Summary
Regarding the issue of the instability of the purple color in Ocimum basilicum
Regarding the issue of the activation of the purple color in Ocimum tenuiflorum
This written contribution, in particular regarding the first two sections, has been induced by recent questions and comments from Noelle Fuller, in the USA, and Conrad Richters (the founder of Richters Seeds), in Canada, about the issue of color stability in Ocimum basilicum and Ocimum tenuiflorum. This is a topic I began to delve into, in the spring of 2025, and here are some of my observations gathered since then.
According to Conrad: «Light intensity, temperature, and micronutrient deficiencies are known to affect colour in purple basils, and those effects are known to be mediated by regulatory genes. It appears that anthocyanin gene expression is modified by these environmental factors, and it appears that these changes can be passed on to successive generations even if the genes themselves are still present. I would not be surprised if the situation in krishna tulsi is similar which may explain our mutual frustration with this Tulsi. »
Conrad mentioned the dissatisfaction of one of his clients regarding the fact that his cultivar of Purple Basil, “Crimson King”, was not stable and turned green. Which is certain but under specific conditions I am going to highlight.
According to Noelle: «It looks like everything sold as Krishna tulsi now appears to be some type of hybrid. And when growing the seed there was variability in appearance between plants as well. Which makes me wonder if the genetics are stable… If you have any insight I would love to hear, as I developed a preference for the Krishna phenotype from my research and now can’t find the seeds in north america. ».
As a reminder, Noelle Fuller is the author of several studies concerning a number of ecotypes of Ocimum, in 2015/2016. In the study: “Yield and essential oils of holy basil (ocimum tenuiflorum l., o. gratissimum l.): varietal comparison and analytical methods”, published in 2017, Noelle presents, in detail, the analysis of the essential oils of “Kapoor” (a misnomer for which Strictly Medicinal Seeds, in the USA, bears the responsibility) and the GRIN/USDA references PI 652059, PI 652056, PI 414205, PI 414201, PI 414202, PI 414203, and PI 414204 – on page 79 – all ecotypes of Ocimum bisabolenum. Regarding the overall rate of β-bisabolene and (E)-α-bisabolene, it varies between 30% and 36% for all these ecotypes. Thus, according to this analysis by Noelle, the major components are: Bisabolene, Eugenol, Estragole, and Eucalyptol. The minor components are: β-pinene, β-ocimene, (E)-α-bergamotene, α-humulene, germacrene D, β-Caryophyllene. [21] .
Regarding the issue of the instability of the purple color in Ocimum basilicum
This year, I grew, in pots and in the ground, the following varieties of basil marketed as “purple”: “Purple Rubin”, “Osmin”, “Rosie”, “Opalescent”, “Aromatto”, in addition to the bicolored Turkish ecotype from GRIN/USDA, “PI 172997”, and two almost-purple specimens of the recent green cultivar from Rutgers, resistant to downy mildew, “Devotion”, crossed with a purple basil “X’”, in 2022.
The temperature conditions we are experiencing this year, in our almost desert-like region of Spain, are as follows: up to 36°C during a period in June and then up to 41°C in August – temperatures dropping by 15°C on August 21. This summer of 2025, no cultivar of Purple Basil, or bicolored, remained purple. They all inevitably turned green – including the veins of the leaves for some. It is a dark greening, but a greening nonetheless.
I have, however, observed, on August 21, that two partially shaded “Purple Rubin” plants – one by an olive tree and the other by huge Mirabilis jalapa – have retained a certain purple coloration, but only on the underside of their leaves.
As a reminder, I saw no difference this year between the varieties “Purple Rubin”, “Osmin”, “Rosie” (and also “Purple Delight” in 2022) in terms of their purple coloration. At least, in the very early stages of cultivation, as plants of 30/40 cm started to lose purple color in their older leaves as early as the beginning of June – at least in this year 2025.
