Charophyceae is a taxon

Taxon

|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

 of green algae

Green algae

The green algae are the large group of algae from which the embryophytes emerged. As such, they form a paraphyletic group, although the group including both green algae and embryophytes is monophyletic...

 whose exact rank is the matter of some current debate. Some botanists

Botany

Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...

 recommend expanding the existing plant kingdom to include charophyceans and chlorophytes

Chlorophyta

Chlorophyta is a division of green algae, informally called chlorophytes. The name is used in two very different senses so that care is needed to determine the use by a particular author...

 while others consider Charophyceae to be a class within either the divisions Chlorophyta

Chlorophyta

Chlorophyta is a division of green algae, informally called chlorophytes. The name is used in two very different senses so that care is needed to determine the use by a particular author...

, Streptophytina

Streptophytina

Streptophytina is formally a subdivision or subphylum which contains two classes: Charophyceae, containing the Charales order ; and Embryophyceae, which contains the embryophytes .The term...

, or Streptophyta. Other systematists

Systematics

Biological systematics is the study of the diversification of terrestrial life, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees...

 classify Charophyceae as a class under division Charophyta, with Chlorophyta remaining a distinct division.

Regardless of the exact classification of charophyceans, the consensus among botanists is that they are the organisms most closely related to embryophytes (land plants). Many of the complex traits related to sexual reproduction, photosynthesis

Photosynthesis

Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

, and other defining characteristics of plants evolved first in charophyceans; analysis of cpDNA (chloroplast

Chloroplast

Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...

 DNA

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

), for instance, reveals that many characteristics of plant chloroplasts evolved first in the charophycean genera

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

Staurastrum and Zygnema.