Effect of Light Quality on Production of Bioprotective Compounds in Red Leaf Lettuce

G.W. Stutte1*, I. Eraso1, P. Bisbee1, C. Ledeker2, and T. Skerritt3.

1Dynamac Corporation,, Kennedy Space Center, FL, USA, 2Dept of Animal and Food Science, University of Delaware,

3Dept Applied Science, Limerick Institute of Technology, Limerick, Ireland

2008 International Meeting on Controlled Environment AgricultureCocoa Beach, FL 8-12 March, 2008

Background

Exposure to ionizing radiation during long-duration space missions increases risk for short term illness and long-term risk for cancer.

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Background

Radiation induces free-radical formation.Anti-oxidant defense mechanisms are over-riddenDamage at membrane, enzyme and chromosome level occurs

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Background

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Increasing levels of anti-oxidants increases resistance to damage.Anthocyanins are pigments with anti-oxidative propertiesRed leaf lettuce is candidate salad crop and a relatively high source of anthocyanins.

Research Objective

To determine whether the production of bioprotective compounds in candidate salad crops can be increased by regulating the morphology, growth, and biochemistry of the plants with though spectral quality using light emitting diodes.

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Research Approach

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Lactuca sativa cv. Outredgeous seedlings were grown in Rockwool under in small (16 x 19 x 24 cm) chambers at 300 µmol m-2 s-1 PPF with 18/6 photoperiod.Environment conditions were 23oC, 65% RH and 1200 µmol mol CO2.Total anthocyanin production in leaves was determined using spectrophotometerAnti-oxidant potential determined using the ORAC methodology

LED arrays with multiple wavelengths were used to alter spectral quality

400 nm

440 nm

530 nm

640 nm

660 nm

730 nm

LED arrays designed and built by Orbitec using Norlux LED engines

Spectral Quality Established by Altering Power to the LED arrays.Light treatments are established using blue (440 nm), green (530 nm), red (640 nm), and far red (730 nm) LED’s. Spectral quality and quantity determined with using spectroradiometer.300 µmol m-2 s-1 PPF from triphosphor fluorescent lamps (TPF; Pentron T-5) was used as the control treatment.

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5

10

15

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25

30

350 450 550 650 750 850 950 1050

Wavelength (nm)

Qua

nta

TPSRGBRBRRFr

Treat PARTPS 287RGB 284RB 276R 279RFr 294

Light quality affected plant morphology alter efficiency of light interception

RGB RB R RFr

0.00.20.40.60.81.01.21.4

RGB RB R RFr

Dry

Mas

s (g

)

Lactuca sativa cv Outredgeous Both blue (440 nm) and

Fr (730 nm) affect leaf morphology and plant

architecture

Light quality has significant effect on anthocyanin concentration in leaves.

RGB RB R RFr

0

1

2

3

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5

RGB RB R RFr

Ant

hocy

anin

(ug/

g FM

)

Blue light (440 nm) is required to maintain

anthocyanin content in the leaves.

Lactuca sativa cv Outredgeous

Blue (440 nm) light increases total anthocyanin content of plant.

RGB RB R RFr

010203040506070

RGB RB R RFr

Ant

hocy

anin

(ug/

plan

t)

Additive effects of light quality on anthocyanin concentration and plant

biomass occurs.

Lactuca sativa cv Outredgeous

Blue (440 nm) light increases total anti-oxidant potential (ORAC) value of plant.

05

1015202530

RGB RB R RFr

OR

AC

(TE/

plan

t)

RGB RB R RFr

Lactuca sativa cv Outredgeous

Threshold for blue (440 nm) was <5% of total PAR for anthocyanin production

Control RedRed/Blue

Conclusions

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LED’s can be used optimize spectral quality in plant chambers for long duration missions in order to increase yields by increasing light interception and increased efficiency of light conversion.Photoregulation of secondary metabolisms has potential to significantly increase the bioprotectant and nutraceutical valuecandidate salad cropsA significant amount of research is required to understand the photo regulation of bioprotectant metabolism in plants.

Funding provided by NASA Kennedy Space Center CTC grant (LSS5-16F)

Acknowledgments

Student SupportChristie Ledeker (University of Delaware) supported though Dynamac Internship Program.Tony Skerritt (Limerick Institute of Technology) supported through FÁS, Irelands Training and Employment Authority.

Funding provided by NASA Kennedy Space Center CTC grant (LSS5-16F)

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