Botany, also called plant science(s), plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term “botany” comes from the Ancient Greek word βοτάνη (botanē) meaning “pasture”, “grass”, or “fodder”; βοτάνη is in turn derived from βόσκειν (boskein), meaning “to feed” or “to graze”. Traditionally, botany has also included the study of fungi and algae by mycologists and phycologists respectively, with the study of these groups returning to their historical roots as part of modern botany.
Plants are mainly multicellular organisms, predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, plants were treated as one of two kingdoms including all living things that were not animals, and all algae and fungi were treated as plants. However, all current definitions of Plantae exclude the fungi and some algae, as well as the prokaryotic cyanobacteria (also known as blue-green algae). By one definition, plants form the clade Viridiplantae (Latin for green plants), a group that includes the flowering plants, conifers and other gymnosperms, ferns and their allies, hornworts, liverworts , mosses and the green algae . This definition excludes red algae (like coralline algae ), which are traditionally grouped with Plants under subkingdom Rhodophyta . Green plants have cell walls containing cellulose and obtain most of their energy from sunlight via photosynthesis by primary chloroplasts , derived from endosymbiosis with cyanobacteria . Their chloroplasts contain chlorophylls aand carotenoids , which give them their green coloration. Some plants are parasitic or mycotrophic and have lost the ability to produce normal amounts of chlorophyll or to conduct photosynthesis; they are sometimes referred to as epiphytes . They are typically heterotrophic , obtaining nutrients from organic matter ; some extract minerals from soil through their roots while others may be dependent on symbiosis with soil fungi . Plants secrete chemicals called allelopathins which discourage other nearby plants’ growth; competition among members different species for space (“niche”) results in an evolutionary arms race between different allelopathins secreted by each species against those secreted by its neighbors; this can lead to biological control if one species outcompetes another for light due either to producing more allelopathins than it receives itself (“allelopathy”), receiving less allelopathic chemicals because its own production deters competitors enough that they need not produce large quantities themselves (“antagonism”), or both. Many terrestrial plants also form symbiotic relationships with mycorrhizal fungi , exchanging carbon dioxide for enhanced mineral nutrient uptake; without these partnerships many land ecosystems would be unable to exist. Aquatic vascular plants are rooted in substrate generally below water level but exposed to air above water level at some point in their life cycles while nonvascular mosses lack such specialized tissues and spend their entire lives submerged under water level except when sporulating