On this subject, Conrad cites a study, from 2000, “Anthocyanin Inheritance and Instability in Purple Basil (Ocimum basilicum L.)”, LINK. This study focuses on the instability, and genetic transmission, of anthocyanins in Purple Basils. Just as the authors present, through photographs, I was able to photograph a leaf of an “Osmin” Basil with one half green and one half purple separated by the central vein.
On the contrary, I did not observe such an extreme degradation of the purple color in the Basil plants during the summer of 2022, as my photographs from the end of July 2022 highlight a beautiful coloration for the “Purple Delight” cultivar (Richters Seeds), a little less for the “Osmin” cultivar (Kokopelli), while there was, however, total greening for the “Red Genovese” cultivar (Richters Seeds). I assume that the summer of 2022 was much less hot.
It should be noted that the drying processes partially destroy the anthocyanins. LINK.
It would seem, therefore, a priori, that under identical solar lighting conditions, it is mainly temperature excesses that induce the Purple Basils to deactivate their anthocyanins and, thus, to lose their red-purple color.
I specify, in principle, because this would require further experiments to determine whether the increase in solar intensity can also impact the stability of anthocyanins. Thus, according to a study from 2024: “Phytochemical compositions and antioxidant activity of Green and Purple Basils altered by light intensity and harvesting time”: « When the plants of both cultivars (green and purple) were grown under maximum light intensity and sampled at noon, they showed the highest levels of phenolics and flavonoids. As for the highest antioxidant activity, it was detected in the Purple Basil cultivars grown under 30% and 50% sunlight during both harvests. » LINK.
Anthocyanins give Basil plants their red, purple, and mauve colors. For the record, there are six main types of anthocyanidins: delphinidins, cyanidins, petunidins, pelargonidins, peonidins, and malvidins. These compounds induce the red, purple and mauve pigmentation of leaves, flowering tops, and other reproductive organs, as well as seeds.
It should be noted that, unlike the Krishna type of Ocimum tenuiflorum, the young seedlings of Ocimum basilicum do not require direct sunlight to activate their purple coloration.
According to a study from 1998, 14 different anthocyanins were isolated, including 11 cyanidin-based pigments and 3 peonidin-based pigments. LINK.
The cultivars of large-leaved Purple Basil, “Purple Ruffles”, “Purple Rubin”, and “Dark Opal” exhibited an average content of extractable total anthocyanins ranging from 16.63 to 18.78 mg/100 g of fresh weight. It is noteworthy that the cultivar “Purple Bush” had 2 to 3 times less anthocyanins than the aforementioned 3 varieties. The maximum concentration of total anthocyanins was observed just before flowering, although by the 8th day, the seedlings had already accumulated the 14 anthocyanins.
According to a 2011 study, the cultivar of Basil, Sweet Petra Dark Red”, had 10 times more anthocyanins than the “Osmin” and “Ararat” cultivars. LINK.
According to a 2014 study on 8 varieties of Purple Basil, the cultivar “Purple Ruffles” had the highest anthocyanin content with 16.6 mg/g, while “Purple Rubin” had the lowest with 7.55 mg/g – on a dry weight basis. LINK.
The question arises as to why, with the increasing intensity of heat, and possibly light, the anthocyanins in purple leaves are destroyed, unlike those in flowering buds. Are they different anthocyanins? This is what the following two studies seem to suggest.
Especially since, according to various studies, flowers and corollas would contain much less anthocyanins than the leaves. LINK. LINK
Thus, according to a study from 2019: «the study revealed that purple leaves mainly contain highly acylated anthocyanins, while purple flowers accumulate anthocyanins with low degree of decoration.». LINK.
Moreover, according to a study from 2020: «The analysis revealed a different composition in intact flowers (Figure 3b). Anthocyanins A and B were not detected, and anthocyanins C and D were only minor compounds. This seemed to be partially compensated by the accumulation of low acylated anthocyanins (i.e., cyanidin-3-Glc-5-(6-Mal)Glc and cyanidin malonyl-glucoside). Moreover, it was observed a higher concentration of cyanidin derivatives with low molecular weight as well as of quercetin derivatives, some of which were also accumulated in white flowers.». LINK.
