Changes and Photoperiod Effects on Sugars in Oncidium Plant at Growth Stages

Objective To investigate the changes in sugar content during different growth stages of Oncidium and the influence of photoperiod on these changes.

Methods The contents of water, soluble sugars such as sucrose, glucose, fructose, and trehalose-6-phosphate (T6P), and starch, as well as the activities of enzymes involved in sucrose and starch synthesis, were analyzed in both the pseudobulbs and leaves during the pseudobulb enlargement stage, leaf bud development stage, and flower bud development stage. The influence of photoperiod on the changes in sugar content was also examined.

Results The contents of water, sugars (mostly sucrose and fructose), and starch in the pseudobulbs were higher than those in the leaves and varied significantly as the leaf and flower buds were developing. Throughout the stages, the pseudobulbs and leaves remained a high activity of sucrose synthase (SS) but low of sucrose phosphate synthase (SPS). The activity of soluble starch synthase (SSS) was higher than that of granule-bound starch synthase (GBSS), but both were relatively high in the expanding pseudobulbs. Photoperiod significantly affected the water and sugar contents and more so in the pseudobulbs than in the leaves.

Conclusion Affected by photoperiod, the sugars in the oncidium orchid pseudobulbs and leaves experienced dynamic and significant changes throughout the development stages.