🌿 Plant Kingdom

1. Algae (Thallophyta)

Chlorophyll-bearing, simple, thalloid, autotrophic, and largely aquatic organisms.

Classes of Algae

1. Chlorophyceae (Green Algae): Chlorophyll a, b. Starch reserve. (e.g., Volvox, Spirogyra).

2. Phaeophyceae (Brown Algae): Chlorophyll a, c, fucoxanthin. Mannitol/Laminarin reserve. (e.g., Fucus, Kelp).

3. Rhodophyceae (Red Algae): Chlorophyll a, d, phycoerythrin. Floridean starch reserve. (e.g., Porphyra, Gelidium).

2. Bryophytes

Called the amphibians of the plant kingdom because they live in soil but depend on water for sexual reproduction. They lack true roots, stems, or leaves.

Main plant body is haploid (gametophyte). Divided into Liverworts (e.g., Marchantia) and Mosses (e.g., Funaria).

3. Pteridophytes

The first terrestrial plants to possess vascular tissues (xylem and phloem). Main plant body is a sporophyte (diploid) which is differentiated into true roots, stem, and leaves.

Includes ferns and horsetails. Leaves can be microphylls (Selaginella) or macrophylls (Ferns).

4. Gymnosperms

Plants in which the ovules are not enclosed by any ovary wall and remain exposed (naked seeds). Include medium-sized trees or tall trees (Sequoia is one of the tallest) and shrubs.

Roots generally have fungal associations in the form of mycorrhiza (Pinus) or coralloid roots (Cycas).

5. Angiosperms

Flowering plants where pollen grains and ovules are developed in specialized structures called flowers. Seeds are enclosed by fruits.

Classes of Angiosperms

Dicotyledons: Two cotyledons, reticulate venation, tetramerous/pentamerous flowers.

Monocotyledons: Single cotyledon, parallel venation, trimerous flowers.

Double Fertilization: Unique to angiosperms. One male gamete fuses with the egg (syngamy) forming a zygote, the other fuses with secondary nucleus forming primary endosperm nucleus (PEN).