Low levels of solutes won't impair water movement across cell membranes to any great degree. The leaf will carry on photosynthesis as long as it has the necessary elements available, otherwise it will translocate stored energy to form roots and shoots. It's unlikely the leaf would grow because the plant will recognize first roots ans then shoots as he strongest energy sinks & focus transfer or energy there.

I've never paid particularly close attn to AVs, and I'm not exactly sure what you mean by plantlets, but my vision of what happens with leaf cuttings is they dedifferentiate leaf tissue that then redifferentiates into root tissue and a meristematic growing point (or perhaps more appropriately 'region') we usually refer to as a crown, from which multiple stems arise.

Al

OK, I got the basics of that.

Your idea of how they produce is very close to how I'd describe it, sans your accurate terminology, lol. The cutting forms roots primarily on the cut edge of the petiole, however it may form them above that point. Usually, immediately above the cut edge of the petiole, a growing region occurs. From this, whole new plants are started. They start as one small petiole/leaf and eventually add additional leaves and form a crown of a new plant, from which new leaves continue to arise. The fully formed, but tiny baby plants (or plantlets) are removed from the propagating leaf when of a certain size and are planted. Until they have 6-8 leaves they are considered plantlets; once they have more they are considered a starter plant.

Back to cuttings and how they work. Let's say the petiole is cut and ready to be propagated. The cut edge is placed either in water or soil (both work with AVs, though most people prefer one over the other). Initially, the leaf is uptaking water for it's sustenance.

At this time, can it uptake nutrients, too?

If there are nutrients in the water, or any other solutes, it will take them up. The plant has no way to selectively eliminate or 'choose' particular dissolved solids from the water it uses.

Al

Makes sense and I realize that wasn't the right question. What I should have asked is,

Does it want or need nutrients at this time or will they hamper root development in any way?

Can someone refer me to a text related to the difference between roots that are formed in soil and ones formed in water? I may not be using the best search terms as I keep searching on the Internet and can't find anything that explains it; or maybe it's not located on the Internet and I need a book.

Hartmann & Kester's Plant Propagation, Principles and Practices, goes into considerable technical detail and great depth on all forms of propagation and the physiology involved. There is probably more information on vegetative propagation (cuttings) than any other method.

ISBN #0-13-679235-9 (is the edition I have [7th] - there may be one newer)

Al

Thank you, Al. Will that also address the water vs soil root question? I keep hearing about it and want to know what really happens!

I'm not sure, but I doubt that rooting in water would be covered in that text because it (text) is targeted more toward the pro grower who wouldn't be considering rooting in water.

I don't know if this will be helpful or not. It's from something I wrote after confirming what I've observed via a little research:

Though roots form readily and often seemingly more quickly on many plants propagated in water, the roots produced are quite different from those produced in a soil-like or highly aerated medium (perlite - screened Turface - seed starting mix, e.g.). Physiologically, you will find these roots to be much more brittle than normal roots due to a much higher percentage of aerenchyma (a tissue with a greater percentage of inter-cellular air spaces than normal parenchyma). If you wish to eventually plant your rooted cuttings in soil, it is probably best not to root them in water because of the frequent difficulty in transplanting them to soil. The "water-formed" roots often break during transplant & those that don't break are very poor at water absorption from solid media and often die. The effect is equivalent to beginning the cutting process over again with a cutting in which available energy has been reduced by root necrosis and regeneration.

If you do a side by side comparison of cuttings rooted in water & cuttings rooted in soil, the cuttings in soil will always (for an extremely high percentage of plants) have a leg up in development on those moved from water to a soil medium for the reasons outlined above.

Al

That confirms that they are different.

I'm curious as to the actual process of how they end up different. Do they actually differentiate into two different types of roots or is a root a root but it adapts to the medium as it grows so the final product are roots that are different?

You're taxing my memory. ;o)

Aerenchyma tissue is filled with airy compartments. It usually forms in already rooted plants as a result of highly selective cell death and dissolution in the root cortex in response to anoxic conditions in roots. In fresh cuttings placed in water, it forms due to the same conditions w/o cell death & dissolution.

Note too, that under hypoxic conditions, Ethylene is necessary for aerenchyma to form. This parallels the fact that low oxygen concentrations, as found in water rooting, generally stimulate trees (I'm a tree guy) and other plants to produce ethylene. It was long believed that high levels of ethylene stimulate adventitious root formation, but lots of recent research proves the reverse to be true. Under anoxic conditions, like submergence in water, ethylene actually slows down adventitious root formation and elongation.

There are 2 types of aerenchymous tissue. One type is formed by cell differentiation and subsequent collapse, and the other type is formed by cell separation without collapse (water-rooted plants). In both cases, the long continuous air spaces that allow diffusion of oxygen (and probably ethylene) from shoots to roots that normally would be unavailable to water-rooted plants.

Al

As an example of water vs. medium used to start plants, some growers of hippeastrum seed prefer to germinate by floating the seeds in containers of water. Once the seeds sprout and a tiny green leaf is visible, they transplant the tiny seedlings to soil.

