CO2 Uptake Behavior and Vegetative Growth of Doritaenopsis Mantefon Orchids as Influenced by Light/Dark Cycle Manipulation

Abstract

This study was performed to investigate how changing the period of light and dark influences the vegetation growth and the photosynthesis of Doritaenopsis. Clones of Doritaenopsis Queen Beer Mantefon at 4-month-old stage were grown in a closed-plant factory system with four different light/dark cycles

06/06 h, 08/08 h, 10/10 h, and 12/12 h. Temperature and relative humidity were set at 28oC and 80%, respectively, with a photosynthetic photon flux density of 160 ± 10 µmol·m-2·s-1. Repetitive measurements showed that the leaf length and the leaf width were the longest under 12/12 h closely followed by 10/10 h. The fresh weight and the dry weight of leaves and roots were the heaviest at 10/10 h treated samples. Different CO2 uptake patterns were observed from different light/dark cycles. Under 10/10 h and 12/12 h treatments, the CO2 uptake started at early dark period. When the light/dark cycles were shortened to 06/06 h and 08/08 h, the CO2 uptake started at the middle of dark period. Total CO2 uptake amounts were the highest under 12/12 h treatment followed by 10/10 h, 06/06 h, and 08/08 h treatments. Quantitative measurements showed that the vegetative growths under 10/10 h treatment were comparable with that of 12/12 h treatment. These studies indicated that manipulating light/dark can modify the photosynthesis patterns and vegetative growth of Doritaenopsis Mantefon, resulting in the reduction of the production period.