Articles
Effects of diurnal and day-to-day fluctuations in photosynthetic photon flux density on leaf photosynthesis and plant growth of cucumber seedlings
Article number
1423_5
Pages
33 – 40
Language
English
Abstract
Photosynthetic photon flux density (PPFD) of sunlight fluctuates in greenhouses at various time scales during the daytime and day to day.
Compared with the well-known plant responses to stably high and low PPFD levels or so-called light acclimation, how plants respond to fluctuating PPFD levels requires deeper understanding.
We have conducted a series of laboratory experiments to investigate the effects of light, of which PPFD fluctuates during the daytime and day to day, on leaf photosynthesis and plant growth of cucumber seedlings.
First, the impact of diurnal PPFD fluctuation on instantaneous leaf photosynthetic rate was examined.
We reproduced changes in PPFD and the spectrum of sunlight under laboratory conditions using the light-emitting diode (LED) artificial sunlight source system.
The effect of photosynthetic induction, the delayed response of photosynthesis to a PPFD increase, was estimated to be smaller than that reported by previous simulation studies under the conditions of this experiment.
Next, the effects of the diurnal PPFD fluctuation of emulated sunlight on plant growth were investigated.
Plants initially exhibited a higher leaf area ratio (LAR) under fluctuating PPFD light than under constant PPFD light.
However, such a difference became ignorable after prolonged light treatment, possibly due to partial mutual shading.
Regarding the effects of day-to-day PPFD fluctuations, we hypothesized that recent PPFD levels experienced by leaves had a more significant influence on current PPFD-responsive leaf traits than past PPFD levels.
To verify this, we grew seedlings under various patterns of day-to-day PPFD levels for a week and evaluated leaf traits on the final day.
We found that some leaf traits, including leaf mass per area (LMA), could be quantitatively estimated by a weighted average of PPFD, with greater weights assigned to recent PPFD levels.
Compared with the well-known plant responses to stably high and low PPFD levels or so-called light acclimation, how plants respond to fluctuating PPFD levels requires deeper understanding.
We have conducted a series of laboratory experiments to investigate the effects of light, of which PPFD fluctuates during the daytime and day to day, on leaf photosynthesis and plant growth of cucumber seedlings.
First, the impact of diurnal PPFD fluctuation on instantaneous leaf photosynthetic rate was examined.
We reproduced changes in PPFD and the spectrum of sunlight under laboratory conditions using the light-emitting diode (LED) artificial sunlight source system.
The effect of photosynthetic induction, the delayed response of photosynthesis to a PPFD increase, was estimated to be smaller than that reported by previous simulation studies under the conditions of this experiment.
Next, the effects of the diurnal PPFD fluctuation of emulated sunlight on plant growth were investigated.
Plants initially exhibited a higher leaf area ratio (LAR) under fluctuating PPFD light than under constant PPFD light.
However, such a difference became ignorable after prolonged light treatment, possibly due to partial mutual shading.
Regarding the effects of day-to-day PPFD fluctuations, we hypothesized that recent PPFD levels experienced by leaves had a more significant influence on current PPFD-responsive leaf traits than past PPFD levels.
To verify this, we grew seedlings under various patterns of day-to-day PPFD levels for a week and evaluated leaf traits on the final day.
We found that some leaf traits, including leaf mass per area (LMA), could be quantitatively estimated by a weighted average of PPFD, with greater weights assigned to recent PPFD levels.
Authors
R. Matsuda, L. Yu, S. Kubo, J.Y. Lee, K. Fujiwara
Keywords
leaf mass per area (LMA), light acclimation, light-emitting diode (LED), light environmental control, photosynthetic capacity, photosynthetic induction, PPFD
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