Plant diversity refers to the variety of plants that exist in the world. Plants compete with other plants and organisms to survive in an ecosystem.
Over time, they develop various characteristics to help them survive, which leads to plant diversity.
Plant diversity is essential because various species depend on each other; therefore, eliminating one species can cause several other species to suffer.
Micro-Organism and Plants
Viruses cannot be fitted into a classification of living things because they are not cellular. Viruses consist of a strand of nucleic acid and a protein coat. They are classified separately according to their chemical and physical properties.
Super-Kingdom Prokaryota and Eukaryota
All the studied cellular organisms fall naturally into one of two major groups, prokaryotes and eukaryotes.
The prokaryotes appeared about 3500 million years ago and comprise a variety of organisms collectively known as bacteria.
The cells of prokaryotes (pro means before and karyons means nucleus) lack true nuclei. In other words, their genetic material DNA is not enclosed by nuclear membranes and lies accessible in the cytoplasm.
Eukaryotes include Protoctista, fungi, green plants, and animals. They appeared first in the late pre-Cambrian period, about 2000 million years ago, and probably evolved from prokaryotes.
The cells of eukaryotes (EU means true) are much more complex and are characterized by a true nucleus, i.e., genetic material is enclosed by a nuclear envelope to form a definite, easily recognizable structure.
The kingdom exhibits the following general characteristics.
The genetic material is circular DNA, occurring naked in the cytoplasm and generally attached to the cell membrane. The cytoplasm contains few organelles, and none are surrounded by a two-membrane envelope.
The cell wall is a rigid structure made of polysaccharides with amino acid residues. Some organisms can fix atmospheric nitrogen into organic compounds such as amino acids.
The kingdom contains all bacteria and cyanobacteria and can be broadly classified into two phyla: cyanobacteria and bacteria.
The phylum includes spherical or rod-shaped unicellular organisms such as Chroococcus or simple or branched filamentous prokaryotes like Oscillatoria, Nostoc, and Anabaena. They exhibit the following general characteristics:
They are photosynthetic with photosynthetic pigments held in plasma membranes around the periphery of the cells.
The photosynthetic pigments are chlorophyll (green), phycoerythrin (red), and phycocyanin (blue). The blue pigment is dominant.
The phylum includes bacteria, the smallest cellular bacteria.
Bacteria exhibit the following general characteristics:
They are unicellular prokaryotes, but the cells often remain attached after division, forming a clump, chains, or simple filaments.
They are about 1 um in diameter and range between 0.1-10 um in length. The nutrition is varied: many bacteria are heterotrophs and absorb externally digested food; others are autotrophs and get nutrition either by chemosynthesis or photosynthesis.
Many bacteria cause decay and, with fungi, facilitate the recycling of nutrients. Certain bacteria are parasites on other organisms and cause specific diseases such as food poisoning in animals and soft rots of various vegetable plants.
Bacteriologists divide bacteria into several phyla based on metabolism and cell structure differences. For example, Escherichia, a rod-shaped bacterium, serves as a typical bacterium for detailed studies.
Protoctista contains eukaryotes generally regarded as identical and similar to modern plants, animals, and fungi ancestors. The Protoctista includes two sub-kingdoms: the protozoa and Algae.
Both sub-kingdoms formerly and taxonomic status. The algae were classified along with fungi in the division: Thallophyta and protozoans as phylum: protozoa in invertebrates.
These two diverse groups are placed together based on a relatively superficial level of organization.
The sub-kingdom includes oxygen-producing photosynthetic eukaryotic organisms with a cell structure similar to green plants.
Algae show great diversity in structure, ranging from unicellular (Chlamydomonas) and simple filamentous (Spirogyra) to giant seaweeds (Fucus). Algae occur in water or on very damp surfaces. Their bodies lack true stems, roots, and leaves, i.e., a thallus.
a-Phylum Chlorophyta (Green Algae)
Green algae are very similar to green plants in cell structure and biochemistry. Chloroplast contains the pigments chlorophylls, carotene, and xanthophyll.
The plant body is single-called Chlamydomonas, or a filament (Spirogyra), or a colonial form (Volvox), or shaped as the flattened thallus, i.e., thalloid (Ulva). Most green algae are found in freshwater.
b- Phylum Bacillariophyta (Diatoms)
Diatoms have unusually well made from celluloses and impregnated with silica. The walls consist of two halves called valves, which fit together like the halves of a petri-dish.
c- Phylum Xanthophyta (Yellow-Green Algae)
The membrane of this division is characterized by its yellow-green color due to the dominance of xanthophyll diadinoxanthin. The cell wall consists of two overlapping halves. The reserve food is oil drops. The most commonly occurring genus is Vaucheria.
d-Phylum Phaeophyta (Brown Algae)
nearly all brown algae are marine and found in the intertidal zone of a rocky shore. There are only three freshwater genera.
The plant body is a multicellular thallus with a degree of tissue differentiation; however, water-conducting cells have not evolved. Chloroplasts contain the pigments chlorophylls carotene and fucoxanthin, a brown pigment that dominates the others.
The food reserves include carbohydrates and laminarin starch. Reproduction is sexual, and many species have a haploid and diploid alternation of generations. They are commonly called seaweeds, for example, Fucus.
e-Phylum Rhodophyta (Red Algae)
The red algae are marine plants in the intertidal zone’s lower part. The plant body is composed of branched filaments or aggregations of filaments.
The life cycle of red algae is complex, usually with alternation of generations. Examples are Batrachospermum and Polysiphonia.
2- Phylum Oomycota
This phylum was initially classified with fungi but is now included in Protoctista. The plant body consists of hyphae with no cross-walls, i.e., non-septate. Asexual reproduction is through biflagellate zoospores produced in sporangia.
Sexual reproduction is by oogamy, involving the fusion of an oospore (female gamete) with a male gamete to produce oospores.
The phylum includes disease-causing agents, for example, phytopathorainfestans, which causes potato blight disease, and pythium, a parasite that causes the damping-off of a seedling.
I hope you found this helpful for you. Will discuss further details about plant diversity in the next blog. Stay tuned with us, stay save and happy!