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Osmundastrum pulchellum
Osmundastrum pulchellum, originally Osmunda pulchella, an extinct royal fern from the Pliensbachian (Lower Jurassic) of Korsaröd, Skåne, Sweden; a probable precursor of modern Osmundastrum known from a permineralized rhizome.
Osteospermum
Osteospermum, the daisybushes or African daisies, is a genus of 74 accepted species in Asteraceae tribe Calenduleae, native from St. Helena and Egypt to South Africa and Arabia, with hard, winged, pappus-less achenes and popular ornamental hybrids.
Osyris
Osyris (African sandalwood, Osyris lanceolata) is a genus of hemiparasitic shrubs in Santalaceae, tribe Osyrideae, published by Linnaeus in 1753; five accepted species ranging from the Mediterranean and Africa to southern Asia, distinct from Colpoon and Rhoiacarpos.
Oval Office Swedish ivy
Oval Office Swedish ivy: Plectranthus verticillatus, a South African mint-family trailer displayed on the White House Oval Office mantel from the Kennedy era until February 2025, now surviving through staffer cuttings.
Ovule
An ovule is the structure in seed plants that contains the female gametophyte and, after fertilization, develops into a seed, tracing back almost 400 million years.
Oxalidaceae
Oxalidaceae, the wood sorrel family (Oxalidales), is a nearly cosmopolitan flowering-plant family of 5 genera, Averrhoa, Biophytum, Dapania, Oxalis, and Sarcotheca, and roughly 570-800 species, including star fruit, bilimbi, and oca.
Oxalidales
Oxalidales (Bercht. & J.Presl 1820) is a rosid order of flowering plants in the COM clade, containing Oxalidaceae, Connaraceae, Brunelliaceae, Cephalotaceae, Cunoniaceae, and Elaeocarpaceae, with Huaceae now excluded by phylogenomic work.
Oxalis
Oxalis, commonly known as wood sorrel, is a large genus of flowering plants with clover-like leaves, five-petaled flowers twisted in the bud, and tissues rich in oxalic acid.
Oxalis acetosella
Oxalis acetosella, wood sorrel (Wald-Sauerklee, Alléluia), a small perennial Oxalidaceae herb of shady Eurasian woods, with white purple-veined flowers, sour oxalic-acid leaves, and a Europe-to-Japan native range.
Oxalis triangularis
Oxalis triangularis (purple shamrock, false shamrock; synonym Oxalis regnellii) is a tuberous South American wood sorrel grown as a houseplant, with triangular purple leaves that fold at night via nyctinastic pulvinus movement and tart edible foliage.
Oxydendrum
Oxydendrum, sourwood (Oxydendrum arboreum), a monotypic genus of Ericaceae; deciduous southeastern US tree with lily-of-the-valley-like white summer flowers, prized honey, red fall color, acid soil needs, IUCN Least Concern.
Oxyrhynchus
Oxyrhynchus (Oxyrhynchus Brandegee), a genus of twining Fabaceae legumes published in 1912; species include O. volubilis (twining bluehood) and O. papuanus, native from Mexico to Colombia, the Bahamas to Cuba, and Maluku to Papuasia.
Oxytropis
Oxytropis (locoweed genus) is a Fabaceae legume genus of about 400 species across subarctic and temperate Northern Hemisphere, distinguished from Astragalus by a pointed keel petal; some species carry swainsonine-producing endophytic fungi toxic to livestock.
Pachira aquatica
Pachira aquatica, the Guiana-chestnut or money tree, is a wetland Bombacoideae tree from Mexico to South America; type of its genus, edible seeds, braided houseplant form, Least Concern.
Pachycereus
Pachycereus, Mexican columnar cactus genus (Britton & Rose 1909) with five accepted species including the giant cardón Pachycereus pringlei, up to 20 m tall, bat-pollinated, native only to Mexico.
Pachyrhizus
Pachyrhizus is a genus of five Neotropical legume species known as yam beans, three cultivated for their edible tuberous roots, including the Mexican species jicama.
Pachyrhizus erosus
Pachyrhizus erosus, jicama or yam bean (Mexican turnip, bang kuang), is a Mexican-Central American climbing legume grown for its edible starchy storage root; its rotenone-rich seeds are toxic but used as insecticide.
Paclitaxel total synthesis
Paclitaxel total synthesis: laboratory construction of the anticancer drug Taxol from simple starting materials. First achieved in 1994 by Holton and Nicolaou; over ten routes exist but none is commercially viable, so production uses semisynthesis.
Paclobutrazol
Paclobutrazol (C15H20ClN3O) is a triazole plant growth regulator, discovered by ICI in 1980, that inhibits gibberellin biosynthesis; used on ornamentals, turf, and mango, with EU approval extended to 31 January 2029.
Pad thai
Pad thai (ผัดไทย), also kway teow pad thai, is Thailand's stir-fried rice noodle dish with tamarind, fish sauce, and palm sugar sauce, promoted as a national dish under Phibunsongkhram in the 1930s-40s, with regional variants like southern coconut-milk Pak Phanang Mee Pad.
Paddy field
Paddy field (稻田, paddy fields): flooded level basin for growing rice (Oryza sativa). Flooding boosts yield and suppresses weeds; major methane source, ~25% of global freshwater use; AWD cuts water 20–40%.
Paeonia lactiflora
Paeonia lactiflora (芍药, shaoyao), the Chinese or common herbaceous peony, is a temperate perennial native to SE Siberia and N & E China, grown as an ornamental and cut flower and used in TCM as Bai Shao root, source of paeoniflorin.
Paliurus
Paliurus (Jerusalem thorn) is a genus of five spiny shrub and tree species in Rhamnaceae, tribe Paliureae, native from southern Europe and southwest Asia to East Asia, recognized by dry orbicular-winged wind-dispersed fruits and a rich Northern Hemisphere fossil record.
Palm kernel expeller and palm fatty acid distillate
Palm kernel expeller (PKE, also called palm kernel cake) is the residue left after mechanical screw-press extraction of palm kernel oil, used almost entirely as animal feed.
Palm kernel oil
Palm kernel oil, an edible lauric oil from the kernel of Elaeis guineensis fruit, distinct from mesocarp palm oil; 44-51% lauric acid, used in foods, soaps, oleochemicals, and cosmetics.
Palm oil
Palm oil: edible oil from the mesocarp of Elaeis guineensis fruit; palmitic-rich semi-solid, highest oil yield per hectare of any crop, produced mainly in Indonesia and Malaysia, distinct from palm kernel oil.
Palm oil carotenoids
Palm oil carotenoids are the carotenoid pigments, chiefly β-carotene and α-carotene, that give crude palm oil its dark red color and its provitamin A value, with conventional refining removing most of them.
Palm sugar
Palm sugar (gula aren, jaggery, ស្ករត្នោត) is an unrefined sweetener boiled down from the sap of Borassus, Arenga, Cocos, Phoenix, and Nypa palms; sucrose-dominant (91–95 g/100 g), with GI values from 35 to 98.71 depending on product, and major production in Indonesia, the Philippines, and Cambodia.
Palm tocotrienols
Palm tocotrienols are tocotrienol forms of vitamin E extracted from oil palm, constituting up to 70% of the crude oil's content, and possess low $\alpha$-TTP affinity.
Palm vinegar
Palm vinegar is vinegar made by fermenting the sweet sap of palms such as nipa, coconut, kaong, and buri, a tradition across Southeast Asia and the Philippines.