While skeptical about the theory about rejuvenation of airlayers/clones as discussed off-topic at this other thread, i, too, wish that the theory is correct, since that would translate to eternal life of all clones of perennials(in the absence of disease/pests).
Now, and pardon my amateurish artistry, but on the illustration below, am really curious when the purported rejuvenation of the clone might actually occur. Does anyone here have the expertise to tell me which, and tell mewhy? Will subject A on sequence 1 already have self-conferred rejuvenation by having grown roots–but still attached to mother tree(B)?
Will subject A on sequence 2 now be considered younger than the mother tree(B)?
And on sequence 3, will removing the top of subject A and grafted back to B effectively result in A reverting to its original age? Or would it actually be ‘younger’ than the mother tree, by virtue of having been removed temporarily and grown on its own roots?
To avoid misinterpretation you need to clarify which rejuvenation you are speaking of. I feel that lead to some confusion in the mentioned thread.
What I think I have learned from the discussion is if you understand cell age as the difference of the cellcondition between its first formation and a later condition, changed by mutation, those methods wont rejuvenate the cells. You will however by cloning create a young tree. Still it would consist out of already aged cells. That wouldn’t harm the tree cause its lifespan will by far end earlier than the theoretical ability of its cells to reproduce itself (the mentioned biological clock).
I know that is far from precise and correct. For instance I don’t know what “the first formation of a cell” would be in that thought. And the cells are constantly reproduced. I understand aging as adding up failures during that reproduction. In the end it will become more and more probable the cells cannot hold up their function in the organism which then translates to death. Maybe I am completely wrong.
I have to admit I am wondering if cloning by tissue culture is in fact rejuvenating even on the cellular level. From what Andrew said that shouldn’t be the case though.
I think that for tree 1 the airlayer (A) would only gain very limited juvenile/vigorous traits because the new root system in the airlayer would be so small, no change to the original tree (B). For tree 2, airlayer (A) will most likely throw suckers (if it has branch refinement and the short internodes of a mature tree) which will grow as a juvenile until a new full sized mature structure is established, chopping a main branch on tree (B) will result in some increased vigor on that branch compared to the rest of the tree until a new structure is established. For tree 3 the portion of (A) that is grafted back to tree B will be similar (moderate vigor) to the cut branch on tree 2, the stump of A will then be even more juvenile than it was in 2, with vigorous suckers guaranteed.
In scenario 2 there would most likely be no change to either if both have a refined branch structure and balanced root systems. But if one was left with more roots than the other the one with more would likely throw suckers or have increased growth, while the one with less would become more mature and grow less. Of course the cut could also stimulate vigorous root growth which could make both more vigorous.
This is a topic that is indirectly discussed for figs often (out of frustration) when talking about how age affects fruiting. From my own experience I’ve seen that age measured in time is mostly irrelevant, freeze damage can keep figs in a constant juvenile state. So varieties that are not precocious refuse to form figs even after years in the ground where they grow large root structures and regrow to 8’x8’ or more every year. But a 2nd year plant of the same variety that is containerized and has much less vigor is much more likely to produce fruit, from a practical standpoint the younger tree is more mature.
case in point! And this is exactly why brought up the above scenarios, because i have no clue where and when the supposed rejuvenation occurs, and if the theory actually holds. To me they are all of the same age, and the only difference is that they are all compromised in one way or other.
As far as mutations that result in cells not being able to produce go… I think nature can take care of that. Say the terminal bud of branch A on tree 1 mutates and is no longer able to grow, axillary buds that are not mutated will be stimulated to grow (just like pruning off a terminal bud) and the tree continues on. There is no reason to think that all the buds and branches of a tree or all the clones around the world would have the same mutation occur and suffer the same fate at the same time.
But nonetheless the created clone can then reach the normal lifespan of a tree. Thats because its cells are able to reproduce longer by far than the lifespan of the single tree can be. You could understand that as rejuvenating, cause you create a “new” tree with a whole new lifecycle of a tree. Thats not precice because of the weaker rootsystem and so. But in general you could say thats rejuvenation and I feel others might have referred to this when using the term.
