The Chlorophyceae are one of the classes of green algae, distinguished mainly on the basis of ultrastructural morphology. For example, the chlorophycean CW clade, and chlorophycean DO clade, are defined by the arrangement of their flagella. Members of the CW clade have flagella that are displaced in a "clockwise" direction e.g. Chlamydomonadales. Members of the DO clade have flagella that are "directly opposed" e.g. Sphaeropleales. They are usually green due to the dominance of pigments chlorophyll a and chlorophyll b. The chloroplast may be discoid, plate-like, reticulate, cup-shaped, spiral or ribbon shaped in different species. Most of the members have one or more storage bodies called pyrenoids located in the chloroplast. Pyrenoids contain protein besides starch. Some algae may store food in the form of oil droplets. Green algae usually have a rigid cell wall made up of an inner layer of cellulose and outer layer of pectose.
The Zygnematales, also called the Conjugatales, are an order of green algae, comprising several thousand different species in two families. The larger family Zygnemataceae, with well-known genera such as Zygnema and Spirogyra, includes members that grow as unbranched filaments, which grow longer through normal cell division. This group includes the desmids. Most members of both families live in freshwater, and form an important component of the algal scum that grows on or near plants, rocks, and various debris.
Chlamydomonas is a genus of green algae consisting of about 150 species all unicellular flagellates, found in stagnant water and on damp soil, in freshwater, seawater, and even in snow as "snow algae". Chlamydomonas is used as a model organism for molecular biology, especially studies of flagellar motility and chloroplast dynamics, biogenesis, and genetics. One of the many striking features of Chlamydomonas is that it contains ion channels (channelrhodopsins) that are directly activated by light. Some regulatory systems of Chlamydomonas are more complex than their homologs in Gymnosperms, with evolutionarily related regulatory proteins being larger and containing additional domains.
The brown algae, comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Most brown algae live in marine environments, where they play an important role both as food and as a potential habitat. For instance, Macrocystis, a kelp of the order Laminariales, may reach 60 m (200 ft) in length and forms prominent underwater kelp forests. Kelp forests like these contain a high level of biodiversity. Another example is Sargassum, which creates unique floating mats of seaweed in the tropical waters of the Sargasso Sea that serve as the habitats for many species. Many brown algae, such as members of the order Fucales, commonly grow along rocky seashores. Some members of the class, such as kelps, are used by humans as food.
Marimo is a rare growth form of Aegagropila linnaei in which the algae grow into large green balls with a velvety appearance.
The Charophyta or charophytes is a group of freshwater green algae, sometimes treated as a division, but also as a superdivision, or an unranked clade. The terrestrial plants, the Embryophyta, most likely emerged within Charophyta, possibly from terrestrial unicellular charophytes, with the class Zygnematophyceae as a sister group.
The Zygnemataceae are a family of filamentous or unicellular, uniseriate (unbranched) green algae. The filaments are septated and reproduction is by conjugation; Spirogyra is commonly used in schools to demonstrate this kind of reproduction. The family is notable for its diversely shaped chloroplasts, such as stellate in Zygnema, helical in Spirogyra, and flat in Mougeotia. The Zygnemataceae are cosmopolitan, but though all generally occur in the same types of habitats, Mougeotia, Spirogyra, and Zygnema are by far the most common; in one study across North America, 95% of the Zygnemataceae collected were in these three genera. Classification and identification is primarily by the morphology of the conjugation, which is somewhat rare to find in natural populations of permanent water bodies; when in the vegetative state, the rarer genera resemble the three most common, and are often mistaken for them and catalogued as such. Conjugation can be induced in low-nitrogen culture. While they occupy many habitats, in North America all are found solely in freshwater or subaerial habitats. Species typically exist as floating mats in stagnant water in ditches and ponds, but some also grow in moving water, attaching themselves to a substrate by rhizoid-like projections of the basal cells of the filament. The mat species rise to the surface in early spring, grow rapidly through the summer, disappearing by late summer. Members of the Zygnemataceae, such as Spirogyra, fall prey to parasites, especially chytrids. Most genera previously assigned to Mesotaeniaceae as well as the Desmidiales actually emerged in the Zygnematacae.
Oedogonium is a genus of filamentous, free-living green algae, first discovered in the fresh waters of Poland 1860 by W. Hilse and later named by German scientist K. E. Hirn. The morphology of Oedogonium is unique, with an interior and exterior that function very differently from one another and change throughout its life cycle. These protists reside in freshwater ecosystems in both hemispheres and are both benthic and planktonic in nature. Forming algal patches on water's surface, they interact closely with a multitude of other algae. These filamentous cell's life cycles include both sexual and asexual reproduction, depending on life cycle stage. Although quite common, Oedogonium is difficult to identify, since key ID factors are only present during reproduction, which is an uncommon life stage among this genus. Oedogonium has been found to be important in the fixation of heavy metals in freshwater ecosystems.
