Update on trialing supplemental lights in Hawaii

By David Kuack

On Dec. 14, 2014, a Hort Americas blog update was posted about University of Hawaii graduate student Robert Saito, who is comparing the growth of pak choi (Chinese cabbage) under T5 fluorescent lamps and Philips GreenPower LED Production Module Deep Red/Blue 120 fixtures. Saito has conducted seven trials. The first four trials were preliminary to determine the best growing medium and which plants should be used to measure light effect differences. Initially Saito was planning to grow mizuna, but he ran into issues with micronutrient deficiencies and switched to pak choi instead. Both of these leafy greens are in the Brassica family.

University of Hawaii graduate student Robert Saito is studying
the differences in growth of pak choi under fluorescent (top)
and LED lights (bottom).
Photos courtesy of Robert Saito

Preliminary results
Saito has measured fresh weight, height and chlorophyll content of the plants grown under the two light sources.

“I also took SPAD readings to measure the relative chlorophyll and there were differences among the treatments,” Saito said. “I am now going to run the data statistically to see if there was a significant difference.”

Plant samples are also being analyzed for nutrient content to see what kind of nutritional value they can offer to consumers.

“I am doing a tissue analysis to measure some of the secondary metabolites,” he said. “I am looking at total phenolics, carotenoids and glucosinolates. A mineral nutrient analyses will measure such things as total nitrogen, phosphorus and potassium. Once the mineral and tissue analyses are done then I hope to publish the results.”

For more: Robert Saito, University of Hawaii, College of Tropical Agriculture and Human Resources, Manoa, Hawaii; rjnsaiot@hawaii.edu.
David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com. 

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