The seed quality of Deutzia Thunb. in the conditions of the Bashkir Urals

Murzabulatova Fanuza Kavievna ORCID: 0000-0002-8024-9863 PhD in Biology Researcher; South Ural Botanical Garden-Institute of the UFIC RAS 450080, Russia, Republic of Bashkortostan, Ufa, Mendeleev str., 195 / 3 murzabulatova@yandex.ru

Polyakova Natal'ya Viktorovna ORCID: 0000-0002-3717-0308 PhD in Biology Leading Researcher; South Ural Botanical Garden-Institute of UFIC RAS 450080, Russia, Republic of Bashkortostan, Ufa, Mendeleev str., 195 / 3 barhan93@yandex.ru

The genus Deutzia (Deutzia Thunb.) belongs to the Hydrangeaceae family (Hydrangeaceae Dumorter) and includes shrubs up to 2.0 m tall. The shoots are smooth, brownish-gray, with slightly noticeable scattered lentils. The leaves are opposite, pointed, ovate or lanceolate, finely filiform and finely toothed along the edge, short-stemmed, without stipules. Inflorescences are more often corymbose or semi-elliptic, racemose or paniculate; occasionally the flowers are solitary. The corolla is 5-petaled, the petals are white, cream, lilac, pink. There are 10 stamens arranged in two circles; the stamens of the inner circle are shorter than the outer ones. The ovary is 3-5 nesting, lower; the seeds are small (0.5-1 mm long), numerous, angular, flat or convex ^[1]. The name was given by K. Thunberg in honor of the Dutch philanthropist Johann van Deutz, thanks to whose assistance Thunberg managed to visit Japan. For a long time, the genus Deutzia was known only from a single representative, D. scabra Thunb., described from the author's own collections in Southern Japan ^[1]. The genus includes about 60 species, growing mainly in East and Southeast Asia (Philippines, Himalayas), a smaller part of the range is located in Mexico, 4 species grow there ^[1]. 2 Korean-Chinese species enter the territory of Russia – D. parviflora var. amurensis Rgl (Middle Amur and the southern part of Primorye) and D. glabrata Kom. (Southern Primorye, Middle Amur) ^[2]. Acacia prefer mountainous habitats, in the south of their range they are found at an altitude of 2000-3000 m above sea level ^[1].

Acacia as decorative profusely flowering shrubs are widely used in decorative gardening in European countries where the climate is quite warm ^[3]. Taking into account the high decorative value of the plants, it becomes necessary to study their introduction resistance in regions with a more severe climate, as a result of which it will be possible to include some taxa in the assortment of ornamental plants of these regions.

An analysis of the literature has shown that at the moment the number of published works on the study of the biology of deuterium seeds is extremely small. The most detailed study of the cytogenetics of various types of action is reflected in foreign literature sources ^[4]. In domestic works, attention was mainly paid to aspects of acclimatization of populations in new conditions: winter hardiness, seasonal rhythm of development and morphological parameters ^[5]. In addition, the literature of recent years has highlighted attempts to use species and varieties of acacia in the landscaping of settlements in the middle belt and arid regions of Russia ^[6]. As for the study of various methods of reproduction of bacteria, only data on vegetative methods are available in the literature ^[7]. There is practically no information on the study of the biology of deuterium seeds, and the available single data relate to works from earlier years ^{[8, 9]}. The most recent data on the weight of smooth action seeds, their quality and features of seed reproduction are contained in the monograph by N.M. Voronkova and co-authors ^[10].

