Comparison of photosynthesis and fluorescent parameters between Dendrobium officinale and Dendrobium loddigesii.

Objective: To investigate the photosynthesis and fluorescent parameters between Dendrobium officinale and Dendrobium loddigesii, based on which to provide helpful information for the artificial cultivation of these cultivars.
Methods: Seeds were placed on the MS medium supplemented with 0.2 mg/L NAA, 2% (w/v) sucrose, 15% (v/v) potato extracts and powered agar (pH 5.8). Two months after germination, seedlings (n = 10) were transferred onto rooting medium containing MS medium supplemented with 0.5 mg/L NAA, 3% (w/v) sucrose, 20% (v/v) potato extracts and 1‰ (w/v) activated carbon (pH 5.8) in a glass bottle (6.5 cm in diameter and 9.5 cm in height) with a white transparent plastic cap. Chlorophyll content was determined using the UV-Vis spectrophotometric method. In addition, rates of oxygen evolution and uptake were measured. The chlorophyll fluorescence was determined at room temperature using PAM 2000 chlorophyll fluorometer (Heinz Walz GmbH, Germany).
Results: From month 5 to month 10, the overall contents of both chlorophyll a and chlorophyll b were higher in D. loddigesii compared with those in D. officinale. No statistical differences were observed in the apparent photosynthetic rate (APR) between D. loddigesii and D. officinale. No statistical difference was noticed in the Fo, Fm and Fv between D. loddigesii and D. officinale (P > 0.05). Significant increase was noticed in the oxygen consuming in PSI in month-8 and month-10 compared with that of month-6 in D. loddigesii. Nevertheless, in the D. officinale, the oxygen consuming in PSI in month-6 was remarkably increased with those of month-8 and month-10, respectively.
Conclusions: The photosynthesis and fluorescence parameters varied in the seedling of D. loddigesii and D. officinale. Such information could contribute to the artificial cultivation of these cultivars.