Ex Situ Conservation and Ornamental Evaluation of the Endangered Amberboa moschata (Asteraceae) in Armenia

Abstract

Amberboa moschata (L.) DC. (Asteraceae) is an endangered species, listed in the Red Book of Plants of the Republic of Armenia. The restricted extent of occurrence and habitat degradation necessitate conservation measures of this species, not only in the wild but also through ex situ cultivation. This study examines the comprehensive morpho-phenological, karyological, palynological, eco-physiological, and ornamental characteristics of A. moschata in the context of ex situ conservation. A. moschata plants cultivated ex situ demonstrated high adaptive traits, undergoing a full development cycle and experiencing less water stress compared to wild populations. The diploid cytotype has been found for the species to be 2n = 32, the karyotype is asymmetric, with chromosomes, 0.77–1.91 µm in size. The average pollen fertility of A. moschata is high, 96.7–96.9% in both natural and cultivated samples. A scale of decorativeness was developed, which includes 15 characteristics of the plant, providing an objective means to assess its visual appeal. The scale can be useful for integrating A. moschata into various landscaping schemes. Under cultivation, the total ornamental period lasts approximately 98 days, with the peak ornamental effect observed during the flowering phase, which spans 68–70 days. The study recommends A. moschata for inclusion in living collections in botanical gardens and for use in ornamental gardening and landscaping as part of its ex situ conservation strategy. A map, original photographs, and tables illustrate the article.

1. Introduction

Armenia is very rich in original and beautiful, predominantly xerophytic flora that grows from Ararat Valley deserts and semi-deserts to the alpine belt, inclusive. The Ararat Valley hosts many threatened ornamental plants, often surviving in fragmented populations within halophytic, psammophytic, and gypsophytic habitats.

This study is focused on the xerophytic ornamental species Amberboa moschata (L.) DC. (Asteraceae). Genus Amberboa (Pers.) Less. includes 12 species distributed in Southwest, Middle, and Central Asia, of which 8 species occur in the Caucasus [1,2]. Wild populations of A. moschata are native only to the Ararat Valley of Armenia, and adjacent areas in Northeast Anatolia [1]. In Armenia, A. moschata grows in the Yerevan floristic region at an altitude of 600–1500 m above sea level: in dry clayey, gypsum-bearing deserts; in wormwood semi-deserts; on gravelly, rocky places; and in crops (Figure 1). It is found in the Ararat Valley xeromorphic gypsiferous red and gravelly clay communities with such species as annuals Actinolema macrolema Boiss., Halanthium rarifolium K. Koch, Szovitsia callicarpa Fisch. & C.A. Mey., perennials Dorema glabrum Fisch. & C.A. Mey., Haplophyllum villosum (M. Bieb.) G.Don, Psephellus erivanensis Lipsky, Rindera lanata (Lam.) Bunge, subshrubs Kaviria cana (K.Koch) Akhani, K. tomentosa (Moq.) Akhani, Salvia hydrangea DC. ex Benth., and others. A. moschata is included in the Red Book of Plants of the Republic of Armenia under the Endangered Species category (EN) based on geographic condition criteria B 1 ab(i,ii,iii) + 2 ab(i,ii,iii) [3]. Limiting factors posing a threat to the species are restricted extent of occurrence and area of occupancy, loss or degradation of natural habitats caused by land development for agricultural crops, and the expansion of human settlements. The collection of A. moschata in the wild for use in flower bouquets has increased significantly, which also has a negative impact on the status of the species [4]. A part of the A. moschata population is protected in the Erebuni State Reserve of RA. Degradation of habitats and reduction in the range and population size of A. moschata necessitates measures to conserve this species not only in the wild, but also outside its natural habitats under ex situ conditions.

An important role in threatened plant species ex situ conservation is played by botanical gardens, where living collections of wild plants, including aboriginal ones, are being created [5]. For the conservation of wild ornamental plant diversity, their maintenance in such centers as botanical gardens and specialized nurseries is of great importance [6]. Research and ex situ conservation of endangered plant species have been carried out in the Yerevan Botanical Garden since 1938, where documented living collections of local flora and models of the most characteristic plant communities are created [7,8]. In the “Flora and Vegetation of Armenia” exhibition plot at the Yerevan Botanical Garden, about 200 species of wild-growing ornamental and drought-resistant species of local arid flora were tested under ex situ conditions [9].

The Asteraceae family, which includes many perennial herbaceous species, plays a significant role in ornamental horticulture. The family is known for valuable crops used in the cut flower industry, such as Argyranthemum, Calendula, Chrysanthemum, Dahlia, Dendranthema, Gerbera, Tagetes, Zinnia, and many others. Wild species of Asteraceae can be also used in ornamental horticulture. We proposed the inclusion of 12 species of Asteraceae local flora in the range of wild ornamental plants for gardening and landscaping in cities and villages of arid regions in Armenia, such as Achillea tenuifolia Lam., Artemisia splendens Willd., Centaurea depressa M. Bieb., Echinops orientalis Trautv., Helichrysum rubicundum (K. Koch) Bornm., Inula aucheriana DC., Xeranthemum squarrosum Boiss., and others [9,10]. Amberboa cultivars and hybrids are popular in floriculture in some countries as a well-known flower crop. Having spread as a result of introduction, they are known in some regions of South and East Asia, Eastern Europe, together with North America and Canada. In culture, the most common is the decorative hybrid form Amberboa moschata f. ’Imperialis’.

