is a shell, composed of compact parenchyma with embedded collenchyma strands. The core of the shell is filled with aerenchyma. Mechanical stability of the petiole strongly depends upon the turgor pressure in the parenchyma of the shell and the core. The petiole collapses upon senescence when the turgor pressure decreases as a result of increasing osmolality of the solution permeating cell walls. The present study supports the postulate that aerenchyma serves a mechanical function. The petiole can be easily broken by animals during a collision. This risk is proposed to be lowered by the mimicry of the color pattern of the petiole's surface, which resembles a stiff tree trunk covered with lichen thalli (in both species) and with bark in the case of A. gigas. The cellular basis of these color patterns is described.

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