Enhanced flowering of sacred lotus (Nelumbo nucifera Gaertn.) by extending the photoperiod with supplemental lighting techniques

Sacred lotus (Nelumbo nucifera Gaertn.) is one of the most popular cut flowers in Thailand and other Asian countries, commonly used for religious purposes. However, basic knowledge regarding the control of flowering is relatively lacking. The effects of photoperiod on growth of N. nucifera were investigated using a completely randomized design experiment with six day-length conditions: 1) 11 h for 2 months, 2) 11 h for 1 month and then to 13 h for 1 month, 3) 11 h for 1 month and then 15 h for 1 month, 4) 13 h for 1 month and then 11 h for 1 month, 5) 13 h for 2 months and 6) 13 h for 1 month and then 15 h for 1 month. Each pot was planted with 90 stem cuttings, filled to 2/3 of the pot level with natural clay soil and then filled to 3/4 of the pot level with tap water after planting. The stolons were grown under natural conditions (ambient temperature 30/18°C with an 11 h day length in mild winter from January-February 2013). Night interruption after 6:00 pm was used to induce a long day-length condition (13 and 15 h). None of photoperiod conditions affected the total number of leaves. However, extending the photoperiod from 11 to 15 h and from 13 to 15 h and a constant photoperiod of 13 h produced the largest leaves. Shortened photoperiods from 13 to 11 h decreased the flowering percentage and number of flowers. Extended photoperiods from 11 to 13 h, 11 to 15 h and 13 to 15 h only increased the flowering percentage compared with that of constant photoperiods of 11 and 13 h. Nevertheless, the extended photoperiod delayed the date of visible flowering.