Many wild plant species are underrepresented in living collections of botanical gardens and are rarely used in ornamental horticulture. This is largely due to limited botanical data, the absence of reliable cultivation techniques, and insufficient knowledge about their adaptability and reproductive behavior in cultivated environments. In Armenia, A. moschata from local wild populations in the Ararat Valley has not yet been used in ornamental horticulture and landscaping, just as no comprehensive study of this species has been conducted for ex situ conservation purposes. This research aims to assess the feasibility of cultivating A. moschata from local populations under ex situ conditions, focusing on its adaptive traits, reproductive success, and ornamental potential. The studied species can be recommended for the creation of living collections in botanical gardens and for use in ornamental gardening and landscaping as measures for its ex situ conservation. The results of the study will guide obtaining material for the reintroduction of this endangered species into natural habitats and its use in landscaping settlements in the arid regions of Armenia.

2. Materials and Methods

2.1. Research Site and Cultivation Techniques

This research was conducted in the Yerevan Botanical Garden and A. Takhtajan Institute of Botany NAS RA during 2022–2023. The botanical garden is located in northeast Yerevan city at an altitude of 1200–1250 m above sea level in the zone of stony wormwood semi-desert characterized by a distinctly continental climate. The annual precipitation is 300–365 mm; the average annual temperature is +11 °C, in summer it is 24–26 °C and in winter −5 (−8) °C; the average annual relative air humidity is 59%. The climatic conditions in the Yerevan Botanical Garden are close to those in the Ararat Valley and differ by an absolute minimum temperature that is 2–3 °C lower. The soils are semi-desert brown, heavy loamy, carbonate and medium stony, with humidity about 5.0% and acidity 7.0%. For the cultivation of desert and semi-desert plant species under ex situ conditions in the Yerevan Botanical Garden, the exhibitions “Flora of Gypsiferous Red Clays” (where the local soil was replaced with clay soil rich in sulfates and containing gypsum crystals (Figure 2a)) and “Flora of Semi-Deserts and Foothills of the Ararat Valley” (Figure 2b) were created at the “Flora and Vegetation of Armenia” plot [7,8]. To identify the adaptive features of A. moschata to edaphic factors, it was also grown on the local soil of the Yerevan Botanical Garden.

The initial material for A. moschata cultivation were seeds collected from natural habitat during expeditions in the Ararat Valley of RA. The voucher data follows: “Kotayk province, near village Voghchaberd, gypsiferous slopes, 1500 m a.s.l., 40°09′49″ N 44°38′45″ E, 30 July 2020. Leg. J. Akopian”; “Ararat province, reservoir near mount Yeranos, dry slopes, 1080 m a.s.l., 40°04′12″ N 44°35′07″ E, 25 July 2022. Leg. & Det. J. Akopian, A. Ghukasyan, L. Martirosyan, A. Elbakyan”. Since A. moschata seedlings do not tolerate pricking out and subsequent transplanting, the best results were obtained when sowing seeds in open ground in a permanent place. To ensure optimal growth of the plants cultivated outdoors, a sunny location was selected. During the first growing season, weeding, soil loosening, and moderate watering were performed twice a week.

2.2. Morpho-Phenological and Ornamental Traits Assessment

During the growing season, biometric measurements, observations on plant growth and development, features of seed germination, and flowering and fruiting were carried out [8,11,12,13].

The seeds were sown both in open ground in the abovementioned exhibitions of the Yerevan Botanical Garden and in laboratory conditions on Petri dishes to determine the germination and viability of the seeds. In order to establish the percentage of field germination, the seeds were sown in open ground in limited spaces (150 × 80 cm) with 50 seeds. For the laboratory germination analysis, 3 seed samples of 50 pieces were taken, respectively, following 1 and 2 years of storage. Each sample was placed in a Petri dish. The optimum germination temperature has been established in laboratory conditions at 18–20 °C. When determining viability, we examined the seeds in three replicates. In each sample after germination, 5 fractions of seeds were isolated (sprouted; full but not sprouted; rotten; affected and empty). The percentage of germination and viability of seeds was determined using the method developed by RBG Kew [11,12] and calculated using the formula for germination followed by derivation of the average value, viz. [a/(a + b + c)] × 100%, and for viability [(a + b)/(a + b+c)] × 100%, where a is the number of germinated seeds, b is the number of non-germinated but full seeds, and c is the number of rotten seeds.

Phenological observations were performed according Beideman [13]. The dates of the onset of phenological phases (emergence, vegetation, budding, flowering, and fruiting) and the duration of the decorative period were recorded. A. Takhtajan Institute of Botany Herbarium (ERE) material of A. moschata and samples collected during our expeditions were examined. The morphological features of plant samples were studied using an MBC-9 stereo microscope. Plants were photographed with a Nikon D3400 digital camera.

To develop the decorativeness scale of A. moschata, the most significant features were used. Since there is currently no officially registered scale for evaluating the ornamental quality of wild plant species within the natural flora, we took into account the methodology of comparative variety assessment of ornamental plants according Bylov [14]. The scale we developed includes 15 main features characterizing the decorative qualities of a shoot, leaf, inflorescence, fruit, and the habit of the plant as a whole. Conversion coefficients for each feature allow us to determine its significance in the overall assessment of the decorativeness of the species.

