Growth phase characteristics are apparently controlled by gene silencing, so I guess the plant can sense its growing situation somehow and adjusts.
I’m not clear on the goal for the avocado stump, is it a seedling you are trying to propagate? I found this on rejuvenating mature avocado trees with pruning.
Another rejuvenation method, pruning field mature plants prior obtaining explants for culturing, has also been tested by avocado researchers. Explants obtained from rejuvenated mature plant by pruning has led to the highest ever rooting percentage reported with mature avocado (90%) [62] . At the same time, this result validates the idea of juvenility induction in mature plants through pruning [24] .http://www.scirp.org/Journal/PaperInformation.aspx?PaperID=80029
Really appreciate you posting that @hoosierbanana. On the forced rejuvenation, i was hoping it would mention anything about life expectancy. Inducing juvenile characteristics on a clone is obviously not good if the life expectancy is contingent to the age of the mother plant, much like the diagrammatic scenarios i posted above. That translates to a long gestation period to fruiting, and then short fruiting period due to early death/decline. The issue about that study is that the specimens were practically reduced to micro plants, which, of course would result in delays in attaining sturdy growth/enough biomass to bear flowers and fruits. It also mentioned of grafting to young rootstock to rejuvenate, which was similar to the avocado study i posted at the other thread, and was hoping they would mention that the rootstocks they used were from those that had undergone forced rejuvenation(especially from mature, senesced stems), and not from seed. That would have clinched it.
was just thinking out loud in case anyone might have an idea what was saying, lol.
but in a nutshell, i was imagining that avocado stump to be the senesced avocado tree which is so old that a stem from it will only respond to tissue culture if that stem spends some time grafted to a young avocado rootstoc first. Now, since am hypothetically putting the theory of rejuvenation through cloning ‘to the test’ and considering that it is impossible to get an airlayer from the avocado being too old( since it is too old even for tissue culture), i was hoping that getting a clone from it by cleaving that stump into two clones would result in rejuvenation. While am certain that cleaving that stump would not rejuvenate the two clones resulting from the division, i was hoping someone who believes in clones being equivalent to rejuvenation would tell me he/she is confident that the clones will be rejuvenated, and explain why they will be.
while thankful for the avocado study you posted above, i went straight to the conclusion of that study, and alas, it says that mature avocado stems cannot be micro-propagated for being too old.
needless to say, am hoping that you or anyone else would convincingly stomp out my pessimism
Primarily because jujubes and mulberries on their own roots are worth more than gold. And worth way more than platinum if their suckers or airlayered clones actually lose what ageing/senescence they ‘acquired’ from mother tree— as soon as they are severed from the mother tree. Quite precious obtaining a clone that is already fruiting, growing on its own roots, and which theoretically has the same lifespan as a seedling!
clonal age was brought up at another thread(which i ended up hijacking) and figured redirecting the topic by posting here. Perhaps a more feasible refutation(or postulation, per @Livinginawe) re: clonal rejuvenation theory. Hard to prove ageing and senescence being passed on from mother plant to the clone if the species being cloned is extremely long-lived(compared to humans), and just recently remembered a perennial one that is relatively short lived. Even shorter lived than some avocado cultivars. From seed, many papaya cultivars start to decline around 4 to 5 yrs of age, and all will have senesced and died within a decade or so. Two decades at the most. The papaya airlayered below will not be rejuvenated, and neither will it live longer than the mother plant it was cloned from. And to take it to the extreme, i can’t envision any rejuvenation being conferred to an airlayer being done on this airlayer. If you have experience growing papayas, you’d have a sense of resignation that airlayering will not make any of the clones immortal.
The first and second scenarios were amazing. I wish I have thought about those! But the “bonus query” takes the cake. A simple way to refute clonal rejuvenation but also the most elegant way. Not just in a pragmatic sense but also in a philosophical sense. Cleaving the stump into two clones will obviously not make any of the clones younger, duh!
