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Conversion - Instantaneous PPF to Integrated PPF

 

Most light meters measure the instantaneous photosynthetic photon flux in μmol m-2 s-1 and yet plant growth is determined by the integrated daily photosynthetic photon flux in mol m-2 d-1.

Here is how to convert from μmol m-2 s-1 to mol m-2 d-1 when using electric lights.

There are 3600 seconds in an hour. If the electric light output is constant, the instantaneous PPF can be added up (integrated) over an hour.

Therefore 1 μmol m-2 s-1 = 3600 μmol m-2 h-1.

This must be divided by a million(106) to convert from micromoles to moles:      3600 μmol m-2 h-1 = 0.0036 mol m-2 h-1

If the electric lights are on continuously (24 hours) the hourly PPF must be multiplied by 24 to get the daily PPF:      0.0036 mol m-2 h-1 = 0.0864 mol m-2 d-1

There are 86,400 seconds in a day (3600 x 24 hours) so the daily PPF can be calculated directly from the instantaneous PPF from the following equation: μmol m-2 s-1 multiplied by 86,400 and divided by 106 = mol m-2 d-1

So:   1 μmol m-2 s-1 = 0.0864 mol m-2 d-1 with continuous light

These conversions are accurate only under electric lights. The integrated daily PPF from sunlight changes during the day so a single measurement cannot be used to estimate daily PPF.

Daily PPF Reference Table

24-Hour Photoperiod

16-Hour Photoperiod

12-Hour Photoperiod

Instantaneous PPF (μmol m-2 s-1)

Daily PPF (mol m-2 d-1)

Instantaneous PPF (μmol m-2 s-1)

Daily PPF (mol m-2 d-1)

Instantaneous PPF (μmol m-2 s-1)

Daily PPF (mol m-2 d-1)

10 0.864 10 0.576 10 0.432
100 8.64 100 5.76 100 4.32
200 17.28 200 11.52 200 8.64
300 25.92 300 17.28 300 12.96
∗ 600 ∗ 51.84 600 34.58 600 25.92
1000 86.40 ∗ 1000 ∗ 57.60 1000 43.20
2,000 172.80 2,000 115.20 ∗ 1,300 ∗ 56.23
        2,000 86.40
∗There are 50 to 60 moles per m2 per day on sunny summer days in outside areas without any shade.