This is really great! Thanks for sharing this review. I find the epigenetics involved here particularly interesting. Much work to be done
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@clarkinks Looks with a great review of the theory of grafting with lots of references.
I am an Engineer with an implantable medical devices company and also an Adjunct Professor at a local University and I am also insatiably curious so, I really like how that is backed by why.
I will bookmark it and consume it later when I have time to consume it carefully.
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Thanks, this is some deep reading. But if anyone hasn’t had enough here is another perspectivegrafting at a cellular level.pdf (846.9 KB)
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thanks, That’s a nice document.
Worth mentioning though, that some of the diagrams picture non woody(tree) plants. Like grasses and vegetables.
And thus are not completely representative of fruit tree grafting. (these diagrams lack hardwood/sapwood and secondary xylem for example.)
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Yes, you’re right, but it has some more basic discussion about the process of healing. It would be better if it dealt with woody plants, but I also wish the other article had better illustrations. So, I guess it’s about piecing together information.
I also notice that the plant Arabidopsis seems to be a research focus since it’s mentioned in both texts. No idea how that particular plant was chosen.
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Arabidopsis is one of the most common plant models used in research. It’s genome was the first plant genome to be sequenced, see below reference.
https://www.nsf.gov/od/lpa/news/press/00/pr0094.htm
"During the last 8 to 10 years, Arabidopsis thaliana has become universally recognized as a model plant for such studies. Although it is a non-commercial member of the mustard family, it is favored among basic scientists because it develops, reproduces, and responds to stress and disease in much the same way as many crop plants.
What’s more, Arabidopsis is easy and inexpensive to grow, and produces many seeds; this allows extensive genetic experiments, often involving tens of thousands of plants. Also, Arabidopsis has a comparatively small genome, thereby simplifying and facilitating genetic analysis. Compared to other plants, it lacks the repeated, less-informative DNA sequences that complicate genome analysis."
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Thanks, that answers that question! It’s great to have the depth of knowledge available here.
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I couldn’t agree more!
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Really good information. TY for posting this for us to read.
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My philosophy is to take everything in growing plants to the next level. These documents are the beginning of understanding this process. The thing I’ve learned about grafting pears and working with pear rootstocks is we have a huge opportunity to improve what we are doing. My fruit production is frequently very heavy. There are even crops on severe drought years now. Focusing on pears has given me a lot of understanding about other things as well. Sure i grow and graft everything like everyone here but i try to focus on pears. There is still a lot we dont know. We are also doing a lot of things right. Grafting, nutrition, soil science , all part of the bigger picture. If we don’t discuss these things in detail on this website then where else can we take things to this level? There are some of the most talented fruit growers in the world on this website. @scottfsmith deserves all the credit for giving us a website to meet.
Something I should bring up is when a plant heals at the graft union it attracts certain pests here in Kansas like the grasshopper. Have had the graft girdled when i removed the grafting tape. Why do rabbits and voles girdle our trees? That nutrition draws things to our orchards. In the case of my wild callery and bet pears they go untouched in an orchard full of rabbits and voles unprotected. It’s one of my goals to try and figure out why insects are attracted to grafts. It’s most likely increased sugars. I’m close to figuring that out and while doing that we may find out why some grafts fail. Imagine if we needed to feed a plant something as simple as sugar but we didn’t know that. Im not suggesting feeding trees sugar is wise in this case but carbohydrates and sugars i believe are worth looking into. Transport in Plants
Think about why we eat fruit.
Sometimes 8 year olds like the one who asked the question below ask the right questions in simple and straight forward manner. Why do trees have sap? | Ask Dr. Universe | Washington State University
Dr. Universe: Why do trees have sap? -Aliyah, 8, Kirkland, WA
Dear Aliyah,
Just as blood moves important stuff around the human body, sugary sap moves important things around a tree.
My friend Nadia Valverdi told me all about it. She’s a researcher at Washington State University who studies how apple and cherry trees survive in different environments.
When we eat food, like a delicious apple or a handful of cherries, we get important nutrients.
Nadia Valverdi, WSU researcher. Credit: TJ Mullinax/Good Fruit Grower
Along with some help from the digestive system, our blood helps carry nutrients to different parts of the body to keep us strong.
