Wild_forager
May be just like everything else it needs some loving touch! Just extrapolating, no experience with many fig cuttings yet.

Roots are opportunistic, so they do not grow in any particular direction. Root growth flourishes where the supply of oxygen, water, nutrients, and warmth are most advantageous.

Roots grow or elongate as a function of cell division in the apical meristem located near the tip of the root. Division of cells in this area produce more meristematic cells, root cap cells (these are a kind of covering and are sacrificed as roots grow to protect the meristematic area), and undifferentiated root cells (same features as stem cells in humans - thus "meri-stem-atic"). The undifferentiated cells will become the main root tissues after first undergoing a process of elongation, which actually pushes the root tip forward in the soil. Eventually, these undifferentiated cells differentiate into various specialized root tissues. Touch does not play a part in the process.

Al

Tapla, From observation, coming into contact with an object seems to stimulate root growth.
I first noticed this with Asarum, hardy ginger. A plant placed against a rock spread quickly along the rock in both directions, while one planted alone took a very long time to establish. Since then I've noticed other plants behaving the same way. Now I usually plant a rock or a board with stoloniferous and rhizomatous plants.
I've also noticed a pronounced growth spurt when potted plants' roots hit the pot bottom.
I don't have any idea why it's happening, but I've seen it often enough to know that it is.

Interesting observation on root growth! We must always be open to learning new, and sometimes oddly unexpected things while observing how our plants grow. I believe God has programmed wondrous abilities into plants that we are only just now really starting to discover. Their complexity is likely NOT fully explainable through the theory of evolution. One obvious example which comes to mind is the hundreds of fig varieties each dependent on a specific fig wasp for pollination! How amazing and wonderful is that???

Fignut - very often in horticulture, and especially often in what is related in/on these forums (not referring to you), the things we believe are causal of what we are observing are not the cause at all. Things are not always as they "seem". For example - you see the roots being stimulated by 'touch' when they reach the bottom of the pot, and that 'touch', causing a growth spurt. I may observe the very same plant and say, "Hmmm, the roots are beginning to fully colonize the entire container, so the plant is now using the water from the soggy layer of soil at the bottom of the container, which allows air back into the soil much sooner, creating ideal cultural conditions for root growth and maximizing root metabolism, which naturally causes the plant to grow with enhanced vitality - your growth spurt."

Al

Unless the plant material is floating in air, it is touching something... soil, rock, mulch, a clay head, etc.

~james

Tapla, Absolutely. This is an observation - it happens - but I haven't the foggiest idea why. Maybe, the two examples cited are entirely different processes - I don't know.
James, I don't see it as "touch" as much as "stop". The Ginger roots growing along the rock "ran" along the rock. They did not spread away from the rock until the clump was much older.

Tapla - don't some roots display geotropism, which IS growing in a given direction, mainly down?

Well - there is general consensus that there is geotropism and gravisensing going on in root structures, but the exact mechanism remains elusive and there is lots of discussion about just how it occurs. It's known that the response varies widely by species. It's also known (and should be obvious) that unfavorable cultural conditions trump the response.

The force of gravity acts on everything. We can see an example in the case of adventitious aerial roots of tropical ficus that grow pretty much straight downward, sometimes for a hundred feet or more until they reach the soil. After that, the root begins to branch out horizontally. It's not so much the case where roots grow toward air and water sources, it's that they do not grow where air and water is lacking. It would make no biological sense for a root to waste energy growing where it becomes an energy sink instead of an organ that aids in water/nutrient uptake.

If you take a tomato (or fig) plant, the roots of which have colonized an entire container, and begin to water it by misting the soil so that only the top inch or two of the soil gets any moisture. All the root growth will be in that top 1-2 inches. Roots that had colonized the lower parts of the container that are now devoid of water would have to reverse direction and grow upward or succumb to a moisture deficit.

Al

bjs496, in fact my roots are growing in air initially. The ones that grow long enough to bend towards something more solid like the paper towel or the edge of the plastic seem to accelerate in their growth. Going by Talpas analysis it may be that some roots simply grow faster and thus eventually touch something. While I think it's possible that that's the case, my observation as to why any one specifcic root suddenly gets a burst and the rest don't seems to indicate that it has something to do with the touch itself.

It might just be that the solid surfaces are holding more water than air and thus the root that is exposed to more water is deemeed worthy of more energy expenditure. What do you guys think of that theory?

When you're dealing with leafless cuttings, the energy for root growth comes from cambial tissues where the cutting's energy is stored. The plant metabolizes stored photosynthate (sugar, starch, oils sometimes) and utilizes it to produce rootage. The roots that emerge where the plant is most able to translocate metabolites grow fastest.

Al

wild_forager, At this point, it's a good a guess as any. No way of knowing what the mechanism is.

I give up. ;o)

Al

Tapla, I wasn't trying to disparage your answer. It wasn't posted when I started answering wild_forager's post.
But I'm certain something else is going on. This spring put in a single bareroot plant of ginger and/or lily of the valley, and next to it plant one with the roots up against a rock. I'll be glad to provide the plants - got some nice pink lily of the valley, LOL.

Don't worry Talpa, your words have not gone unheeded. But I also don't want to think that we know everything there is to know. I plan on running some tests to see what I can come up with, even if it is that the roots I select are able to translocate metabloites the best. If we stop trying to learn something new for ourselves just because it's already in a text book we might miss out.

I am no expert, but this is my 2 cents...

Roots grow randomly and flourish under their favorable
conditions, aka, the right moisture and (soft) soil texture.
If they hit dry air/soil, they dessicate; too much water,
they rot; if they hit a hard object, they turn.

Think of the air-pots mentioned by James... On the other
side, I have seen pictures of mature fig trees wrapped in
plastic in a warm winter basement with roots coming from
all the kazoo (top to bottom). I also observed, that some
of my new (domed) fig rootings, sometimes produce surface
roots that once they hit the container, they go up in the
moist air!

New houses are notorious as hard to landscape because the
soil was compacted by heavy machinery during construction.
Rocks may help to shade and maintain desired moisture.

Figs (like maples) are mostly shallow rooted, though I
recall somebody mentioning that his/her figs had deeper
roots.

Some other plants produce tap-roots that do down to China
(I guess for water).

George (NJ).

Some other root abnormalities:

Strangler Fig:
Some bird eats the fruit, and poops on top a mature tree
canopy, some seeds manage to sprout up there and survive,
send roots down to earth circling the host tree, eventually
the host tree gets strangled by the roots and dies leaving
a happy 'strangler fig' flourishing.

Rock Splitting Fig:
Similarly, some bird does its thing on the rock. Seed
germinate and manage to find the smallest crevice in the
rock. The root flourishes and gets very fat, spliting
the rock.

Moisture:
Not all roots rot in water, think of mangrove trees that
first shoots roots down (to spread - some figs do that too,
cannot remember which for now) and also shoot roots
for oxygen. And how about the tree roots that clog our
sewers?

Heads up for ficus:
http://www.figweb.org/Ficus/index.htm