Poster: Ecophysiology

Abs # 2: Stomatal Conductance of Lettuce Grown Under or Exposed to Different Light Quality

Presenter:	Kim, Hyeon-Hye , HyeonHye.Kim-1@ksc.nasa.gov
Authors	Kim, Hyeon-Hye  (A) (C)  Goins, Gregory D (B)   Wheeler, Raymond M (A)   Sager, John C (A)
Affiliations:	(A): NASA Biological Sciences Office (B): North Carolina A&T State University (C): NRC Resident Research Associate

The objective of this research was to examine lettuce plants to characterize the pattern of stomatal conductance and to investigate the effect of changes in the spectral environment on stomatal conductance. The plants were grown under or exposed to four light sources, (1) red and blue LEDs (RB), (2) red and blue LEDs with green fluorescent lamps (RGB), (3) green fluorescent lamps (GF), and (4) cool white fluorescent lamps (CWF). The diurnal stomatal conductance for lettuce leaves grown under different light quality for 23 days showed less variation in plants grown under RB, RGB, and GF than CWF. The conductance of the plants grown under CWF rose rapidly at the beginning of the photoperiod and peaked near the middle of the lighting period. Following the mid-day peak, conductance decreased for the remainder of the photoperiod and reached a minimum during the dark period. This investigation demonstrated that growth spectral quality affected the pattern of diurnal stomatal conductance. Various morphological or physiological adaptations occurred, since the dry weight accumulation was the highest in plants grown under RGB although the conductance was lower in plants grown under RGB than CWF. Temporarily changing the spectral quality of the plants grown under CWF for 23 days to RB, RGB, or GF changed the stomatal conductance with the highest conductance under RB and the lowest conductance under GF. In all cases, the stomatal responses were reversible, i.e. conductance returned to original rates following temporary changes in spectral quality. The temporary changes in spectral quality affected stomatal conductance and this tendency agreed with previous studies on stomatal responses of epidermal strips.