No one has dared refute the query LOL
If that was a papaya stump then will probably shorten the lifespans of both clones instead of prolonging. But this is coming from someone who has no experience with papaya trees. Are they really short lived?
crazy as it sounds-- i actually wish someone would engage me on that one. For a lazy orchardist like me, planting trees is not worth my time and effort if the trees i plant won’t live long enough to be producing fruits for my great, great, great grandchildren
there are few things more productive and rewarding to do, than to go to a neighbor’s or friends house on a lazy sunday afternoon to plant an extremely long-lived tree that produces delicious and nutritious fruits that require little care.
have recently been propagating juju cultivars on their own roots, so if i am right about clonal ageing/senescence on own roots, that would be a bummer!! I’d be celebrating that day when somebody proves my hypothesis wrong. As that would mean my self-rooted sihongs and chico’s will get rejuvenated by the simple process of airlayering/cuttings. Or simply by digging up their future suckers.
the process would make desired cultivars immortal(without having to graft to seedlings, or having to process with plant hormones), and who doesn’t want that?
yes, papayas are short-lived, but they are true perennials, which is why i used it as tangible proof of clonal age being the same as mother plants’ age. It debunks the idea(at least for the species) that a self-rooted clone separated from a tree will automatically become a ‘young’ plant. An airlayered papaya stem will not grow taller than its mother, and will not produce fruits larger than its mother’s when its mother was at its peak. Papayas peak for just a few years past one year of age, then fruits start getting smaller around 4 or 5 yrs of age and stop producing anything substantial around 6, then die of old age a few years thereafter.
Thanks @jujubemulberry. I looked up papayas and cloning and found the website below. It says the variety “Honey Gold” has been cloned for more than 40 years! I am wondering how it is done if papayas cannot live much longer than ten? If age and senescence gets passed on to the cuttings, then the clones they have today should not have been productive/alive?PROPOGATION OF ‘HONEY GOLD’ PAPAYAS BY CUTTINGS | International Society for Horticultural Science
interesting right? And you make a valid point. My doubts about it is that they use a battery of hormonal treatments, and not just IBA rooting hormone, which may equate to rejuvenation via grafting to seedling rootstock as mentioned in the avocado study i posted at my other thread. . Also, the study you posted mentions of 1-2 year old trees being the source of the clones. It did not say if they were clones from honey gold papaya seeds that were germinated the past 1-2 years, or clones serially taken from the original papaya tree(which would be wonderful!). That would make a huge difference. A 1 to 2 yr old papaya seedling is nearing at(or already in the beginning of) its prime, so it would be great to obtain clones from them as that is when they start producing the biggest fruits-- and will bear big fruits at much shorter heights since the growth spurt of juvenile stage has been passed. As far as i know, when cloning papayas, they don’t clone them from old specimens, but from younger specimens.
couldn’t find my reference for this now but will post it when find it.
btw, i do appreciate the scrutiny, and it is quite obvious that you are so much into this too as i am
i found it @Jenna1. So on the link posted below, papaya cultivars are cloned by taking tissue samples from young seedlings(not from tissues of old trees of cultivars). It is a long journal but really interesting if you are familiar with the papaya life cycle. It also mentions of clone senescence, which means ageing of clones has been taken into consideration, and is probably the reason why the clones were obtained from seedlings.
Plants and animals are fundamentally different, and i think our understanding of how animals work can be confusing when looking at plants.
Animal cells age. They have a little “clock” that keeps track of how many times they have reproduced, and eventually they stop being able to reproduce. This is probably in the telomere. Plant cells, in contrast, are theoretically immortal, as i understand it.
But plants, as organisms, mature. Maturity is not directly related to the age of the cell. In fact, the Israeli article above points out that older cells near the base of a tree are often less mature (and easier to root) than younger cells from the crown of the tree. Maybe it’s because they have reproduced less, (like animal cells) but I think it’s due to hormonal and similar influences.
On a cellular level, a stem cell is an immature cell even if it has split many times.
But you can not only force plants to produce less mature tissue, you can also force a branch to mature quickly. When researchers breed apples, they graft a piece of the seedling into the crown of a mature tree, to force it to mature and produce flowers and fruit quickly.
I guess it’s easier for some plants to revert to juvenile traits than others, and that’s where the talk discussion of how to promote juvenility comes from.
Fun discussion and thought experiments! Definitely not an expert in this field, but just for the heck of it (and because I may learn something)…
I’m not sure that I entirely grasp the point of your query, but from what you say here,
and here:
it appears that you are concerned with the question of whether and/or to what degree the age of the mother plant is passed on to clones/scions, thus compromising their life expectancy. Am I understanding that correctly?
