Life-forms with a parenchymatous tissue construction develop when cell divisions are free to occur in various planes and when cytoplasmic connections are maintained
Table 1 Life-form classification system for algae based on developmental features and tissue construction
A. Unicellular (motile or nonmotile) - single cells (with or without flagella or cilia).
a. Uninucleate - with a single cell wall and a single nucleus.
b. Siphonous (coenocytic) - with a single cell wall and a multinucleated protoplasm with no transverse cell walls.
B. Colonial (noncoenobic, or coenobic) - cell aggregates lacking symplastic interconnections (indefinite in cell number, or with a fixed number of cells at its origin).
C. Multicellular-aggregates of cells connected by cytoplasmic interconnections or once having had interconnections during ontogeny.
a. Filamentous (unbranched, or branched) - cells arranged in a threadlike structure possessing symplastic interconnections (resulting from cellular division confined to one plane, or two or more). Branched life-forms may have a pseudoparenchymatous tissue construction (composed of inter-weaving, branched filaments). Plant body may be monostromatic, membranous-foliar, tubular, coraloid, kelp-like, etc., in general appearance.
b. Heterotrichous - plant body consisting of two distinct parts: a prostrate creeping system and a projecting erect system of filaments.
c. Parenchymatous - tissue composed of cells each possessing the potential of form symplastic cellular interconnects with all adjoining cell walls.
in an organized manner among adjoining cells belonging to the same or physically juxtaposed cell division lineages. Parenchymatous algae are among the largest aquatic plants known, some species reach body lengths of 50 m, which rival those of trees (e.g., Macrocystis). Some possess systems of conducting tissues that are physiologically and anatomically similar to vascular plant phloem (e.g., sieve element cells of Laminaria and Nereocystis). The multi-cellular algal plant body can take on many different forms depending on the number and location of meriste-matic regions. Tubular, monostromatic, membranous-foliose, and tree-like shapes are among the variety of morphologies achieved with this body plan.
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