The Biology of Flowering and the Pollinating Insects of Results and Discussions

92 JOURNAL OF BOTANY VOL. VIII, NR. 1 (12), 2016 JOURNAL OF BOTANY VOL. VIII, NR. 1 (12), 2016 93 THE BIOLOGY OF FLOWERING AND THE POLLINATING INSECTS OF RESULTS AND DISCUSSIONS THE SPECIES POLYGONUM SACHALINENSE F. SCHMIDT Polygonum sachalinense is one of the valuable plants for the Republic of Moldova, since it can be UNDER THE CONDITIONS OF THE REPUBLIC OF MOLDOVA used as raw material in preparing fodder, medicines and food. It is a perennial, herbaceous plant with shoots that lignify and turn brown in winter, the leaves fall, and, in spring, they renew from the dormant Cîrlig Natalia1, Cîrlig Tatiana2 buds located at the base of the stem. In the ontogenetic development of the plant, several phases of 1. Botanical Garden (Institute) of the ASM development have been highlighted: 2. Tiraspol State University E-mail: [email protected] 1. Juvenile phase – includes the period of time from the germination of seeds to the formation of the first true leaves. Abstract: The species Polygonum sachalinense F. Schmidt is native to Far East, and was introduced in Moldova in the 80s. 2. Vegetative phase – is characterized by an intense development of the aerial part of the plant and This article describes the peculiarities of flowering of the given species under the conditions of our country, the length of the formation of the shoots of the 1st, 2nd and 3rd order on the stem. In this phase, the period of mass flowering period, the life of inflorescences and flowers and the number of inflorescences on a plant and on a shoot. We made a list formation of seeds coincides with the period of seed ripening. The vegetative phase lasts 115-122 of insect species that pollinate Sakhalin knotweed in the Republic of Moldova. days from the beginning of vegetation. (Fig.1) Key words: Polygonum sachalinense, biology, flowers, inflorescences, pollinating insects, phases of development. 3. Generative phase – this phase, at Sakhalin knotweed, begins with the formation of flower buds, then – of inflorescences and fruits. This phase is characterized by less intensive growth of vegetative INTRODUCTION organs. Under the conditions of the Republic of Moldova, the generative phase lasts 58-62 days. Flower buds appear from the buds located in the axils of younger leaves, from the top of shoots, The study of biology of flowering is of particular interest in the research on plant biological which then will form inflorescences. characteristics, with the purpose of introducing and acclimatizing new, valuable species. Each species 4. Senescence phase – covers the period from the end of the fruit formation to natural death. The has developed individual characteristics that allow it to adapt to environmental conditions, such as natural death of the plant takes place in late autumn, when temperatures below 0 ºC are recorded; morpho-anatomical or physiological changes in the structure of flowers that make pollination easier, leaves turn brown, necrotize and fall from shoots. At this moment, the growing season of a plant regardless of its type – direct, indirect or cross pollination, carried out through various factors like: ends. gravity, insects, wind, birds, water etc. Flowering is usually defined as the development phase of a flower from the opening of the corolla Sakhalin knotweed has small flowers (0.5 cm in diameter), white-cream or green-cream until its withering, with the maturation of the gynoecium and androecium, followed by pollination and coloured, grouped in compound inflorescences, branched, with 20-48 secondary inflorescences, they seed formation. Particular attention is paid to these phases in the study of plant development. are 17-20 cm long, forming a compound, dense panicle with an abundance of small flowers (Fig. 2). Without pollination carried out by insects, many plants would not be able to reproduce. Pollinating Polygonum sachalinense is a species with hermaphrodite flowers and female flowers on separate plants, insects are of great use in agriculture. In order to obtain a stable seed yield, it is necessary to have a in a population, there are both types of individuals [3, 5]. The perianth is simple, haplochlamydeous, sufficient number of pollinators, because if flowers aren’t pollinated, they will not form seeds. Pollination consisting of 5 petals, obovate or elliptical, the petal tip – obtuse