title: Stomatal conductance of lettuce grown under or exposed to different light qualities.
abstract: OBJECTIVE
  The objective of this research was to examine the effects of differences in light spectrum on the stomatal conductance (Gs) and dry matter production of lettuce plants grown under a day/night cycle with different spectra, and also the effects on Gs of short-term exposure to different spectra.
  
  
  METHODS
  Lettuce (Lactuca sativa) plants were grown with 6 h dark and 18 h light under four different spectra, red-blue (RB), red-blue-green (RBG), green (GF) and white (CWF), and Gs and plant growth were measured.
  
  
  CONCLUSIONS
  Conductance of plants grown for 23 d under CWF rose rapidly on illumination to a maximum in the middle of the light period, then decreased again before the dark period when it was minimal. However, the maximum was smaller in plants grown under RB, RGB and GF. This demonstrates that spectral quality during growth affects the diurnal pattern of stomatal conductance. Although Gs was smaller in plants grown under RGB than CWF, dry mass accumulation was greater, suggesting that Gs did not limit carbon assimilation under these spectral conditions. Temporarily changing the spectral quality of the plants grown for 23 d under CWF, affected stomatal responses reversibly, confirming studies on epidermal strips. This study provides new information showing that Gs is responsive to spectral quality during growth and, in the short-term, is not directly coupled to dry matter accumulation.
authors.affiliation: NASA Biological Sciences Office, Mail Code: YA-E4-B, Kennedy Space Center, FL 32899, USA. hyeonhye.kim-1@ksc.nasa.gov
authors.forename: Hyeon-Hye
authors.initials: HH
authors.lastname: Kim
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Goins
authors.forename: Raymond M
authors.initials: RM
authors.lastname: Wheeler
authors.forename: John C
authors.initials: JC
authors.lastname: Sager
mesh_terms: D003470:Culture Media; D018545:Lactuca / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D008027:Light; D008029:Lighting / Q000379:methods; D017785:Photons; D017440:Photoperiod; D010788:Photosynthesis / Q000528:radiation effects; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*
chemical_list: D003470:Culture Media