green immune function

The science behind plant immunity and how we in turn can use those phytochemical responses as holistic growers to help fruiting plants resist disease gets explored in the January 2015 edition of the Community Orchardist newsletter.

I want to highlight one particular bit of advice given there:
Activating multiple mechanisms with an assortment of foliar inducers is key.

The promise of "living teas" delivering calcium and silica oomph is exciting stuff.

Thoughts? Experiences? Observations?

Lost Nation Orchard
Zone 4b in New Hampshire

Nice article Michael. I wouldn't go so far as to say your comment was blasphemous. perhaps prophetic would be a better term. there is a researcher at Cornell that is working on better enhancing the jasmonic acid levels in fruit as a insect pest deterrent. it appears there is a negative relation between JA and SA levels, though I am not clear on the specifics. This is an exciting new area of research that could lead us places we've only started to realize (as a whole and scientifically speaking). looking forward to seeing scientists verify and validate holistic methods, since they haven't been able to see the forest for the trees to this point. mostly that is.

Mike Biltonen, Know Your Roots
Zone 5b in New York

Here in an obscure and seldom visited corner of Michael's forum resides a hibernating conversation holding keys to potential gateways of knowledge and practical technique which may steer agriculture through phases of disease without inelegant environment destroying chemical carpet bombing.

As one reads about how plants and trees respond to pathogen attack, you rapidly initiate into a subtle world of chemical and hormonal genetic transactions, triggered cell death, and states of induced resistance which have been studied and summarized in what seems like many hundreds of scientific publications spanning over a hundred years. Surprisingly, despite these processes being both artificially inducible, and demonstrably effective, there seems to be little public knowledge or general practical exploration in terms of developing a protocol which would allow the farmer, orchardist, or gardener to implement this powerful healing response. Therefore, let us light a new fire in this dusty room and post any and all relevant information and thoughts pertaining to SAR, ISR, and all methods of inducing these states.

I wonder if there is something of a divide in need of bridging between the people doing this research and the agriculturalist. In my mind, having free access to research publications on the internet is a tremendous asset and serves to partially erase the divide if the right questions are asked. I have been finding that each question leads to numerous others and one can begin to sense a phantasmic model of how things tend to interrelate and operate.

Personally, I came upon the concept of SAR (Systemic Acquired Resistance) while informally studying Pseudomonas siringae and the effect of UV light for a post on this forum and have come to understand that there is a great deal of highly specialized knowledge and interactive complexity which rears itself immediately upon diving into this topic.

Generally speaking, a plant will respond to a microbial pathogen by triggering something called a Hypersensitive Response (HR). If I understand this correctly, the HR trigger results in localized cell death, the production of what are known as reactive oxygen species (peroxides, superoxide, hydroxyl radical, and singlet oxygen), and the production of antimicrobial compounds at the infection site. This is interesting when one observes the visual symptoms of Pseudomonas Siringae, as it seems that certain aspects of the disease symptoms are potentially the results of the plants healing response (sunken dead patches in bark). The HR state first establishes a type of quarantine by self destructing the area of acute infection and a subsequent phase of what appears to me to be a binary resistance response is induced in the remaining cellular tissue through a hormonal trigger of Salicylic acid which activates SAR, or a Jasmonic Acid / Ethylene pathway which regulate ISR (Induced Systemic Resistance).

What is the difference between ISR and SAR?

I do not fully understand this, but ISR could be described as a plants generalized pathogen resistance. It is induced and enhanced by non pathogenic rhizobacteria. ISR requires hormones, jasmonic acid, and ethylene to maintain ISR. Jasmonic acid functions as a regulator which effects the plant response to stresses and pathogen attacks. Interestingly, Jasmonic Acid can form as a volatile compound which off gasses and warns / signals nearby plants to trigger their defenses. Ethylene induces plant responses which seem to reduce inessentials: rapid leaf abscission, fruit fall, things of this nature...

This is off topic, by perhaps the black stem borer is an exploiter of the ISR signaling.

SAR is an acquired resistance and has been compared to an immune system which has received a vaccination. It is activated by pathogen exposure which is recognized by receptor proteins. SAR once activated confers a prolonged degree of immunity to a wide spectrum of pathogens and affords curative actions within the plant. SAR is triggered by Salicylic Acid hormones which trigger a number of genes in the PR family. These can be antimicrobial, some PR genes dissolve the cell walls of pathogens, some are antibacterial, anti fungal, and antiviral. They possess a number of compounds effective against additional pathogens and they also function as pathogen signalers which induce
the formation of lignin barriers which entomb infecting threats. An infection is required for the induction of SAR and this state can potentially be successfully triggered with a highly diluted aspirin foliar spray (1/10,000 ratio).

Karn Piana
Zone 7 Semi-Arid Steppe
Northern New Mexico



Edited 2 time(s). Last edit at 07/18/2018 06:11AM by Karn Piana.

