Why excess rain drops alkaloid content, and what increases it

[--Shadow]

So there seems to be a general consensus that following a period of heavy rain, alkaloid content is lower. There is evidence of why alkaloids increase following drought stress, but there seem not much on what causes the decrease following heavy rain (or watering).
In helping understand what could be happening at the cell level, I will try to give a brief understanding of where and how alkaloids are stored in the plant, as well as mechanism that could be responsible for the removal or degradation of them.

Dimethyltryptamine is an indole alkaloid derived from the shikimate pathway. It is a crystalline alkaloid compound that is the product of decomposing proteins that contain tryptophan.

Alkaloids are accumulated in the central vacuole of alkaloid-producing plants after synthesis. Among its roles in plant cell function, the central vacuole acts as a storage container for water, salts, minerals, nutrients, proteins and pigments. Alkaloids frequently occur as water soluble forms, dissolved in the cell vacuole. This is where your tryptamine's are stored.

Transport of alkaloids across the tonoplast into the vacuolar space has been characterized as an active, engergy-requiring mechanism, which is sensitive to the temperature and pH of the surrounding medium, stimulated by K+ and Mg2+, and inhibited by N,N′-dicyclohexylcarbodiimid and Cu2+.
The transport of the strongly basic tryptamine into the vacuoles is probably also driven by the pH gradient. However, the mechanisms involved in alkaloid transport across the tonoplast are still poorly understood.

The low pH of the vacuole also allows degradative enzymes to act.

It is generally assumed that organic solutes are preferentially accumulated in response to drought stress because they do not interfere with metabolism. This view is held despite the relative energy cost of compatible solute synthesis being more expensive than import and translocation of available inorganic ions. In acacias, all the solutes found to increase significantly in response to drought stress were closely associated with primary C metabolism.

So that's the 'storage' of tryptamine's out of the way...

The contractile vacuole and associated membranes may be regarded as special adaptation to dilute environments, in which osmotic influx of water occurs at a rate faster than other osmoregulatory mechanisms can handle. So, if water is in excess, the contractile vacuole will remove it.

Plants also produce certain excretory materials which have to be expelled out via the stomata of leaves and lenticels of stems.

Alkaloids were considered waste products for a long time (an argument likely derived from animal physiology). However, plants are energetically efficient organisms - they simply do not waste energy in the production of compounds they don't need. The predominant activity of alkaloids in plants seems to be as defence and signalling methods to deter herbivores.
But even though there is 'use' for them, they still may be expelled in the same fashion of a waste product.

So, if DMT salts are soluble in water, then they may either get expelled with water via the stomata and lenticels, or the contractile vacuoles, or they may get degraded by enzymes as the pH of the vacuole drops...

I'm hoping someone with more expertise in these fields may be able to help validate or dispel any of these possibilities..

 

[Vodsel]

I cannot claim to have more expertise in the field, just want to leave my thoughts.

As you suggested, there's two strong possibilities - leaching and changes in enzymatic activity. There might be a third in some cases, which is that alterations in the micro-biota due to the humidity and rainfall (such as fungal development) might alter alkaloid content, but I don't think this is the main reason.

I wouldn't rule out leaching at all. We know many indole alkaloids can be easily extracted with cold water, and actually alkaloids might vanish soon in the medium leaving no trace, due to bacteria or other chemical processes.

Regarding what increases alkaloid content, we have some references that are not surprising according to what has been already said. Some mimosoids like M. Tenuiflora show higher alkaloid yields during the dry season; in phalaris grasses, the alkaloid levels are bossted by a rich nitrogen fertilization; micronutrients like Cobalt seem to have an effect in alkaloid yield (at least in some Solanaceae species, iirc).

And according to practical experience, there seems to be a correlation between non-photosynthetic metabolic processes and alkaloid production, since there's several examples of higher alkaloid yields when aerial parts of the plant are harvested in the early morning.

 

[AlbertKLloyd]

From my own studies there is indication that rain triggers active growth, and that enzyme function is then directed towards metabolism with the goal of growing, but that when there is a dry spell the metabolism slows and the plants gear towards protective alkaloid content to protect established growth.

However translocation can also occur, just like it can with various macro and micro minerals, in phalaris alkaloids tend to be concentrated in the fresh new leaves, when there is rain there is a flush of new growth and the alkaloids in the plant in general seem to be directed to the new tender growth, which can still be quite strong in content despite the decrease in plant tissues in general.

As also indicated the link between acid metabolism for respiration and alkaloid content is worth further exploration and study.

