@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”. 
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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.”
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Apples are insect pollinated, NOT wind pollinated!
It is more that trees need to reach a certain size to produce fruit.
There is a theological and scientific answer to the question. Opinions will not always align with our own. I will give you my perspective and the supporting documentation. Everything has a season. To quote Ecclesiastes 3:1-8 and Psalms 126:5
“For everything there is a season, and a time for every matter under heaven: a time to be born, and a time to die; a time to plant, and a time to pluck up what is planted; a time to kill, and a time to heal; a time to break down, and a time to build up; a time to weep, and a time to laugh; a time to mourn, and a time to dance; a time to cast away stones, and a time to gather stones together; a time to embrace, and a time to refrain from embracing; a time to seek, and a time to lose; a time to keep, and a time to cast away; a time to tear, and a time to sew; a time to keep silence, and a time to speak; a time to love, and a time to hate; a time for war, and a time for peace”
Psalms 126:5
“5 Those who sow with tears will reap with songs of joy.”
We also know in science we also believe in structure
" the nitrogen-containing bases adenine (A) and thymine (T) pair together, and cytosine (C) and guanine (G) pair together . The binding of these base pairs forms the structure of DNA."
To be more specific i will quote Base Pair
“base pair consists of two complementary DNA nucleotide bases that pair together to form a “rung of the DNA ladder.” DNA is made of two linked strands that wind around each other to resemble a twisted ladder — a shape known as a double helix. Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases: adenine (A), cytosine (C), guanine (G) [GWA-NeeN] or thymine (T). The two strands are held together by hydrogen bonds between pairs of bases: adenine pairs with thymine, and cytosine pairs with guanine.”
We also know how common nitrogen is since 78% of our atmosphere is nitrogen. Much of the world is covered in H20 and hydrogen in the water is very abundant. Sugars are available in many forms eg. Fruit.
We also know
" One copy of the human genome consists of approximately 3 billion base pairs of DNA, which are distributed across 23 chromosomes. Human chromosomes range in size from about 50 million to 300 million base pairs. Because the bases exist as pairs, and the identity of one of the bases in the pair determines the other member of the pair, scientists do not have to report both bases of the pair — which is why DNA sequence is typically represented as single strings of letters. DNA sequencing involves determining the exact order of the base pairs across a DNA segment of interest or across an entire genome. A signature goal of the Human Genome Project was to generate the first high-quality sequence of the human. The effort was successful in generating a such a sequence for over 90% of the human genome, but it took nearly two more decades to sequence the remaining bits of the human genome — which were heavily enriched for highly repetitive and difficult-to-sequence stretches of DNA. "
I’m suggesting we are looking at a structured system much more complexed than our best computers. A planet called earth perfectly placed in the goldilocks zone that is just perfect for human beings. Everything follows its structure here. The system has aseries of checks and balances to ensure it continues to operate as designed.
“Fruit set has traditionally been attributed to the action of three hormones, auxin, and/or gibberellin, and/or cytokinin”
I
(Mariotti et al., 2011).
" Fruit Set
Fruit set is the first step in fruit development; it is established during and soon after fertilization. Seed bearing plants have a unique double fertilization event with two pollen nuclei fertilizing the embryo and the endosperm (Dumas et al., 1998; Raghavan, 2003; Hamamura et al., 2012). The role of hormones during embryo development and seed maturation has been well reviewed (for example: Gutierrez et al., 2007; Sun et al., 2010). The fertilization event leads to the development of the seed that de-represses cell division and fruit growth in a synchronized manner (review: Fuentes and Vivian-Smith, 2009). Fruit set has traditionally been attributed to the action of three hormones, auxin, and/or gibberellin, and/or cytokinin (Mariotti et al., 2011). Application of these hormones alone can trigger fruit development to a certain extent and, in many plant species, application in combination will induce normal fruit growth even in the absence of fertilization (parthenocarpy; Nitsch, 1952; Crane, 1964; Gillaspy et al., 1993; Vivian-Smith and Koltunow, 1999), indicating that an interplay between these hormones is necessary for fruit set and fruit growth. In many species, auxin and cytokinin levels in the seed increase during seed development until maturity (Nitsch, 1950; Blumenfeld and Gazit, 1970; Varga and Bruinsma, 1976; Yang et al., 2002; Devoghalaere et al., 2012) and in pea, removal of the seed leads to reduced gibberellin biosynthesis in the pericarp (García-Martínez and Carbonell, 1980; Ozga et al., 1992). These observations led to the “seed control” hypothesis where the seeds communicate through hormones to the surrounding tissue(s) to promote fruit growth through firstly cell division and later on cell expansion (Ozga et al., 2002).
