| Abstract | Phalaenopsis orchids are one of the most popular and beautiful flowering plants in the world. Leaf tips segments from in vitro young plant of Phalaenopsis hybrid ‘Pink’ were cultured on half-strength Murashige and Skoog (MS) and Vacin and Went (VW) media supplemented with different concentrations of auxin [α-napthaleneacetic acid (NAA)] and cytokinins [6-benzylaminopurine (BAP) or thidiazuron (TDZ)]. The explants that were cultured on 0 mg L–1 NAA and 3 mg L–1 BAP supplemented to half-strength MS medium formed shoots successfully within 10 weeks of culture with 5% regenerants and 50% survival frequency. The explants that were cultured on 0.5 mg L–1 NAA and 1.5 mg L–1 TDZ supplemented to half-strength MS medium developed calli and shoots within 11 weeks of culture with 25% regenerants and 90% survival frequency.
The effects of various sucrose concentrations as carbon source and natural additives in the mentioned media on plantlet growth of Phalaenopsis hybrid ‘Pink’ were studied. Plantlets were cultured on two media (half-strength MS and VW) supplemented with 0, 10, 20, 30 or 40 g L–1 sucrose either with 0, 10 or 20% (v/v) coconut water (CW) or carrot juice (CJ) as natural additives. After four months of culture, the combination of sucrose and CW supplemented to both media significantly affected plantlet growth where most of the plantlets showed slow growth and survival frequency (0–80%) with increasing concentrations of CW in all sucrose concentrations. However, plantlet growth on both media containing only 20 g L–1 sucrose without CW was optimal in terms of root number, root length, leaf number, leaf length, leaf width, fresh weight, dry weight and plant height. The combination of sucrose and CJ supplemented to MS medium resulted in overall good plantlet growth with 100% survival frequency. The combination of sucrose (20 g L–1) and CJ (10%) supplemented to MS medium increased root length, leaf length, leaf width and plant height. Plantlet growth was also optimal in the combination of 20 g L–1 sucrose and 10% CJ supplemented to VW medium. The results of this study indicate that Phalaenopsis hybrid ‘Pink’ cultured on the combination of sucrose (20 g L–1) and CJ (10%) supplemented to either MS or VW media can be used for plantlet growth of this species.
After four months of culture, plantlets were transferred to a greenhouse under natural environmental condition for measuring net CO2 exchange rate of Phalaenopsis hybrid ‘Pink’. The results showed that the combination of 30 and 40 g L–1 sucrose with 10% (v/v) CJ supplemented to half-strength MS and VW medium, respectively, optimally enhanced root length, leaf length, plant height, leaf greenness, total chlorophyll content and CO2 uptake. The combination of 30 g L–1 sucrose and 10% (v/v) CJ supplemented to half-strength MS medium resulted in the highest leaf length (5.00 ± 0.07 cm), plant height (7.20 ± 0.20 cm), SPAD leaf greenness (35.50 ± 0.26), total chlorophyll (15.13 ± 0.25 μg mL–1) and CO2 uptake (1.11 ± 0.15 μmol m–2 s–1). The combination of 40 g L–1 sucrose and 10% (v/v) CJ supplemented to VW medium resulted in the highest leaf length (5.40 ± 0.10 cm), leaf width (2.60 ± 0.10 cm), plant height (6.50 ± 0.22 cm), SPAD leaf greenness (37.43 ± 0.26), total chlorophyll (17.07 ± 0.39 μg mL–1) and CO2 uptake (1.77 ± 0.04 μmol m–2 s–1). The uptake of CO2 and chlorophyll content was slightly higher in VW medium with higher sucrose concentration (40 g L–1) compared with half-strength MS medium with lower sucrose concentration (30 g L–1) at the same concentration of CJ. |