It seems though, at least to me, that there is not as much conservation in this as we would like, insofar that different species, clones, genera and families and alkaloids may all vary to a significant degree regarding metabolism.

 

[Auxin]

I've always been suspicious of the default explanation of alkaloids as defense chemicals, in many cases the alkaloid in question would be feeble or useless against both animals and insects. Its a bit like archeologists calling any unknown artifact a religious item, the cliche blind guess.

Take DMT, its a stable, easily moved compound that is easily and cheaply metabolized by ubiquitous metabolic enzyme systems to a plant hormone! DMT is metabolized to IAA (and can be further hydroxylated by subsequent metabolism, as it is in humans).
Perhaps DMT is there so when it rains and the sun comes out the plant can produce all the IAA it wants while not wasting energy making it from scratch. When the sun comes out it wants to bend toward the light, not do a bunch of work so it can bend toward the light in a little while.
Same with the phenethylamines, they look like alkaloid analogs of auxins. That could explain why genera like the gymnocalyciums be so consistent in making and storing alkaloids at a concentration too low to poison anything or even be bitter? (The Gymnos consistently contain tiny, tiny amounts of mescaline and mescaline or its analogs can be found in parts per million quantities in the Opuntias).
Perhaps some alks decrease after a rain because they were finally used for their intended purpose.

Fascinating experiments for the college student or home scientist:
¤ Get radiolabeled DMT and get it into a plant, then water the plant and stick it in the light. Does radiolabeled IAA or its metabolites appear?
¤ Oxidize mescaline in the lab, or extract mescaline metabolites from tripper pee, and test the compound in varying concentrations on plant tissue cultures.

 

[AlbertKLloyd]

While a general statement that alkaloids are defensive is overly simplistic and thus inaccurate, alkaloids are in many cases insecticidal or reduce herbivory, and are associated with reduced survivorship in animals that ingest them, this is well demonstrated for psychedelics in mammals. Likewise in many genera alkaloids are generally not present until hebivory occurs and then production increases responsively.

So in at least some cases alkaloids, including tryptamines, seem to play defensive roles, though this does not mean they do not play other roles such as relating to hormones or even carbon storage in their methyl-groups for later use in respiration.

In relation to the topic of variation due to rain and such, in some cases this correlates well with a defensive role.

 

[nen888]

^..what evidence is there for tryptamines specifically as a plant defence? ..i haven't seen any evidence of this in the acacia genus..alkaloid content in general appears to play no role, as some species contain them and others do not, while rates of predation remain similar..i don't think there's any evidence that tryptamines discourage animals from grazing..

the alkaloid as defence argument i feel is part assumption, part generalisation..despite it being widely proposed in literature..as you say AlbertKLloyd "overly simplistic"..
but this is mostly a separate topic to the OP's question, except perhaps the notion that plants have less worry of herbivores during growth/rainfall...but this is not a really strong argument either..


focusing on the OP's question, i'm afraid i have no in depth expertise, and i imagine this would be a good topic for a plant biology phd, as there isn't any clear answer out there (that i can find, at any rate)

..it's been found in the scientific literature across a wide range of plants that in general rainfall decreases alkaloids, and drought increases them..also, higher nitrogen levels increase alkaloid levels, and higher phosphorus levels decrease them..[Poppy: The Genus Papaver, Jeno Bernath ed. 1999] ..
"Our results suggest that the cultivation of medicinal plants like C. roseus in water deficit areas would increase its PRO metabolism, osmoregulation, defense system and the level of active principles. [Alterations in osmoregulation, antioxidant enzymes and indole alkaloid levels in Catharanthus roseus exposed to water deficit C. Abdul Jaleel et al 2007]

..in the case of tryptamines: i wrote in ~Phalaris = The Way Of The Future~ - Collaborative Research Project - Welcome to the DMT-Nexus

Ball and Hoveland (1988 Agronomy Journal) found, for P. aquatica:
Quote:

The order of alkaloid concentration in aerial portions of individual plants of two genotypes was: upper one-half of leaves and leaf sheaths and stems.
Drought stress caused greater alkaloid increases both in field and environmental chamber studies than did any other factor.

..a reminder, though, that phalaris toxicity in animals is no longer associated with alkaloids..

...now, i can see 2 possibilities as to what happens to the alkaloids..