2.3. Chromosome Analysis

A karyological investigation was performed on the mitotic metaphases of the meristematic cells from root tips of germinated seeds. The root tips were pretreated in 0.4% colchicine solution and fixed in fluid 3:1 alcohol and glacial acetic acid; following hydrolysis in HCl and staining with Schiff reagent, the root tips were crushed with 45% acetic acid on a glass slide. A minimum of 10 plates were examined for each taxon. The preparations were placed in butyl alcohol for 5 min, and then in xylene for 5 min, and were then placed in Canadian balsam. Slides were examined under a Photomicroscope (AmScope 2000×LED LAB Trinocular Compound Microscope SKU:T120B-5M, China, 2020), using an oil immersion objective (100×).

2.4. Pollen Fertility Analysis

Pollen fertility of A. moschata was studied by taking pollen from the flower buds in natural habitats during seasonal collections from different years and various regions of Armenia, including from specimens introduced in the Yerevan Botanical Garden. Pollen fertility is relatively constant and practically does not change over time, so both fresh and dry material from the ERE Herbarium were used (

Table 1. Amberboa moschata herbarium (ERE) specimens used for pollen study.

Specimen Number	Locality
ERE 130754	Abovyan distr., Zovashen, vicinity of the Azat reservoir, hammada. 14 June 1985, E. Gabrielian
ERE 139664	Abovyan distr., between villages Djrvej and Shorbulakh, on dry clay slopes, 1100–1500 m a.s.l. 27 June 1985, E. Gabrielian
ERE 130754	Abovyan distr., Zovashen, vicinity of the Azat reservoir, hammada. 14 June 1985, E. Gabrielian
ERE 139664	Abovyan distr., between villages Djrvej and Shorbulakh, on dry clay slopes, 1100–1500 m a.s.l. 27 June 1985, E. Gabrielian
ERE 145154, 145156	Nubarashen, on clay slopes. 2 July 1997, E. Gabrielian
ERE 151800	Near Nubarashen, on tertiary red clays. 24 May 2000, E. Gabrielian
ERE 153193	Kotayk province, Abovyan distr., between villages Shorbulakh and Vokhchaberd, 3 km SSW of Vokhchaberd, Erebuni reserve, mountain steppe, 1350 m a.s.l., 1 July 2003. M. Barkworth, F. Smith, E. Gabrielian, A. Nersesyan, M. Oganesyan
ERE 202314	Yerevan, southern border of city at Sovetashen, 1040 m, 40°07′22 N/44°32′36″ E 11.07.2003, M. Oganesian, H. Ter-Voskanyan, E. Vitek
ERE 161, 644	Sovetashen, 1190 m a.s.l. 40°06′100″ N/44°33′25″ E. 26.05.2006. K. Tamanyan, G. Fayvush
ERE 190335	Kotayk marz, vicinity of Vokhchaberd village, on the territory of the Erebuni Nature Reserve, on clays. 5 June 2008. J. Akopian
ERE 182109	Vedy region, near v. Urtcadzor, on dry clay slopes, 1100 m. 24 May 2011, E. Gabrielian
ERE 202313	Ararat province, slope between river and road Vedi to Lusashogh, 3.5 km SE of Urtsadzor, 1165 m, 39°53′50″ N/40°50′58″ E 17 May 2017, E.Vitek, M.Oganesian, M.Sargsyan, A.Khachatryan
ERE 202334	Ararat Marz 5.6 km from Lanjasar, near Azat reservoir, 40°05′13″ N/44°38′06″ E, 1110 m to 40°05′17″ N 44°38′05″ E, 1130 m, 4 June 2018, E.Vitek, P. Escobar-Garcia, G. Fayvush

).

Pollen fertility was determined by staining with acetocarmine on temporary preparations [15]. Statistical processing of the experimental data was carried out according to Dospekhov [16] and Wolf [17]. The fertility of each collected sample was tested in 5 replicates of 100 pollen grains. For data comparison, the arithmetic mean Sx was calculated according to Sx = Σ ($\overline{x}$ − x) × k, where the absolute value was subtracted from the arithmetic average number of fertile grains and the sum was multiplied by k, which is the number of replicates. In our case, the number of replicates corresponded to the number 0.1253 [17]. Preparations were examined under a light microscope, OPTIKA B-510BF microscope (OPTIKA S.r.l., Ponteranica, Italy, 2021), at a magnification of 400 times.

2.5. Eco-Physiological Features Evaluation

Eco-physiological features (total water content, water deficiency, intensity of transpiration and photosynthetic productivity, cell sap density content) of the A. moschata specimens were studied during the vigorous vegetative period, implementing the methods of Sheremetyev [18] and Salnikov & Maslov [19]. The measurements were carried out within the period between 11:00 and 13:00, each in 3 samples and 3 repetitions; 7–10 shoots were chosen for each sample. The content of photosynthetic pigments (chlorophylls “a” and “b”, and carotenoids) was determined by a modified method based on the use of an organic solvent, dimethyl sulfoxide, which allows for obtaining stable extracts [20]. The data represent statistically processed average results of the analysis. Fresh samples were weighed immediately (KERN ABS220–4N) and dried in a thermostat (Binder BF–56) set at 105 °C, to determine the whole water content in the leaves.

$$\mathrm{X}={\displaystyle \frac{{{\mathrm{P}}_1-\mathrm{P}}_2}{{\mathrm{P}}_1}}\times 100$$

where X is the total water content, % from the wet weight; P₁ is the wet weight of the leaf before drying, in grams; P₂ is the dry weight of the leaf sample, in grams; and 100 is for expressing the total water content in the leaf from the wet weight in percentages.

