title: Effect of 16 and 24 hours daily radiation (light) on lettuce growth.
abstract: A 50% increase in total radiation by extending the photoperiod from 16 to 24 hr doubled the weight of all cultivars of loose-leaf lettuce (Lactuca sativa L.) 'Grand Rapids Forcing', 'Waldmanns Green', 'Salad Bowl', and 'RubyConn', but not a Butterhead cultivar, 'Salina'.  When total daily radiation (moles of photons) was the same, plants under continuous radiation weighed 30% to 50% more than plants under a 16 hr photoperiod.  By using continuous radiation on loose-leaf lettuce, fewer lamp fixtures were required and yield was increased.
authors.affiliation: University of Connecticut, Storrs 06268, USA.
authors.forename: H V
authors.initials: HV
authors.lastname: Koontz
authors.forename: R P
authors.initials: RP
authors.lastname: Prince
mesh_terms: D004780:Environment, Controlled; D018527:Hydroponics; D018545:Lactuca / Q000145:classification / Q000254:growth & development* / Q000502:physiology; D008027:Light; D017785:Photons; D017440:Photoperiod; D010788:Photosynthesis / Q000502:physiology; D013997:Time Factors