Developmental and Structural Section
Tomlinson, P. Barry , Horn, James W. , Fisher, Jack B. .
Palms and Ponce de Leon: the secret of eternal youth exemplified by sustained primary growth in Arecaceae.
We describe late changes in the structure of the tissues of the palm stem (sustained primary growth) that are of considerable physiological interest. When the Spanish explorer travelled through the swamps and forests of Florida in the sixteenth century in search of the mythical Fountain of Youth, whose waters could eternally rejuvenate, he passed through groves of the common native cabbage palm, Sabal palmetto, unaware that they had already established the principles he sought. Palms are constructed entirely from shoot and root apical meristems, without the advent of secondary tissues developed from some kind of vascular cambium. But in contrast with standard concepts of primary growth, tissue regions of otherwise mature palm stems and roots remain incompletely differentiated for many years (or perhaps decades). Further, such zones may also sustain limited mitosis, producing divisions that, in concert, enhance stem and root girth, yet do not form complex tissues. Consequently both kinds of organ remain metabolically active throughout the life of the individual. This can certainly extend over one or more centuries, making palms the longest-lived of all trees. Longevity applies not only to the continually functional sieve-tubes, which are not different from those of other angiosperms, but also to the normal cytoplasmic make-up of ground tissue parenchyma and fibers of the vascular bundles. Metabolic processes include cell division, cell expansion, wall thickening and lignification, storage and release of starch, and the retention of hydrostatic properties of the cell vacuole. We describe how taxa vary in the expression of these processes and some of the adaptive benefits, in so far as they are known.
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Fairchild Guide to Palms
1 - Harvard University, Harvard Forest, Po Box 68, Petersham, Massachusetts, 01366, USA
2 - Smithsonian Institution, Dept. of Botany, MRC166, NMNH, P.O. Box 37012, 10 & Constitution Ave, NW, Washington, DC, 20013, USA
3 - Fairchild Tropical Botanic Garden, Center for Tropical Plant Conservation, 11935 Old Cutler Rd., Coral Gables, FL, 33156-4242
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Ballroom 3/Cliff Lodge - Level B
Date: Monday, July 27th, 2009
Time: 3:45 PM