The water deficit was determined based on leaf-water saturation [19]. One gram of leaf circles were weighed and placed in a Petri dish filled with distilled water. After 2 h, the circles were removed, dried with filter paper, and reweighed. This process was continued until the weight of the sample stopped changing and the leaves were considered completely saturated. The last weighing data were used as the final result. Afterward, the samples were dried in a thermostat at 105 °C for 5 h, weighed, and then dried again up to stable weight. Following formula was used:

$$\mathrm{W}\mathrm{s}\mathrm{D}={\displaystyle \frac{\mathrm{W}\mathrm{s}-\mathrm{W}\mathrm{f}}{\mathrm{W}\mathrm{s}-\mathrm{W}\mathrm{d}}}\times 100$$

where WsD is the water deficit, % from the wet weight; Ws is the leaf mass after complete saturation with water (mg); Wf is the fresh weight of leaves (mg); Wd is the leaf dry weight (mg); and 100 is for expressing the water deficit as a percentage of wet weight.

The intensity of leaf transpiration was measured using the rapid weighing method with an analytical balance (ABS 220–4N), under conditions of full leaf water saturation [19]. The leaf material was cut with scissors and weighed; after 5 min, the weighing was repeated. The following formula was used:

$$\mathrm{Y}={\displaystyle \frac{{\mathrm{B}}_1-{\mathrm{B}}_2\times 60\times 10000}{\mathrm{S}\times \mathrm{T}}}$$

where Y is the intensity of transpiration (mg/dm² from wet weight, hour); B₁ is the initial weight of the leaf (mg); B₂ is the weight of leaves after 5 min; 60 is 1 min in seconds, 10,000 is 1 cm² expressed in dm²; S is the leaf surface (dm²); and T is the period in minutes between the initial and the final weighing.

The photosynthetic productivity was measured by the method of leaf-halves saturation [19]. No less than 20 leaves were selected. Half of the leaves were cut along the length of the main vein and placed in a bowl filled with water for 0.5 h to saturate the tissue with water. Next, the leaves were removed and dried in a thermostat for 4–6 h at 105 °C. This determined the initial dry weight per unit leaf area (mg/dm²). The other half of the leaf with the petiole remained on the plant for 4–5 h, after which the dry weight of their surface (mg/dm²) was determined as described above. The amount of dry material accumulated during photosynthesis was determined by the difference between the dry weight of the last and the first determinations, which, dividing by the time between the determinations, expressed the photosynthetic productivity in mg/dm²·h.

$$\mathrm{P}={\displaystyle \frac{{\mathrm{P}}_2-{\mathrm{P}}_1}{0.5\times ({\mathrm{L}}_1+{\mathrm{L}}_2)\times \mathrm{N}}}$$

where P is the photosynthetic productivity; P₁ is initial weight of the leaves; P₂ is the final weight of the leaves (after 3 h); 0.5 × (L₁ + L₂) is the average working area of the leaves during the experiment; and N is period between two determinations (after 3 h).

To determine the leaf surface area, the leaves are laid out on paper and their contours were outlined, cut out, and weighed. A square of 100 cm² was cut out of the same paper and weighed.

$$\mathrm{L}={\displaystyle \frac{\mathrm{P}}{{\mathrm{P}}_1}}\times 100$$

where L is the leaf surface area (cm²); P is the weight of leaf contours (gram); and P₁ is the weight of 100 cm² square (gram).

The content of photosynthetic pigments (chlorophylls “a” and “b”; carotenoids) was determined by a modified method based on the use of an organic solvent, dimethyl sulfoxide [20]. For the determination of plastid pigments, 100–500 mg weight of fresh leaf sample was placed in 25 mL graduated and ground-necked test vials; 7–10 mL of dimethyl sulfoxide (DMSO) was added to the vials, which were then closed with a cork, wrapped with black cloth, and placed in a wooden box. To dissolve pigments, the test vials with the samples were placed in a water bath (WB7 2) at a temperature of 65 °C until the leaf tissues were completely discolored, after which the extract was obtained. Measurements were carried out on a spectrophotometer (UV−6300PC Double Beam Spectrophotometer). The quantitative accounting of chlorophylls “a” and “b” and carotenoids was carried out according to the procedure described by Shlyk [21]:

chlorophyll “a” = 12.7E663 − 2.69E645;

chlorophyll “b” = 22.9E645 − 4.68E663;

sum of carotenoids = 4.695E440.5 − 0.268 (“a” + “b”),

where E is the spectrophotometer reading.

The cell sap density content was determined with a DigitalHJ96801 refractometer (Hanon Instruments, Jinan, China, 2021).

3. Results and Discussion

3.1. Morpho-Phenological Characteristics

Amberboa moschata is an annual plant 20–70 cm tall, with an erect, weakly branched stem and a thin root. After autumn sowing in the Yerevan Botanical Garden in open ground, A. moschata seed germination was observed during the following spring in first ten days of March. The seeds should be sown at a shallow depth of 4–6 mm, since in addition to moisture, A. moschata seeds require sufficient light to germinate. When seeds are sown in spring, seedlings appear in 2–3 weeks. Autumn sowing is more effective in terms of seed germination than spring sowing. Seed field germination is about 75–90%. In plants of the Asteraceae family, the seeds have a fully developed embryo and are characterized by the absence of dormancy or shallow physiological dormancy; the seeds of more than 60% of species of the Asteraceae family have an accelerated type of germination [22,23]. As a result of determining the laboratory germination and viability of A. moschata seeds in the first and second years of storage, fairly high indicators were obtained (

Table 2. Germination and viability parameters of Amberboa moschata seeds in laboratory conditions.

