Myth or fact: red seedlings are stressed

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Jaybizzle
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Myth or fact: red seedlings are stressed

Post by Jaybizzle »

Conventional wisdom says keep small seedlings away from direct sunlight or they turn red, which indicates that they are stressed.

Well in habitat they get direct sunlight and they do fine, correct?

So I try to move my seedlings to get some direct sun a couple of weeks after germinating, and yes they turn reddish.

So is it really/truly bad to expose the seedlings to direct sun and have them turn reddish, or is this a myth? Is reddish coloration really indicating stress?
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Aeonium2003
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Re: Myth or fact: red seedlings are stressed

Post by Aeonium2003 »

That is usually why they grow slower in the habitat. Lack of water, intense sunlight. Which causes them to become stunted. Just my theory. 8-[
Sonoran Jackalope
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Re: Myth or fact: red seedlings are stressed

Post by Sonoran Jackalope »

I have spent hundreds if not thousands of hours hiking in the Sonoran Desert, Chihuahuan Desert, Great Basin Desert, Mojave Desert, the Atacama(wasn’t looking for cacti there but didn’t notice seedlings in direct sun), etc.... and in my experience, I have never seen a cacti seedling in complete direct sun exposure. I have seen them get partial sun or where they get some sun exposure in the morning or afternoon. Usually, cacti seedlings, young cacti, small cacti etc are “shielded” by a nursery plant or mother plant, or shielded by a rock or rocks, grass, a bush,etc. Many times the cacti outgrow the nursery plant or rock and become exposed to direct sunlight.

Seems like reddish coloration indicates stress as I have seen “adult” or bigger plants reddish or purplish in native habitats.

Just my experience in the habitat.

At home, some of my seedlings turn reddish, or orangish and seem stressed. I try to move them to where the light isn’t as bright or perhaps provide a little more water. Seems to help
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greenknight
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Re: Myth or fact: red seedlings are stressed

Post by greenknight »

Indeed, cactus seedlings in habitat survive only where they have some shelter - they need protection from drying out and from strong light.

Pink is fine for most seedlings (maybe not for Ariocarpus), slight light stress leads to good, stout growth in most species.

Darker red indicates greater stress, and too much stress will slow growth. At the extreme they'll turn purple, at which point growth has pretty much stopped - they can recover from this, but they'll be greatly set back.
Spence :mrgreen:
keith
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Re: Myth or fact: red seedlings are stressed

Post by keith »

Mesa gardens told me if they turn red and stop growing its too much light, if they keep growing its OK '

For what its worth . They do have allot of experience growing seeds.
LateBloomer
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Re: Myth or fact: red seedlings are stressed

Post by LateBloomer »

I grow all my seedlings in "full sun" from month 2-3. They grow slowly at first due to excess light stress but I don't put them in full summer sun at once... was in full sun from spring. The growth IMO will even out after the summer from the stored energy from the excess light and my seedlings will be the same size as babied however will already be accustomed to full sun. I have lost a few seedlings due to overstressing some however I'm not looking to keep weak seedlings since these will be my mother plants for strong seeds.

Red seedlings are fine... purple or brown is too much which happened to most of mine but thats fine. Only the strongest survive.

My full sun is not all day full sun but until noon

Full sun will "stunt" growth however the growth when it returns will be thick spines and compact not weak growth.

Some seedlings of astrophytum asterias didn't change one bit in full sun while others have yet to grow at 7 months after 5 months in full sun. Ariocarpus ALL became purple but do grow slowly and never stopped growing and lophophora were mixed with most still red from the sun some are normal and others are completely black and grew next to zero.
Jaybizzle
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Re: Myth or fact: red seedlings are stressed

Post by Jaybizzle »

Thanks—seems like a split opinion. I guess for spiny species, probably matters less once they grow spines, which will shade their bodies.
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MikeInOz
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Re: Myth or fact: red seedlings are stressed

Post by MikeInOz »

Red pigment protects the plant from excess UV which can damage it and certainly reduce growth. I find it best when there is the very slightest hint of colour and no more. That seems to keep the seedling plant growing yet hard enough to protect it from possible infections, cold temperatures and strong light. Too much red is no good for the plants continued development. Simply keeping the seedling on a warm bed can green it up without a change of light intensity if the red is due to cold temperatures.

Nature's Swiss Army Knife: The Diverse Protective Roles of Anthocyanins in Leaves
Kevin S. Gould*............

''Anthocyanins, the pigments responsible for spectacular displays of vermilion in the leaves of deciduous trees, have long been considered an extravagant waste of a plant's resources. Contemporary research, in contrast, has begun to show that the pigments can significantly influence the way a leaf responds to environmental stress. Anthocyanins have been implicated in tolerance to stressors as diverse as drought, UV-B, and heavy metals, as well as resistance to herbivores and pathogens. By absorbing high-energy quanta, anthocyanic cell vacuoles both protect chloroplasts from the photoinhibitory and photooxidative effects of strong light, and prevent the catabolism of photolabile defence compounds. Anthocyanins also mitigate photooxidative injury in leaves by efficiently scavenging free radicals and reactive oxygen species. Far from being a useless by-product of the flavonoid pathway, these red pigments may in some instances be critical for plant survival.''
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greenknight
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Re: Myth or fact: red seedlings are stressed

Post by greenknight »

Jaybizzle wrote: Sun Feb 27, 2022 5:22 pm Thanks—seems like a split opinion. I guess for spiny species, probably matters less once they grow spines, which will shade their bodies.
The stem that's produced before any spines develop will color very readily, since it has no other way to protect itself except pigment. The part that has spine cover should be green.
Spence :mrgreen:
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