At the molecular level, the main advances have been on how gibberellin and auxin pathways interact to promote fruit set in both dry fruit, such as Arabidopsis thaliana (Arabidopsis), and fleshy fruit, such as tomato (de Jong et al., 2009a; Carrera et al., 2012; Ruan et al., 2012). Early studies showed that elevated levels of gibberellins and auxin are present in fruits from plants that exhibit parthenocarpy (Talon et al., 1990) and auxin levels increase during seed development while gibberellin levels increase in the ovaries following fertilization (Olimpieri et al., 2007; Hu et al., 2008). In Arabidopsis, fruit development induced by auxin occurs solely through activation of gibberellin signaling and the current, simplified model, of auxin and gibberellin action is the following: auxin, synthesized in the ovules on fertilization is transported to the pericarp where it induces gibberellin biosynthesis (Zhao, 2010). In turn, the newly synthesized gibberellin will lead to the release of growth repression (Fuentes et al., 2012). There are additional layers of regulation, for example, it has been shown that a threshold level of gibberellins in the gynoecium is required to initiate auxin biosynthesis, providing a feedback loop (Vivian-Smith and Koltunow, 1999). Tomato fruit set can be achieved by application of auxin or gibberellin. Auxin appears to act partly through gibberellin, as it can induce gibberellin biosynthesis early during fruit development (Serrani et al., 2008), but each hormone seems to also play a specific role on its own. Auxin-induced fruit contain many more cells compared to gibberellin-induced fruits, which contain fewer larger cells (Bungerkibler and Bangerth, 1983). One of the key players in gibberellin–auxin crosstalk is an auxin response factor (ARF), SlARF7, which when mutated causes parthenocarpic fruit development. The mutated fruit display a thick pericarp with large cells having a similar appearance to gibberellin-induced fruit. Molecular analysis has showed that SlARF7 was partly controlling both auxin and gibberellin signaling (de Jong et al., 2009b, 2011). This pathway was further characterized through the analysis of the tomato procera parthenocarpic mutant, with a constitutive gibberellin response, and indicate that activation of the gibberellin signaling pathway after fertilization also controls SlARF7 expression (Carrera et al., 2012).
Cytokinin levels also increase after pollination (Matsuo et al., 2012). Although cytokinins are generally considered to play a critical role in the stimulation of cell division during fruit development (Wismer et al., 1995; Srivastava and Handa, 2005), very few experimental data support the involvement of this hormone in the initial cell division phase of fruit growth (Mariotti et al., 2011). It is well known that cytokinin promotes cell proliferation at shoot apical meristems and interact closely with auxin (Murray et al., 2012) and are likely to function in a similar manner in the developing gynoecia (Lindsay et al., 2006; Bartrina et al., 2011). A recent study in Arabidopsis showed that cytokinin plays at least two roles during fruit development: an early proliferation-inducing role at the medial region of the developing gynoecia and a later role during formation of fruit valve margins (Marsch-Martinez et al., 2012). Finally brassinosteroids might also have a role in fruit set (Fu et al., 2008), however, the interaction with other hormones has not been investigated.
