What factors control the direction a pitcher will face, if any?

[Sashoke]

Ive noticed on some of my plants the pitchers are all facing the same exact direction, regardless of the position of the leaf theyre attached to. Some have tendrils that make journies across their pots just to make sure they inflate right next to several other pitchers (see my N. burkei a few months ago, was only inflating pitchers in one corner of the pot.) One seems to only inflate pitchers facing away from the sun.

So out of curiosity, what factors (if any) control the direction a pitcher will inflate/face in. Is it just entirely random?

 

[KATastrophe]

I would like to think its random... But you never kno I'm just guessing. I heard some plants grow very in groups so maybe they are growing next too other pitchers for these reason() but i couldn't be sure. Its like seeing which way a leaf will open..I've tried to get them to open on a particular side but in the end they really open and fall where ever they want to i guess lol!

 

[Stranger]

Actually a good question, I was wondering this myself.

I can only speak for my own plants, but I've noticed a solid tendency for my plants to have their pitchers facing more towards the sun and away from their pots and the back of the greenhouse (against a brick wall). I suppose there's something about efficiency in there, it'd be harder to attract and catch insects if the mouth is facing a solid object.

That said, my glabrata pitchers seem to dislike the sun, the ones between the pot and the wall are both larger and last longer. Go figure?

 

[J.Gennaro]

I would suspect that the plant hormone auxin plays some role in the direction a pitcher will face, this process is called phototropism. In my friend's Nepenthes greenhouse I have noticed most pitchers face towards the glass where the sunlight enters, with the back of the pitcher directed to the side of the greenhouse that doesn't let light in. If my suspicion is correct; this would mean that auxin collects on the shady side of the tendril, causing those cells to elongate and leading to a pitcher that forms facing the source of light.