In the big picture, I think @chriso’s answer makes the most sense to me. We know that grafts (and successive generations of grafts) can and do outlive the original mother tree, so evidently the process works in a practical way.
But beyond that, reading your posts together with the text posted by @hoosierbanana, and specifically the part about the “cone of juvenility”, it seems like part of your question involves a confusion of terms.
Intuitively, it seems like “mature” should equal “old” and “juvenile” should equal “young”, so that the oldest part of the tree is the most mature and the youngest part of the tree is most juvenile. According to the text posted by HB, however, precisely the opposite is true: the oldest part of the tree is the most juvenile, while the youngest part of the tree is most mature.
So, when I cut off a scion and graft it to a rootstock, I am taking material that is young but relatively mature and putting it in a position where it will effectively become juvenile (because a scion cut from what would have becoming a fruit-bearing branch will develop, at least initially, into a non-fruiting stem/trunk).
But this rejuvenation doesn’t mean that the propagation material has now become younger; in fact, due to the simple passage of time, it will of necessity be older than it was when it was more mature. The point is that it will be younger than the corresponding parts of the tree that the scion was taken from, and that having been made more juvenile, it has the potential to generate more growth in the future (because it will become a trunk rather than a fruiting branch). So, if I succeed in grafting a relatively young scion onto relatively young roots, I can expect to to produce a tree that will live longer into the future than a tree than the tree that I took the scion from, all other things being equal.
Looking at your series of examples and queries with this in mind:
In step 1, I don’t think the maturity/juvenility of A will be impacted (though I could be wrong - does air layering impact fruiting prior to separation from the mother plant?)
In step 2, A will become more juvenile, but not younger.
In step 3, A will be less mature than a corresponding branch that had simply been left on the tree (in other words, fruiting will be delayed), but again, it will not be any younger. Depending upon how long you wait to harvest scion from A, and what part of A you harvest for scion, the part of A that you harvest for scion may be younger than the part you initially harvested from the tree via layering, but not any younger than the corresponding growth of branches that were left on the tree (though the growth on A may be less mature - not sure about that).
With respect to Y and Z, I assume that we are looking at a sucker growing off of a tree or bush. It seems like there could be a number of variables to consider, but my answer is that neither would necessarily be rejuvenated, and that if they were rejuvenated, neither would be made younger.
With respect to Q and R, it seems to me that the terms “mother plant” and “clone” are inapplicable here because neither has been produced from the other. Assuming that the tree survives the operation, I would say the same thing I said about Y and Z.
Again, I think the important point is that making plant material more juvenile should not be confused with making it younger. But that’s just my understanding, and again, I’m far from being an expert, so I’m sure that there are things that I’m missing or misunderstanding, and I’d be happy to learn more from those that know better.
it really is, right? So happy to see more people chime in
i don’t think anyone is, really. I am an absolute amateur on this myself, lol
this is absolutely true. It seems though we see it in different terms. I think the clones outlast the mother plant simply because the rootstock is juvenile, and that there are rejuvenating effects of grafting to recently seed-germinated rootstock(as i pointed out with the study on avocados). The question really is imho, is if we airlayer the clone(of a true perennial like papaya but also a short-lived perennial–in human terms) and have it grow on its own roots, would it have the same lifespan as the mother plant it was originally taken from?
the study posted by @Jenna1 would have been a bullet-proof rebuttal to my query, but the clones pertained to were obtained from recently germinated seedlings/young trees grown recently from seedlings(unless there might be proof otherwise ), and not from senesced papaya trees. Of course-- the clones would still perform and reach their peak of production because they were obtained as clones of youngsters/adolescents and are still inherently pre-programmed to peak
i guess my answer is yes and no. My answer is yes-- the age is passed on-- but only if it is grown as a simple airlayer or untreated rootstock sucker being removed from the mother tree(in the absence of hormones/cytokines, etc) I think it will be the same age as the mother tree, and will peak, senesce, and die at about the same time as the mother tree. The papaya scenario posted on the youtube video is a prime example of tangible senescence with simple airlayers.