Experiment Repetition Number	Seed Germination (%)		Seed Viability (%)
	Seeds from the 1st Year of Storage	Seeds from the 2nd Year of Storage	Seeds from the 1st Year of Storage	Seeds from the 2nd Year of Storage
I	82	70.5	96	94.4
II	73.3	67.6	98	100
III	81.3	71.8	93.8	94.8
Average	78.7 ± 3.22	70 ± 1.3	95.9 ± 1.2	96.5 ± 2.1

, Figure 3). The beginning of germination in laboratory conditions is observed 10–12 days after seed placement and continues for about 20–25 days. During storage, A. moschata seeds retain their germination capacity for an average of six-seven years.

Achenes of A. moschata are large, 6–7 mm long, densely appressed–hairy; hilum lateral, surrounded by a bare strongly elevated ridge, with a pappus 5–7 mm long (Figure 4a). Germination is epigeal. The cotyledons are green, fleshy, naked, spatulate, 0.6–1.0 × 0.3–0.5 cm; the hypocotyl is up to 2.5 cm long, turning into a thin rootlet, the epicotyl not developed (Figure 4b). Approximately 10 days after emergence, the first pair of leaves located across the cotyledons appears (Figure 4c). At the juvenile stage of development, the leaves of A. moschata are entire, elliptical, and irregularly serrated along the edge; the growth form is represented by a rosette (Figure 4d). The appearance of new leaves and the formation of the basal rosette continue throughout April. Up to 7–9 leaves are formed in the rosettes, ranging in size from 2 × 0.5 cm to 11 × 2 cm. When the sixth pair of rosette leaves appears, the cotyledons dry up. Budding is observed in early May and continues along with the beginning of flowering in mid-May. Flower buds are formed in the center of the rosette. By the end of June, yellowing of some of the rosette leaves is observed. The branching of the plant is sympodial, shoots branch up to 3–4 orders; the first leaves at the base of the shoots are opposite, following ones are alternate. The plant is heterophyllous, the leaves bright green, range from entire, slightly serrated to dissected or lyre-pinnate. The basal and lower leaves are petiolate; the upper ones are sessile. Stems of the plant up to 37–40 cm end with light lilac-pink inflorescences up to 4–7 cm in diameter (Figure 4e). Baskets are single, apical, very large, broadly ovate or hemispherical on long curly pubescent stalks. The involucre is curly woolly, appendages of involucre are large, 2–3 × 4–6 mm, obtuse at the apex. The marginal florets are funnel-shaped, significantly larger than the median ones (10–15 mm), many lobed. Florets are fragrant and often visited by bees. In June–July, the flowering, budding, and ripening of fruits occur simultaneously.

The end of the growing season and drying of the plant is observed from the third decade of July to the end of August. Seed ripening continues until mid- or late August. In general, the duration of the growing season of A. moschata is 125–130 days, the flowering period is 68–70 days, and the duration of the plant decorativeness period is about 98 days (Figure 5). However, in the cultural conditions of the Yerevan Botanical Garden, with regular watering, the vegetation can be delayed and a second repeated flowering of introduced specimens is possible. Flowers and leaves of the second vegetation are significantly smaller. The plants give good autumn self-seeding. A. moschata is usually free from pests, but can be affected by powdery mildew. In the Yerevan Botanical Garden, it grows well in open sunny places with loose soil and moderate watering. Mature plants are drought and cold resistant.

3.2. Cytogenetics and Pollen Fertility

Karyologically studied samples of A. moschata collected from Ararat Valley (Ararat province, near village Zovashen, 2 July 2022. Leg. & Det. J. Akopian, A. Ghukasyan, L. Martirosyan, A. Elbakyan; Ararat province, reservoir near mount Yeranos, dry slopes, 2 July 2022. Leg. & Det. J. Akopian, A. Ghukasyan, L. Martirosyan, A. Elbakyan) revealed a diploid cytorace for this species, 2n = 2x = 32. According to the literature data, mainly the diploid cytorace is characteristic for this species (2n = 32), with basic chromosomes number x = 16. Our result agrees with other previous counts from Armenia [24,25,26,27] and Iran [28,29]. It should be noted that Moore [30] indexed two results for A. moschata: 2n = 28 and 2n = 32. However, all the other counts in the genus Amberboa have the basic number of x = 16, which is rare in the subtribe Centaureinae.

The karyotype of A. moschata is asymmetric, with very small chromosomes, 0.77–1.91 µm in size, consisting of 5 pairs of submetacentric and 11 pairs of metacentric chromosomes (Figure 6). The karyotype formula is 2n = 32 = 10SM + 22M.

The detection of the diploid cytotype is important because it represents the primary chromosome set characteristic of the species, and its presence helps us understand genetic stability and potential evolutionary flexibility. Chromosome asymmetry and differences in chromosome size may indicate adaptive advantages: more asymmetric chromosomes are sometimes associated with increased genetic variability, which can contribute to a species’ better adaptability to changing environmental conditions. Based on results, we see several areas that require further research. For example, in-depth genetic studies could provide more detailed information on adaptive mechanisms and the species’ resilience to environmental changes. It would also be useful to examine how variations in karyotype affect genetic stability and the species’ ability to adapt to different conditions.

