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| Category | Rate of light transmittance (%) | Treatment | Illumination intensity (μmol m–2 s–1) |
|---|---|---|---|
| NL | 100 | Normal illumination | 1000 |
| TL1 | 75 | A layer of white gauze | 750 |
| TL2 | 50 | A layer of black shading with 50% transmittance | 500 |
| TL3 | 25 | A layer of black shading with 25% transmittance | 250 |