It should be noted, for example, that the anthocyanins from the floral tops of the highly ornamental cultivar, “Cardinal”, are not at all affected by excess temperatures during its growth.
Around August 30th, I noticed that green plants of the varieties “Osmin”, “Purple Rubin” (completely stripped of fruiting calices by the ants), and “Aromatto” have started to produce young leaves that are very purple again.
And this is due to the drastic cooling that has occurred over the past ten days. It can be deduced that in the sunniest and warmest regions, the anthocyanins of Purple Basil will be protected in half-shade cultivation situations.
On the other hand, a very beautiful plant of the “Purple Rubin” cultivar has remained completely green even though it is almost entirely hidden under very lush Mirabilis jalapa – that is, deprived of direct sunlight.
Conclusion. The Purple Basilics, or variegated with purple, tend – more or less quickly depending on the cultivars – to turn green, almost entirely, when the summer temperatures are too high for the stability of their anthocyanins. On the other hand, they regain their purple color as autumn approaches, as soon as the temperature drops drastically – while requiring direct sunlight (UV) that is essential for the reactivation of these anthocyanins.
Regarding the issue of the activation of the purple color in Ocimum tenuiflorum
This year, I cultivated, in pots and in open ground, the following ecotypes of Ocimum tenuiflorum – formerly known as Ocimum sanctum: “Thai Green Tulsi” (Kokopelli), two accessions of “Krishna” (Kokopelli), a green ecotype from Cuba (GRIN/USDA. “PI 652057”) and a green ecotype from Gujarat in India (GRIN/USDA. “PI 288779”).
The “Thai Green Tulsi” should rather be named the “Thai Light Green Tulsi” because its leaves are decidedly much lighter than those of the ecotypes generally offered from India. In fact, there is a huge diversity of ecotypes within Ocimum tenuiflorum – throughout Southeast Asia. A study from 2020, for example, analyzed 109 from only a part of India. LINK.
Some studies mention ecotypes of Ocimum tenuiflorum referred to as “intermediate”. Are these intra-specific crosses between the green and purple types? Have some “intermediate” ecotypes stabilized over the centuries?
The ecotypes, known as intermediates”, have leaves variegated with green and purple with stalks, and flowering tops, that are indeed very purple.
By the way, the Thai study from 2022, “Physiological responses and variation in secondary metabolite content among Thai holy basil cultivars (Ocimum tenuiflorum L.) grown under controlled environmental conditions in a plant factory,” presents an analysis of 10 ecotypes of Ocimum tenuiflorum, originating from Thailand, of which the “Krishna” type seems to be decidedly “intermediate”. LINK.
And if I may express myself, “du fond du coeur”, these “intermediate” ecotypes, of “Krishna”, are of very beautiful elegance with their floral stems of a pronounced red-purple against a backdrop of green or variegated violet leaves!
First of all, let’s recall that according to the ad hoc scientific literature, the green ecotypes, called “Rama”, and the purple ecotypes, called “Krishna”, of Ocimum tenuiflorum, represent two different genetic entities – as highlighted by the following few studies.
Ecotypes with very dark leaves are sometimes referred to as “Shyam” or “Shyama” – which means dark, blue, black, or dark in Sanskrit.
