Chlorophyta is a division of

green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...

informally called chlorophytes.

Description

Chlorophytes are

eukaryotic The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

organisms composed of cells with a variety of coverings or walls, and usually a single green

chloroplast A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...

in each cell. They are structurally diverse: most groups of chlorophytes are

unicellular A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and ...

, such as the earliest-diverging prasinophytes, but in two major classes (

Chlorophyceae The Chlorophyceae, also known as chlorophycean algae, are one of the classes of green algae, within the phylum Chlorophyta. They are a large assemblage of mostly freshwater and terrestrial organisms; many members are important primary producers i ...

and

Ulvophyceae The Ulvophyceae or ulvophytes are a class of green algae, distinguished mainly on the basis of Ultrastructure, ultrastructural morphology, Biological life cycle, life cycle and molecular phylogenetics, molecular phylogenetic data. The sea lettu ...

) there is an evolutionary trend toward various types of complex

colonies A colony is a territory subject to a form of foreign rule, which rules the territory and its indigenous peoples separated from the foreign rulers, the colonizer, and their '' metropole'' (or "mother country"). This separated rule was often or ...

and even

multicellularity A multicellular organism is an organism that consists of more than one cell, unlike unicellular organisms. All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- and pa ...

Chloroplasts

Chlorophyte cells contain green chloroplasts surrounded by a double-membrane envelope. These contain

chlorophyll Chlorophyll is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words (, "pale green") and (, "leaf"). Chlorophyll allows plants to absorb energy ...

s '' a'' and '' b'', and the

carotenoid Carotenoids () are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, archaea, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, corn, tomatoes, cana ...

s carotin,

lutein Lutein (;"Lutein"

zeaxanthin Zeaxanthin is one of the most common carotenoids in nature, and is used in the xanthophyll cycle. Synthesized in plants and some micro-organisms, it is the pigment that gives paprika (made from bell peppers), corn, saffron, goji ( wolfberries) ...

, antheraxanthin, violaxanthin, and neoxanthin, which are also present in the

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

land plant The embryophytes () are a clade of plants, also known as Embryophyta (Plantae ''sensu strictissimo'') () or land plants. They are the most familiar group of photoautotrophs that make up the vegetation on Earth's dry lands and wetlands. Embryophyt ...

s. Some special carotenoids are present in certain groups, or are synthesized under specific environmental factors, such as siphonaxanthin, prasinoxanthin, echinenone,

canthaxanthin Canthaxanthin is a keto-carotenoid pigment widely distributed in nature. Carotenoids belong to a larger class of phytochemicals known as terpenoids. The chemical formula of canthaxanthin is C40H52O2. It was first isolated in edible mushrooms. It ...

, loroxanthin, and

astaxanthin Astaxanthin is a keto- carotenoid within a group of chemical compounds known as carotenoids or terpenes. Astaxanthin is a metabolite of zeaxanthin and canthaxanthin, containing both hydroxyl and ketone functional groups. It is a lipid-solu ...

. They accumulate carotenoids under nitrogen deficiency, high irradiance of sunlight, or high salinity. In addition, they store

starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diet ...

inside the chloroplast as

carbohydrate A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' ...

reserves. The

thylakoid Thylakoids are membrane-bound compartments inside chloroplasts and cyanobacterium, cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. Thylakoids consist of a #Membrane, thylakoid membrane surrounding a #Lumen, ...

s can appear single or in stacks. In contrast to other divisions of algae such as

Ochrophyta Ochrophytes, also known as heterokontophytes or stramenochromes, are a phylum of algae. They are the photosynthetic stramenopiles, a group of eukaryotes, organisms with a cell nucleus, characterized by the presence of two unequal flagella, one o ...

, chlorophytes lack a chloroplast endoplasmic reticulum.

Flagellar apparatus

Chlorophytes often form

flagellate A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and the ...

cells that generally have two or four

flagella A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

of equal length, although in prasinophytes heteromorphic (i.e. differently shaped) flagella are common because different stages of flagellar maturation are displayed in the same cell. Flagella have been independently lost in some groups, such as the

Chlorococcales Chlorococcales is a formerly recognized Order (biology), order of green algae in the Class (biology), class Chlorophyceae. , the type family Chlorococcaceae was placed in the order Chlamydomonadales. Conventionally, many groups of coccoid green ...

. Flagellate chlorophyte cells have symmetrical cross-shaped ('cruciate') root systems, in which ciliary rootlets with a variable high number of

microtubule Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nanometer, nm and have an inner diameter bet ...

s alternate with rootlets composed of just two microtubules; this forms an arrangement known as the "X-2-X-2" arrangement, unique to chlorophytes. They are also distinguished from streptophytes by the place where their flagella are inserted: directly at the cell apex, whereas streptophyte flagella are inserted at the sides of the cell apex (sub-apically). Below the flagellar apparatus of prasinophytes are

rhizoplast The rhizoplast (also known as internal flagellar root, fibrous root or cross-banded root) is an organelle present in a variety of flagellates, including ochrophyte and chlorophyte algae and some fungi. This term is used for a variety of striated, ...

s, contractile muscle-like structures that sometimes connect with the chloroplast or the cell membrane. In core chlorophytes, this structure connects directly with the surface of the nucleus. The surface of flagella lacks microtubular hairs, but some genera present scales or fibrillar hairs. The earliest-branching groups have flagella often covered in at least one layer of scales, if not naked.

Metabolism

Chlorophytes and streptophytes differ in the enzymes and organelles involved in

photorespiration Photorespiration (also known as the oxidative photosynthetic carbon cycle or C2 cycle) refers to a process in plant physiology, plant metabolism where the enzyme RuBisCO oxygenates RuBP, wasting some of the energy produced by photosynthesis. Th ...

. Chlorophyte algae use a

dehydrogenase A dehydrogenase is an enzyme belonging to the group of oxidoreductases that oxidizes a substrate by reducing an electron acceptor, usually NAD+/NADP+ or a flavin coenzyme such as FAD or FMN. Like all catalysts, they catalyze reverse as well as ...

inside the

mitochondria A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is us ...

to process

glycolate Glycolic acid (or hydroxyacetic acid; chemical formula ) is a colorless, odorless and hygroscopic crystalline solid, highly soluble in water. It is used in various skin-care products. Glycolic acid is widespread in nature. A glycolate (sometimes s ...

during photorespiration. In contrast, streptophytes (including land plants) use

peroxisome A peroxisome () is a membrane-bound organelle, a type of microbody, found in the cytoplasm of virtually all eukaryotic cells. Peroxisomes are oxidative organelles. Frequently, molecular oxygen serves as a co-substrate, from which hydrogen perox ...

s that contain glycolate oxidase, which converts glycolate to glycoxylate, and the hydrogen peroxide created as a subproduct is reduced by

catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting ...

s located in the same organelles.

Reproduction and life cycle

Asexual reproduction Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the f ...

is widely observed in chlorophytes. Among core chlorophytes, both unicellular groups can reproduce asexually through autospores, wall-less zoospores, fragmentation, plain cell division, and exceptionally budding. Multicellular thalli can reproduce asexually through motile zoospores, non-motile

aplanospore {{Short pages monitor