Bibb lettuce (Lactuca sativa L., cv. Ostinata) was grown in peat-vermiculite plugs placed in a recirculating hydroponic (NFT) system. Supplemental lighting was used to reach different PPFtarget levels in each of 35 treatments. A second order exponential polynomial was developed to predict DW accumulation for PPFtarget levels between 8 and 22 mol nr -2 d-1. Little difference in DW production was noted between lettuce grown under daytime and nighttime lighting. Tipburn was prevented using a fan blowing greenhouse air vertically down onto the lettuce plants. Marketable (150 g FW) lettuce heads were produced in 24 days after transplant while receiving an average PPFintegrai of 17 mol m-2 d-1.
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