1) they are expelled from the plant into the environment

2) they are metabolised into different compounds , and serve a function in this regard..

i go with 2) as expoused by Auxin:

Take DMT, its a stable, easily moved compound that is easily and cheaply metabolized by ubiquitous metabolic enzyme systems to a plant hormone! DMT is metabolized to IAA (and can be further hydroxylated by subsequent metabolism, as it is in humans).
Perhaps DMT is there so when it rains and the sun comes out the plant can produce all the IAA it wants while not wasting energy making it from scratch. When the sun comes out it wants to bend toward the light, not do a bunch of work so it can bend toward the light in a little while.

..certainly indole acetic acid is one of the primary plant growth hormones..and can be metabolised from tryptamines, or vice versa..

..this is an area rich for future bio-molecular research..

an afternote: afaik tryptamines are usually present in plants in salt form..
.

 

[jamie]

as far as I understand there is no defense role known for tryptamines in mushrooms either..

 

[--Shadow]

Great input everyone! Got me thinking many more things now...

EDIT: just tidied up this post a little, been away for a few days with no internet

I think the fact that alkaloids are low during flowering time as well, may also support the idea of them being used as as 'temporary states' to be synthesised later for plant growth. This would be a good explanation of the 'use' of alkaloids.
If the plant synthesises alkaloids in preparation for the days work ahead (photosynthesis or tropism as mentioned), then this could explain why levels of alkaloids are high in the morning and lower in the evening.

I don't think that alkaloids play no role for the benefit of the plant - evolution doesn't work this way afaik. Even though it may seem stupid to effect a herbivore after he has demolished the plant, bee stings would also fall under this category

^..still seems odd to me to go to all the trouble to make an alkaloid then let it wash away...?

Even though the plant may make alkaloids for possibly even more than one reason, washing it away may just be the only response the plant has to deal with an overwhelming influx of water.

Do alkaline's drop just after a normal period of raining/watering, or only after prolonged saturation? This would help maybe in determining whether alkaloids are 'used' following water intake, or whether they are expelled as a method to cope with 'too much water too fast'

The difference between varieties or species could be due to the difference of carbon between leaves and root and being able to adjust osmotically. Elasticity of the vacuole cell wall may play a role as well. I would be interested to see the difference between acacias in Australia vs Malaysia (where it pretty much showers every day all year - would they even accumulate significant amounts?) Previous exposure to water stress contributes to water resistance and improved recovery after stress.
The differences could also be simply the level of rhizobium bacteria on each plant..

If respiration was the method to expel alkaloids, would we find low amount first thing in the morning, whilst peaking at night? (ie does respiration mainly occur at night?)

I'm really excited about this thread guys - thank you all again for ALL input, I'm learning a ton in the process which hopefully others following this thread will also do.

 

[--Shadow]

PLANTS RESPOND TO LEAF VIBRATIONS CAUSED BY INSECTS' CHEWING
www.sciencedaily.com July 1, 2014 Source: University of Missouri-Columbia

Previous studies have suggested that plant growth can be influenced by sound and that plants respond to wind and touch. Now, researchers at the University of Missouri, in a collaboration that brings together audio and chemical analysis, have determined that plants respond to the sounds that caterpillars make when eating plants and that the plants respond with more defenses.

...I wonder how this would play on alkaloid content if:
a) vibrations influence plant growth (with the presumption that alkaloids are converted to growth hormones or similar), or
b) vibrations influence plant to produce more defenses (with the presumption that alkaloids are a defense mechanism)

 

[Psilosopher?]

This thread is a treasure trove of information.

Is there any data on how long it takes for alkaloid levels to reach normal levels after rainfall?

If not, I'll be doing around a gajillion extracts in the near future testing a bunch of variables. I'll post my results soon.

 

[--Shadow]

If we want to look at ways to increase alkaloid production in plants, it makes sense that an approach could be to increase the materials the plant uses to synthesize DMT, or to enhance the metabolic process.

To do so, we need to take a closer look at understanding alkaloid synthesis and it's metabolism... I will keep it simplified in laymans terms.

The process that leads up to the synthesis of N,N-dimethyltryptamine (DMT) basically goes like this:
Shikimic acid > L-Typtophan > Tryptamine > NMT/DMT

The question of "How to increase DMT?" seems to be preceeded by the following questions:
How do we increase Tryptamines?
How do we increase L-Tryptophan?
How do we increase Shikimic acid?

So, lets start at the beginning...

1) Shikimic acid
Shikimic acid is made via the "pentose phosphate cycle".
It mainly comes directly from photosynthesis or from glycolysis (preceded by photosynthesis).
It can also come from pyruvic acid (which is made from glucose thru glycolysis).

