EFFECTS OF LIGHT-INTENSITY AND LIGHTING DIRECTION ON THE PHOTOAUTOTROPHIC GROWTH AND MORPHOLOGY OF POTATO PLANTLETS IN-VITRO

Photoautotrophic growth and morphological characteristics of potato (Solanum tuberosum L. cv. 'Benimaru') plantlets culture in vitro with sideward lighting were compared with those cultured with conventional downward (overhead) lighting at four different photosynthetic photon flux densities (PPFDs) ranging between 30 and 120 mumol m-2 s-1. The shoot length was about 20 mm shorter in the sideward lighting treatment than in the downward lighting treatment at each PPFD. Dry weight, fresh weight and leaf area of the plantlets cultured in vitro photoautotrophically for 21 days in the sideward lighting treatment were similar to those in the downward lighting treatment at each PPFD. They increased with increasing PPFD to about 90 mumol m-2 s-1, then leveled off. The shoot length of the plantlets decreased with increasing PPFD in both lighting treatments. The sideward lighting system provided higher quality micropropagated transplants with reduced shoot length than the downward lighting system at each PPFD.