While auxin, gibberellins, and cytokinin levels are increasing at fruit set, abscisic acid (ABA) levels decrease (Hein et al., 1984; Kojima et al., 1993). Consistent with these observations, a transcriptomic analysis showed that mRNA levels of several ABA biosynthesis genes decrease after pollination, while expression of ABA degradation genes increases (Vriezen et al., 2008). ABA has also been shown to counteract the effect of gibberellin on fruit set in pea (García-Martínez and Carbonell, 1980). Expression of ethylene biosynthesis and signaling genes also decrease after pollination while in unpollinated tomato ovaries ethylene biosynthesis and signaling genes are highly expressed.
Overall, these data demonstrate that fruit set relies on a fine balance between plant hormones; the concerted action of auxin and/or gibberellin and/or cytokinin (dependency toward a specific hormone will likely depend on the plant species) will ultimately lead to activation of core cell cycle genes. We can also speculate that ABA and ethylene could have an antagonistic effect on fruit set but this will require further investigation (Figure 1A).
Fruit Growth
The developing seed continually sends signals to the surrounding tissue to expand and there is usually a positive correlation between seed number and fruit size (Nitsch, 1970). The developing fruit must also signals back to the rest of the plant so that it is provided with enough nutrients and does not abort. The extent of growth of the fruit from anthesis to maturity is extremely variable; in some species the fruit enlarge relatively little while in others they may increase in volume many thousand times. Unique to fleshy fruit, concomitant with cell expansion, there is an accumulation of storage products and an increase in sugar accumulation (Coombe, 1976). While fruit expansion is a key event, there is little literature covering the role of hormones in the transition for the division to the expansion phases and to the sustained growth of the fruit. Drawing on literature outside the fruit environment it is clear that cell expansion is regulated by auxin, gibberellin, and brassinosteroid (Davies, 2010; Pattison and Catala, 2012).
Cell enlargement depends on both cell wall loosening and increases in turgor pressure (Cosgrove, 2005). While auxin mostly controls cell division during fruit set, it is thought to play an important role during the growth phase by influencing cell enlargement together with gibberellins (Csukasi et al., 2011). In tomato, the maintenance of auxin gradients, through the precise localization of auxin transporters, such as the PIN transporters, will be essential for fruit growth (Pattison and Catala, 2012). A transcriptomic approach focusing on the cell expansion phase revealed that in the growing exocarp and locular tissues, a range of cell wall-related proteins are up-regulated during the expansion stage of the fruit, as well as sugar transport proteins and various glycolytic enzymes. Some genes belonging to the expansins, endo-xyloglucan transferase and pectate lyases families have been shown to be regulated by either auxin, gibberellin, or both in tomato (de Jong et al., 2011; Carrera et al., 2012). A genome-wide approach in apple, focusing on the role of auxin during cell expansion, showed that auxin action potentially involves an ARF gene, which is linked to quantitative trait loci (QTLs) for fruit size (Devoghalaere et al., 2012). ABA has also been associated with the expansion phase in tomato (Gillaspy et al., 1993) and ABA-deficient mutants have a reduced fruit size (Nitsch et al., 2012). The source of these hormones originates mostly from the seed and has to be transported to the surrounding tissue and/or is synthesized directly in the expanding tissue but, expect for auxin, our current knowledge is, however, limited in this area.
