Photosynthetic Efficiency and Supplemental Greenhouse Lighting

Advanced Techniques
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#1

This is a nice lecture on photosynthetic efficiency, light levels, and DLI.

Dr Marc van Iersel discusses increasing effectiveness and decreasing costs when using supplemental lighting in greenhouses.

Quantum efficiency of PSII decreases as light intensity increases.
Plants grown under longer photoperiod with lowered light intensity have higher light interception over the life of the plant and higher relative quantum efficiency.
Higher light intensity but shorter photoperiod results in lower quantum efficiency.
Longer photoperiod but with reduced light intensity possibly shows an increase in biomass.

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#2

Very interesting.

My first thought is that this would be easy to apply to veg cycle. Just lower the power a bit and run 20/4 instead of the normal 18/6.

Im not sure how this could be applied to flowering though. You need a certain amount of dark time, or the plant wont flower. Might be good for autos though?

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#3

Thanks very much for the info, is really useful in understanding a base on how the plants use the light so if i recall what he said , turning our lamps when the day start full is not efficient and we are wasting that energy, so will be awesome i think if had a single t 5 tube illuminating and awaking plant at the beginning of the day 30 mins to an hours then the other lights turn on and the plants can use the full light and the other one can just be turned off as soon as the main lights comes in , even in a commercial environment then run 20 percent of your fixtures for an hour then full , will decrease power consumption in a significant way

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#4

Funny, my first thought is “I want to measure this” :upside_down:

https://www.photosynq.org/buy-multispeq

$$$ finding excuses, yeah right. :smile:

I like his metric, DLI target set to 90% of the overall PSII efficiency curve. So, maybe determine the PPF required to achieve the DLI needed for both scenarios, veg and flower. Then, perhaps slowly ramp up the intensity coming out of veg to meet the target DLI when switching into flower? Or, maybe the other way around, determine the 90% for flower with reduced intensity in veg. idk. Of course, I’d think that the PSII efficiency could be optimized to some extent with the environment, e.g. CO2 to ensure easy access to carbon for fixation.

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There was also some interesting research on the effect to the PSII efficiencies when we enter into photoinhibition or damage the leaf from overly high intensities, and how/if the leaf can recover. All of which can be measured, apparently.

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#5

Yes, so many cool ideas and possibilities when we can better understand some of the underlying processes / effects.

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#6

light bars donated by fluence
:sob::sob::sob:

Have heard it posited that at low light levels the efficiency of blue is greater than red. Wonder how that would change these results

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#7

@Worcestershire_Farms Well i think will be better quality as sugested before and i have done some research and even people in the old days use to use 10000k bulbs in the last 3 weeks to increase terps and they swear 30% increase in yield

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