The shikimic acid concentration in plant organs is not constant and depends on the synthesis rate of aromatic amino acids. It accumulates in those tissues wherein the metabolic processes are stopped or slow, such as storage tissue of seeds and fruits.
Glyphosate can be used to increase shikimic acid, but it does this by inhibiting the shikimic acid pathway (specifically the enzyme 5-enolpyruvoylshikimate 3-phosphate synthetase), but we don't want to inhibit this pathway, we wan to catalyze it. Enzymatic activity is markedly influenced by elements such as potassium or ammonium.

Obviously more light can enhance photosynthesis, but how else can we optimize the "penthose phosphate pathway"?
Glucose-6-phosphate dehydrogenase (G6PDH) is the rate-controlling enzyme of the "penthose phosphate pathway"
It would be worth looking at how to increase G6PDH.


2) L-Tryptophan
L-Tryptophan is synthesize by the Shikimate pathway, which involves quite a few steps I won't go into for simplicity sake.
It can be externally applied to plant soil, which has shown in studies to increase uptake of nitrogen, phosphorus and potassium, resulting in increased plant growth.

Another thing is smoke/ash water which contains karrikinolide and gibberellic acid.
When used on plants, gibberellic acid:
* produces bigger leaves and longer stems.
* enhances photosynthesis.
* stimulate seed germination.
* trigger transitions from the vegetative to the flowering stage.

In some studies, the rate of tryptophan metabolism in the presence of gibberellic acid was increased by 100%!

Note: Anthranilic acid is also a precursor to L-Tryptophan via a different pathway, by attaching phosphoribosyl pyrophosphate to the amine group.
Maybe there is a way to increase phosphoribosylpyrophosphate synthetase activity in plants, which has been show to increase biomass in some studies. Hmmm....


3) Tryptamine
L-Tryptophan converts into tryptamine by "decarboxylation" (ie "removing a carbon atom from the chain" )
This process is mediated by an enzyme called "L-tryptophan decarboxylase", also known as "Aromatic L-amino acid decarboxylase" (AADC).
The enzyme uses pyridoxal phosphate, the active form of vitamin B6, as a cofactor.
So maybe supplementing with vitamin B6 will help?


4) NMT/DMT
Tryptamine undergoes a process called "transmethylation" (ie "transfer of a methyl group" ) which produced N-methyltryptamine (NMT). NMT then gets transmethylated by the same process to produce N,N-dimethyltryptamine (DMT).

An enzyme called "indolethylamine-N-methyltransferase" (INMT) catalyzes the transfer of the methyl group from cofactor S-adenosyl-methionine (SAM), via nucleophilic attrachment, to tryptamine.


A few notes on Nitrogen:

Higher leaf alkaloid content is thought to result from higher nitrogen and cation availability.
It does seem that alkaloid content is generally related to nitrogen levels available to plants.

Two basic factors seem to influence this relation:
(1) the biosynthetic nature of alkaloids themselves, and
(2) the balance of nitrogen and other nutrients in the soil.

The alkaloid biosynthetic pathway is important in this sense that during synthesis the nitrogen existing in the precursor can be liberated, or additional nitrogen may bind.

High or low concentrations of nitrogen in soil seem to influence alkaloid content in the plant despite the biosynthetic nature of alkaloids.
In both mentioned cases, the plant suffers from nutritional stress and the production of alkaloids seems to increase.
Nutritional stress is affected by absences and a high demand for nitrogen during metabolism. Plant stress in this sense can be determined as a force which strengthens alkaloid production for both continuing storage in vacuoles and for continuing their departure from vacuoles for the metabolic regulation of stress.

Soil acidity and temporary drought stress are also known to block nitrification and may contribute to low leaf alkaloid accumulation.

 

[twitchy]

If alkaloids are being excreted due to excess moisture, it seems to me that a simple way to test this idea would be to look at the soil directly beneath the plants after a period of prolonged saturation and see if the plant's alks are being deposited there by rainfall. They are soluble and not likely to be volatile compounds, so maybe you could confirm or eliminate excretion simply by looking for them in the top layers of soil. A change in PH is probably unreliable due to contamination from the other soluble stuff in the soil but I would imagine there are tests that would be sensitive enough to detect them in the runoff?
As to the content being higher in the morning, I honestly wouldn't rule out sleep as the cause for this. Crazy as that sounds, more and more evidence is pointing to plant sentience and without going into my own personal beliefs about plants, it's possible they have similar circadian based metabolisms going on. If so, I wonder what they dream about? LOL