Why do trees have to be certain age to produce fruit?

@Vlad I’d love to discuss further with you and get your opinions since you’re well versed in many fields and I’m an aspiring scientist/PhD student. Message me!

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There should be ‘dumb’ trees if cropping involves a tree being smart or ‘evolving’ from some previous condition. I don’t subscribe to theory of evolution.

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Anthropomorphizing again

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One last reference that addresses the question much better that the link I provided earlier. I should have done a better search. It just depends on search terms.

No Flower no Fruit – Genetic Potentials to Trigger Flowering in Fruit Trees by Hanke et al. You can download and read the pdf if wanted. If you go to page 5, they address shot length, internode number, day length, some hormonal factors or growth regulators. There is also light wavelength.

Thanks @Vlad for prompting me to delve a little deeper into the research. It’s interesting. I’m also very curious about whether my apple hybrid seedlings will flower in a few months. On the one hand, I doubt it. On the other hand, looking at the spurs, I think “maybe”. :grinning:

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As in all or most living creatures epigenetics, environmental conditions determining gene expression, is involved. I’m not surprised the chemical details are not known. Is there any practical use of that knowledge? It certainly is an interesting academic question.

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@danzeb, creating new varieties can take many years and many generations of trees. Or in the case of annuals, many generations of plants. If fruiting can be induced earlier, then new varieties may be developed years, even decades sooner. For a multibillion dollar industry like apples, that can mean real money. Also, adding in features like disease resistance, can mean less dependence on fungicides for example. By the genetics and signals involved, developers can focus on genetic traits that will speed up the process. For the home grower it doesnt matter as much to know these things, unless out of pure curiosity. For someone who is trying to grow their own seedlings, it might help to know how to prune or what stock to graft onto.

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The youngest human to give birth was Lina Medina who gave birth at 5 years old to a healthy baby boy iirc in 1934. Warning, if you search for her, you can find a nude picture about 7 months pregnant. They never found out for sure who was the father and her son died iirc age 42 in the mid 1970’s. She was still alive the last I knew.

This statement is false. It is routine with pecan breeding to graft juvenile stage seedlings into the top of large bearing trees to force the transition to adult phase earlier. Forcing plants to transition from juvenile to adult is complicated but feasible using other methods. One I have personal experience with is girdling a tree to trigger fruiting. This can be done on a 4 year old pecan tree by making a dozen or so slanting cuts in a ring around the trunk. Don’t entirely cut off the top from the roots, just constrict the transfer of nutrients from the top into the roots. Make the cuts in spring after leafing out and leave them to heal over the summer. Most of the time, the tree will flower and set nuts the next spring. There are elements of sunlight intensity sensitivity, carbohydrate storage in the roots, daily temperature, and phytohormones that affect the transition. It is NOT just a matter of now many nodes are present though the presence of a certain number of nodes may be a typical indicator that adult phase tissue has been produced. Some plants use a phytochrome moderation system to induce transition to adult phase. Maize is a well known example.

What is the difference between adult and juvenile phase? Most flowering plants produce 2 or 3 types of buds; vegetative, flowering female, and flowering male. If the plant is dioecious, it will only produce fully reproductive buds one or the other, male or female. If monoecious, it will produce both male and female or combined male/female flowers on a single plant. Many plants have protective reproduction strategies to limit or prevent self-pollination. Pecan as an example uses heterodichogamy where a plant produces male flowers first and female flowers later (protandry) or the reverse with female flowers first and male flowers later (protogyny). The key takeaway is that juvenile plants produce only vegetative buds. Only after the transition from juvenile phase to adult phase can a plant produce flower initial buds. If you want to drive a geneticist crazy, ask them to explain why a natural stand of pecan trees tends to have 1/2 protandrous and 1/2 protogynous trees. Hint - it does NOT follow mendelian segregation though protogyny is dominant.

There are genes that specifically affect transition to adult phase. One I am familiar with is the ft gene and another is the precocious gene in tomato. Most tomato plants have to reach a specific size and have a specific size canopy of leaves before flower initials will be produced. With the precocious and/or ft genes, both plant size and temperature requirements are reduced. I have a couple of varieties that will set perfectly healthy and viable blooms when only 6 inches tall.

All the above to say that I don’t think anyone fully understands why and how plants transition from juvenile to adult. We know a little and can read a bit more.

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@Vlad – I see now what you were trying to ask. You are (I think) trying to ask how the tree’s genes manage to delay reproduction. But the question posed in the title of the thread is why. That’s the question a few of us attempted to address.

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This is true for several reasons. One of them is that plants are not strictly Newtonian cause-and-effect machines: they have time-dependent feedback loops and hysteresis.

Bear, this is a really good summary base on my own reading of the subject. I’d add to it that about twenty-five years ago there was a guy out of, I think it was, a southern university that I don’t recall who published an article in Scientific American claiming that long chain alcohols produced by roots were a mediator in fruiting, specifically dodecanoic acid and maybe undecanoic acid. I never saw anything else about it.

Some people graft seedlings onto precocious rootstocks or already-fruiting branches to induce early transition from juvenile through to productive phases. I don’t know how successful they are.

Very successful. This was the strategy that Luther Burbank used to speed up his own breeding program. In fact, it left a legacy of unidentified grafted fruit on trees on his estates that has quite well occupied a PhD student who has tried to sort them out.

I’ve lined up precocious rootstocks for the same purpose so hopefully I will eventually be able to report personally on how well it works.

I think it would be fun if apples could be grown like tomatoes

You may get your wish. The folks at the Appalachian Fruit Research Station (AFRS) led by Chris Dardick have developed a breeding system with an annual breeding cycle for stone fruit called the Rapid Tree Breeding Program. They have gotten three generations of crosses in four to five years.
They used the method to cross their plum pox resistant cultivar “Honeysweet” with California prune plums

I had some correspondence with him about it last year. He told me that they have extended the system to apples and that they are working on deregulating the early flowering lines so anyone can use them.

From a scientific paper describing the project: “We have overcome the juvenility and environmental limitations of flowering and fruiting by incorporating a gene that induces trees to flower and fruit early and continually. In plum, the crop with which we are now working, we have reduced the generation cycle from 3–7 years to less than one year.”

https://www.researchgate.net/publication/267342864_'Fastrack'-A_Revolutionary_Approach_to_Long-generation_Cycle_Specialty_Crop_Breeding
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