In the botanical garden of Ufa, the collection of collections began to form in the 80s of the last century. The first species in the collection were D. parviflora and D. parviflora var. amurensis. By 2020, the collection included 23 taxa of deutzias from 2 sections: Mesodeutzia (Deutzia melkotsvetnaya, D. Amur, D. smooth, D. corymbose) and Deutzia (deutzia rough, D. Maksimovich, D. Ningboanskaya, D. elegant, D. corymbose, D. bicolor, D. Vilmorena, D. long-leaved, D. Vicha, D. Schneider loose-flowered). In addition, the collection contains interspecific hybrids (Deutzia hybridica, D. kalmietsvetkovaya, D. magnificent) and 6 varieties. According to the results of the introduction studies, it was found that most species of breeding in the climatic conditions of the Republic of Bashkortostan are unstable and do not tolerate low temperatures in winter; only a small part of the collection is promising for introduction ^[11].

The purpose of this work is to identify the characteristics of the seed quality of stable and promising species of the genus Deutzia for cultivation in the Southern Urals.

Materials and methods

The objects of the study were 3 species of action from the Mesodeutzia section, the most adapted to the climate of Bashkortostan and steadily passing all stages of phenological development: small-flowered action (D. parviflora Bge.), small-flowered Amur action (D. parviflora var. amurensis Rgl.) and smooth action (D. glabrata Kom.). All these species entered the collection YUUBSI from the Main Botanical Garden of the Russian Academy of Sciences (Moscow): The first two were planted in 1986, and the third type was planted with seeds in 2006.

The city of Ufa (Republic of Bashkortostan, Russia) is located at latitude: 54°44.5836' s. w. and longitude: 55°58.0674' v. d. The climatic conditions of the region have significant differences from the climate of the natural habitats of the studied species of deutsii. The main characteristics of the climate of the Republic of Bashkortostan are moderate continentality, a long winter period and hot summers. There are frequent late spring and early autumn frosts. In winter, thaws often occur, which negatively affect the condition of even hardy plants. The average temperature in January is from -12.4 °C to -14.5 °C, the minimum is fixed at -48.5 °C. The average height of the snow cover reaches 80 cm. In July, the average temperature is +19.5 °C, the absolute maximum temperature is fixed at +37.5 °C. The duration of the frost-free period is on average 144 days. The amount of precipitation in the warm period is about 350 mm, the annual average is up to 590 mm, the maximum falls in June–July ^[12].

The winter hardiness of introduced species of plants was determined on a 7-point scale of the Main Botanical Garden of the Russian Academy of Sciences: I – there is no damage, II – a small part of the annual shoot freezes (up to 25%), III – a significant part of the annual shoot freezes (over 25%), IV – annual shoots freeze completely, V – two-year-old and older ones freeze shoots, VI – the crown freezes to the level of snow cover, VII – the entire crown freezes to the root neck, VIII – the plant freezes completely ^[13].

The seasonal rhythm of the development of bacteria was studied according to the generally accepted method of phenological observations ^[14].

The weight of the seeds was determined by weighing: the result was the average weight of 3 1000-piece canopies. Seed germination and germination energy were determined according to GOST ^[15]; the germinated seeds were counted in 4 repetitions on the 5th, 10th, 15th and 20th days after sowing.

The soil germination and duration of organic dormancy of seeds were determined by sowing 100 pieces in 3 repetitions in a soil-sand mixture (3:1).

The following statistical procedures were used for statistical processing of the obtained data: arithmetic averages, standard deviations, and correlation analysis.

Results and discussion

The main limiting factor for the successful introduction of spices in the Republic of Bashkortostan is low temperatures at the beginning of winter (-25 °C and below), when the snow cover is still low. In such winters, shoots freeze above the snow level. All the buds located below the snow level were preserved and shrubs bloomed in the lower tier of the crown. However, in recent years, the nature of winter conditions has changed, winters have become milder and more snowy, as a result of which the flowering and fruiting of acacia has increased significantly. Even the most thermophilic species of acacia began to bloom more abundantly and set viable seeds. A comparative analysis of the winter hardiness of the YUUBSI collection allowed us to identify 3 species characterized by absolute winter hardiness, abundant flowering and a high level of fruiting, regardless of winter conditions in the region.

