Hydroponic lettuce with a dark period grows stronger without overgrowth.

I have been conducting a personal experiment to see how the growth of lettuce changes with different light exposure times.
After sowing, germinating, and growing seedlings in plastic containers, I had to end the experiment when the lettuce grew too large to fit in the containers, but in the end, I felt that the lettuce I gave a dark period grew healthier.
Here is a video.

This experiment is a sequel to the article “Hydroponic lettuce seedling growth rate and germination rate changes with light exposure time”.
The lettuce that was exposed to a lot of light grew a lot, but many of them were overgrown, and as a result, the 16-hour lettuce with an 8-hour dark period seemed to grow healthier.
The following are the observations.

Thinning out the seedlings that were exposed to 16 hours of light and those that were exposed to 24 hours of light.

Fifty seedlings of 16 hours and 24 hours each, which were germinated with germination treatment and grown in the container with nutrient solution, are now growing step by step.


As the lettuce leaves seemed to be overlapping each other, I took out the seedlings that were not growing well from each container and replanted them in another container.


I selected about 20 seedlings of lettuce that had been growing well for 16 hours and 24 hours each, and replanted them at intervals.

Of the 20 seedlings grown in the 16-hour irradiation, half of the 10 seedlings will be grown again in the 16-hour irradiation.
The remaining 10 seedlings will be grown in the 24-hour container.
Also, for the 20 seedlings grown in the 24-hour irradiation, half of the 10 seedlings will be grown in the 16-hour irradiation and the rest in the 24-hour irradiation.

The lettuce with a dark period grew better without overgrowth.

The lettuce seedlings that were grown in the 24-hour period grew larger leaves in both the 16-hour and 24-hour containers.
As for the roots, the lettuce that was exposed to light for longer seemed to have more roots.
I thinned out the lettuce and observed the growth for a few days, but the leaves grew so much that they overlapped even after thinning out, so I ended the experiment.
In terms of the size of the lettuce alone, the lettuce that had been exposed to the light for 24 hours grew larger, but the stems also seemed to have grown longer at the same time.
In other words, they became overgrown.
On the other hand, the lettuce that was repeatedly exposed to light for 16 hours after germination, followed by 8 hours of rest in the dark, looked inferior to the 24-hour lettuce in terms of growth, but the leaves were coming out from the root and seemed to be growing healthily.
If I’m going to let my lettuce grow long without resting for 24 hours, I want to let it rest for 8 hours to make it healthy.
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