1. “The complete chloroplast genome of Ocimum tenuiflorum L. subtype Krishna Tulsi and its phylogenetic analysis”. 2021. LINK. According to this study:
« The cp genome is 151,758 bp in length, including a large single copy (LSC) region of 82,794 bp, a small single-copy region (SSC) of 17,592 bp, and a pair of inverted repeated (IR) region of 25,686 bp. The cp genome of Krishna Tulsi encodes 129 genes, including 90 protein-coding, 31 transfer RNA (tRNA), and eight ribosomal RNA (rRNA) genes »
2. “The complete chloroplast genome of Ocimum tenuiflorum L. subtype Rama Tulsi and its phylogenetic analysis”. LINK. 2021. According to this study:
« The length of the complete circular chloroplast genome was 151,722 bp. It comprises an inverted repeat (IR) region with a repeat length of 25,677 bp, a large single-copy (LSC) region of 82,781 bp, and a small single-copy (SSC) region of 17,587 bp. The GC content of complete chloroplast genome, LSC, SSC, IR regions is 37.9%, 36.0%, 31.8%, and 43.1%, respectively. The chloroplast genome contains 134 genes, including 88 protein-coding genes, 38 transfer RNA genes, and eight ribosomal RNA genes. »
3. “Molecular differentiation of the green and purple Tulsi (Ocimum tenuiflorum L.) and its application in authentication of market samples”. 2024. LINK. According to this study by researchers from Chennai, Tamil Nadu, India, green Tulsi was identified by two fragments (539 bp and 258 bp), and purple Tulsi was recognized by a single fragment (797 bp).
This very recent study aimed to determine the ratio of methyl eugenol – more present in the purple type than in the green type – consumed by the population of India as this phenylpropanoid would be, supposedly, genotoxic.
Furthermore, concerning the identification of what is marketed as “Tulsi” in India:«Analysis of 40 Tulsi market samples revealed that only 36 (90%) were derived from O. tenuiflorum. The majority of the market samples were purple Tulsi (60%) or a mixture of green and purple Tulsi (27.5%), with some mixed samples containing up to 50% purple Tulsi.» LINK.
All that being said, my main discovery this summer of 2025, regarding the “Krishna” type of Ocimum tenuiflorum, concerns the activation of its purple color by direct sunlight – at least, by certain spectrums such as ultraviolet light.
According to a study from 2014, “Photocontrol of differential gene expression and alterations in foliar anthocyanin accumulation: a comparative study using red and green forma Ocimum tenuiflorum”: « It was observed that red forma gradually changed to green upon transfer to a particular greenhouse with limited transmission of ultraviolet light (both UV-B and UV-A). The sequential monitoring of anthocyanin content confirmed positive correlation between visible and ultraviolet light intensity with leaf colour and antioxidant activities. An ultra-performance liquid chromatography method of <3.5 min was developed for rapid and precise quantification of anthocyanidins. Expressions of PAL, CHS and CHI were down-regulated by low light in both forma. The F3H and F3′H genes had reduced expression in both forma and were supported by reduced levels of cyanidin in red forma plants within greenhouse. The expression of late biosynthetic genes, DFR and LDOX, also plummeted within the greenhouse. The regulatory transcription factors bHLH and WD40 were severely down-regulated within the greenhouse suggesting that bHLH and WD40 control the expression of F3′H, DFR and LDOX to regulate the biosynthesis of anthocyanin pigments in leaves of O. tenuiflorum, whereas the expression of Myb remained almost unaffected». LINK.
Indeed, this year, I grew my hundreds of Basil plants in pots in wall greenhouses sheltered under a roof of transparent polycarbonate sheets. Including, towards the end of June – and even more so because of the high temperatures at that time – the two types of “Krishna” that I had just received from Kokopelli. And as the seedlings were green – at 10 cm – I informed the seed sector that indeed, one of the seed producers had rightly raised the alert regarding the improper color.
I have, therefore, transferred, to the compost pile, the seedlings of the two types of “Krishna”, with the exception of a few, out of pure curiosity about their fate, which I transplanted into pots or into the garden, towards the end of July – alongside Swiss chard that I had also just replanted.
And I discovered that all the “Krishna” plants turned red in full sun except for two plants that remained green: one, 25 cm tall, in open pollination, while its pot was in the shade of two huge seed-bearing Basil plants, of the “Greek” and “Floral White Spire” cultivars, and the other, 35 cm tall, growing under the tent of insect-proof mesh partly shaded by olive trees.
