Received date: 18/08/2015

Accepted date: 19/02/2016

This study was carried out to determine the effects of color LED light intensities and different photoperiod regimes on the growth of hydroponic lettuce. Four different light intensity treatments were used including 1 LED light NCM 3000K – purple LED: 75% red, 25% blue (48 μmol/m².s PPFD - Photosynthetic photon flux  density); 2 LED lights NCM 3000K – purple LED: 75% red, 25% blue (80 μmol/m².s  PPFD); 3 LED lights D NCM01 L/30W – White LED (60 μmol/m².s PPFD) and 3 LED lights NCM 3000K – purple LED: 75% red, 25% blue (98 μmol/m².s  PPFD), with a combination of five photoperiod regimes of 6/18, 9/15, 12/12, 18/6 and 24/0 (light/dark). Results showed that the 80-24/0 (2 purple LEDs – 24 hours light/0 hour dark) treatment yielded the highest production on fresh weight (34.93 g/plant) and the production of 60-24/0 (3 white LEDs -24 hours light/0 hour dark) and 80-18/6 (2 purple LEDs – 18 hours light/6 hour dark) treatments were 28.95 and 27.22 g/plant, respectively. The highest length of main stem values at interaction treatments among 3 white LED treatment were 26.18 and 20.04 cm for the 24/0 and 18/6 treatments, respectively and the leaf number (17.60 and 16.38 leaves), leaf length (10.31 and 10.97 cm) and leaf width (9.91 and 7.36 cm) at interaction treatments between 2 purple LEDs with 18/6 and 24/0 treatments were higher than others. The interaction among 18/6 and 24/0 treatments with 2 and 3 purple LED treatments showed the highest chlorophyll value (3.92-4.75 µg/g) and the lowest value at 6/18 treatment with four different light intensities (1.25-1.40 µg/g). Thus, 80-24/0 and 80-18/6 treatments showed the best result for the growth of hydroponic lettuce variety GN 63.

KEYWORDS

Color LED lamps, light intensity, photoperiod, lettuce, hydroponic