I've tried this method, but I seem to lose more seedlings from the stress of transplanting. I get better results when I germinate the seeds directly in a medium.

The tiny roots on the seedlings floated in water seem more brittle, and they don't seem to take to the transition to soil very well.

I know I'm not talking about cuttings, but I think the same things apply when talking about the roots. Starting them in soil gives a distinct advantage, I think.

What you said makes good sense to me, from a physiological viewpoint.

Al

I'm curious because - and again I'm focusing only on leaf cuttings of one species - there are a few issues that people often encounter and one may be helped by partial water rooting.

The leaves that are potted have to sustain themselves until they root. They continue to degrade until that time, which they first stabilize and then actually start to look healthier.

If you have fragile leaves - leaves with less mass to sustain themselves - they are more susceptible to rotting as they are not as strong. But some varieties are more fragile so you have to find a way to start them without losing them. Of course you make sure the plant is watered at day prior, you only take from certain rows, you make sure the leaves you take are not compromised...but that doesn't mean success, particularly if these leaves get stressed in any way, such as someone shipping them to you. With at least 15,000 named varieties, chances are you're going to want a leaf from someone who needs to ship it to you.

I've noticed, as have others, that if you keep the leaf in water just until you can see the differentiation taking place - the area expands, you can see bumps on the cut edge - and then stick it in soil, you have nearly 100% success.

On the basis of me trying it a few times and talking to a person who always roots at first in water and then in soil - again, before any roots form), I decided to do an experiment.

I bought an unnamed (NoID) AV from a big box store just for leaves to experiment with. I cut the petioles at differing lengths (much discussion about how that affects results) and planted two in soil and one in water. The ones that were in soil the whole time suffered. One rotted (the petiole end), one got more and more limp and has yet to root (it's been a month and it looks very sad). The one in water and then in soil made strong, large white roots and never suffered at all.

It's not a process you'd use if you were a large company, but if you have a fragile leaf that you want to make sure you don't lose, so far it's looking as if it works well in this situation.

It's your call, but the first question I would ask is what made the cuttings you stuck in 'soil' collapse. Was it a fungal issue because the medium wasn't sterile, or something else that was attributable to some operator error?

I'm not being snitty, only logical when I say that if either of the issues mentioned were at work, and undoubtedly at least one of them was, it's really not fair to award the blue ribbon to rooting in water. It might be the only effective way that you can root these cuttings at this point, working within the limitations of your current abilities; but if you could shed those limitations, the negatives of rooting in water compared to a well-aerated, sterile medium would immediately take the fore.

I think it's a case of just doing what you need to do to get the job done. At some point, you may add to your skill set the ability to achieve a very high rate of success when rooting in solid media, or maybe not. It's certainly not the end of the world if you prefer to continue to root in water so long as your success rate is something you're happy with. While I make some noise from the sidelines, my only real interest is making sure I give you all the info I'm capable of sharing, so you can decide for yourself.

This is another question very much like the unglazed clay vs plastic thing, but hopefully w/o the mêlée. ;o)

Al

I'm far from an expert when it comes to Saintpaulia, but I've tried many times to root leaves, both in water and in moist vermiculite... and I've never been successful. I think there's some variable or group of variables that I'm not taking into consideration. Something is not quite right with the environment or methods I've tried. I'm just not sure what it is.

Luckily, I've only got one Av... or I'd really be a disappointed grower!

I can't seem to resist the lovely flowers when I see them on the sale rack, and the price is right at under $2... but I'm a horrible AV grower!

You are potentially right, Al. But, identifying what is happening to prevent success is not an easy task.

The cuttings that are sturdy - thick leaf, very turgid - are not at issue for many. Sure, some people struggle with those, but it's usually an obvious thing, like too much water, not a sharp enough cut so they damage the cut end, or similar. It's these more fragile ones that are the problem. If you have the plant at home and you cut it yourself, the fragile ones usually are fine. But, when someone ships them to you, they are a problem.

They do not contain enough to sustain themselves. Even if you soak them in water for hours prior to planting, they quickly become limp. They start sagging. They then don't have good defenses and are susceptible to things like rot. They take longer to root. Even when they root, they still are likely to die before they produce. I'd guess that rot is a problem in many of the cases. You could have 50 leaves and if they are sturdy, they won't rot. But, the fragile one next to it that is limp and weak? It's just about guaranteed to.

Given that the types of fungus that cause rot in AVs are just about everywhere, it makes it hard to prevent even with good sanitation practices.

If you only start your own leaves, this isn't an issue. But millions of leaves are shipped to people every year. I just want to find a way that the average home AV hobby grower can get better results. And, since many of them may not have better skills, then this may be one way to do it.

But, I'm all ears to find other methods. I just see a problem and am wondering the solution so am trying things, which is why I wanted to know how the process works to see if what I was doing would cause problems some where.

It sounds like you've made up your mind.