Deutzia parviflora Bge. is a shrub up to 1.5 m tall. The leaves are ovate or oblong-ovate, pubescent, up to 8 cm long and 3.5 cm wide, with a finely filiform margin. The inflorescence is corymbose. The flowers are 1.5 cm in diameter, the petals are white, with a cream tint, rounded or obovate. The fruit is a rounded box. The seeds are elliptical, sometimes almost rounded, with a short apical wing, dark brown. The distribution area is Northern China, Korea, Mongolia. A rare protected species, listed in the Red Book of the Amur region ^[2]. It grows along the mountain slopes in a strip of oak forests at an altitude of 400-1400 m above sea level. The plants in the YUUBSI collection are 28 years old, their height is on average 1.0 m, the crown diameter is 0.70 m. The duration of flowering is 17 days (on average from 9 to 23 June). Winter hardiness is I point.

Deutzia Amur (Deutzia parviflora var. amurensis Rgl.). Shrub up to 2.0 m high. The bark of young shoots is brown, old ones are gray. The leaves are ovate and oblong-ovate, up to 7 cm long and up to 3 cm wide, with a finely serrated edge. The color of the leaves in spring and summer is bright green, in autumn - brown-yellow. The inflorescence is corymbose, up to 7 cm in diameter; the flowers are white, odorless, the petals are rounded or obovate. The fruit is a rounded or slightly spherical capsule. The seeds are dark brown and small. It grows naturally in Northeastern China, Korea, and the southern part of Primorye. It is widespread in mixed forests, occasionally in oak forests, often near rocks, prefers illuminated habitats. It is protected in several Far Eastern nature reserves. At the age of 28, plants in the South Ural Botanical Garden Institute have the following characteristics: The average height is 1.55 m, the crown diameter is 1.2 m. The beginning of flowering is celebrated on May 24 and lasts for 19 days. The seeds ripen mainly in the second decade of October, leaf fall begins in late September-early October. In comparison with natural habitats, the duration of the growing season in the culture in the Southern Urals is shorter by 8-10 days. The species is absolutely winter-hardy (I point).

Deutzia glabrata (Deutzia glabrata Kom.). Shrub up to 2.0 m in height. Young shoots are red-brown, older ones are gray or brownish–gray with peeling bark. The leaves are lanceolate and broadly lanceolate up to 11 cm long and 4.5 cm wide, with a more or less elongated pointed tip. The inflorescence is a loose half–cone. The petals are obovate, white. The fruit is a truncated elliptical or hemispherical capsule. The seeds are small, oblong or elliptical, with a triangularly pointed apical wing. It is naturally distributed in the south of Primorsky Krai, in Northeastern China, on the Korean peninsula. It grows in the forest along the edges, in shrubby thickets near streams, near rocks, on rocky slopes of mountains and ravines and always in the shade. Rare and protected species: listed in the Red Book of the Russian Federation and the regional Red Books of the Jewish Autonomous Region and Primorsky Krai, protected in the Far Eastern Marine Reserve. The limiting factor is the breaking off of branches into bouquets, the natural limiting factor is weak seed renewal. In the YUUBSI collection, plants aged 7 years are characterized by the following parameters: an average height of 1.10 m, a crown diameter of 0.80 m. Blooms, on average, from May 24 to June 7, for about 14 days. In the conditions of the Bashkir Urals, it blooms 2 weeks earlier than in natural habitats. The seeds ripen mainly in the first decade of October. The winter hardiness score is high (I); for all the years of observation, specimens of this species were not damaged by winter frosts, except for the first 2-3 years after planting, when annual shoots froze in young plants.

All three of the most stable species of action belong to the Mesodeutzia section. Their high winter hardiness is due to the fact that in the conditions of the Southern Urals they manage to go through all phases of seasonal development, first of all, to complete the phase of complete lignification by the beginning of stable frosts. The seeds of these species also have time to fully mature by the beginning of the winter period. The remaining types of the collection belong to the Deutzia section and are distinguished by a later start of vegetation, a longer period of shoot growth and fruit ripening, which does not allow them to completely complete the vegetation and prepare for winter.

