Life and health

Crocus vernus

Crocus vernus, the Dutch or spring crocus, is a dwarf perennial iris-family plant native to the Alps and western Balkans, with purple, white, or striped early-spring flowers.

Crohn's disease: chronic inflammatory bowel disease of the digestive tract, first described in 1932 as regional ileitis by Crohn, Ginzburg, and Oppenheimer; treated with biologics, immunomodulators, and surgery.

Cronartium ribicola

Cronartium ribicola, white pine blister rust, is an Asian-origin rust fungus of five-needle pines requiring Ribes alternate hosts; introduced to North America around 1910, it causes lethal cankers and drove a vast, failed eradication program ending in 1967.

Cronkhite-Canada syndrome

Cronkhite-Canada syndrome (CCS), a rare nonhereditary gastrointestinal polyposis disorder with alopecia, nail dystrophy, hyperpigmentation, diarrhea, and protein-losing enteropathy; first described 1955, over 500 cases, mostly Japan, treated with corticosteroids.

Cronobacter sakazakii

Cronobacter sakazakii, formerly Enterobacter sakazakii, is a Gram-negative Enterobacteriaceae bacterium surviving in dry foods like powdered infant formula, causing rare but often fatal infant sepsis and meningitis; genus Cronobacter has seven species.

Crop

A crop is a plant grown deliberately by humans for food, feed, fiber, or energy, including annual staples like wheat, maize, and rice and perennials such as fruit trees.

Crop milk

Crop milk (pigeon milk) is a nutritive secretion pigeons, doves, flamingos, and emperor penguins feed their young, made from sloughed crop or esophageal cells, prolactin-regulated, protein- and fat-rich, and produced by both sexes in pigeons.

Crop production

Crop production: growing crops from land preparation, seeding, and weeding to harvest. Key facts: water and nitrogen as limiting resources, green revolution doubling of grain output, organic yields about 80% of conventional, FAO 2026 cereal forecast 2,979 million tonnes.

Crop protection

Crop protection is the set of practices limiting damage that pests, diseases, and weeds inflict on crops, today guided by Integrated Pest Management, which minimizes pesticide use.

Crop rotation

Crop rotation: planned sequence of different crops on the same field over a rotation cycle, also called rotational cropping. Distinguished from monoculture by legume pre-crop yield gains of 23%, 14–27% whole-system yield, nutrition, and revenue gains, and required in USDA organic rules.

CropLife International

CropLife International, a Belgian A.I.S.B.L. federation of BASF, Bayer, Corteva, FMC, Sumitomo Chemical, and Syngenta, promotes pesticide stewardship, the FAO Code of Conduct, and regulatory advocacy, and faces documented lobbying criticism.

Cropping (animal)

Cropping (animal) is the surgical removal of part of a dog's ear flap (pinna), also called cosmetic otoplasty, done mainly for breed-standard appearance. Performed on 6-12 week puppies, opposed by AVMA and WSAVA, banned in the EU, UK, and Ontario except for medical need.

Cross Reactions

Cross Reactions (cross-reactivity): serological reactions where an antiserum against one antigen also reacts with a closely related, non-identical antigen; basis of allergy cross-reactivity, immunoassay interference, and serology false positives.

Cross-circulation (surgery)

Cross-circulation is a surgical technique in which a second person, usually a parent, served as the living oxygenator for a child undergoing open-heart surgery at the University of Minnesota from 1954.

Cross-domain homology of translation factors

Cross-domain homology of translation factors traces which translation GTPases across bacteria, archaea, and eukaryotes descend from a common ancestor and which arose convergently, including release and recycling factors.

Cross-dominance

Cross-dominance (crossed laterality, mixed dominance): dominant hand and dominant eye on opposite body sides. Affects marksmanship learning (86.1% vs 56.5% rifle qualification) but shows no reliable link to academic achievement or intelligence.

Cross-frequency coupling

Cross-frequency coupling (CFC) is a neurophysiological analysis method measuring statistical interactions between neural oscillations at different frequencies in EEG, MEG, and other brain signals, consolidated as a field in 2007.

Cross-linking and immunoprecipitation

Cross-linking and immunoprecipitation (CLIP) is a method for identifying the RNA targets of RNA-binding proteins in living cells, combining UV cross-linking with immunoprecipitation and sequencing.

Cross-matching

Cross-matching (crossmatch) is pretransfusion testing mixing patient plasma with donor red cells to detect ABO and IgG antibody incompatibility before transfusion. Methods include immediate spin, IAT (Coombs), and computer crossmatch; introduced in 1907 by Hektoen and Ottenberg.

Cross-sectional study

Cross-sectional study: an observational epidemiologic design (a survey) measuring exposures and outcomes simultaneously in a population sample; yields prevalence and prevalence ratios, not incidence or causal proof.

Cross-species transmission

Cross-species transmission (host jump, zoonotic spillover) is pathogen transfer between host species, requiring encounter, infection, and propagation; RNA viruses jump most often, host phylogenetic distance predicts zoonotic risk, and humans also export viruses to animals.

Crossbreed

Crossbreed: offspring of mating two or more different breeds or strains of the same species; also called hybrid when between species. Valued for heterosis (hybrid vigor) and breed complementarity in livestock systems.

Crosslinking mass spectrometry

Cross-linking mass spectrometry (XL-MS) is a structural biology method that covalently links amino acid residues close together in proteins, then uses tandem mass spectrometry to identify the pairs as distance restraints for modeling.

Crossover junction endodeoxyribonuclease RuvC

RuvC (crossover junction endodeoxyribonuclease) is the E. coli Holliday junction resolvase, a 19-kDa homodimeric endonuclease that cuts two strands symmetrically at 5′-(A/T)TT↓(G/C)-3′ sites, working with RuvAB in the RuvABC resolvasome.

Crotalaria

Crotalaria (rattlebox) is a genus of about 717 accepted legume species (Fabaceae, tribe Crotalarieae) native from the tropics and subtropics to central and eastern USA, centered in Africa and Madagascar, containing toxic pyrrolizidine alkaloids and including the crop sunn hemp (Crotalaria juncea).

Crotalaria juncea

Crotalaria juncea (sunn hemp, Indian hemp) is a tropical Fabaceae annual legume from Afghanistan to Indo-China, grown for bast fiber, green manure, and weed- and nematode-suppressing cover crops, fixing 50–60 kg N/ha in 60–90 days.

Crotalus

Crotalus, the typical rattlesnakes, is a New World pitviper genus erected by Linnaeus in 1758 (type species C. horridus), with about 55 species from Canada to Argentina, rapid Pliocene diversification, and medically important venoms such as crotoxin.

Crotalus cerastes

Crotalus cerastes, the sidewinder or horned rattlesnake, is a small venomous pit viper of the Mojave, Sonoran, and Colorado deserts of the southwestern US and northwestern Mexico, known for sidewinding locomotion, horn-like supraocular scales, and hemorrhagic venom.