That should be right. But it doesn’t have to be the same mutation. It simply could be a game of probabilities. Every reproduction cycle has certain probabilities for mutations to happen. We know some mutations even are beneficial. But over time with more and more mutations adding up probabilities are rising for a “system failure”. It won’t happen the same second to all clones but round about after the same timescale. When speaking about lets say 10.000 years for instance, 200 years more or less are not that much of a difference.
yes, but have airlayered innumerable mature citrus clones, and while they will continue to bear flowers and fruit like the mother tree, none will present with juvenile/vigorous traits(even after a decade), and will never develop 3" spines typical of seedling youngsters. They can’t possibly be mature, and immature at the same time if growing on their own roots.
again with citrus, the airlayers can’t possibly be juvenile if it is already fruiting. Airlayered citrus will bear fruit at 5" tall even if recently removed from mother tree. Will continue to be bushy the rest of their lives as well.
are you saying longer than the lifespan of the mother tree(both on their own roots)? Also, why would it be a whole new life cycle if, say, the citrus clones mentioned above did not skip a beat with fruiting and flowering despite recent removal from mother tree, and have not reverted to juvenile characteristics?
Ok, but you then have to consider cell age of that replacement. It also is already compromised by aging (mutation) and probabilies are it will fail too in about the same timeframe the other cell did.
The difference in our argumentation is you are talking about mutation on a larger scale (bud mutation). I am talking about cell mutation of all the cells affecting their ability to function as “designated”.
thanks for the resource. Excellent but difficult reading. Reading that feels more like studying for a test in college than enjoying reading the posts on growingfruit. Reading that material shows that it is a complex subject.
seems like google won’t allow me to read certain pages of that e-book, as from what is available–i actually concur with-- in fact. And from what could see, it is notable that the studies brought up there are artificially induced in lab settings. Was there a page there that would shed light on the day-to-day diagrammatic scenarios i posted above?
i forgot to add that the hypothetical scenario includes hypothetically- similar environmental conditions, such as being grown close to each other, or in a place where diseases/ pests are absent. Am also quite curious about the super-old avocado tissue-culture study i brought up at the other thread. If that really old avocado tree should be cleaved longitudinally(as in the Q/R scenario above)in half forming two clones of equal above-ground and below-ground biomass-- if any of its halves would be rejuvenated and again resume being responsive to tissue-culture. Also curious how it might respond if the separation of clones is similar to the Y/Z scenario posted above where the cut is below ground(but this time cross-sectional) and resulting in two specimens of identical logistics. Would there be epigenetic or hormonal effects that would jumpstart the otherwise senescent avocado tree, growing on their own roots?
From empirical observation, most mother trees of most fruit trees of known varieties grown originally from seed have long died of old age (hundreds or even thousands of years ago) according to their predetermined lifespan. Yet, their clones survive and thrive to this day. These have been passed down through generations of skilled growers. The question is not whether this is happening or not, but rather how it happens. Stem cell science that is progressing by leaps and bounds as we speak answers this question. Vegetative reproduction is in essence allowing mature cells to revert back to stem cells, and then grow anew into a brand new clone ready to live a full lifespan. As to the different scenarios presented above, one can take a guess, but there’s no solid science to address them properly.
Google seems to limit page views so if you scroll up and down they disappear after a while, it let me see them again when I followed the link again. Some pages are not included in the preview unfortunately.
The section on rejuvenation, p. 406, says that mature apple trees can produce juvenile growths by repeated hedging or pruning to the ground, which relates to the pruning scenarios you described and my experience with figs.
“Partial juvenility” can sometimes be achieved by rooting or grafting the apexes of mature shoots, repeated rooting or grafting of the apex improves the result. When grafting to seedling rootstocks, rejuvenation is encouraged by including as little mature wood on the scion as possible and allowing leaves on the rootstock, rejuvenation is discouraged by the mature leaves that form on the scion.
i still couldn’t access pages, but will try at a later time. Would be too much of me to ask anyone to do ‘print screen’ of pertinent page/s but will really appreciate if anyone here will.
the question is, if this is reproducible and repeatable on the same tree, and for how long? Will doing this result in immortality, say, in a hypothetically disease/pest-free environment? It is very likely that it won’t. Or should cloning it as in my diagrams above do the same? I still can’t reconcile that cloning via cuttings on own roots will rejuvenate if serially done. There is a need to graft to young seedling rootstoc at some point.
again i go back to avocado, since it is a perennial, but supposedly exhibits tangible senescence compared to figs(grown on own roots), and unresponsive to tissue-culture unless grafted to young seedling rootstoc first. Since tissue-culture involves more than just the grocery-obtained iba/naa hormones to created rooted cuttings, it is clear that a rooted airlayer can no longer be produced from an old avocado tree, and the only way to test my hypothesis is to cleave the old avocado tree as in my last two diagrams above and see if it will rejuvenate. I really don’t see it happening. The clones will be as old as they’ve always been. Thus said, i feel cloning on own roots has limits, especially among those with relatively short lifespans. Grafting to young rootstoc seems to be the only way, at least per current available technology