“Krishna”, with its leaves in a process of anthocyanin-activation under the solar light
The anthocyanins present in the ‘Krishna’ type are peonidin, cyanidin, delphinidin, and their derivatives. According to a study from May 2025, there is a ratio of 188.16 mg/g of anthocyanins and CI50 values of 12.28 and 20.74 μg/mL. LINK.
The anthocyanins present in “Krishna” type seedlings need to be activated by sunlight unlike those in Ocimum basilicum seedlings.
About five days after being exposed to direct sunlight, the leaves of the “Krishna” green plant began to take on purple hues.
In conclusion: it is direct sunlight, particularly its ultraviolet rays, that activates the purple/red color, and thus the anthocyanins, of the “Krishna” ecotypes of Ocimum tenuiflorum – including their so-called “intermediate” types.
Plants of the “Krishna” type, purple-red in color, will therefore turn green as soon as they are transferred to an area lacking ultraviolet light.
In the Basils, is it Linalool, or another Terpene cocktail, that certain species of fruiting calyxes-cutting ants are fond of?
In September 2022, in my monograph, “Les Qualités Extrêmement Médicinales de la Tulsi, Ocimum americanum”, (LINK) I wrote:
«And to finish on a naturalistic note! It is not just the perfumery industry that is obsessed with linalool: ants are too. Indeed, throughout the summer of 2022, I had to fight against columns of ants that systematically tore apart the flower stems – before the seeds were fully mature – only from varieties of Ocimum basilicum that possessed a “Linalool” chemotype. These columns of ants left behind, once their spoils were secured in the anthills, only strictly “are flower stems. They never targeted the ecotypes of Ocimum that had a “Citral”, “Camphor”, “Bisabolene”, “Cinnamon” or “Anise” chemotype. Only linalool motivated them. Linalool is known, among other medicinal activities, for its acaricidal, bactericidal, and fungicidal properties».
Regarding the medicinal qualities of Linalool, see the section dedicated to it in my French article: “Propriétés Médicinales des composés d’huiles essentielles de Basilics et autres Plantes Médicinales”. LINK.
And I asked, then, the following question: « Perhaps Linalool, in the ant nest, is the equivalent of Propolis in bee hives?»
As a reminder. In fact, there are not one Linalool, but two, because Linalool has two enantiomers – the R and S forms. According to the classical definition, enantiomers are chemical isomers that are non-superimposable mirror images. LINK.
The first, (S)-linalool (Coriandrol), has a sweet, floral, herbal scent similar to that of petitgrain with fruity citrus notes. As for the second, (R)-linalool (Licaréol), it has a woody aroma reminiscent of lavender. For the human nose, the detection threshold is 0.8 ppb (parts per billion) for the R form while it is 7.4 ppb (parts per billion) for the S form. LINK LINK
This summer 2025, once again, the ants started to shred the flower stems of the Basils – although later and only since mid-August.
During the summer of 2022, the raid of the Basils by the ants was of significant magnitude, and I had to build walls of ash to calm their ardor – which is pretty effective… especially in a garden where it never rains! Because the raids could last for days and days on the Linalool Basils
I observed and photographed them: they cut, with their jaws, the fruiting calyxes – whether with mature or immature seeds. Then, either they carry them down the plant, or they drop them so that other ants can take over.
Do you know that the ant, Odontomachus bauri, is the Kung Fu of the animal world? Indeed, it snaps its jaws at such a speed that it seems very improbable, specifically 0.13 milliseconds. To date, this is the fastest animal strike ever observed, with a speed ranging from 130 to 230 km per hour. LINK.
