Non-Vascular Plants Overview

Divisions of the Plant Kingdom

• The Plant Kingdom consists of two primary groups: Cryptogams (flowerless or seedless plants) and Phanerogams (flowering or seed-bearing plants), also known as Spermatophyta.

Cryptogams

• Divided into three main groups: Thallophyta, Bryophyta, and Pteridophyta.

Thallophyta

• Composed of undifferentiated thallus; lacks roots, stems, or leaves.
• Consists of single-celled or simple multicellular organisms.
• Includes organisms like Algae and Fungi.

Bryophyta

• Simple plants featuring stems and leaves, but do not possess true roots.
• Common examples include Mosses and Liverworts.

Pteridophyta

• Possess true roots, stems, leaves, and a vascular system, yet do not flower.
• Primarily include Ferns and their related species.

Phanerogams (Spermatophyta)

• Characterized by the presence of flowers that produce seeds.
• Comprised of two categories: Gymnosperms (naked-seeded plants, e.g., Cycads and Conifers) and Angiosperms (closed-seeded plants).

Angiosperms

• Further categorized into Dicotyledons, which have embryos with two cotyledons, and Monocotyledons, having embryos with one cotyledon.

Non-Vascular and Vascular Plants

• Thallophyta (Fungi and Algae) and Bryophyta are classified as non-vascular due to the absence of specialized internal tissues (xylem and phloem) required for transporting water, minerals, and food within the plant.
• Pteridophyta, Gymnospermae, and Angiospermae are considered vascular (or tracheophytes) as they contain specialized vascular tissues (phloem and xylem) in most of their organs.

Cell Structure in Algae

• Algal cell structure features uniformity throughout various divisions.
• Chloroplasts are present in Chlorophyta, while chromatophores are present in other groups.
• The term "chloroplast" applies to algae with chlorophylls a and b, similar to higher plants.
• "Chromatophore" refers to algae lacking chlorophyll b but having excess carotenoids.
• Chloroplast positioning is crucial:
  • Parietal—towards the cell’s periphery.
  • Axial—towards the cell’s center.
• Pyrenoid is a notable feature within chloroplasts, often associated with stored products.

Morphologic Diversity of Algae

• Algae exhibit a range of forms categorized as thallus—can be unicellular, colonial, filamentous, siphonaceous, or complex parenchymatous.

Unicellular Forms

• Unicellular algae exist in all groups except Rhodophyta and Phaeophyta; these may produce unicellular stages during their lifecycle.
• Types include:
  • Motile (flagellated),
  • Non-motile (coccoid),
  • Amoeba-like forms.
• Flagellated solitary cells are primitive and believed to be the origin of other types, varying in flagella number and arrangement.

Multicellular Forms

Colonial Forms

• Colonial structures arise from cells not separating after division.
• Coenobial:
  • Cells are embedded in a mucilaginous matrix.
  • Consist of a defined colony with consistent size and shape; no vegetative division occurs after formation.
• Aggregations:
  • Are variable in size and shape, with vegetative division allowing cell number to increase.
  • Common forms include:
    • Palmelloid—embedded in irregular mucilage,
    • Dendroid—tree-like structure formed by localized mucilage production,
    • Rhizopodial—amoeboid cells connected by cytoplasmic processes.

Filamentous Forms

• Characterized by vertical cell division with linear arrangements.
• Types:
  • Uniseriate—single series of cells.
  • Multiseriate—multiple series, maintaining a thread-like appearance.
• Filaments can be branched or unbranched; more complex varieties may differentiate between branches.
• Heterotrichous filaments display two systems: prostrate (attached) and erect (free) branches.
• Pseudoparenchymatous thalli form compact masses that obscure individual branches.

Siphonaceous Forms

• Thalli are multinucleate with no cell divisions, except for reproductive structures.
• Considered acellular rather than unicellular.
• Often elaborate in structure.