Pollen fertility is a significant determinant of whether in a population there will be enough regeneration through sexual reproduction to ensure the survival of that species; it is very important in fruit and seed production in flowering plants. Pollen plays an important role in the formation of the hereditary properties of seeds [31]. The pollen fertility knowledge for any plant species is essential for plant breeders and commercial growers. Fertile pollen is that pollen which, under favorable conditions, after falling on the stigmas of the same plant or other plants of the same species, the pollen tubes germinate and the male gametes enter the embryo sac, producing fertilization. For the successful production of fruits and seeds of flowering plants, information on pollen fertility is required, which can be determined using in vitro tests. How important information about pollen fertility is for obtaining productive offspring can be seen from our previous works and from literary sources [32,33,34,35,36,37,38]. In addition to pollen fertility, the size of pollen grains plays an important role. According to the morphological heterogeneity of pollen, one can assume failures in microsporogenesis, which can lead to unsuccessful seed formation.

The sizes of pollen grains of each species from the collections obtained for different years do not differ much from each other. A. moschata pollen fertility investigation results are presented in

Table 3. Pollen parameters of Amberboa moschata under cultivation in the Yerevan Botanical Garden and in the natural habitat of Ararat Valley.

Amberboa moschata		Pollen Grain Size, Μm	Pollen Fertility Percentage
	Range	Average Size, μm	Range	Average Fertility, %
Yerevan Botanical Garden
Cultivated specimens	61.4–63.2	62.1 ± 0.6	92–100	96.7 ± 0.9
Herbarium samples (ERE) collected from natural habitats
N 130754	62.4–67.1	64.1 ± 1.1	93–100	96.0 ± 2.2
N 139664	60.2–62.8	61.7 ± 0.5	96–100	97.8 ± 0.7
N 145154	59.8–61.6	60.6 ± 0.4	95–100	98.2 ± 1.1
N 151800	59.4–62.4	60.6 ± 0.6	95–99	97.4 ± 0.9
N 153193	62.4–63.6	62.6 ± 0.4	95–100	97.6 ± 1.3
N 202314	57.4–62.6	59.8 ± 1.3	92–100	96.8 ± 1.4
N 161644	58.2–62.4	59.7 ± 0.8	98–100	99.4 ± 0.5
N 182109	58.8–63.0	60.6 ± 0.8	94–100	96.6 ± 1.3
N 202313	60.2–62.8	61.7 ± 0.5	95–99	95.8 ± 1.6
N 202334	60.3–64.5	62.2 ± 1.1	95–100	98.1 ± 1.2

.

Previously, we studied the pollen of eight samples of Psephellus erivanensis Lipsky taken from the arid regions of the Ararat Valley of Armenia. Pollen fertility rates averaged 96.9 ± 0.6% [10]. According to literary sources, many species of the Asteraceae family are characterized by high pollen fertility. Our data were also compared with the work on other species from the family Asteraceae [31,38], where, despite the different growing conditions, high fertility of pollen of different species of this family was noted. The results show that the average pollen fertility of A. moschata is quite high, both in freshly collected samples from the Yerevan Botanical Garden (Table 3, Figure 7) and those taken from the herbarium specimens, collected in the natural habitats of the Ararat Valley. This indicates that under favorable conditions in the botanical garden there will be a high seed set, which will contribute to the successful reproduction of these endangered species for further use in landscaping gardens and parks in order to preserve their gene pool.

3.3. Ecological–Physiological Characteristics

Some physiological features of A. moschata were revealed in the natural conditions of the gypsophilous semi-desert of the Ararat Valley and under ex situ conditions in the Yerevan Botanical Garden. Comparative analysis of the data obtained makes it possible to assess both the degree of their adaptability to extra-arid conditions and the degree of ecological plasticity when they are transferred to the conditions of the Yerevan Botanical Garden. The following parameters were determined: total water content of the plants, intensity of transpiration, and photosynthetic productivity (

Table 4. Indicators of the total water content, photosynthetic productivity, and intensity of transpiration of Amberboa moschata in natural habitat and in the Yerevan Botanical Garden (mean ± standard deviation, n = 9: in 2022 and 2023 with three plants studied for each ecosystem).

Plant Species and Habitat	Total Water Content, %	Water Deficit, %	Intensity of Transpiration, mg CO2 dm2/h	Photosynthetic Productivity, mg/g Wet Weight, h
Amberboa moschata cultivated in the Yerevan Botanical Garden	50.02 ± 0.91 c	35.83 ± 0.82 d	135.62 ± 0.92 b	2.13 ± 0.902 cd
Amberboa moschata in the natural habitat of the Erebuni State Reserve	48.01 ± 1.08 d	37.81 ± 0.81 b	130.43 ± 0.91 b	2.03 ± 0.821 d

Note: within each column different letters indicate samplings which significantly differ from one another according to the results of the Tukey test (p < 0.05).

). In the Yerevan Botanical Garden, compared to natural habitat, the studied plants have higher total water content, indicating their adaptability. With constant but moderate watering, all examined plants in the botanical garden showed a decrease in water deficiency.