The fruit of the deuterium is a 3-5 nest box, truncated spherical or hemispherical. When ripe, they open from above and from below along the partitions with the opening of the nests inside the box.

The seeds are small, numerous, depending on the species up to 1.0 mm long and up to 0.8 mm wide. They are oblong, elliptical or almost rounded in shape. The seed peel is translucent, cellular wrinkled and often larger than the seed in size, tubularly expanded near the hem, and extended into the wing at the apical end. The embryo is straight, small, and occupies a large part of the endosperm ^[8]. The seeds of plants of the genus Deutzia do not have a dormant period.

The results of determining the weight of 1000 pieces of seeds are presented in Table 1. The weight of seeds of all three studied species is approximately the same, and in some years it coincides, such as in 2015. However, according to the average long-term indicators, the seed weight of the Amur acacia is slightly lower compared to the other two species.

Table 1

The weight of 1000 pieces of seeds of different types of spices

The first shoots of deuterium seeds in laboratory conditions appeared on the 7th accounting day, mass shoots in D. parviflora var. amurensis and D. parviflora - on the 10-15 th day. With ground sowing, the first shoots appear after 10-12 days, mass shoots ‒ after 14 days in all the studied species. According to literature data, in laboratory conditions without pre-sowing preparation in the Main Botanical Garden (Moscow), the seeds of deuterium germinate on the 7th day, after freezing, the germination period does not change ^[10]. Consequently, the germination period of deuterium seeds obviously does not depend on climatic conditions, to a greater extent this property is determined by species (genetic) characteristics.

There is very little literature data on the soil and laboratory germination of deuterium seeds. According to some data, in the Far East, the laboratory germination of deuterium seeds was 97-100%, and in the Main Botanical Garden ‒ about 14% germination ^[10]. In the conditions of the South Ural Botanical Garden-Institute, the maximum germination, both laboratory and soil, was noted in D. parviflora, and in both conditions the germination was approximately the same – about 67% (Table 2). The germination energy was noted by us only in laboratory sowing conditions; the maximum energy germination was also recorded in D. parviflora and is 31%, the minimum values of this indicator were noted in Deutzia glabrata (15%).

Table 2

Laboratory and soil germination of seeds of deuterium species

Germination energy and germination of deuterium seeds were also determined after several years of storage in paper bags at room temperature. It was found that the germination energy remains low during the first two years of storage; laboratory germination after 1 year of storage remains relatively high, after the second it decreases sharply; after 3 years of storage, the seeds no longer germinate (Table 3).

Table 3

Germination energy and germination of deuterium seeds after various storage periods

Conclusion

Of the 27 taxa of the genus Deutzia in the collection of the South Ural Botanical Garden-Institute of the Ufa Scientific Center of the Russian Academy of Sciences, only 3 species are the most stable in the conditions of the Bashkir Urals: D. parviflora, D. parviflora var. amurensis, D. glabrata. All of them bloom and bear fruit annually, have absolute winter hardiness. In recent years, due to global climate changes, the duration of flowering of acacia has increased significantly, the decorative effect has also increased due to the absence of long periods of severe frosts in winter: if earlier flowering was observed only in the lower part of the crown, up to the level of snow, now the entire crown is covered with flowers. Accordingly, the seed productivity of the plants has also become higher. The germination rate of seeds collected in the period 2011-2016 is higher than average, the maximum parameters were noted in D. parviflora (about 67% of both laboratory and soil germination). The laboratory germination of seeds lasts only 1 year. Thus, the studied types of actions are promising for introduction into culture and wide application in landscaping of settlements of the Republic of Bashkortostan.

The study was carried out within the framework of the state task No. 122033100041-9 of the UUBSI UFIC RAS. The authors declare that there is no conflict of interest.