How do Orchid roots actually work?

[King_of_orchid_growing:)]

Epiphytical and sometimes lithophytic orchid roots are not very different from the general anatomy of any other roots of other monocotyledons.

Essentially the roots can be broken down into 3 general sections:

1. The epidermis.

2. The cortex.

3. The vascular bundles.


It's how the roots function that sets epiphytical and certain lithophytic orchid roots apart from the roots of other kinds of plants.

In epiphytical and some lithophytic orchids, the epidermis is thickened and comprises of dead cells. This layer is often referred to as the velamen layer in epiphytical and some lithophytic orchids. The velamen is a spongy type of tissue that is both somewhat water retentive, and water absorbent. It has a very limited capacity to collect mist or dew from the air.

The cortex in epiphytical or certain lithophytic orchids is a thick layer of tissue that comprises of both cells that are capable of photosynthesis, as well as cells that are used for storing water, food, and other nutrients.

The center (the stringy portion of the root) is actually the root's vascular bundle. These vascular bundles are like pipes that carry water, food, and nutrients to the different parts of the plant. Look up phloem and xylem on your own time.

The root tip comprises of cells that are similar to those of the cortex (if not the exact same type of cells as the cortex). If you feel the root tips, sometimes you will feel how slick and slimy it feels. That slimy feeling comes from the mucilage that surrounds the root tips and comprises of dead root tip cells. The root tips are the ones that collect the majority of the water and nutrients.

Roots can also breathe, but I don't understand how this works.

Keep in mind, I've only given you a basic understanding of how epiphytical and some lithophytic orchid roots work. There are certain details that go way beyond me and the hobbyist's needs.

[King_of_orchid_growing:)]

As a kind of fun fact...

Epiphytical and certain lithophytic orchid roots will absorb water faster in the form of droplets or mist, versus a stream of water such as that coming out of a faucet or hose.

You can try it out and see for yourself. The time differential is not always terribly large, but it can be noticeable at times.

[King_of_orchid_growing:)]

Orchid leaves can also absorb water, btw.

[Ray]

My two cents, based upon the conversation, so far:

Roots exist both for the gathering of water and nutrition, and for mechanical support of the plant.

Misting can be a fine way to water, assuming you are applying a sufficient volume over time. many epiphytes in nature get less water and nutrition than do the same plants in cultivation, and they look like it!

Misting, as a way of raising humidity, should be done by spraying it into the air, not wetting the leaves, which is what most folks do. Fine droplets in the air can have millions of square meters of surface area per liter, while a wetted leaf might only be a few square centimeters. Which is going to evaporate faster and raise the humidity, and which is going to potentially lead to rots?

The trouble with hand-misting for humidity is that it is very transient, and none of us is likely to do it sufficiently (in an open environment).

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[King_of_orchid_growing:)]

Originally Posted by Ray

My two cents, based upon the conversation, so far:

Roots exist both for the gathering of water and nutrition, and for mechanical support of the plant.

Misting can be a fine way to water, assuming you are applying a sufficient volume over time. many epiphytes in nature get less water and nutrition than do the same plants in cultivation, and they look like it!

Misting, as a way of raising humidity, should be done by spraying it into the air, not wetting the leaves, which is what most folks do. Fine droplets in the air can have millions of square meters of surface area per liter, while a wetted leaf might only be a few square centimeters. Which is going to evaporate faster and raise the humidity, and which is going to potentially lead to rots?

The trouble with hand-misting for humidity is that it is very transient, and none of us is likely to do it sufficiently (in an open environment).

Yup.

Evaporative coolers or humidifiers do a better job at providing adequate amounts of humidity to the orchids.

	Mistking Looking for a misting system? Look no further. Automated misting systems from MistKing are used by multitude of plant enthusiasts and are perfect for Orchids. Systems feature run dry pumps, ZipDrip valve, adjustable black nozzles, per second control! Automatically mist one growing shelf or a greenhouse full of Orchids. See MistKing testimonials

[King_of_orchid_growing:)]

I forgot to mention.

The velamen also prevents excessive water loss from the roots due to the roots being exposed to the air.

[cythaenopsis]

This is really fascinating.

When you pull on a dead root, often the fleshy part pulls away and you're left with a very strong thin string left behind... and it sounds like this is the vascular bundle. I guess on a healthy root, the vascular bundle would be thicker, allowing more water movement within it?

Originally Posted by King_of_orchid_growing:)

Even Phals can be misted - if they're grown how they naturally orient themselves in the wild.

Usually Phals are potted and artificially propped up vertically to grow upright, which is not natural for Phals at all.

[...]

Other orchids are desert growers. Misting is not necessary and can promote rotting.

I had no idea... only photos I'd seen of phals in the wild had them growing upright from tree crevices. How do they normally grow in the wild? Do phals do better growing in a basket, whereby their crowns can angle downward?

[King_of_orchid_growing:)]

Originally Posted by cythaenopsis

When you pull on a dead root, often the fleshy part pulls away...

That fleshy part that pulls away is the velamen.

Originally Posted by cythaenopsis

...and you're left with a very strong thin string left behind... and it sounds like this is the vascular bundle.

Yes, it is. The vascular bundle is also referred to as the vascular cylinder.

Originally Posted by cythaenopsis

I guess on a healthy root, the vascular bundle would be thicker, allowing more water movement within it?

I don't believe that in a healthy living root that the vascular bundle would be thicker, idk.

From what I understand, the stringy part encompasses the xylem, phloem, and pith, which pretty much makes up the vascular bundle/vascular cylinder.

Originally Posted by cythaenopsis

I had no idea... only photos I'd seen of phals in the wild had them growing upright from tree crevices. How do they normally grow in the wild?

From what I understand, this is how:

Sarawak Lens: Phalaenopsis Habitat

Originally Posted by cythaenopsis

Do phals do better growing in a basket, whereby their crowns can angle downward?

Well...you got the Phals hang downwards thing right. That's how they grow in the wild.

See - you didn't really need me to answer your previous question.

[cythaenopsis]

Thank you for your response, Philip. I'm enlightened!

And that link is terrific. Wow, especially on that last phal where it's hanging off the tree by its roots. How cool is that?

[Fernando]

But the question is still there: how do they actually work? Let me explain: where does the active/passive transport of nutrients an water happen? If the velamen harvests water (including the dissolved nutrients), even for a short time until the entire liquids has been absorbed by the/into the vascular bundle, a overfeeding would be very likely to occur...
But if the velamen does not act a a sponge but acts as a barrier, than it would make sense to flush water regularly to clean substrate AND roots from excess of salts.
I have two Phal. lindenii, happily rooting. I've watched the roots now for a few months and a few cm length - the tip of the root goes up and down as if "looking" for the best place to dive... one root I gently pushed into one way that looked interesting to me - I did it three times but the root tip didn't want to follow me and still is going his way - still on the surface, still silvery shining velamen and photosinthetic tip. The roots of Phalaenopsis really grow quick - they tell it is a real living - and moving - being!

Fer