Grasses (Poaceae Barnhart or Gramineae Jusseu) are monocotyledonous plants, annual or biennial therophytes or perennials, herbaceous, rarely woody. Usually, grasses have hollow stems with internodes. The arrangement of the leaves varies: from alternate, to spiral or opposite. The root system is fasciculate. The inflorescence is a spike. Grasses are the largest family in the monocotyledonous class. In Flora Europaea (Tutin, 1980) 155 genera have been described. The Russian researcher Цвелев Н. (1987) classified grasses into Bambusoideae and Pooideae. According to the current classification developed by the Angiosperm Phylogeny Group (APG), grasses are found in the following subfamilies: Anomochloöideae, Pharoideae, Puelioideae, Aristidoideae, Panicoideae, Arundinoideae, Micrairoideae, Danthonioideae, Chloridoideae, Oryzoideae, Bambusoideae, Pooideae. In the latest version of The Plant List, the Poaceae family lists 759 genera with 47,428 scientific names of species, of which only 11,554 are accepted names (32,806 are mentioned as synonyms). Poaceae occur on every continent, including Antarctica. Some species are appreciated, since ancient times, as cereal, fodder, medicinal and ornamental crops. In the flora of the Republic of Moldova, there are 1834 specific taxa, of which 147 species are grasses, making up about 8 % of the total number of species, although it is one of the most representative families (Pînzaru, Sîrbu, 2016). In the Red Book of our country (2015) 6 species of grasses have been included. The species, varieties and cultivars of the Poaceae family from the collections of annual and perennial plants and the experimental sector of the Laboratory of Ornamental Plants of the NBGI, the germplasm collection and the herbarium specimens served as materials for the research. Classical methods have been the basic tool in identifying characters and determining the taxonomic affiliation of species (Negru, 2007; Ciocîrlan, 2009). The nomenclature is given according to Cerepanov S., but with some current additions promoted by The Plant List (2021). The geoelements and the spectrum of life forms were analyzed and specified according to Cristea et al. (2004) and Aeschmann et al. (2004). The grasses family in the collections and on the experimental field of the Laboratory of Ornamental Plants is currently represented by 22 genera, 30 species and 26 cultivars. The representatives of the genus Miscanthus Anderss. are the most numerous – 3 species and 18 cultivars, followed by Stipa L. – 4 species. The other genera are represented by 2-3 species or even by a single one. Currently, the collection includes 50 intraspecific taxa. Some species have been present in the collection for over five decades (Briza maxima L., B. media L., Festuca glauca Vill., Miscanthus sinensis (Tunb.) Anderss etc.). Others were added to the collection about four-five years ago (Imperata cylindrica (L.) Raeusch, Nassella tenuissima (Trin.) Barkworth, Lagurus ovatus L. etc.) or two years ago (Koeleria glauca (Scharad.) DC., S. zalesskii Wilensky etc.). Analyzing the distribution of the studied species of grasses, we have found that they belong to the following geoelements: Eurasian and European, Mediterranean, North American, Asian, Pontic-Caucasian, Circumpolar. The predominance of Eurasian, Asian and Mediterranean species is obvious, due to the geographical position of our country. Besides, the adaptive potential of North American species is very high, although they are represented by only 3 species (9 %). For example, Chasmanthium latifolium (Michx.) Yates. – a species less known in our country, blooms, bears fruit, produces viable seeds, tolerates thermal and humidity oscillations. It prefers sunny spaces, but also tolerates partial shade. We consider this floristic region a promising one and we will continue to enrich the collections with new taxa originating from North America. Other species, although vegetate abundantly and go through the flowering stage, still do not produce viable seeds: Imperata cylindrica (L.) Raeusch, Nassella tenuissima (Trin.) Barkworth, Roegneria canina (L.) Nevski, Koeleria glauca (Scharad.) DC., Arrhenatherum elatium (L.) P. Beauv. ex J. Presl. & C.Presl. etc. Circumpolar and Pontic-Caucasian elements are less represented in the collections of ornamental plants (3 %). Most grasses are xerophytes, but can also grow in conditions of high humidity, behaving as xeromesophytes or even mesophytes. As for the light requirements, they are usually heliophytes, but some species can also be included in the sciophyte category. The most numerous taxa are perennial, rhizomiferous hemicryptophytes. Only seven species of grasses are annual therophytes. The minority of annual taxa is explicable: first of all, only species with valuable indicators of decorativeness can be found in the collection. But the most important factor is the dependence of development rates on climatic factors. The impact of drought, heat, early frost in some years threatens the yield of seeds, but also their viability. Therefore, in order to maintain and develop a collection of plants, it is appropriate to collect, store and preserve the germplasm correctly every year. In conclusion: the Poaceae family is represented in the collections of ornamental plants by 22 genera that include 30 species and 26 cultivars of high ornamental value. The plants are resistant to adverse environmental conditions, pathogens and pests. The predominance of Eurasian, Asian and Mediterranean elements is conditioned by the geographical position of our country. The researched taxa of grasses are xerophytes, but can also behave as xeromesophytes or mesophytes. In the collections, the grasses are represented by two life forms: annual therophytes and perennial hemicryptophytes. Due to their hardiness and minimal requirements to water, soil and temperature, ornamental grasses can be used successfully in rockeries, pools, in floral decorations together with other plants, in solitary groups, borders, containers etc. References Cartea Roşie a Republicii Moldova. Î.E.P. Ştiinţa, Ediţia 3-a, Chisinau, 2015. С. 115- Cristea V., Gafta D., Pedrotti F. Fitosociologie, Cluj-Napoca: Ed.: Presa Universitară Clujeană: 394 p. Negru A. Determinator de plante din flora Republicii Moldova. Tipografia Ed. Universul. Chişinău, 2007. P. 305-338. Pînzaru P., Sîrbu T. Flora vasculară din Republica Moldova (Lista speciilor şi ecologia). Ediţia 2. Tipografia UST. Chişinău. 2016. 261 p. Tutin T. Gramineae (Poaceae). In: Flora Europaea. V5. Cambridge University Press. 1980. P.118-267. Цвелев Н. Н. Порядок злаки. In: Жизнь растений. Т.6. Под ред. Тахтаджяна А. Л. Изд. «Просвещение» 1982, Москва. С. 341-378. URL: http://www.theplantlist.org/1.1/browse/A/. (last accessed: 08.09.2021). URL: https://edis.ifas.ufl.edu/topic_family_poaceae. (last accessed: 08.09.2021). URL: https://plants.usda.gov/core/profile?symbol=IMCY. (last accessed: 08.09.2021). URL: http://www.mobot.org/MOBOT/research/APweb/. (last accessed: 16.09.2021).
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