My answer is no- but only if if the clone budwood is grafted to juvenile rootstock. By serially grafting old cultivar clones to young rootstock, we are effectively imparting artificial immortality to the clone.
one of the reasons why i am growing long-lived jujus from seed is because if they happen to have quality fruit, they would make excellent rootstock to poach suckers from and graft over with old cultivar clones, as i will have first-hand assurance the rootstock clones will not only have quality fruit, but that the rootstock clones were obtained from a veritable youthful seedling-- and that the old cultivar clones(vintage cars) will be grafted to a brand new engine and tranny
for step 1, i agree with you it will not be rejuvenated unless the airlayer was bombarded with plant steroids. As for ability to fruit(and in the absence of hormone treatment), it may even make the airlayer more productive simply because the phloem channels are severed by the act of girdling, so the sugars and proteins produced by the stem distal to the girdle gets concentrated on that stem. Girdling effectively transforms the stem above it into a self-serving parasite.
for step 2, i think it will still be the same age as the branch it was taken from, but will be compromised and not be as productive(feigning juvenility) simply because it will not have the advantage of being sustained by a strong taproot. Only adventitious roots. I see this first-hand when airlayering citrus. Citrus from seeds will start out with strong apical growth, strong
main trunks, and plenty thorns, then when trees mature, the fruiting side branches lose their spiny habits. Airlayering these side branches and removing from the mother trees will not result in vigorous apical growth and no reversion to thorny habits. The airlayers will initially slow down in production, and will be bushy in growth.
for step 3, i agree fruiting will be delayed, but mainly because the act of grafting compromises vascular flow.
exactly! I hope didn’t sound abrasive posting that, merely obliged to do it to prove a point when many say a clone gets ‘young’ by the very act of cloning(on its own roots)
i totally agree. Many dwarfing rootstock will nurture an old clone whilst also ‘force’ it to bear fruits sooner than when grafted to regular rootstock. Then die sooner than when grafted to regular rootstock. It seems like the dwarfing rootstock is inherently programming the scions to produce fruit(and therefore, seeds) soon, and when the reproductive stage has been consummated, it would have inherently aged and senesced.
Inserting usual disclaimer about my lack of expertise…
JinMA:
We know that grafts (and successive generations of grafts) can and do outlive the original mother tree,
this is absolutely true. It seems though we see it in different terms. I think the clones outlast the mother plant simply because the rootstock is juvenile, and that there are rejuvenating effects of grafting to recently seed-germinated rootstock(as i pointed out with the study on avocados). The question really is imho, is if we airlayer the clone(of a true perennial like papaya but also a short-lived perennial–in human terms) and have it grow on its own roots, would it have the same lifespan as the mother plant it was originally taken from?
[/quote]
To clarify where I’m coming from, the point that I’m making refers to this part of the text HB posted: “When a plant is juvenile, it puts on juvenile growth. This becomes the oldest part of the tree as it ages. These lower and older parts of the tree retain their juvenile characteristics. On a tree, this includes the trunk and the portion of the lower branches near the trunk. […] It is not until a tree is sufficiently large and old that it goes through phase change and develops adult characteristics. These characteristics will manifest themselves on the newest growth. Therefore, the outside and higher portions of a mature tree are the most adult.”(406)
So, if I’m understanding correctly, the terms “juvenile” and “mature” refers to types of growth (non-flowering vs. flowering), and not (or at any rate not precisely) to age or degree of vitality/senescence. In fact, as the passage I just quoted observes, the oldest part of an adult tree will be the most juvenile, while the newer growth will be the most mature.
My experience is mostly limited to apples and pears, but as I understand it, the preferred wood for grafting is relatively new, non-flowering growth. My understanding was that it was the type of growth and not the age of the tree that made the difference, and that the right kind of “new” growth from a very old tree would work perfectly well and could be expected to have as long a lifespan as any other grafted tree (all other things being equal).
In other words, with respect to your point above, it seems (to me) that the key factor is not only the vitality (notice that I’m avoiding the word “juvenility”…) of the rootstock, but the suitability of the scion. (And that this suitability has less to do with time-to-senescence per se and more to do with ability to form a graft union and achieve vigorous growth?)
Interestingly, I have seen something similar happen with pears. Growth from the OHxF rootstock I use will often have noticeable “spines.” Growth from scions grafted on the same roots will generally not (maybe exceptions but I can’t think of one). And in this instance, I would presume that the OHxF is clonal propagated. I haven’t tried grafting an OHxF scion to OHxF rootstock, but I suppose that might be an interesting experiment.
