Substrate Water Content Influences the Flowering of Doritaenopsis Queen Beer ‘Mantefon’

Automated irrigation systems based on soil moisture sensor measurements can reduce water and fertilizer use while adequately meeting plant water requirements. In this study, the effects of substrate volumetric water content (theta, v/v) on the flowering of 17-month-old Doritaenopsis Queen Beer 'Mantefon' (from the time of deflasking) were examined. The plants were transplanted in plastic pots (10.5 cm width x 9.5 cm height) filled with sphagnum moss and the theta of sphagnum moss was maintained at 0.2, 0.3, 0.4, or 0.5 m(3).m(-3) using an automated drip irrigation system. Plants grown at a theta threshold of 0.2 m(3).m(-3) had thinner leaves and lower SPAD value than those grown at higher theta thresholds. The net CO2 uptake of the uppermost fully expanded leaf increased with increasing theta between 0.2 and 0.4 m(3).m(-3), but there was no significant difference in the net CO2 uptake between plants grown at 0.4 and 0.5 m(3).m(-3) thresholds. The number of flower buds at the time of the first open flower was lower in plants grown at theta thresholds of 0.2 and 0.3 m(3).m(-3) as compared with that in the plants grown at 0.4 and 0.5 m(3).m(-3) thresholds. Early flower abscission, flower bud dropping, and flower senescence during the 2 weeks after flowering occurred in 55% and 30% of the plants at 0.2 and 0.3 m(3).m(-3) thresholds, respectively, whereas plants at theta thresholds of 0.4 and 0.5 m(3).m(-3) had negligible flower abscission. Although vegetative growth parameters were similar among theta thresholds of 0.3 m(3).m(-3) or higher, plants grown at a theta threshold of 0.3 m(3).m(-3) produced fewer flowers than those grown at 0.4 and 0.5 m(3).m(-3) thresholds. During the 83-day experimental period, the systemirrigated the plants approximate to 0.79, 1.93, 2.46, and 2.84 L/pot at theta thresholds of 0.2, 0.3, 0.4, and 0.5 m(3).m(-3), respectively. Overall, 0.4 m(3).m(-3) was considered to be an optimal threshold theta level for producing high-quality Doritaenopsis Queen Beer 'Mantefon' during the flowering period with most efficient water use.