Fruit Maturation
Fruit maturity is a developmental point where the fruit has reached the competence to ripen, but has yet to start the ripening process. Auxin and maybe cytokinin appear to be key regulators of fruit maturation. Genetic studies have shown that the tomato ripening inhibitor (rin) mutant that displays a non-ripening phenotype, have higher levels of auxin and cytokinin at breaker stage compared to wild-type fruit (Davey and Van Staden, 1978; Rolle and Chism, 1989). The suppression of a rin-like MADS-box gene in apple (Ireland et al., 2013), resulted in a maintenance of high auxin concentration during fruit maturation and fruit that did not ripen (Ireland et al., 2013; Schaffer et al., 2013). In Arabidopsis and Brassica napus, a low auxin is required for seed dehiscence (pod shatter) to occur (Chauvaux et al., 1997; Sorefan et al., 2009). A mutation in INDEHISCENT (IND) results in high levels of auxin within the valve margins of the dehiscence zone compared to wild-type controls and it has been postulated that this high intracellular auxin at least partially inhibits dehiscence (Sorefan et al., 2009). In tomato, reduction of auxin by the over-expression of a Capsicum chinense auxin-conjugating enzyme (GH3) leads to decreased auxin and an increased sensitivity to ethylene at an earlier stage of development (Liu et al., 2005). In strawberry, when achene’s are removed from immature fruit, precocious ripening of the receptacle occurs (Given et al., 1988), this ripening can be stopped by the application of exogenous auxin. During fruit growth, auxin levels in the seed are higher than in the surrounding fruit tissue (Devoghalaere et al., 2012) and this suggests as the seeds become dormant, auxin biosynthesis or transport to the rest of the fruit is inhibited, allowing the mature fruit to ripen. This appears to be supported across fruit species as addition of auxin to mature fruit invariably delays ripening (Vendrell, 1985; Manning, 1994; Davies et al., 1997; Aharoni et al., 2002). It should also be noted that although seeds have a strong influence on maturity, parthenocarpic fruit still ripen suggesting a developmental regulation may also be involved.
The role of cytokinin during fruit maturation is less well documented but cytokinin-deficient Arabidopsis fruit show non-synchronous ripening with fewer viable seeds compared to controls suggesting cytokinin also has a role in the regulation of silique maturation and ripening (Werner et al., 2003). Finally decreases in free cytokinin and auxin levels are also observed before ripening in orange and grape (Minana et al., 1989; Bottcher et al., 2011).
One of the challenges in future work will be to better understand the molecular mechanisms underlying fruit maturation and interaction between these hormones.
Fruit Ripening/Senescence
The progression of fruit ripening or senescence is a complex process involving changes to the metabolic and physiological traits of a fruit. In all fruit, in the tissue surrounding the seed, there is a color change and a change in cell wall composition causing either a dehiscence or a softening (Klee and Giovannoni, 2011). Unique to fleshy fruit there is often a breakdown of stored carbohydrates to sugars and a decrease in acidity along with an increase in flavor and aroma volatiles (Klee and Giovannoni, 2011). The control of ripening appears to be achieved predominantly through the ripening hormones ABA and ethylene (reviews: Fedoroff, 2002; Giovannoni, 2004; Setha, 2012), ethylene being the most studied. Fruit types that have a strong requirement for ethylene to ripen such as tomatoes, peaches, bananas, apples, and melon have previously been labeled climacteric and the role of ethylene in both these fruit types has been extensively reviewed (for example, Bapat et al., 2010; Paul et al., 2012). In peaches and tomato, indole-3-acetic acid (IAA) has also been reported to have some crosstalk with ethylene during ripening as (i) production of ethylene can be concomitant with an increase of IAA and (ii) auxin-signaling components can be up-regulated by ethylene and vice versa (Jones et al., 2002; Trainotti et al., 2007). In fruit that have a lower requirement of ethylene to ripen (referred as non-climacteric fruit such as grape and citrus), ABA appears to have a stronger role (Setha, 2012). It has been shown that in the climacteric fruits tomato and banana, there is an increase in ABA preceding an increase in ethylene. Exogenous application of ABA induces ethylene through the biosynthesis genes (Jiang et al., 2000; Zhang et al., 2009), while a suppression of ABA leads to a delay in fruit ripening (Figure 1B; Sun et al., 2012a). In the dry dehiscent fruit Arabidopsis, again ABA increases with silique maturation (Kanno et al., 2010) and has been linked with the promotion of dehiscence, an ethylene mediated event (Child et al., 1998; Kou et al., 2012).