Earlier, in the forum postings regarding light induced SAR, I came across a distinction between SAR and ISR which drew a line between the type of pathogen attack. As I understand the issue, Salicylic Acid induced SAR is triggered by attacks of pathogenic microorganisms, while the rhizobacterial ISR is triggered by wounding and necrotrophic pathogens such as gray mold (Botrytis cinerea). This is a very complex process and it has been challenging to find total comprehension due to the fact that these processes seem to be something akin to sophisticated orchestrations or cascading myriad actions involving a host of interrelated phytochemical constituents. I will reach an insight and then, as I read more, call that insight into question due to seeming contradiction in another publication. For example this necrotrophic distinction between ISR and SAR was something I encountered many weeks ago, but subsequent studies have passingly mentioned SAR responses to necrotrophic attacks (I no longer have that publication to refer to) and the comprehension once again blurred.

Currently, I am reading a publication titled "Induced systemic resistance (ISR) in plants: Mechanism of action", by Devendra K. Choudhary, Anil Prakash, and B. N. Johri in order to further understand ISR. I have gone through a number of articles on this subject and I have found this one useful for it's definitive nature and it's coverage of distinction between ISR and SAR. In my current state of ignorance, ISR is more complex, nuanced and mysterious than SAR. SAR seems like a more easily comprehended chain reaction whereas ISR is, again, orchestral and enigmatic. I have many questions and I do not feel satisfied with my simplistic reduction of ISR to wounding and necrotrophs. For example, ISR also utilizes ethylene signaling to communicate with nearby plant communities and, possibly, to signal predators, or to produce unpleasant tasting secretions...

With ISR, one is also looking at the role of a diverse population of non pathogenic rhizobacteria in tree immunity and health equiibrium within and surrounding an antagonistic trophic microbial environment of plant roots. These are known as plant growth-promoting rhizobacteria (PGPR). The rhizobacteria not only suppress, consume and destroy pathogens in the soil but also activate enhanced defense within the plant. Earlier, I was posting on this forum on the topic of adding diluted sugars to the root zone of trees.. The benefits conferred resembled that of mycorrhizal fungi, but it would seem that what was occurring was that the sugars provided the food source for a massive population increase in bacteria. I wonder if the experiment I referenced was describing a method of propagating PGPR.

Karn Piana
Zone 7 Semi-Arid Steppe
Northern New Mexico



Edited 1 time(s). Last edit at 07/27/2018 08:49PM by Karn Piana.

Appreciate you're digging deep in the science archives here to further our understanding of plant resistance mechanisms, Karn. My simple rendition of explaining these distinctions falls along these lines. I wrote this recently for a consult report for a medicinal herb farm . I'm aware of the ethylene pathway as being a kind of in-between response. Again, the take home point here remains that multiple mechanisms deliver a more complex immune response in our fruit trees. That's the thing health-oriented growers need to understand.

"The immune function of plants has both an innate aspect and an adaptive aspect. What's known as systemic acquired resistance (SAR) is triggered by environmental stressors. Be it insect, disease, mechanical wounding, or severe climatic conditions. SAR invokes the medicine of the salicylic acid pathway, the final result of which are phytoanticipins. These secondary plant metabolites are important medicine, to be sure, bought about by environmental reality each and every time. What's known as induced systemic resistance (ISR) is triggered by holistic elicitors on the surface of the plant and mycorrhizal fungal "tickling" within the root cells of the plant. Multiple mechanisms of ISR at play invoke the jasmonic acid pathway, leading to production of phytoalexins. These adaptive resistance metabolites are primarily phenol compounds such as terpenoids, flavonoids, and alkaloids. Exactly what is desired from most healing plants!"

Lost Nation Orchard
Zone 4b in New Hampshire

Thanks Michael.

One of the most compelling and rewarding aspects ​of reading the​​ web​s of connectivity ​amongst the ​myriad ​organisms forming the rhizosphere is how conducive this model is to free associative thought. A singular area of inquiry can be integral to several others and one begins to see an architecture of pattern and relationship begin to resolve and lead into labyrinths of deeper inquiry and potential.

Plant immunity is a complex and specialized subject to which ​brilliant and dedicated minds may expend years of life investigating the role of an isolated gene within a microcosmic dance of antagonisms, instigations, and communications. The​se dynamics are swampy vortex of ​fugal​ inte​​racti​vity amongst different kingdoms of biology; and they lead to the instigation of a cohesive resistant state against those pathogens which would break apart the sustaining chains forming the foundations of their very existence.

​ISR and SAR are innate in nature whether we are aware of them or not. ISR can be argued to be intrinsic to holistic practice already with regard to an enlightened stewardship of the fungi and beneficial bacteria inhabiting the rhizome. SAR, possibly, may represent an advanced inducible tier of tool against diseases and stress​. I still find the distinctions between what each state covers confusing as so much of this information describes contradictory parameters and overlap between the two vaguely observable reactionary conditions, but this lack of comprehension is certainly due to my own ignorance and unfamiliarity with basic foundational concepts which would likely clarify some of this fog.

