Table 1

Species	Trivial name	Family	Species	Trivial name	Family
Adoxa moschtellina L.	Muskuskruid	Viburnaceae	Galium verum L. *	Bed straw	Rubiaceae
Allium oleraceum L.	Field garlic	Alliaceae	Hylotelephium maximum L. (Holub.)	Stonecrop, orpine,live-for-ever	Crassulaceae
Anthriscus sylvestris L.	Wild chervil, cow parsley	Umbelliferae	Phlomoides (Phlomis) tuberosa L.	Jerusalem sage	Lamiaceae
Artemisia campestris L.*	Wormwood field , sage-brush	Asteraceae	Saponaria officinalis L. *	Soapwort	Cariophyllaceae
Centaurea phrygia L.	Swiss centaury, knapweed	Asteraceae	Scabiosa ochroleuca L.	Cream pincushions, morning bride, scabious	Cariophyllaceae
Centaurea scabiosa L.	Greater knapweed, cornflower	Asteraceae	Sedum acre L.	Wall pepper	Crassulaceae
Eryngium planum L.	Sea-holly planum, blue-headed flat-leaf	Umbelliferae	Tanacetum vulgare L.**	Ordinary tansy	Asteraceae
Euphorbia virgata Waldst. et Kit.	Spurge	Euphorbiaceae	Thalictrum minor (minus) L	Meadow rue	Ranunculaceae
Festuca pratensis L.	Fescue	Poaceae
Filipendula vulgaris Hill.*	Dropwort	Rosaceae

Table 1: Studied plant species with blue or silver color of leaves. * and ** folk and medicinal

Table 2

Species	Month of observation		Maxima, nm	Optical density in maximum, nm	Species	Month of observation		Maxima, nm	Optical density in maximu m, nm

Adoxa moschtellina L.	April	upper	No		Filipendula vulgaris Hill.	April	upper	No
		lower	606	0.0905			lower	No
	May	upper	No			May	upper	No
		lower	No				lower	No
	June	upper	595	0.0589		June	upper	585	0.580
		lower	580	0.0525			lower	599	0.457
Allium oleraceum L.	April	upper	No		Gailium verum L.	April	upper	No
		lower	617	0.0405			lower	No
	May	upper	596	0.0512		May	upper	594	0.0596
		lower	No				lower	No
	June	upper	No			June	upper	No
		lower	No				lower	No
Anthriscus sylvestris L.	April	upper	586	0.0478	Hylotelephium maximum L. (Holub.)	April	upper	No
		lower	599	0.0478			lower	No
	May	upper	No			May	upper	No
		lower	No				lower	588	0.069
	June	upper	599-600	0.0657		June	upper	593	0.0598
		lower	580	0.0623
			590	0.0576			lower	602	0.0517
			595	0.0725				620	0.0598
Artemisia campestris L.	April	upper	599	0.0516	Phlomoides (Phlomis) tuberosa L.	April	upper	611	0.044
			616	0.0696			lower	598	0.0276
		lower	No			May	upper	No
	May	upper	578	0.0661			lower	609	0.0615
		lower	579	0.0401		June	upper	No
	June	upper	No				lower	No
		lower	No
Centaurea phrygia L.	April	upper	No		Saponaria officinalis L.	April	upper	620-621	0.568
		lower	No				lower	No
	May	upper	593	0.0880		May	upper	No
		lower	611	0.0780			lower	No
	June	upper				June	upper	602	0.0708
		lower					lower	628	0.0700
Centaurea scabiosa L.	April	upper	No		Scabiosa ochroleuca L,	April	upper	No
		lower	No				lower	No
	May	upper	No			May	upper	No
		lower	586	0.0662			lower	No
	June	upper	579	0.0670		June	upper	592	0.0636
		lower	593	0.0665			lower	599	0.0598
Erytrigiumplanum L.	April	upper	No		Sedum acre L.	April	upper	No
		lower	598	0.0478			lower	No
	May	upper	591	0.0580		May	upper	621	0.0628
		lower	No				lower	No
	June	upper	598	0.0619		June	upper	No
		lower	592	0.0838			lower	No
Euphorbia virgata Waldst. et Kit.	April	upper	No		Tanacetum vulgare L. A	April	upper	No
		lower	No				lower	618	0.0636
	May	upper	600	0.0652		May	upper	No
			610	0.0636			lower	618	0.0457
		lower	No			June	upper	617	0.0597
	June	upper	618	0.0602
		lower	586	0.0819			lower
Festuca pratensis L.	April	upper	600	0.529	Thalictrum minor L.	April	upper	No
							lower	No
	May	upper	No			May	upper	No
							lower	No
	June	upper	No			June	upper	No
							lower	590	0.0563

Table 2: Maxima in the absorption spectra of the studied plants. Significant optical density values (above 0.05) are highlighted in bold. The average error for optical density units was less than 10 percent.

Tables at a glance

Table 1

Table 2

Figures at a glance

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

FIGURE 1

Figure 1: Common views of some studied plants with blue color in April of 2024 just after the snow missed

FIGURE 2

Figure 2: The absorbance spectra of the surface of the leaf of musk weed Adoxa moschtellina in April (the first derivative of curves to identify maxima). The area of azulenes without noticeable maxima is highlighted with a parenthesis (a - upper side of leaf). The recorded maxima of azulenes are marked with circles, and the maximum of chlorophyll is shown with asterisks (b - lower side of leaf). The absorption spectra (a, b) were compared with the spectrum of a blue crystal (c) of artificially synthesized azulene (“Fluka”, Germany).

FIGURE 3

Figure 3: Spectral analysis of the leaves of Centaurea phrygia in May. (a) The absorbance spectra (the first derivative of the curves for detecting maxima) in May. The maxima of azulenes are marked with circles, and the maximum of chlorophyll is marked with asterisks. The azulene region without noticeable maxima is highlighted by a parenthesis; (b) and (c) – The absorbance and fluorescence spectra of 10 minute extracts with ethanol (leaf weight/volume 1 :10).

FIGURE 4

Figure 4: Seasonal dynamics of azulene content (in mg/g of fresh mass) in 10-minute ethanol extracts (leachates) from plant leaves depending on the time of collection, 1 - collection on April 13, 2 –collection on April 29, - 3 from May 13, - 4 from June 1 and 5 from June 11, 2024

FIGURE 5

Figure 5: The concentration of azulenes in 24-hour ethanol extracts in May (m) and June(s) from the studied plants minus the data of 10-minute extracts related to surface blue pigments. These data for azulenes can be considered as the content of azulenes inside.