Oscillatoria is a genus of filamentous cyanobacterium which is named after the oscillation in its movement. Filaments in the colonies can slide back and forth against each other until the whole mass is reoriented to its light source. It is commonly found in watering-troughs waters, and is mainly blue-green or brown-green. Oscillatoria is an organism that reproduces by fragmentation. Oscillatoria forms long filaments of cells which can break into fragments called hormogonia. The hormogonia can grow into a new, longer filament. Breaks in the filament usually occur where dead cells (necridia) are present. It occur in fresh water ponds. Oscillatoria uses photosynthesis to survive and reproduce. Each filament of oscillatoria consists of trichome which is made up of rows of cells. The tip of the trichome oscillates like a pendulum. in reproduction, it takes place by vegetative means only. Usually the filament breaks into a number of fragments called hormogonia. Each hormogonium consist of one or more cells and grow into a filament by cell division in one direction.
Bryopsidales is an order of green algae, in the class Ulvophyceae.
Draparnaldia is a genus of freshwater green algae in the family Chaetophoraceae. Draparnaldia are uniseriate; each filament is composed of a chain of cells arranged in one row. Chloroplasts appear as a band within the center of each cell. The length of the main axis cells are generally the same, regardless of whether or not they bear branches. These side branches are divided extensively into terminal hairs. The entire plant is enveloped in loose, slippery mucilage. Draparnaldia is a cosmopolitan genus with wide distribution and it is usually found in cold aerated waters. They are either attached to sand or grow epiphytically on other aquatic plants. Draparnaldia can be seen growing in clear streams trailing on stones and boulders. Herman S. Forest of The Southern Appalachian Botanical Club has stated that while not common, it is present frequently enough to be recorded in almost all local flora lists of green algae that have been compiled. A multitude of species are present in Lake Baikal, Siberia and have been described by Meyer and Jasnitzky. A species of the genus had been placed and described in the Linnean Herbarium as Conferva Mutabilis Roth in 1797. Nowadays Conferva is no longer used and the species is described as Draparnaldia mutabilis (Roth) Bory. Bory is added in honour of the researcher of the same name, based on whose description the genus was separated from similar appearing forms. Bory is accredited with the establishment of the genus.
Trebouxia is a unicellular green alga. It is a photosynthetic organism that can exist in almost all habitats found in polar, tropical, and temperate regions. It can either exist in a symbiotic relationship with fungi in the form of lichen or it can survive independently as a free-living organism alone or in colonies. Trebouxia is the most common photobiont in extant lichens. It is a primary producer of marine, freshwater and terrestrial ecosystems. It uses carotenoids and chlorophyll a and b to harvest energy from the sun and provide nutrients to various animals and insects.
In taxonomy, Desmidium is a genus of green algae, specifically of the Desmidiaceae.
Coccomyxa is a genus of green algae, in the family Coccomyxaceae. This genus is defined by their small, elliptical to spherical shape, and the presence of a simple parietal chloroplast. These features, along with their occurrence in various lifestyles such as free-living, parasitic, or as photobionts, have been used to identify over 40 species. Using additional morphological features, such as brown akinetes formation, allows for the differentiation between Coccomyxa and the genus Pseudococcomyxa, as they tend to share some morphological characteristics like the general cell shape and one-sided mucilage cap. Recent molecular analysis, however, indicates that the genus Pseudococcomyxa is contained within different Coccomyxa clades, signaling the fact that the two genera are the same. Coccomyxa has often been used as a model organism, and its genome is being completely sequenced. The genus is also an attractive candidate for biofuels.
This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary of leaf morphology. For other related terms, see Glossary of phytopathology and List of Latin and Greek words commonly used in systematic names.
Halimeda tuna is a species of calcareous green seaweed in the order Bryopsidales. It is found on reefs in the Atlantic Ocean, the Indo-Pacific region and the Mediterranean Sea. Halimeda tuna is the type species of the genus Halimeda and the type locality is the Mediterranean Sea. The specific name "tuna" comes from the Taíno language, meaning "cactus" and referring to the resemblance of the thallus to the growth form of an Opuntia cactus.
Bangia is an extant genus of division Rhodophyta that grows in marine or freshwater habitats. Bangia has small thalli with rapid growth and high reproductive output, and exhibits behavior characteristic of r-selected species. The plants are attached by down-growing rhizoids, usually in dense purple-black to rust-colored clumps. The chloroplasts of Bangia, like others in the division Rhodophyta, contain chlorophyll a and sometimes chlorophyll d, as well as accessory pigments such as phycobilin pigments and xanthophylls. Depending on the relative proportions of these pigments and the light conditions, the overall color of the plant can range from green to red to purple to grey; however, the red pigment, phycoerythrin, is usually dominant.
Zygnema is a genus of freshwater filamentous thalloid alga comprising about 100 species. A terrestrial species, Z. terrestre, is known from India. Zygnema grows as a free-floating mass of filaments, although young plants may be found anchored to streambeds with a holdfast. The filaments form a yellow-green to bright green colored tangled mat, and are composed of elongate barrel-shaped cells, each with two star-shaped (stellate) chloroplasts arrayed along the axis of the cell.
Scytothamnus australis is a brown alga species in the genus Scytothamnus found in New Zealand. It is a sulphated polysaccharide and the type species in the genus.
Cyclotella is a genus of diatoms often found in oligotrophic environments, both marine and fresh water. It is in the family Stephanodiscaceae and the order Thalassiosirales. The genus was first discovered in the mid 1800s and since then has become an umbrella genus for nearly 100 different species, the most well-studied and the best known being Cyclotella meneghiniana. Despite being among the most dominant genera in low-productivity environments, it is relatively understudied.
