Photosynthetic light requirements and effects of low irradiance and daylength on phalaenopsis amabilis

Woei-Jiun Guo, Yu Zu Lin, Nean Lee

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

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 ≈200 μmol·m-2·s-1, whereas the fluorescence ratio values were significantly reduced to 0.68 to 0.75 above 325 μmol·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 μmol·m-2·s-1), suggesting highly efficient use of light energy by 'TS97' plants. Leaves developed under 30 μmol·m-2·s-1 PPF exhibited lower light requirement of 125 μmol·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 μmol·m-2·s-1 and a 12-hour daylength are sufficient for maximizing photosynthesis and flower production in 'TS97' plants.

Original languageEnglish
Pages (from-to)465-472
Number of pages8
JournalJournal of the American Society for Horticultural Science
Volume137
Issue number6
Publication statusPublished - 2012 Nov

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Orchidaceae
Phalaenopsis
light requirement
Photons
photoperiod
Light
carbon dioxide
uptake mechanisms
Photosynthesis
Photosystem II Protein Complex
flowers
photosynthesis
leaves
photosystem II
Carbon Cycle
flowering
Calvin cycle
container-grown plants
photoinhibition
photons

All Science Journal Classification (ASJC) codes

  • Horticulture
  • Genetics

Cite this

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title = "Photosynthetic light requirements and effects of low irradiance and daylength on phalaenopsis amabilis",
abstract = "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 ≈200 μmol·m-2·s-1, whereas the fluorescence ratio values were significantly reduced to 0.68 to 0.75 above 325 μmol·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 μmol·m-2·s-1), suggesting highly efficient use of light energy by 'TS97' plants. Leaves developed under 30 μmol·m-2·s-1 PPF exhibited lower light requirement of 125 μmol·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 μmol·m-2·s-1 and a 12-hour daylength are sufficient for maximizing photosynthesis and flower production in 'TS97' plants.",
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Photosynthetic light requirements and effects of low irradiance and daylength on phalaenopsis amabilis. / Guo, Woei-Jiun; Lin, Yu Zu; Lee, Nean.

In: Journal of the American Society for Horticultural Science, Vol. 137, No. 6, 11.2012, p. 465-472.

Research output: Contribution to journalArticle

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