For example, when looking at the relationship between ISR and SAR one encounters the term "mutual antagonism". In daily life this means something like a shared dislike or opposition, but in biology the definition becomes, " A relationship in which the effect of competition between two or more species (interspecific competition) exceeds that of competition within each species (intraspecific competition)". In chemistry mutual antagonism is defined as, "Mutual opposition in action among structures, agents, diseases, or physiologic processes". Or, "A situation in which the combined effect of two or more factors is smaller than the solitary effect of any one of the factors."

For my mind, these kind of definitions allude to a host of other subtle meanings and understandings that may not be entirely accessible to a dilettante such as myself. The point then, I think, is to boldly take the methods under experiment and apply them to an operational problem with an idea similar to the one that one not need to comprehend the molecular structure of gasoline in order to use it to power an engine.

So, rather than continue this airy preamble, I want to share the abstract and introduction to an article titled, "The Interactive Effects of Arbuscular Mycorrhiza and Plant Growth-Promoting Rhizobacteria Synergistically Enhance Host Plant Defences against Pathogens", which elaborates on plant growth promoting Rhizobacteria (PGPR) and their relationship to arbuscular mycorrhiza and plant roots. A three kingdom symbiosis. Here is another article from the European Journal of Plant Pathology titled, "Plant Responses to Plant Growth-Promoting Rhizobacteria." It discusses ISR and SAR in a useful and clear way, and then goes on to discuss the roles and functions of the bacteria and their effect on the roots, the exudates they secrete, the role of these exudates in attracting other microorganisms and in responding to environmental stressor in a combined action with arbuscular mycorrhiza.

​

Karn Piana
Zone 7 Semi-Arid Steppe
Northern New Mexico



Edited 3 time(s). Last edit at 08/29/2018 06:49PM by Karn Piana.

ISR is innate, SAR is adaptive. SAR follows the salicylic acid pathway and is associated with Hypersensitive Response (programed cell death / Harpin protein / H202), while ISR is an orchestral melange between rhizome microorganisms and the plant.

Some examples of immune processes in ISR arguably might be:

• The degradation and rupture (lysis) of attacking cellular membranes through enzymes, viruses, or osmotic mechanisms.

• Siderophore metabolites which chelate the iron within the rhizosphere, make it plant available, and deprive it from competing pathogenic microorganisms. Siderophore metabolites are the secretions of bacteria, yeasts, and fungi.

• Other ISR phenomena are the production of phytoalexins (antimicrobial / antioxidative compounds), fungistatic and bacterio-static excretions, predation (nematode trapping fungi, soil amoeba lysing into and consuming pathogenic fungi), and parasitism (inter-fungal parasitism where one fungus will immobilize and penetrate into another differing type through a lytic process).

With ISR, it seems we are describing a larger spectrum of activities than those found exclusively in phytochemical pathways.

I found a great resource for anyone interested, Biocylopedia, and I've been referring to an article called, "Antagonism, the Mechanism of Bio-Control". Antagonism in phytopathology describes the action of an organism that suppresses or interferes with plant pathogens. When one encounters the word antagonism in microbiology it seems to describe an inhibitory relationship that is not always or even often negative. Many beneficial bacteria and fungi are described as antagonistic. So, again, I am confused by what is meant by a "mutually antagonistic" relationship between ISR and SAR.

It seems now that there is overlap and these states are not binary due to the appearance of ISR as an innate and complex fugue that is defined by the microorganisms surrounding the roots and phytochemical relationships between them and the plant itself. Am I mistaken in thinking that ISR and SAR can coincide and overlap?

More from Biocylcopedia:
"Vesicular-arbuscular mycorrhizal fungi retard the development of pathogens in root systems and increase disease severity in non-mycorrhizal roots. This systemic influence can be attributed to better nutrition, enhanced plant growth and physiological stimulation in mycorrhizal plants. Roots colonized by a VAM fungus exhibit high chitinolytic activities. These enzymes can be effective against the other fungal pathogens. Under direct influence of mycorrhizal fungi, root tissues become more resistant to pathogenic attack. This induced resistance is strictly limited to the site of host-endophyte interaction and will only affect soil-borne pathogen. Thus, application of selected VA mycorrhizal fungi offers the possibility of increasing resistance against soil-borne pathogens (Dehne, 1982)."

The reference to chitinolytic activities is describing the ability to dissolve the cellular membrane of pathogens (chitin = beetle wing / fingernail / fungi cell wall -lytic = disintegration of cell wall). It would appear that much of the arsenal of fungi and other microorganisms consists of melting or digesting through barriers in order to induce havoc.

Karn Piana
Zone 7 Semi-Arid Steppe
Northern New Mexico



Edited 2 time(s). Last edit at 09/01/2018 05:24AM by Karn Piana.

This is just a great post. I am engaging with a struggling orchard that has high fungal disease pressure. Our main plot is to massively inoculate the phyllo-sphere as well as the soil surface in order to bolster the ecology that will then support the SAR in full capacity. Also expecting to improve soil health over all. thanks for the thoughtful inputs.