The presence or concentration of an element in a plant does not signify that elements essentiality to the plant. Plants are limited in which elements they are able to absorb, regardless of its essentiality or toxicity to its growth. Their selective uptake of elements can be to their own detriment depending on whether the elements they take up are toxic or inert. Therefore, determining a plants essential element can not be derived purely from a present elemental composition. Micro and macro nutrients are essential groups of nutrients that can reveal a plant’s requirement of an element. But what determines a plants essential elemental criteria? According to Marschner’s Mineral Nutrition of Higher Plants, there are three criterion that must be met in order for an element to be considered essential.
The three criteria:
An element’s presence in a plant is necessary for that plant to complete its lifecycle. Without that particular element, the plant can not complete its lifecycle.
No other element can replace or substitute the function of an essential element.
The element must be directly involved in the plant’s metabolism.
If an element were to alleviate the toxic effects of another element, such as silicon for manganese toxicity, or the element were to replace another element, such as sodium for potassium, those elements could not be qualified as essential for plant growth. Most micronutrients are constituents of enzyme molecules and are therefore essential only in small concentrations. On the other hand, macronutrients are constituents of organic compounds, such as proteins and nucleic acids.
Image: The 16 essential elements required for plant life.
You completely left out the macro nutrient silica and its importance to gene expression and plant immune response. Theres alot more to it than what you listed.
@potentponics don’t worry we will be sure to discuss silicon and other beneficial elements in the future! Unfortunately it’s not considered an essential nutrients so we did not discuss it in this article.
Thanks for reading!
It very much is considered a macro nutrient in newer literature. Its incredibly important and ignoring it is a huge reason so many aquaponic people have nutrient and pest issues.
@potentponics the volume of a nutrient consumed is not a factor in the definition of an essential plant nutrient.
For Si like other nutrients the volume required is dependent on the plant therefore I refrain from saying it is always required in macro quantities
I hope this helps explain why we avoided mentioning it for essential nutrients and thanks for drawing attention to Silicon! As you mentioned and I have spoke about repeatable it is a beneficial nutrient, that is often limiting in aquaponic systems.
Accept it is tho if its required more than a few ppms for plant health its a macro nutrient.
Si is not dependent on the plant thats completely false. Plants need Si at different levels depending on the plant but they need Si to properly activate multiple plant immune system genes as well as for synthesis of many secondary metabolites. Any plant which is a huge % of all plants that has trichomes of some form or another also very much needs silica. To leave it out when discussing this topic is just silly and ignores a very important plant essential nutrient. It is always required at macro quantities for any plant tho some prefer very high levels all plants need it.
You should be mentioning it, your doing a disservice teaching nutrients and leaving it out especially when its part of a proper pH up solution for aquaponics. It very much is a plant essential nutrient just as much as nitrogen or potassium.
@potentponics I think you’re getting confused with nomenclature. Macro /micro has to deal with volume of uptake not essentiality to the plant.
For Essential nutrients there are 3 criteria.
- An element’s presence in a plant is necessary for that plant to complete its lifecycle. Without that particular element, the plant can not complete its lifecycle.
- No other element can replace or substitute the function of an essential element.
- The element must be directly involved in the plant’s metabolism.
Right now, Silicon is not widely considered an essential element, regardless if a plant uses it in macro or micro qty.
We could debate all day if scientist classifications are wrong or right but it doesn’t really benefit anyone to do that.
That is why for this blog we’ve decided to stick with discussing essential nutrients as clearly defined by various industries and in the future we will write about beneficial elements (like Silicon) separately
Not confusing anything your still to stuck on old definitions that ignore modern discoveries. The modern definition is a nutrient required for plant health above 4ppms for a macro nutrient.
But lets humor you for a second.
- Silica is needed for a healthy plants lifecycle. If it is not present multiple immune system genes are not activated, the plant can not properly form trichomes or other protective structures, the leaves are more susceptible to fungal infection and much more. Plants cant complete a healthy life cycle with out silica present its literally the most bioavailable nutrient in soil after carbon.
- No other element can replace silica for chemical function. This also is not any part of the scientific definition of essential plant nutrients as molybdenum doesn’t even meet that definition as it can be replaced with vanadium if need. Thats not at all a requimrent for definition you don’t know what your talking about.
- Silica is directly involved in plant metabolism in multiple ways from cell walls to trichome construction to root exudates its used in multiple parts of plant metabolism.
So now that we have established that your requirements are either uneducated at best like point 2 or that it actually does meet those definitions lets not misslead people into not thinking its just as important as the others you listed.
Silica is widely considered an essential element by any one who has real world commercial experience yes. It also is by much of the academic world now that we better understand how plants immune systems work as far as gene activation and SAR response. I get it you didnt learn this stuff in school but you need to stay up to date if your going to teach this stuff.
Nothing much to debate here you just need to get with the times.
“According to this strict definition, an element which alleviates the toxic effects of another element (e.g., Si for Mn toxicity), or one which simply replaces another element (e.g., Na for K) may not be described as essential for plant growth.” Marschner
I spoken about the importance of silicon for years but unfortunately regardless of how “essential” we may feel it is, by definition (see images below) it is not. It is a beneficial nutrient; One that I would not grow with out
Please cite any claims you make. As to not mislead anyone. Marschner was one of the highest respected people in his field.
Ancient out of date references from dead people are irrelevant in the face of current science. The newest definition splits macro and micro at the 4 ppm threshold. Theres literally dozens of papers on min silica levels for gene activation now this isnt a dabate at all.
Fact of the matter is it is an extremely plant essential element every bit as much as all other macro nutrients. By ignoring it your misleading people about what nutrients they need in there system.
Silica adds a week to shelf life, prevents mold, boosts yields, increases flavor, reduces bolting, reduces heat and cold stress and more to say its not plant essential is to admit ignorance.
Potassium silicate is literally half of the main pH up combination all aquaponics people should be using at this point again its every bit as essential as potassium or calcium or anything else.
Your own micronutrients didn’t even fit your own definition you don’t know what your talking about.
Thanks for the comments Steve; you should submit your complaints with current industry standards and any citations of corrections to someone who can change them.
I’m just educating people on current industry knowledge, as agreed on by the respective industry leaders. Have a great evening.
Then you should educate them on the nutrients by ppms needed for plant health not old and dead irrelevant definitions that aren’t even used any more.