While there is a considerable amount of literature on fruit ripening, researchers have often only focused on a small number of physiological changes to document the ripening process. For example color change and/or fruit firmness are often used as a surrogate for ripening, with other ripening characters completely overlooked. It is becoming clear that some ripening traits are independently controlled from each other (Johnston et al., 2009; Ireland et al., 2013). The use of single physiological marker(s) may hence lead to a misrepresentation of this complex process. Here we have summarized the literature based on how different traits respond to hormones rather than considering ripening as one single process.
Sugar Accumulation
There is little literature on the hormonal control of starch hydrolysis and the resulting sugar accumulation. There have been a number of studies that have documented the metabolic changes that occur during maturation and ripening (Fait et al., 2008; Osorio et al., 2011, 2012), though the link between hormonal control and metabolite accumulation is limited; however, Johnston et al. (2009) observed in apple that, while this could progress independently of ethylene, it was highly sensitive to ethylene. In melon, the application of exogenous ABA was shown to promote starch hydrolysis (Sun et al., 2012b), different from growth section, however, this was confounded by the fact that the ABA also increased the ethylene levels.
Color Change
Much of the literature documents the control of color change during fruit ripening. This is achieved by a combination chlorophyll loss (degreening) and production of secondary color metabolites such as carotenoids and anthocyanins. Color change in many fruit species is associated with an increase of ABA and/or ethylene. In apple, the degreening occurs independently of ethylene but ethylene can accelerate the process (Johnston et al., 2009). Citrus and melon also both require ethylene for the degreening of the skin. The production of secondary color metabolites is strongly ethylene regulated in tomato, though some intermediates can be produced in the absence of ethylene. Application of ABA to tomato fruit results in an enhanced onset of breaker stage compared to controls, further implicating ABA as being positive regulator of ripening in tomato (Buta and Spaulding, 1994). In grape and strawberry, the color change is strongly regulated by ABA (Deytieux et al., 2005; Jia et al., 2011), though application of 1-methylcyclopropene (1-MCP; an inhibitor of ethylene response) can delay this process, suggesting that ethylene may play a role (Chervin et al., 2004). There are also reports of color change being inhibited by brassinosteroids in grape and strawberry (Symons et al., 2006; Chai et al., 2013).
Cell Wall Hydrolysis
There is a considerable set of literature covering ripening related changes in the cell wall (review: Brummell, 2006). Depending on the fruit type these can manifest as a formation of a dehiscence zone, or through the softening of the flesh tissue. In each case there is a suite of cell wall-related genes that are up-regulated, and in many instances each is differentially regulated. In the case of fruit softening, loss of a single gene can be compensated by other gene action (Powell et al., 2003). In apple and melon, there are both ethylene-independent and ethylene-dependent softening which can be observed in the differential regulation of cell wall-related genes. In banana, it has been shown that ABA can act synergistically with ethylene to promote softening (Lohani et al., 2004) and in grape ABA has been shown to cause fruit softening (Cantin et al., 2007).
Studies of Arabidopsis silique dehiscence indicate that ethylene, jasmonic acid, and ABA work in conjunction with each other to promote normal floral organ abscission via the up-regulation of genes like POLYGALACTURONASE (ADPG1; Ogawa et al., 2009). In Arabidopsis, a delayed dehiscent phenotype is associated with reduction in the ability of Arabidopsis fruit to produce ethylene and that a wild-type time to dehiscence can be restored with treatment of exogenous ethylene (Child et al., 1998; Patterson, 2001). Finally salicylic acid has been shown to delay softening in banana (Srivastava and Dwivedi, 2000).
Flavor and Aroma Production
In apple, aroma volatiles are the least ethylene sensitive, and most ethylene-dependant of the ripening traits. Consistent with this, there are a significant number of publications linking the production of aroma with ethylene (Flores et al., 2002; Botondi et al., 2003; Defilippi et al., 2005; Schaffer et al., 2007). There is, however, remarkably little literature examining if other hormones contribute to the regulation of volatile production in fruit.
