title: Stimulation of lettuce productivity by manipulation of diurnal temperature and light.
abstract: 'Salad Bowl' and 'Waldmann's Green' leaf lettuce (Lactuca sativa L.) were exposed to photosynthetic photon flux densities (PPFD) of 444 or 889 micromoles s-1 m-2 for 20 hours day-1 under a diurnal temperature regime of 25 degrees C days/15 degrees nights or 20 degrees days/15 degrees nights. Leaf dry weight of both cultivars was highest under the high PPFD/warm temperature regime and lowest under the low PPFD/cool temperature regime. 'Waldmann's Green' yielded more than did 'Salad Bowl' at 889 micromoles s-1 m-2 and 25 degrees days/20 degrees nights. Under high PPFD, both cultivars yielded better with 25 degrees days/25 degrees nights than with 25 degrees days/20 degrees nights, although relative growth rates were the same under both temperature regimes.
authors.affiliation: Department of Horticulture, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Knight
authors.forename: C A
authors.initials: CA
authors.lastname: Mitchell
mesh_terms: D018533:Biomass; D003624:Darkness; D004780:Environment, Controlled; D018545:Lactuca / Q000254:growth & development* / Q000528:radiation effects*; D008027:Light; D010507:Periodicity; D010775:Photic Stimulation; D017785:Photons; D018515:Plant Leaves / Q000254:growth & development* / Q000528:radiation effects; D013696:Temperature