5. Conclusion
Our results clearly demonstrate that, compared to other light
treatments, from 300 to 450 mol m−2 s−1, the biomass and heath
index of young plants were better. Meanwhile, the mesophyll tissue,
palisade cells and spongy cells in the leaves were thicker, and
the stomatal frequency and stomatal area per unit leaf area were
higher. More important, 300 mol m−2 s−1 induced the highest
energy efficiency and activity of Pn. In our research, we found that
there was no substantial gain from a PPFD above 300 mol m−2 s−1.
Based on the purpose of high efficiency and energy saving, compared
to other light treatments, 300 mol m−2 s−1 was fit for the
culture of young tomato plants.