Effect of RGB LED Pulse Lights in Photomorphogenesis of Brassica chinensis Nurul Najwa Ani 1 , Robiah Ahmad 1 and Che Radziah Che Mohd Zain 2 1 Razak School and Advanced Technology, Universiti Teknologi Malaysia Kuala Lumpur, Malaysia. 2 School of Biosciences & Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Malaysia. Abstract. The study aims at evaluating the effects of combination of red (R) green (G) and blue (B) LED lights on Brassica chinensis under pulse lighting treatment (1 h dark 15 minutes lights) during the day. Brassica Chinensis were grown with different photon flux density (PFD) at 100 μmol m -2 s- 1 as treatment 1 (T1) and 50 μmol m -2 s- 1 as treatment 2 (T2). The combination of RGB LEDs ratio was 4:3:3 and plants were hydroponically cultured at ±28 o C (day/night), 45% relative humidity, and 400 ppm CO 2 level inside control environment room for 25 days (5 days after sowing). Results showed that Brassica chinensis grown under RGB with pulse lighting treatment at 100 μmol m -2 s- 1 promote plant growth and photomorphogenesis. Keywords: Brassica chinensis, LED, Photomorphogenesis. 1. Introduction Light is not only a primary energy source for photosynthesis but also a vital regulator for numerous processes in plants. The lights intensity and quality are essential for plant growth, morphogenesis and other physiological responses [1]. Combination of red (R) and blue (B) LED light was an effective light source for plant growth and development, and the light spectra, intensities, and durations can easily be controlled by growers in artificial growing environments. Plants appear green because the plant reflects green light. Therefore, green light has been thought to be of no use for plant growth, particularly for photomorphogenesis and photosynthesis. Plants grow normally under sunlight or combined artificial red and blue light [2], but irradiation with green light induces stem elongation [3]. Among the various environmental factors, light is one of the most important variables affecting growth and development of many plant species such as, potato [4], and grape [5], strawberry [6]. Red and blue LEDs were used because red (650–700 nm) waveband is known to be involved in the photosynthetic and blue (450–500 nm) waveband in the photomorphogenic and phototropic responses of plants. It is well known that action spectra have action maxima in the B and R ranges [7]. The absorption of red or blue light by plant leaf pigments was about 90%, and that of green light was about 70–80% [8]. Plant physiological reactions to green light and the effects of green light on plant growth have been investigated, but there is no report of plants being cultivated under pulse lighting treatment in combination of RGB. In this study, two experiments using RGB light emitting diode (LED) with pulse lighting treatment and different light intensities were used to investigate the effect of RGB on Brassica chinensis growth and photomorphogenesis. 2. Material and Methods 2.1. Plant Materials and Lights Treatment  Corresponding author. Tel.: +(603-2615 5231); fax: +(603-2615 5380). E-mail address: (robiahahmad@utm.my) 2014 2nd International Conference on Agriculture and Biotechnology IPCBEE vol. 79 (2014) © (2014) IACSIT Press, Singapore DOI: 10.7763/IPCBEE. 2014. V79. 3 15