Phaeophyta - Brown Algae-5

Meristems in Laminariales

Members of this taxon typically have three parts. They are

a] Holdfast which attaches the alga to the substrate,

b] Stipe which is stem-like

c] Laminae (blades) which are leaf-like

d] They may also have a hollow Float

Meristematic Transition Zone

Whole plants can live from two to seven years.

Laminae usually persist for six months.

Algae in this taxon have an Intercalary Meristem that is called the Transition Zone.

ElkHornKelpTZLab500.jpg (164107 bytes)

It is located at the base of the Blade or Lamina and produces derivatives in both directions. Consequently it contributes to the blade and the Stipe.

It also leads to an increase in Diameter.

The tissues produced by the Transition Zone are True Tissues because they are produced by meristematic cells which divide in three planes.

Adjacent cells are attached from inception but may become separate due to the degradation of the Middle Lamella.

False Tissues have separate filaments which become attached some time after their inception.

This occurs in the Red Algae (Rhodophyta) and in some Brown Algae like Leathesia & Desmarestia.

Leathesia	Desmarestia
These two Phaeophytes produce False Parenchyma

Meristoderm (Dividing Dermis)

Meristematic activity is also observed in the Surface Layer. This is Analogous to the Protoderm of land plants. This is called the Meristoderm.

They are Perennial and regenerate their Laminae.