Plantae

Broadly defined, plants include green plants, red algae and glaucophytes, with land plants forming only one branch.

Mosses, liverworts, hornworts, lycophytes, ferns and seed plants represent different branches of land-plant evolution, not successive stages in the life of one organism.

Protected embryos, vascular tissues, roots, seeds, flowers and fruits arose in different plant lineages; none occurs in every group.

The liverwort Marchantia polymorpha illustrates a body plan very different from a flowering tree: its conspicuous generation is the gametophyte, while its short-lived sporophyte develops attached to the female plant.

Even an underwater flowering plant can retain familiar organs: the eelgrass Zostera marina has roots, leaves and flowers, although it lives submerged in seawater.

Photosynthesis uses light to produce sugars and other energy-rich compounds that support growth.

In oxygen-producing photosynthesis, the protein machinery called Photosystem II extracts electrons from water, releasing oxygen in the process.

The primary plastids of green plants, red algae and glaucophytes trace their origin to an ancient partnership between a eukaryotic cell and a cyanobacterium.

Carbon absorbed from the atmosphere during photosynthesis can enter plant biomass and, later, soil; decomposition returns some of that carbon to the atmosphere.

Land-plant life cycles alternate between a diploid sporophyte and a haploid gametophyte, both of which are multicellular.

The sporophyte produces spores through meiosis; spores develop into gametophytes, which produce eggs or sperm through mitotic divisions.

Fertilization joins egg and sperm to form a zygote, from which the next sporophyte develops.

In Marchantia, sperm swim to the female reproductive structure, and the resulting sporophyte remains dependent on the female gametophyte.

Marchantia can also reproduce without fertilization through small vegetative propagules called gemmae, formed in cups on the plant.

Field dodder, Cuscuta campestris, is a parasitic flowering plant that winds around a host instead of developing the familiar combination of proper leaves and roots.

Its attachment organs, called haustoria, penetrate host tissue and connect with the host’s transport system, allowing access to water and other compounds.

Its low photosynthetic activity is associated with losses of genes needed for high photosynthetic performance, rather than evidence that it is not a plant.

At a very different scale, a single-cell genomic study placed the marine, non-photosynthetic Picozoa near red algae and found support for the absence of plastids in this lineage.

Green plants occupy both land and water, with diverse structures and physiology.

Seagrasses demonstrate that a flowering-plant lineage can return to marine life and form the foundation of productive coastal ecosystems.

In Zostera marina, gas exchange occurs through the leaf surface, and the genome study found the loss of the stomatal gene repertoire associated with its submerged lifestyle.

Plants also connect biological growth with the carbon cycle: carbon storage in living vegetation is not necessarily permanent, because decay and combustion can release it again.

Plant diversity underpins agriculture, while aquatic plants help sustain coastal ecosystems.

The 2019 One Thousand Plant Transcriptomes study combined transcriptomes from 1,124 sampled species with published genome resources to investigate relationships across green-plant diversity.

Its nuclear and plastid analyses disagreed at some nodes, so a classification list should not be treated as a fully resolved evolutionary tree.

The Marchantia investigation compared DNA methylation across vegetative, reproductive and sporophyte tissues of one liverwort species.

That design supports comparisons among stages in Marchantia, not a claim that every plant has the same methylation pattern or the same relative sizes of its two generations.

The Zostera study sequenced material from a clone collected in southwest Finland and interpreted gene losses in the context of a marine flowering plant.

The result does not imply that all aquatic plants lack stomata or that a leaf from any marine organism is a seagrass leaf.

The Cuscuta study combined genome assembly and annotation with the biology of a shoot parasite; its conclusions about nutrient acquisition belong to that host-dependent system.

The Picozoa analysis used 43 single-cell genomes from natural samples and supported a position within Archaeplastida near red algae and rhodelphids.

The authors considered alternative histories involving complete plastid loss or a different pattern of plastid acquisition, rather than demonstrating one settled history of every archaeplastid plastid.

Scientific name

Plantae

Taxonomic rank

kingdom

Provider status

accepted

col identifier

P

Source lineage

1. Eukaryota (Chatton, 1925) Whittaker & Margulis, 1978 domain
2. Plantae kingdom

Source classification release