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rhines81 · February 17, 2018

In warm climates, seed can easily be direct sown. Cotyledons are the initial leaves to get the plant started with the photosynthesis process - basically they stop functioning as such once the 1st true leaves start developing. The timeline for this transition is a few days, maybe 4-5 days under good conditions. Because of this they are not as prone to the change from artificial to 'real' sunlight. They basically start dying off quickly. They will remain green and grow with the plant, but their function to the plant is complete once the 1st set of true leaves come out ... they become suckers.
On onset of 3rd set of leaves, I always pinch them, because there is no purpose for them to exist as 'suckers' any longer. I could probably do this earlier, but I never have. The true leaves are more sensitive to changes because they are 'new' growth and serve a long-term purpose to the plant.
Yup, I have definitely had the true leaves turn almost solid white due to the transition, but new growth happening at that time quickly is adapted and the plant thrives.

February 17, 2018	#2
rhines81 Tomatovillian™ Join Date: Mar 2015 Location: Zone 5A, Poconos Posts: 959	In warm climates, seed can easily be direct sown. Cotyledons are the initial leaves to get the plant started with the photosynthesis process - basically they stop functioning as such once the 1st true leaves start developing. The timeline for this transition is a few days, maybe 4-5 days under good conditions. Because of this they are not as prone to the change from artificial to 'real' sunlight. They basically start dying off quickly. They will remain green and grow with the plant, but their function to the plant is complete once the 1st set of true leaves come out ... they become suckers. On onset of 3rd set of leaves, I always pinch them, because there is no purpose for them to exist as 'suckers' any longer. I could probably do this earlier, but I never have. The true leaves are more sensitive to changes because they are 'new' growth and serve a long-term purpose to the plant. Yup, I have definitely had the true leaves turn almost solid white due to the transition, but new growth happening at that time quickly is adapted and the plant thrives. Last edited by rhines81; February 17, 2018 at 11:02 PM.