I don’t know anything about papayas, but given what you’ve said about the shortness of their life span, I wonder if the limited growth of air-layered plants is due not to senescence being “passed on” and more to the fact that the adventitious roots simply don’t have time to catch up with the stronger root system of a seedling before senescence starts to set in. Total speculation (and possible misunderstanding) on my part!
Given the fact that papayas have only a very short lifespan while jujubes have a very long one, I also wonder how well the lessons gleaned from one can be applied to the other.
This is an intriguing point and I wonder if there are situations where it might offer a useful way of enhancing fruit production. Quite possibly not, but fun to think about!
oh i see now, and yes, we are in agreement on that one
scion on a rootstock does involve vitality of rootstock-- plus compatibility. For my intents and purposes though, am more interested on whether or not a clone(that is not papaya), will run parallel to a papaya’s projected lifespan if an airlayer was to be obtained from a much longer-lived species, say, jujube. I don’t know how old the cultivar honey jar is when it was first grown from seed, or obtained as a sport, but it seems like it struggles when grown as an airlayer/cutting treated with iba hormone-- but it will be so much more vigorous when grafted to seedling rootstock.
i guess what applies to citrus applies to pear rootstock, when grown from seed. And similarly, scions from fruiting branches of certain citrus will have lost their thorny habits, even if grafted to seed-grown rootstock. Calamondin citrus is a reproducible and tangible study that would demonstrate this.
i actually think it is both, and that the age passed on to the clone will hold much more. From my experience, a clone will not have a projected lifespan longer than its mother tree(simply because the act of cloning makes the clone “younger”). This is not true as demonstrated by relatively short-lived papayas and avocados. An avocado in decline won’t even respond to airlayering(wont form roots) or to tissue culture hormones unless its stem is first grafted to a seedling. And if a stem from a 6 yr old(which is old for the species) papaya tree were airlayered, it will continue to behave like an old papaya tree, bearing small fruits, and senescing like its mother, and will not peak in production like its mother did when it was 3 yrs of age. But if i take self-rooted clones from a papaya seedling or a 1-2 yr old , the clones will still grow up and peak in production with large fruits, and then slow down in production with smaller fruits as they reach 5 yrs or more…
hey,that is my expertise as well, lol
it does work, but can kill the tree if you do it on the main trunk, as the roots need to eat too!
it applies if one does not know the age of the original scion of a jujube. Honey jar seems to be a laggard on its own roots, probably because it is an old cultivar and that its ‘true age’ gets exhibited as soon as removed from young rootstock-- have had a couple of them that died on me on their own roots.
I failed to do my due diligence @jujubemulberry. If the clones were obtained from papaya seedlings or young trees, then you are right the study I posted does not mean much. That study is rather vague if not misleading ! I cant find anything online about papaya cloning wherein a clone taken from an already declining tree actually gets rejuvenated .
Bear with me, my ignoramus about papayas is showing LOL
BTW @jujubemulberry, I ordered your book and learned from your Amazon profile you have a background in biological sciences. What fruits do you specialize in apart from what you mentioned there? Papayas are tropical which makes me curious. Ok, yes, I am also nosy.
everyone has some degree of ignoramus. Have lots of it myself. It is only subject to SNL ridicule when bearers of ignoramus also project a cavalier attitude.
as for the book, you shouldn’t have! Pretty much everything written there i already posted here. And can’t say i specialize in anything either. It is just that was fortunate enough to have grown a bazillion tropicals when lived in southeast asia(papayas being one of them), and then grown scores of temperate plants and xerophytes living in usa.
going back to the subject matter of papayas and senescence: papayas will start bearing smallish fruits as adolescents(around 1-2 yrs of age), then produce the largest fruits around 2-3 yrs of age, then at around 4 or 5 years old, the fruits gradually get smaller again and subject to fruit drop. At around 6 yrs or older, the trees won’t be worth keeping anymore, especially if trying to grow them commercially. Trees will be too tall with very small fruits, declining rapidly and probably half-dead if not dead altogether around 10 yrs of age.
if one manages to airlayer a papaya branch, say, at 7 yrs of age, that self-rooted clone will not be rejuvenated and neither will it be able to produce large fruits(it will not peak), and will likely die at about the same time as its mother, if not sooner than its mom. It is only when clones are obtained from younger trees will the clones be able to peak in fruit production.
Still browsing through it.
JinMA: