4.3 Article

Photosynthetic Light Requirements and Effects of Low Irradiance and Daylength on Phalaenopsis amabilis

Journal

Publisher

AMER SOC HORTICULTURAL SCIENCE
DOI: 10.21273/JASHS.137.6.465

Keywords

orchid; crassulacean acid metabolism; CAM; PPF; photoperiod

Categories

Funding

  1. National Science Council [NSC-101-2313-B-006- 001-MY3]

Ask authors/readers for more resources

Phalaenopsis has become one of the most important potted plants around the world. Thus, we used a key commercial Phalaenopsis amabilis cultivar, TS97, as a model to determine the light requirements for maximal carbon fixation and photosystem II (PSII) efficiency in its leaves and to investigate the effects of low irradiance and daylength on photosynthesis and flower development. In mature 'TS97' leaves, the daily total CO2 uptake capacity and net acid fixation increased with increasing photosynthetic photon flux (PPF) and saturated at approximate to 200 mu mol.m(-2).s(-1), whereas the fluorescence ratio values were significantly reduced to 0.68 to 0.75 above 325 mu mol.m(-2).s(-1) PPF, indicating photoinhibition of PSII. Positive assimilation of the nocturnal CO2 uptake occurred at a very low PPF (less than 5 mu mol.m(-2).s(-1)), suggesting highly efficient use of light energy by 'TS97' plants. Leaves developed under 30 mu mol.m(-2).s(-1) PPF exhibited lower light requirement of 125 mu mol.m(-2).s(-1) PPF to reach maximal CO2 uptake, below which the daytime CO2 uptake declined dramatically. Under a 12-hour daylength, exposing the leaves to a low PPF for 4 hours at any time during the day did not affect the photosynthetic capacity in 'TS97' leaves, suggesting that 8 hours of optimal irradiance is required for high-level photosynthesis, whereas the 12-hour daylength resulted in a higher CO2 uptake rate and the daily total CO2 uptake than the 8-hour daylength. Moreover, the 12-hour daylength promoted earlier flower formation and higher flower count compared with the 6- to 8-hour daylengths. Longer daylengths neither accelerated flowering formation nor enhanced total flower count. In conclusion, 8 hours of saturating PPF at 200 mu mol.m(-2).s(-1) and a 12-hour daylength are sufficient for maximizing photosynthesis and flower production in 'TS97' plants.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.3
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available