FWIW - I have a 10 gallon aquarium with a 24" hooded fluorescent light with 2 bulbs suspended over it. I have pieces of plastic that I slide into place over the top so I can keep the humidity at near 100% and still have some air flow. I have a propagation mat in the aquarium that helps me keep soil temperatures around 75*. If I had cuttings that were very important to me, I would use this set-up and root in a medium of 50/50 screened Turface/chopped sphagnum moss, or 50/50 perlite/ chopped moss (sphagnum moss, not sphagnum peat).

I no longer root anything in water because I've found this setup to be much superior to that method. I really only use this for hard to root things or material that is precious for one reason or another. Usually I root in screened Turface or perlite only.

Take care.

Al

I'm not explaining myself well if you think I've made up my mind. The only thing I've made up my mind about is to find a solution. I'd never make up my mind on such a small trial; I have made up my mind to do more experiments with the technique, but not to say that it's the be all and end all.

As I tried to say above, if you have better ideas, please pass them on (which you did). I think I may have an inherent issue in my quest - I want something that the "average" home grower can use but I also want the "best practice" that takes in account what is best for the plant. This may be antithetical.

There is much conflicting information, which is a part of the problem. Many people swear that AV cuttings rot with bottom heat and that they need no light... I keep running into people who say that there are no set rules because we're all different. I just don't buy that. Something works best from the plant's perspective!

I need about 1000 leaves and about a year to experiment, apparently.

I have often wondered if bottom heat would help. Some people say they get their highest prop rates when they put their leaves over the lights on their carts. This very slight heat appears to help them. Yet, people using prop mats have said they lose more to rot. Maybe they have them set too high?

So many variables...

From my experiments rooting Jade leaves, I would say that one of the main keys to success is simply starting with a healthy leaf. I also avoid direct sunlight - even a Jade leaf, which holds a significant store of moisture, can dry up in direct sun before it has a chance to send out roots. Plants with more delicate leaves, I assume, would dry out even faster.

Josh

I have a little propagation area set up for seed and cutting starting... it's a lower shelf with a cheap grow light on a timer, and a heat mat. I think the heat mat is a little too warm for some items, so I use different things as a buffer zone between the pot bottom and the mat... such as a plastic lid from a Cool Whip container, turned upside down.

I don't know whether this is fact or fallacy, but I've always heard that cuttings root faster if kept away from direct light. I don't use the grow light until I see new growth on a cutting, indicating that roots have formed. This seems to work pretty well.

Some items may require a more humid environment in which to root... in which case, sealed baggies work pretty good for me.

To be quite honest, I think there are too many variables to say for certain that one way of rooting leaf cuttings is the easiest or the best. I think that the best way will be whatever is best from the plant's perspective, so to speak.

And I think that the best instructions for rooting leaf cuttings will reflect that, but will end up being in general terms, because of the many variables from person to person and their environments.

Jodi - you've basically nailed what I want...the principles. Each of us can apply them as we chose. And, I'm only talking about one type of plant in my quest - like you I assume that each species may have a different set of guiding principles.

Josh - you are right that a healthy leaf is extremely important. But, when a leaf is stressed or if that leaf is less strong genetically even on the best grown plant, how can we still be successful as possible?

I can't choose what someone sends to me, even if I purchase it - I can't see the plant, choose what row they pick it from, or ensure they watered it sufficiently the day before so its hydrated. I also can't prevent stress from the environment on that leaf's trip to my house. So, my quest relates primarily to finding how to ensure the best outcome for leaves that are more tender/fragile, that may have been stressed, and that traditional methods tend to fail.

And when you're having a leaf cutting sent to you, you're talking about even more variables, in addition to the normal ones from person to person! You've got a complete set of unknowns... general health and genetic health of the Mother plant, whether it was watered prior to taking the cutting, shipping and weather, other stresses encountered...

It would be difficult, at best, to put together a list of precise instructions that guarantee success. There can be no guarantees because everyone will treat their leaf cuttings slightly differently, and the stress will vary from shipping destination to shipping destination.

And even if you experiment and find the perfect way to root leaf cuttings, yourself... the variables instantly change with the next person.

The variables are still relatively limited in terms of how it affects the leaf, I'd think - it got too hot, so it's wilted. It was cut from a plant not watered recently, so it's wilted. It was cut a long time ago, so it's wilted. I may be completely misguided - it has happened before, lol - and I may not be able to find principles. But, I'm guessing I can. As I noted above, it won't guarantee anything. But, it will improve chances, which is all most of us really want, isn't it?

I received some leaves today - maybe 15 of them. These, compared to those sent in the heat, were lovely. Nary a one fell into the "fragile - special care needed" category. While that makes me happy in that I probably won't lose any, I also don't get to experiment regarding what will save them!

This summer I'll have to start mailing myself leaves, lol.

LOL! I was just gonna say... you'd need a control group, and a group that was stressed on purpose, so you could test your theories! Mailing some leaves to yourself... that was funny! :-)

Actually, it might help if you worked with a partner... someone who could mail you leaves using different methods and shipping methods, so you could test your theories with real accuracy. Just a thought...

I'm glad you got nice, healthy leaves in the mail!