At the end of August, in our garden, the “Philocimum” Ants have been very motivated for the following Basils: Ocimum campechianum and, for Ocimum basilicum, “Devotion”, “Obsession”, “Vert de Gènes a feuilles moyennes”, “PI 175793”, “PI 190100”, “White Spires”, “Osmin”, et “Purple Rubin” – but this is just the beginning of their harvest season…
… and, as the days went by, the ants then took hold of two “Siam Queen” plants, but only stripping the flower stems by 40%… and disappearing overnight…
… while others were attacking plants of the ecotype “PI 211586”.
Motivated is an understatement, in fact, because in some plants, all the floral stems have been stripped bare – without exception. From a gardener’s perspective – who is not a seed producer – the diligent ants, which cut the fruiting calyxes, are definite allies because they prevent him from doing it so that his basils can continue to produce leaves!
This year, I will, somewhat, let the ants organize their harvests of Basil fruiting calyxes in order to elucidate what their favorite targets of appetite are.
Today, I am therefore asking the question of determining what the substance, or cocktail of substances, of their essential oil is, namely the common denominator among all these Basil plants, so that the ants are so fond of it. Is it Linalool?
Especially since there is information circulating, on the web, that Basil and Lavender are insect repellents… particularly for ants. This is due to the presence of Linalool. No joking? Furthermore, there are indeed blogs that explain how to get rid of ants on Basil!
Some gardening blogs are sometimes just gibberish nonsense and aggressive advertisements.
In fact, according to a study from 2022, the two enantiomers of Linalool have distinct functions. Coriandrol primarily attracts pollinators, while Licareol appears to act as an insect repellent. LINK.
The authors of this study found that flowers emitting linalool as the dominant volatile substance attract a wide range of pollinators, while some pollinators generally have strong preferences for these flowers as well.
It is very understandable, moreover, that Basil is associated with Linalool because the vast majority of Basil cultivars imposed on the general public, by the food industry, have a predominant chemotype of Linalool – sometimes up to 75% in their essential oil.
I expressed myself on this subject in my recent “Mischievous Whistle-Singing!Predominance of Linalool in Basil and Cannabis… For the People’s Sedation?”. LINK.
Notwithstanding, today, in light of my own gardening experience, it does not seem wise to assert that “Basil” is intrinsically a repellant for ants… due to the number of species, varieties, and ecotypes that characterize the genus Ocimum, and the extreme diversity of the chemotypes of their essential oils.
Likewise, the term “Ant” certainly requires clarification due to the plethora of ant species on the planet – namely, about 20,000 as far as we know. In our garden, by the way, we have a species of ant that lives peacefully under the Lavenders!
Moreover, the terms “Ant invading the Basils” certainly requires further clarification as it may refer to aphid-farming ants or agricultural ants – with cutting and carrying jaws – gathering food or medicinal substances in anticipation of the long winter months.
In order, therefore, to determine the substance of their essential oil, common to all these finely chopped basils by the foraging ants, I went in search of the relevant analyses – when they exist.
“Devotion”. This new acquisition is presented by Rutgers University as a type of “Classic Italian” Basil – thus with a Linalool chemotype.
“Obsession”. This new acquisition is presented by Rutgers University as a type of “Classic Italian” Basil – thus with a Linalool chemotype.
“Vert de Gènes a feuilles moyennes”. This cultivar is caracterised by a Linalool chemotype.
“PI 175793”. Originating from Çanakkale, Turkey, this ecotype is characterized by a chémotype Linalol – sometimes, up to 70%.
“PI 190100”. Originating from Iran. Depending on the analyses, this ecotype is characterized by a Linalool content of about 10% and an Estragole content ranging from 10% to 65%.
It should be noted that within the span of a night, all the flower stalks of a plant from the ecotype “PI 190100”, measuring 70 cm in height, were stripped of their fruiting calyxes – without exception.
I suspect that “PI 190100” is actually an Ocimum americanum var. pilosum, especially since a study characterizes it – in an analysis of supposed accessions of Ocimum basilicum – as having the highest citral content and the highest antioxidant activity. Indeed, its essential oil contains up to 26% citral and up to 12% β-citral. With such a third of Citral, or more, it is definitely a type of Basil known as “Lemon”.
