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PHYCOLOGICAL SOCIETY OF AMERICA

Growth

in what used to be called Pelvetia, now

Silvetia compressa (J. Agardh) Serrão, Cho, Boo et Brawley

Growth in Silvetia is by 4-sided apical cells which have dominance and inhibit the development of laterals below. The apical cells, however, only divide to form the forks of the plant. They stimulate the cells around them, called promeristem, to divide. The promeristem is made of very small cells. The secondary meristem is primarily responsible for increase in girth and is called the meristoderm.

The large pyramidal shaped cell at the base of the furrow is the apical cell. Below it lie the promeristem cells.

It has been found that the growth rates of Silvetia have a diurnal variation in length following the variation in irradiance. They have maximum growth at noon, unlike most photosynthetic plants. Growth for Silvetia may be limited by light. S . compressa has also been reported to have negative growth. The image to the right illustrates such growth. On the left is a normal healthy frond. To the right, the frond has lost most of its branches and apices.

© 1996 R. H.  Lin