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Quixote

Discovery: San Pedro avoids light

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I just discovered that my big Pachanoi (about 1.80 metres tall) actively bends AWAY from the light.

It's growing in a pot by the window, and for many months I have been trying to straighten it up, since it's leaning in one direction. So I turned it so that it was leaning away from the window, into the apartment. My idea was that it would stretch towards the sun. But it never straightened up. Just kept growing more and more off-center.

Then finally I tried turning it around again, so that it was leaning towards the window. In just one single day, it straightened up, and even started to lean the opposite way! I was really surprised about this, as it goes against everything I thought I knew about plants.

Have any of you noticed the same?

Edited by Quixote
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Maybe you're just 'funking it out' too much.

-see what I did there...

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the photosynthetic surface on them does not face up, many lean obliquely.

They get most of their light at an angle, unlike leafy plants that face up.

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gunter drops some science on ya

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my curly nob-like thelegonous is bending toward the light but has the shade of many others towering above it ...

I have noticed a large(for houseplant standards) flowering pachanoi do the opposite tho , rather frustratingly ...

thanks for the post and the science guys!

perhaps a uniform rotating of 90 degrees precisely at the same time every day would bring some equilibrium over time ?

would be nice to have some sort of automated rotating pot tables

so long as the plants were[/nt too top heavy/]strapped down and wouldnt bash eachother :P

Edited by ☽Ţ ҉ĥϋηϠ₡яღ☯ॐ€ðяئॐ♡Pϟiℓℴϟℴ

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I haven't noticed a particular bend away or toward the sun with my plants.

But I mark any of mine that are in pots so I know which way is north and make sure they always face the same way if I move them. I just figure it would "confuse" the plant to be getting rotated and may make it grow slower. I also do it mainly because I thought flowering would be interrupted by rotating since I thought light duration was pretty important for flowering...

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My plants all seem to bend towards the light.

Are you sure its not just gravity causing this?

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In my case they seldom reach towards it when well lit, but in dim conditions may do so.

Nor do they tend to lean away, however I have consistently noted an oblique angle for most specimens with the exception of robust specimens or very young plants still establishing their initial central trunk or stem.

With lower light levels many specimens exhibit phototropism.

Edited by Gunter
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Edit coming...

Edited by M S Smith

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(Please note that I am in the northern hemisphere.)

Mine lean away from the sun in one location and towards the sun in another, which I suspect is simply to angle the surface for the best use of light. Obviously this isn't going to happen with plants that get a full day of sun...I mean their not heliotropic. It seems to be related to shade zones near the plants. Both locations of my plant stands are to the north of shade barriers, one the house and the other trees. The plants north of the house lean towards the south, which is to mean towards the sun, but that is so they can get a good angle on the northern sky and suck up as much of it's light as possible. The other stand is north of a large stand of trees and gets only a little overhead direct light in the middle of the day, but are mostly shaded. These lean north, away from the trees, for maximum exposure to southern light filtering through the trees.

So they can lean any direction, it all depends on the lighting conditions.

Man, I know I can say this all better, but I hope you get the point.

~Michael~

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Mine lean towards the light and they do a complete bend within 24 hours - I was amazed at how quickly they bend though a full 60 degrees! These plants are 1ft tall and 2 inches wide at the widest point. I tried doing half turns for a month to see if I could get a twist happening, but it didn't work, they just happily bend away.

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my plants grow straight up, unless they were planted at an angle

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I say let it lean whichever way it wants to. Who are we to tell it what to do?

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I disagree.. Something should be done about this..

To quote Mark Twain - "Everyone complains about the weather, but no one does anything about it.."

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I think in the long run your plant is aiming to what it believes is "up" or towards the light... I have several grafted ones in a window and inspite of the mylar reflector they bend obviously towards the window, especially the ones further away from the reflected light which also have the backside light obstructed by other plants...

The consensus seems to be they go for more light and shade in the location can make that vary... I have seen some small ones outside move a little when they are starting to pup... I also have a bending bridgesii which bends all the time like a snake but thats cause so far the growth has been fairly thin... but when it bends it appears to be due to weight and corrects itslef by going back up again

Edited by Spine Collector
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I have another hypothesis: it's a behaviour meant for mountainsides.

In my case, the cactus is in a pot by a window that goes from floor to ceiling. That means it's getting a lot of light from one direction, and nearly nothing from the other.

This seems similar to the conditions of a plant growing on a mountainside, with the sunlight coming from one direction and the mountain on the other. So, why would the cactus bend towards the mountain in this case?

To avoid falling over. Imagine that you are standing on a thin ledge with a vertical drop in front of you and a cliffside behind you. What do you instinctively do? Lean back towards the mountainside of course. If you stand straight or lean towards the sun in this case, winds sweeping along the mountain might topple you off.

Well, it's just an idea for now.

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Update: Nothing happens without direct strong sunlight. Todays is overcast, and the cactus keeps leaning towards the window.

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NOOOOO!!! it just shuns the light,..... because it's "The Patchanoi of Darkness!"

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OK .what about this as an explanation......the exposed side is photo synthesising , therefore growing faster , sun side is elongating more than shade side ?

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i've read somewhere that clouds do not block sun rays or most of them, and in fact just sort of disperse them causing it to be a bit brighter, particularly for plants, and may seem more subtle to the eyes, but isn't.

"Diffuse light increases plant energy production because the light bends around corners to reach the lower leaves, not just the upper canopy." and theres other articles explaining how one can still get sunburned on an overcast day
from: http://www.greenhousecatalog.com/greenhouse-light

also ran across this really cool article about plant photosynthesis
http://io9.com/new-evidence-that-plants-get-their-energy-using-quantum-1498695627

Edited by Optimystic

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OK .what about this as an explanation......the exposed side is photo synthesising , therefore growing faster , sun side is elongating more than shade side ?

Except that photosynthetic tissue is seldom growing but translocates nutes to the apical meristem which is the site of active growth, and examples of variation in growth patterns relative to light source exist, making the theory falsified.

Edited by Gunter
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I've had plants bend away from light when it's too strong and towards it when it's too weak. I think they literally just make a decision bend themselves. I have no clue how though. Lol.

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growing conditions, light conditions (gunter + smith said it)

in the house, by the window aint a normal position, its artificial... with very 'positional' light - I think gunter nailed it with the angle of light and all.

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also in regard to Gunters comment, most growth is at the tip, however many collection plants are still gaiing girth, be it slowly

WHAT IF...

the watering has just caused an air bubble, causing the soil to deplete in a spot, this giving way and the result is the cactus leaning
in the direction, while the cactus is still trying to go "up" it keeps going over the tipping point so to speak... like a see saw... I know i've had some cacti that were straight up in the fall and by the spring they were leaning before the first watering.. some stand back up but some remain as leaners... maybe just a chance lean .... this is only in the hypothetical stage... is it bending or is the whole thing leaning?

in time I betcha the tip would bend, pointing up, if it were grown in full saturation of sun on either side..

and btw WB Mutant!

Edited by Optimystic
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