Effects of shading on growth and bulb quality of tulip ‘Strong Gold’ produced on highland of Chiang Mai

Abstract

Tulip is an important commercial flower bulb crop which annual turnover of tulip in the world market was about 215 million euros. Although light and temperature on highland of Thailand has high potential for tulip bulb production, but it was necessary to adjust lighting for related temperature. However, the research involved this topic was rarely reported. This research was aimed to study the effects of shading on growth, bulb formation and photosynthesis of tulip ‘Strong Gold’. Three levels of net shading i.e., 1) no shading (average light intensity is 568.67 µmol/m²/s²), 2) 50% net shading (average light intensity is 388.09 µmol/m²/s²) and 3) 70% net shading (average light intensity is 100.09 µmol/m²/s²) were studied in Hod district, Chiang Mai, at 1,000 m above sea levels with average temperature of 25.4 ^oC and RH 63.9 % (during the experimental). The experimental design was completely randomized design (CRD) with 3 treatments and 20 replications (1 bulb per replication). Plant height, number of leaves per plant, SPAD unit, photosynthetic rate, stomatal conductance, transpiration rate, bulb fresh and dry weights, number of new bulbs per plant, and total non-structural carbohydrate (TNC) were measured. The results indicated that plants grown under 50% net shading had the highest TNC content, fresh and dry weights of bulb (227.1 mg/bulb, 9.37 and 3.01 g, respectively). Number of new bulbs were not significant difference among treatments. Therefore, 50% net shading is suitable for growing tulips on highland of Chiang Mai.