Trees need nutrients, too. They use their roots to suck up nutrients and water from soil. They also have the ability to make their own food: sugars.
Trees absorb sunlight through their leaves and can use this energy from the sun to make sugars from water, carbon dioxide gas from the air and a few other ingredients.
A lot of sugars are made in the leaves, but they don’t do the tree much good if they just stay in one spot. The sugars have to get to other parts of the tree to help it survive. That’s where the sap comes in.
“Its main task is to make sure that every organ is well-fed and growing,” Valverdi said.
While our blood moves through tube-like veins and arteries, sap flows through two different tube-like parts of the tree.
One part, called xylem, moves important stuff like water and nutrients from the bottom of the tree to the top—from its roots to its leaves.
The other part, called phloem, moves important stuff from the leaves to other parts of the tree, such as the branches, roots and fruit.
I asked Valverdi how a sticky, gooey liquid like sap could move through these tubes. After all, sap doesn’t seem to move on its own.
It turns out that some liquids, such as sap, can move through a narrow space without any help from gravity or other outside forces.
This can happen in plants or trees when sap escapes through tiny, microscopic holes in the leaves. When sap molecules escape the leaf, more sap molecules move in to fill the empty space and keep the sap flowing upwards through the tree.
It’s a phenomenon we find happening everywhere from house plants to big apple trees to celery stalks.
“All trees and plants have sap,” Valverdi said. “The difference is that sometimes in big trees, we can see it with our eyes because it is more gooey.”
One really gooey kind of sap you might have seen before comes from sugar maple trees. You may even put it on your pancakes or waffles. You guessed it, maple syrup is a kind of sap.
Just like us, trees have systems that help them move important stuff around. These systems help the plants survive. When trees do well, that’s good for us, too. They do so many things for us from making the oxygen we all breathe to giving us delicious fruit to eat.
Sincerely,
Dr. Universe
Not to overly simplify things but when we realize most of these systems are in fact built around sugars it helps us to be better at what we do as Orchadists or Gardners. Honey bees are attracted to the sugar in the form of necter in the blooms, rodents are attracted to sugars in the barks , insects and animals are attracted to sugars in the fruits. Sure sugar is only a small part of the big picture. Grafting is done at a specific time for a reason. Temperatures are ideal for grafting during limited times of the year. Sunlight is another factor , like carbon dioxide and water. Look at the diagrams below again. All of these concepts are simple but we must take the time to analyze them.
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Fascinating info. Observant grafters have long noticed that interactions vary considerably between individual stock/scion combinations. I tried a new cultivar that died to the trunk most winters. After five or six years of that, I concluded it wasn’t hardy enough here and regrafted with something that is. But I decided to give it one more chance and grafted it on a frankentree, where it thrived and bore fruit in a couple years. It’s never shown any trace of winterkill, and I’ve also grafted it to other stocks with no problem. As for the original stock, the replacement also thrived and is now bearing. Apparently there were some personality conflicts going on. A bit of divorce and remarriage solved that!
Here is an interesting example demonstrating the interactions between stock and scion. I think it’s from one of Niels Hansen’s publications:
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Rootstock can have a huge influence over scion growth. This is a difficult to graft rootstock. Successfully grafted it using a tbud after many failed attempts. The graft would wilt many times but did take. My small yellow unknown pear was the pear wood that took. It’s a bridge species allowing anything to be grafted. The rootstock is a genetically unique callery. The growth of the tree comes from the rootstock.
