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Reynoutria japonica (イタドリ)
Reynoutria japonica (イタドリ, itadori; syn. Fallopia japonica, Polygonum cuspidatum), Japanese knotweed: an East Asian Polygonaceae perennial, IUCN 100-worst invader abroad, single female clone in Europe, spring vegetable in Japan.
Rhamnaceae
Rhamnaceae, the buckthorn family, is a Rosales family of trees, shrubs, and vines with c. 50-60 genera and 900-1,200 species, cosmopolitan, including Ziziphus jujubes, Rhamnus buckthorns, and Ceanothus ornamentals.
Rhamnus (plant)
Rhamnus (buckthorn) is a genus of about 139 accepted species of shrubs and small trees in Rhamnaceae, native to temperate and subtropical to tropical mountains, with drupes bearing 2-4 stones; R. cathartica is invasive in eastern North America.
Rhamnus alaternus
Rhamnus alaternus (Italian buckthorn, evergreen buckthorn) is a Mediterranean evergreen Rhamnaceae shrub, dioecious, with black 3-stoned drupes; used in North African folk medicine and invasive in California, Australia, and New Zealand.
Rhamnus cathartica
Rhamnus cathartica (common, European, or purging buckthorn) is a dioecious Eurasian Rhamnaceae shrub introduced to North America in the early 1800s as an ornamental and medicinal plant, now an invasive forest understory tree, alternate host of oat crown rust and the soybean aphid, with no approved biocontrol agents.
Rhinanthus minor
Rhinanthus minor, yellow rattle, is a hemiparasitic annual of Orobanchaceae native from Europe to western Siberia, parasitizing grasses via haustoria and used to create wildflower meadows; seeds rattle in its papery calyx.
Rhipsalis
Rhipsalis, the mistletoe cacti, is a genus of about 45 species of spineless epiphytic cacti native to tropical America, with R. baccifera reaching Africa and Sri Lanka.
Rhizoid
Rhizoid: unicellular or multicellular root-like filament anchoring bryophytes and fern or clubmoss gametophytes, absorbing water and ions; unlike true roots, lacks vascular tissue, root cap, and endogenous branching.
Rhizome
Rhizome: a horizontally growing modified plant stem at or just below the soil surface, bearing buds and roots at nodes; examples include iris, bamboo, and ginger; distinct from bulbs, corms, tubers, and stolons.
Rhizomnium dentatum
Rhizomnium dentatum is an extinct moss of the family Mniaceae, the first fossil species of the genus Rhizomnium, described in 2014 from five gametophyte fragments in Eocene Baltic amber and distinguished by shortly dentate leaf margins.
Rhizophora
Rhizophora is a genus of six accepted mangrove tree species in Rhizophoraceae, including the red mangrove R. mangle, defined by prop roots, over 90% root salt exclusion, and buoyant viviparous propagules that disperse by floating.
Rhizophora apiculata
Rhizophora apiculata (kongkang) is an Indo-West Pacific mangrove tree of Rhizophoraceae, dominant on estuarine mud from South Asia to Queensland, parent of two hybrids, used for charcoal and wood, IUCN Least Concern.
Rhizophora mangle
Rhizophora mangle, the red mangrove, is a viviparous stilt-rooted evergreen tree of tropical intertidal coasts of America and West Africa, tolerating 0-90 ppt salinity, IUCN Least Concern, invasive in Hawaii and Queensland.
Rhizophora mucronata
Rhizophora mucronata, Asiatic or loop-root mangrove (Rhizophoraceae), is a viviparous Indo-Pacific mangrove tree to 25 m with stilt roots and pointed leaves; bark yields tannin, parts serve traditional medicine, and it is IUCN Least Concern.
Rhizophoraceae
Rhizophoraceae, the red mangrove family, is a mainly Old World tropical family of 15–16 genera and about 145 species in Malpighiales, including about half of the world's true mangrove species.
