Poster: Photosynthesis

Abs # 318: Photosynthetic gas exchange and chloroplast fluorescence in wheat leaves developed under narrow-spectrum light-emitting diodes (LEDs)

Presenter:	Goins, Gregory D., gregory.goins-1@ksc.nasa.gov
Authors	Goins, Gregory D. (A)   Sanwo-Lewandowski, Monica M. (B)   Yorio, Neil C. (A)   Brown, Christopher S. (C)   Wheeler, Raymond M. (D)   Sager, John C. (D)   Kim, Hyeon-Hye  (E)
Affiliations:	(A): Dynamac Corporation, Kennedy Space Center, FL (B): Citrus Res. and Educ. Ctr., Univ. of Florida, Lake Alfred, FL (C): Kenan Institute for Engineering, Tech. and Science, N.C. State Univ., Raleigh, NC (D): Biological Sciences Office, Kennedy Space Center, FL (E): National Research Council Resident Research Associate

Red (R) and blue (B) light-emitting diode (LED) technology is a relatively new concept for long-term growth of plants, despite common use as a light source in photobiological research. While providing a background moderate irradiance using red R LEDs with and without B LEDs, the responses of wheat to spectral quality differences were compared to wheat grown under cool-white fluorescent (W) light at the same photosynthetic photon flux. When developed under R light without supplemental B light, flag leaves displayed structural and photosynthetic characteristics analogous in several respects to shade tolerant plants. B light level was a major factor in determining leaf structural trade-offs between light interception and photosynthetic capacity. Light-saturated photosynthesis data at low versus elevated CO₂ levels indicated that plants developed under R light may experience CO₂ limitations. Among all spectral environments, the nature of the relationship between Vcmax and Jmax was complicated by the interaction between leaf structure and gas exchange characteristics. Under red light alone as irradiance, there was a rapid decline in the actual efficiency of PSII and greater non-photochemical quenching, suggesting that narrow-spectrum R light without B light has the potential to over-excite PSII relative to PSI. Steady-state fluorescence parameters were similar between W- and R+B-grown flag leaves, except at saturating irradiances.