This suggests that they have evolved structural and metabolic mechanisms to efficiently use water, typical to dry conditions. Xerophytic plants usually have characteristics such as increased concentration of cell sap and increased osmotic pressure, which contribute to increased water absorption. Moreover, their cells contain hydrophilic colloids that retain water, resulting in reduced transpiration and optimal use of water resources. Common adaptation features of xerophytic plants to the arid environment are the preservation and minimization of the rate of water loss, along with the maximization of the rate of photosynthesis [39]. These plants also maintain stable photosynthetic productivity at high temperatures, further reducing water consumption and indicating efficient water use.

The density of the cell sap was also determined, amounting to 6.3% per gram of the substance under investigation in the Yerevan Botanical Garden and 6.5% in its natural habitat.

The absorption and transformation of solar energy during photosynthesis is carried out by photosynthetic pigments of plants, in particular, chlorophyll “a” and “b” and carotenoids. To assess the state of the photosynthetic apparatus of A. moschata, the content of these pigments in them was studied, which is a very important internal factor in plant adaptation to unfavorable environmental conditions. Chlorophyll “a” primarily absorbs light in the red and blue regions of the spectrum and plays a central role in photosynthesis. Chlorophyll “b” extends the range of light absorption, particularly in the blue and red-orange regions, thereby enhancing the plant’s ability to capture light energy—especially under low-light or extreme growing conditions (

Table 5. The content of plastid pigments in fresh leaves of Amberboa moschata, mg/g, grown in the Yerevan Botanical Garden.

Optical density of chlorophyll “a”, λ 663	0.932 ± 0.015 d
Optical density of chlorophyll “b”, λ 645	0.847 ± 0.001 c
Optical density of carotenoids, λ 440.5	1.261 ± 0.014 d
Chlorophyll “a” content, per wet leaf (mg/g)	22.308 ± 0.114 c
Chlorophyll “b” content, per wet leaf (mg/g)	26.612 ± 0.112 c
Chlorophyll “a” + ”b”	48.920 ± 0.102 cd
Chlorophyll “a”/“b”	0.8 ± 0.022 c
Carotenoids content, per wet leaf (mg/g)	6.85 ± 0.271 d

Note: mean ± standard deviation n = 9: in 2022 and 2023 with three plants studied for each ecosystem; λ—the length of the wave. Within each column different letters indicate samplings which significantly differ from one another according to the results of the Tukey test (p < 0.05).

). The results of the study indicate that A. moschata is well adapted to dry climates characterized by high summer temperatures and elevated soil surface evaporation. These traits make the species a promising candidate for use in xeriscaping, a water-efficient landscaping method that reduces or eliminates the need for irrigation.

Observations at the Yerevan Botanical Garden show an increase in water content in plants, along with an increase in the rate of transpiration and photosynthesis, leading to a significant reduction in water stress. The content of pigments in A. moschata indicates the intensity of physiological processes related to the life activity of this plant. The studied species demonstrate ecological plasticity, which allows for successful adaptation to the conditions existing in the Yerevan Botanical Garden.

3.4. Ornamental Traits and Practical Application

The ornamental period is the total duration of the highest manifestation of aesthetic qualities, including the vegetative formation of the plant until the end of flowering and fruiting, and the maximum degree of decorativeness during the flowering period. The developed scale of A. moschata decorativeness includes 15 main features characterizing the decorative qualities of the shoot, leaf, inflorescence, fruit, and the plant as a whole (

Table 6. Assessment of Amberboa moschata decorativeness.

Traits of Decorativeness	Traits Value and Score (Points)	Trait Significance Coefficient	Number of Points
1	2	3	4
Inflorescence color and stability	Color is bright, stable or slightly unstable (5)	3	15
Inflorescence shape	Large fringed basket (5)	2	10
Inflorescence size (diameter and height)	Diameter 5–7 cm, height from 3.5–4.5 cm (5)	2	10
Petal quality	Dense, retaining shape under adverse weather conditions (5)	1	5
Number of inflorescences on one generative shoot	One inflorescence (5)	2	10
Number of simultaneously open inflorescences on a plant	In the mass flowering phase about 70% (5) and more or about 50% (4)	3	15
Inflorescence density	Dense, compact (5)	2	10
Shoot strength	Not subject to deformation under the influence of external factors (5)	2	10
Shoot coloring	Bright (5) or middle bright (4)	1	4
Leaf color stability	Stable (5) or slightly unstable (4)	2	8
Durability of leaf decorativeness	Most decorative during the phases of budding and flowering (5)	1	5
Fruit decorativeness	Fruits slightly enhance the decorative effect (5)	3	9
General condition of plants during the flowering period	Presence or absence of breaks during flowering (5)	2	10
Plant originality	Habitus attractiveness (5)	1	5
Period of decorativeness	From the phase of formed vegetative habit of the plant until the end of flowering (5)	1	5
Sum of points	131

). Conversion coefficients for each feature allow us to determine its significance in the overall assessment of the decorativeness of the species. When assessing the decorative qualities of the shoot, its resistance to weather and climatic conditions and color were taken into account. We received 14 points, since shoots are slightly susceptible to lodging during heavy rainfall and are able to return to their original position. The decorative qualities of the leaves were assessed by such features as their resistance to fading and durability. Since the leaf color does not fade significantly, and the leaves themselves are decorative before fruiting, these features received 13 points. Since the appearance of the fruits is insignificant, but they enhance the decorativeness in the fruiting phase, thereby prolonging the decorativeness of the plants, this feature attained 9 points. The general condition of the plants, due to friendly flowering, uniformity in height, and their density in the absence of gaps during mass flowering, allowed us to evaluate this feature at 10 points. The originality of the plant received 5 points. The overall assessment of the decorativeness of A. moshata was 131 points, thus permitting us to recommend this wild annual for landscaping.