Rhizosphere
Rhizosphere: the soil zone influenced by plant roots, coined by Lorenz Hiltner in 1904. Extends under 1 mm to about 10 mm; root exudates drive microbial activity, nutrient cycling, and rhizosphere engineering.
Rhodiola rosea
Rhodiola rosea (rosenroot, arctic root, golden root), Crassulaceae succulent perennial of the subarctic Northern Hemisphere; root used traditionally as an adaptogen for stress and fatigue; EU traditional-use monograph; clinical evidence inconclusive; wild stocks overharvested.
Rhododendron
Rhododendron, including azaleas, is a large Ericaceae genus of 850+ woody species native from the temperate Northern Hemisphere to tropical Asian mountains and NE Australia, with leathery leaves, showy bell-shaped flowers, and winged seeds.
Rhododendron ferrugineum
Rhododendron ferrugineum, the alpenrose or alpine rose, is a dwarf evergreen Ericaceae shrub of the European Alps and Pyrenees, the type species of Rhododendron, flowering rosy scarlet at 1,700–2,500 m on acid, non-limestone soils.
Rhododendron ponticum
Rhododendron ponticum, an evergreen Ericaceae shrub native to the Black Sea region and Iberia, introduced to Britain in 1763, now one of the most destructive invasive plants of the British Isles, forming dense thickets and hosting Phytophthora ramorum.
Rhubarb
Rhubarb (Rheum rhabarbarum) is a hardy perennial buckwheat-family vegetable grown for tart edible stalks; leaves are toxic from oxalic acid, and it needs winter chill, division propagation, and cool summers.
Rhus typhina
Rhus typhina (staghorn sumac, Rhus hirta) is a suckering North American shrub or small tree of Anacardiaceae, 15-25 ft tall with velvety branches and red hairy fruit; harmless, unlike poison sumac (Toxicodendron vernix), and a 17th-century European introduction.
Rhynchospora
Rhynchospora (beaksedge) is a cosmopolitan genus of about 392 sedge species in Cyperaceae, tribe Rhynchosporeae, defined by a persistent beak-like style base on the nutlet, richest in tropical America, with holocentric chromosomes.
Rhytidiadelphus squarrosus
Rhytidiadelphus squarrosus, springy turf-moss (Square goose neck moss), a Hylocomiaceae lawn and grassland moss with right-angled squarrose leaves giving star-like shoot tips; widespread in Europe, introduced in New Zealand and Tasmania.
Ribes
Ribes (currants and gooseberries) is a genus of about 195 accepted shrub species in Grossulariaceae, native from subarctic to tropical American mountains, cultivated for black, red, and white currants and gooseberries, and alternate host of white pine blister rust.
Riccia fluitans
Riccia fluitans, floating crystalwort, is a thallose aquatic liverwort (Ricciaceae) that floats in mats worldwide, switches between water and land forms regulated by abscisic acid, favors eutrophic waters, and is a popular aquarium plant.
Rice
Rice (Oryza sativa), annual grass staple for over half the world's people; japonica domesticated in the Yangtze valley ~11,000 BP, indica via japonica introgression; 552.5 Mt milled output forecast 2026/27.
Rice bran extract
Rice bran extract is a water-extracted ingredient from rice bran used as a moisture retention agent and sodium phosphate alternative in processed meats, GRAS under FDA GRN 884 (Florida Food Products, closed August 2020) at up to 1.25% by weight.
Rice bran fiber
Rice bran fiber, a concentrated dietary fiber mechanically isolated from defatted rice bran; GRAS in the US under FDA GRN 373 (CJ America, 2011, no-questions letter) for food use excluding meat and poultry.
Rice bran oil
Rice bran oil (RBO, rice oil) is an edible oil from the bran of Oryza sativa, rich in gamma-oryzanol and vitamin E, requiring bran stabilization against lipase, refined physically, and shown in meta-analyses to lower LDL and total cholesterol.