Summary
It is clear that there is still considerable work needed to better understand the way that hormones interact during fruit development. While there are areas that have been quite extensively covered such as fruit set and the role of ethylene in fruit ripening, there are considerable gaps in our understanding of the hormonal control and crosstalk of other areas, such as fruit expansion, endoreduplication, starch hydrolysis, and flavor development. While much of the physiology is now documented there are considerable opportunities to further our molecular understanding of these complex processes.
Conflict of Interest Statement
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest."
I’m a believer in both Science and theology for obvious reasons. Read the quotes and make your own determinations. The short answer is yes hormones trigger fruit set. I dont expect everyone to agree with everything i said and that’s no.problem as long as what i said still has some value to them. Our ideals evolve over time based on our experiences thankfully. We all are constantly learning or stagnating. I have much to learn and much to share. We don’t presume to know everything, but i do give an honest answer when asked.
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Mulberries minimize the wait time.
Silk hope yr 2.
It fruited some last year … year 1 in ground.
Buds open in the spring and bam… fruit.
I have a EU Plum and Lapins cherry… no fruit until year 7.
I have some apple trees that fruited in year 2… gold rush, novamac… and others HGG Akane that started fruiting this year year 4…after summer pruning the past two seasons.
Some can obviously mature … get to the point of being ready to fruit earlier than others.
If I could choose… i want them to all be like mulberries… get right to it
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Producing fruit requires a certain amount of energy and nutrients. A tree needs to be a certain size before it can supply the needed inputs to make a fruit without compromising on other energy and resource needs that support survival and successful competition with other plants. Trees with genetics causing them to fruit too early will not br able to successfully compete across many generations.
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Exactly, a young tree does not have enough roots or branches and leaves to feed the system by which fruit is produced. Photosynthesis drives the entire process with energy from the sun.
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My mulberry fruited year 1 but now in year 2 a snow broke it in half. Luckily it was self rooted so hopefully it spurs a new shoot. That has been the downside of mulberries for me. The bark seems to be very frail.
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Having read through the articles posted above I agree that it’s the capability to take in the energy from the sun that ultimately drives fruit setting and production. I have a small thicket of volunteer plums that seem to illustrate why sunlight makes such a difference. (Refer to the two pics below)
Prior to my intervention the trees were getting scant sunlight or nutrients to survive. Their natural tendency was to grow vertically to fight for more sunlight. I realized that if I could train them to grow more horizontally towards the east that they would be able to collect many more hours of sunlight. Today all trees of this natural thicket are very productive. Over the past five years the fruit production has steadily increased and every fruit can be harvested while standing on the ground below. Recently I completely mulched this thicket to improve its soil moisture retention and the nutrients available next growing season.
From a distance you can see looking to the west there are two mature western cedars that shade this group of plum trees. When I purchased the property in 1993 to build my home these plum trees were all growing straight up and had no fruits at all. Virtually no sunlight could reach them after about mid day due to the shade of the two cedars.
Some years later I recognized them to be plum trees but began to research why they were bearing no fruits. My hunch was that the cedar trees were taking away all nutrients as their roots are very invasive. My neighbor did not wish to remove the cedar trees but there was a Maple tree growing on my side of the property line that I could cut and lay across the several x-rests I created to serve as the ballast I could use to tie down each of the plum trees. (My research had suggested that bending and tying a vertical fruit limb over to a more horizontal direction can increase fruit production, so that was what I started doing around 2018)! So this current photo shows how each tree is trained to grow towards the east to collect maximum sun exposure.
Dennis
Kent, Wa
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More specifically, it is the ability to store enough energy - in the form of carbohydrates - that triggers fruiting. Pecan as an example has huge soft roots - almost like a sweet potato - in which to store carbohydrates. Once the roots are full, female flower initials are formed which overwinter then turn into pecan flowers in the spring.
For other plants, surplus energy triggers fruiting for the current year. Look up annual, biennial, and perennial to see how different plants handle energy storage and fruiting.
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