The decorativeness assessment scale we provided will help a specialist gardener to objectively evaluate the visual appeal of the plants under study in combination with other landscape elements. This scale can be used as a tool for planning and maintaining the aesthetics of a garden, as it allows, firstly, evaluation of the visual effect, i.e., to determine how decorative a plant is at a certain time of year. Secondly, the scale allows choice of the most suitable zones for a plant in landscape design. Thirdly, the scale makes it possible to plan seasonality, i.e., to take into account the period when the plants reach their peak of decorativeness. In our case, given the decorative period of A. moschata (from mid-May to early August) and the flowering period (from late May to early August), it can play a significant role in the landscape as a mid-ground plant in mixed flower beds of continuous flowering, to create beautiful and lush groups of several specimens against the background of a lawn, on rocky hills, and in natural-style gardens. Using the decorative scale, gardeners can create more balanced and beautiful compositions, making the garden attractive at any time, taking into account their preferences in care and style.

The distribution of the Asteraceae family on all continents and their ecological adaptability to a variety of habitat types make them one of the most popular in ornamental gardening [40,41]. The Asteraceae family is widely used in landscape design due to the diversity in ornamental species, with priority often given to native plants. Climate global warming dictates the need to conduct studies to select ornamental species that are more resistant to drought [40,42]. In this regard, drought-tolerant native species are of considerable interest for ornamental xerogardening and xerolandscaping [43,44]. Representatives of the Asteraceae family not only decorate urban landscapes, but have been shown to be useful for the bioremoval of a wide range of pollutants in urban areas when incorporated into urban green spaces [45]. The arid natural conditions of the Ararat Valley, where the capital of Armenia, the city of Yerevan, and other settlements are located, significantly limit the use of many species, forms, and varieties of cultivated flower crops in landscaping. The wild ornamental drought-tolerant species A. moschata can be used in urban plantings for decorating borders and mix-borders; planted in flowerbed groups; incorporated as patio and container plants; easily adapted in rockeries; grown on balconies, terraces, and in flowerpots; and cultivated within cottage, informal, and wildlife gardens. Flowers of A. moschata are suitable for cutting in bouquets and keep perfectly fresh in a vase. It has been found that ornamental Asteraceae used for landscaping can be a source of pollen for urban bees [46]. A. moschata, which is visited by bees during the flowering period, can have a similar significance in urban plantings. In order to create functional and aesthetically attractive spaces in the Yerevan Botanical Garden, we used such landscape design methods as multi-leveling in rockeries and mixed flower beds and a seasonal method that allows for maintaining an attractive appearance of the garden throughout the growing season. Also important is the ecological approach method—the inclusion of local plants, which helps maintain the local ecosystem and facilitates garden maintenance. Long-term observations show that in the conditions of Yerevan’s distinctly continental climate, wild species with high ecological plasticity and wide vertical amplitude are most easily introduced into culture for the creation of living collections, as well as species whose ranges coincide with the territory of the botanical garden (Yerevan floristic region) or are close to it, as in the case of A. moschata. The use of these methods helps to design a harmonious and balanced landscape that meets both aesthetic and functional requirements.

4. Conclusions

This study assessed various aspects of A. moschata, an endangered species of the Armenian flora, including its morpho-phenological, karyological, palynological, ecological–physiological, and ornamental characteristics, within the context of ex situ conservation. The species’ ability to complete its life cycle and regenerate from seeds under controlled conditions confirms its viability and adaptive potential for long-term cultivation. Plants cultivated at the Yerevan Botanical Garden, compared to those in their natural habitat, exhibit higher total humidity, greater photosynthetic intensity, and a reduction in water deficit. The identification of the diploid cytotype of A. moschata is significant, as it represents the primary chromosome set typical for the species. Further genetic research could provide deeper insights into its adaptive mechanisms in response to environmental changes. Regarding pollen fertility, the values obtained from plants grown at the Yerevan Botanical Garden, along with those collected from nature over several years, indicate very high fertility. This is consistent with studies on pollen fertility in other species within the Asteraceae family. An assessment was also made of A. moschata ornamental qualities under the conditions of the Yerevan Botanical Garden. A scale was developed to evaluate the decorative features of the inflorescence, shoots, leaves, fruits, and plant habit. The scale can be useful for integrating A. moschata into various landscaping schemes. Currently, no officially recognized scale exists for assessing the ornamental value of wild plants or some taxa from the natural flora. Therefore, the creation of these scales is particularly relevant for introducing ornamental species from the natural flora into cultivation. The study shows that A. moschata achieves its highest degree of decorativeness during its 68–70-day flowering period, with the entire ornamental phase lasting approximately 98 days. Due to its rarity, aesthetic appeal, and adaptability in cultivation, A. moschata is recommended for inclusion in living collections in botanical gardens, and for use in ornamental gardening and landscaping as part of ex situ conservation efforts. Given the challenges posed by global warming, there is a growing need to introduce drought-resistant ornamental species into cultivation. In this context, the wild xeromorphic species A. moschata is of particular interest for ornamental xerogardening and xerolandscaping. This species can be particularly beneficial for landscaping arid regions of Armenia.