https://www.jstor.org/stable/2435772
"JOURNAL ARTICLE
Studies on Callus Tissue
Dontcho Kostoff
American Journal of Botany
In studying the callus of intergeneric and interspecific simple whip grafting macroscopically and microscopically, the following phenomena were observed: 1. The callus tissues joining the scion and the stock are chiefly the product of the stock. 2. There are large accumulations of starch at the base of the scion just above the callus line. 3. During the growing together of stock and scion, the latter produces various types of proliferations-tumorical formations and numerous small leafy shoots or roots-near the callus line. 4. The callus is asymmetrical, due to the great accumulation of food in the lowest part of the scion. 5. The cambium and its derivatives interrupt the callus line first in the lowest zone. 6. When the scion activity predominates and kills the stock, necrosis begins at the lowest zone of the joining tissues and then spreads in the stock in all directions. 7. The gradual disappearance of the cells injured during the graft operation throughout the union of the graft components is apparently due to certain lytic phenomena in vivo. 8. Nests of bacteria were observed in the callus between the scion and the stock plane only in young (15-days-old) calluses. 9. Abnormal vascular cells, either single or in groups, were frequently found in the joining tissues both in the pith region and in the proliferation tissues. 10. Abundant accumulation of sand and groups of crystals of calcium oxalate around the callus were observed. 11. When the tissue of one component is pigmented, the pigment is limited by the callus, and no effect in the other component was observed. 12. The proliferations in the callus, its asymmetry, and other phenomena observed, are interpreted as due to specificity and interactivity of the graft components. 13. While no strictly Lamarckian influence of stock on scion was observed, it was found that certain plants, which before grafting exhibited normal meiosis and produced uniform progeny, after being used as scions exhibited non-disjunction and other abnormal types of meiosis and produced a variable progeny.
Journal Information
Published by the Botanical Society of America continuously since 1914, the American Journal of Botany (AJB) is the Society’s flagship research journal. AJB publishes peer-reviewed, innovative, significant research of interest to a wide audience of scientists in all areas of plant biology (e.g., biodiversity, structure, function, development, genetics, evolution, reproduction, systematics), all levels of organization (molecular to ecosystem), and all plant groups and allied organisms (cyanobacteria, algae, fungi, and lichens)."
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For those in warmer zones how are your grafts coming along?
No grafting for me this year but thanks for bumping this very interesting post.
I’ll be honest I didn’t make it very far into reading before getting distracted by a citation that led me to finding this similarly interesting (and slightly easier to read) paper:
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Zone 9a, southern Louisiana
This is my first year grafting so take my comments with several extra strength grains of salt.
I placed about 40 grafts on 5 different trees. More than half took.
Since then I’ve lost about 10 more to drying out after I’ve gotten a foot or more of graft wood growth.
I’ve also lost some to wind.
So I think I have about 6 remaining but I’m not holding my breath for sure.
I will change how I do this next year. Some I lost after unwrapping the raffia I used to strengthen the grating point.
I still intend to try some bud grafting late August or early September.
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The rootstock i grafted over produced fruit very quickly. Years ago @fruitnut helped me out with learning to tbud. Using the small yellow pear every tree i grafted over took. The rootstock in this situation has a huge influence on the scions. The branches go horizontal like that on their own. The parent rootstock grew like that not the scion tree. The rootstock is totally influencing growth and fruiting. Attempted to infect the rootstock with fireblight and learned even in direct contact it is highly resistant showing no signs of fireblight at all.
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Do you have pictures of your grafts? Try this method Grafting large Callery and Betulifolia pear rootstocks
At this point it wouldn’t be too helpful to show photos.
Regardless of the method I used to try my first grafting this year (cleft, modified cleft, tongue and groove, raffia or not, parafilm, electrical tape or not, wax, etc.), some didn’t take which I expected.
Many took. By took I mean seeing at least 3-4 inches of new bud wood growth on the scionwood. I know the energy in the scionwood itself is often enough to get a few leaves to show, but after a few inches of branch growth it has to be connected to the parent wood.
So I got great growth on many grafts… 10 inches, 1 foot, 2 feet, even multiple laterals of 1+ feet long in single graft bud growth (I headed some new growth to get laterals).
Concerned about girdling I removed the electrical tape and raffia if present then rewrapped with parafilm.
Some grafts dried out after this and some were lost to windy days.
My thoughts:
On some grafts the raffia wrap appeared to be talking the load from new growth movement relative to the parent wood. Once that was removed, the scar tissue was not strong enough to handle the torque from wind loading.
On the dried out ones, I am also making an assumption that the scar tissue must have been interrupted or broken enough from movement to lose sufficient contact with the parent wood to feed the new growth and it dried out.
I didn’t find your long grafting writeup until last week so I did not benefit from that info. I will read before I try again next spring.
For this year I will, however, do some but grafting in late August or so…
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It might be hard to believe but this is tbat tbud from the photos above that @fruitnut gave me advice on growing several years ago. It has been a very productive 25-30 foot tall pear tree. The drought is taking a toll on everything here. We have ever increasing droughts and increased diseases and insects in this area.
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