Application of PI control of PPFD during LED-low light irradiation storage for quality preservation of green plants.
Fujiwara K., Sawada T., Kimura Y., Kurata K.
5th International Postharvest Symposium . Volume of Abstract . Verona, Italy 6-11 June 2004, p.68
2004
บทคัดย่อ
Application of PI control of PPFD during LED-low light irradiation storage for quality preservation of green plants.
A low light irradiation (LLI) storage system that provides stored green plants (transplant, postharvest green vegetables or herbs) with photosynthetic photon flux density (PPFD) at which CO2 exchange rate of the plants becomes zero can be considered to suppress the dry weight change of the plants during storage and to contribute to long-term quality preservation of the plants.We have built a light emitting diode (LED)-LLI storage system that automatically controls PPFD using a proportional-integral (PI) controller so that CO2 exchange rate of stored plants becomes zero.The supplied voltage to red LEDs was cintrolled based on the difference between the CO2 concentration of inflow (C in: 400 mmol mol-1) and outflow (C out) air of the storage case.Grafted tomato plug seedlings were stored at 10 °C for 35 d under two different LLI conditions: red light PPFD-PI control with either blue light 0 mmol m-2 s-1 PPFD (B0) or blue light 0.2 mmol m-2 s-1 PPFD (B0.2).Count in both B0 and B0.2 was satisfactorily maintained at around 400 mmol mol-1 during storage except for the first 12 h.Total PPFD was almost stabilized in the latter 25 d and the mean values were roughly 2.3 and 3.6 mmol m-2 s-1 in B0 and B0.2, respectively.Dry weight of the seedlings on day 35 was not significantly different from that before storage in B0 and B0.2.These results indicate that the PI control of PPFD during LED-LLI storage contributed to suppress the dry weight change and that the addition of a low percentage blue light reduced the PPFD required to suppress the dry weight change.