Moreover, in view of the very pronounced differences in several analyses, given its chemotype, it is likely an Iranian “ecotype” with a very diversified “population” status. It is noteworthy that there exists a plethora of ecotypes of Basil, in the Turco-Iranian region, still considered as Ocimum basilicum – or as Ocimum ciliatum, a non-accepted species – with Citral levels of up to more than 66% (including 38% of Geraniol), whereas they actually pertain to the species Ocimum americanum var. pilosum. LINK. LINK. LINK. LINK. LINK. LINK.
“Osmin”. This purple cultivar is characterised by a chémotype Linalol – sometimes up to 65%. LINK
“Purple Rubin”.This purple cultivar is characterised by a chémotype Linalol – sometimes up to 60/65%.
“Floral Spires White”. This cultivar, known as ornamental, is incorrectly presented on a plethora of commercial sites as a cultivar close to a Thai type with an aniseed scent – therefore, apparently, with an estragole chemotype.
It should be noted that I was not able to determine the breeder of this pair of so-called ornamental Basilisks: “Floral Spires White” and “Floral Spires Lavender”.
I introduced it in 2014 at Kokopelli – with such a characterization that I copied from the Internet – and this is the first time I personally cultivate it this year. In reality, its growth habit has nothing to do with that of the Thai types – namely, Ocimum basilicum var. thyrsiflorum.
Pending an analysis of its essential oil, I am inclined to lean, based on the volatile substances, towards a Linalool chemotype.
Indeed, the plants of “Floral Spires White” are characterized, strictly speaking, by a very compact and rounded shape, reminiscent of the dome of the “Greek” cultivar, sometimes called “Greco a Palla”. “Floral Spires White” reaches, in fact, 55 cm in diameter and 35 cm in height, while “Greek” reaches 45 cm in diameter and 30 cm in height.
The genetic resource center, of the GRIN/USDA, offers another such globular ecotype – namely, PI 170578 originating from Aydin in Turkey – which it presents as an Ocimum basilicum, while its reported 46% Citral content rather emphasizes its belonging to Ocimum americanum var. pilosum. LINK
Furthermore, like some ecotypes of Greek or Anatolian type, the foliage of “Floral Spires White” – with leaves of up to 5 cm in length, of which 1 cm is petiole – tends to turn to yellow with senescence, and seed maturity, in synergy with high solar intensity… whereas more shaded plants maintain green foliage.
As for their flowering stems, they are very short – just like those of the Greek or Turkish ecotypes… or of the Genovese type.
“PI 211586”. Based on the analyses, this ecotype is reported with a Linalool ratio ranging from 30% to 42% – as well as up to 36% Methyl Eugenol, 8% Citral, and high ratios of α-trans-bergamotene and epi-α-cadinol.
I suspect it to be an Ocimum americanum and not an Ocimum basilicum.
“Siam Queen”. It is difficult to find studies (and I refuse to pay for access to PDF of scientific articles) regarding the chemotype of this (alleged) strain introduced in 1997 – just as much, by the way, as for the chemotype of other Thai varieties, Ocimum basilicum var. thyrsiflorum. While it is clear that some Thai ecotypes are characterized by a high Estragol ratio, some studies also mention Linalool as a major component. LINK LINK LINK
Awaiting an analysis of its essential oil, this is not one of the varieties whose plants are the most favored by Ants – as the stripping of their stems is only partial.
In conclusion, after chemosystematic investigation focusing on the Basil species preferred, by the fruiting calyxes-cutter “Philocimum Ants”, it seems that the possibility of Linalool as a common denominator is the most plausible.
It remains to determine the reason for the consumate love, of these Ants, for certain cultivars or ecotypes, of Basil, with a generous ratio of Linalool!
