The underside of the leaf can absorb light, but most of the chlorophyll containing cells are concentrated near the upper surface. So energy absorption will be much less efficient. Also the surface tissue on the underside is different in composition than that on the upper surface, and tends to be more reflective.
Chromophore Reviewed by Chromophore on . Will 150w HPS outperform 372w of T5HO? Well, I'm going to Find out! Only really applies to me and my particular grow, but a worthy effort anyway. A couple day's ago I put two under the T5's, and two under the HPS. I think the HPS at 150w is about 18,000 Lumen?...and the T5's are pushing 35,000 Lumen. I will throw a couple pics up when the "wakeup" tonight, should be interesting anyway. Predictions? Rating: 5