or acute. A small percentage of flowers is nothing but the act of transferring pollen grains from anthers to stigma. Entomophile plants (from are fertilized during the flowering phase, but since there are a lot of flowers on a plant, relatively many “entomos” - insect) are those that are pollinated by insects and have various adaptations of flower shape seeds are produced [4]. and structure [1]. MATERIALS AND METHODS The research on the biology of flowering was conducted during the growing season of 2015, in August-October, on the experimental plot of the Plant Resources Laboratory of the Botanical Garden (I) of the ASM, planted with Polygonum sachalinense in 2013. The research was carried out according to: Методические указания по семеноведению интродуцентов (Methodical Guidelines for the Study of Seeds of Introduced Species), 1980, Методика изучения фенологии растений и растительных сообществ (Methods of Studying the Phenology of Plants and Plant Communities), Бейдеман И., 1974 [6, 7]. The pace of seasonal flowering and the pace within 24 hours were studied by analyzing about 50 plants. The dynamics of flowering was studied during the flowering of the first 10% of all plants from the experimental plot, until the total completion of the flowering phase. The dynamics within 24 hours was examined during the mass flowering phase. The examination of pollinating insects was done during the flowering phase, at different times of the day, by taking photos and collecting insects for further study in laboratory conditions. In order to Fig. 1 Polygonum sachalinense in the Fig. 2 Inflorescences of Polygonum identify the insects, the “Определитель насекомых” (“Insect Identification Manual”), 1994, and the vegetative phase of development sachalinense encyclopaedia “Insectele” (“Insects”), 2010, were used [2]. 94 JOURNAL OF BOTANY VOL. VIII, NR. 1 (12), 2016 JOURNAL OF BOTANY VOL. VIII, NR. 1 (12), 2016 95 The flowering phase of the species Polygonum sachalinense is long (August - September), it lasts Table 2. List of species of pollinating insects of Polygonum sachalinense 37-40 days. In this period, about 650-2000 flowers bloom in an inflorescence, depending on the size Order Family Species and position of the inflorescence. There are inflorescences on every shoot, the number of inflorescences 1 Diptera Sarcophagidae Sarcophaga carnaria ranges between 20 and 85. The number of inflorescences on a plant can reach 350. A flower lives 2-4 days, an inflorescence – about 10-15 days (Tab.1). 2 Califoridae Lucilia caesar Flowering begins with the better developed central stems, on which bigger inflorescences with a 3 Syrphidae Syrphus ribesii larger number of flowers are formed. The flowers open at 5-6 a.m., depending on light intensity and 4 Eristalis tenax temperature fluctuations between 16 and 20 ºC. At 9.30-10.00 a.m., up to 80% of all flowers open, and after 5 Spherophoria scripta 14.00 o’clock, 100% of the flowers open, according to their staggered maturation in inflorescences (Fig. 3). 6 Tachinidae Tachina fera 7 Hymenoptera Apidae Apis mellifera Table 1. The biology of flowering of the species Polygonum sachalinense 8 Scoliidae Scolia hirta 1. Number of inflorescences on a pant 300-350 9 Formicidae Formica rufa 2. Number of inflorescences on a shoot 20-85 10 Lasius niger 3. Number of flowers per inflorescence 650-2000 11 Vespidae Katamenes arbustorum 4. Lifetime of an inflorescence 10-15 days 12 Coleoptera Coccinelidae Coccinella septempunctata 5. Lifetime of a flower 2-4 days 13 Adalia bipunctata The beginning of flower bud formation, in the growing season of 2015, occurred in the first half of 14 Adalia quadrimaculata August, and flowering began 10-12 days later. On a Sakhalin knotweed plant, at the same time, can be 15 Harmonia axyridis found flower buds, flowers, unripe and ripe seeds, because flowering and fruitage are staggered. 16 Cantharidae Rhagonycha fulva As a result of the examination of generative shoots, we found out that if the inflorescences were slightly touched, the flowers fell, and on some inflorescences, flower abortion took place. Insects of the order Diptera are cosmopolitan species that easily adapt to different habitats, are of various types: pollinating, parasitic, predatory, saprofagous, haemophagous. The order Hymenoptera is represented by ants, bees, bumblebees, wasps, etc. Most adults are phytophagous, feeding on nectar and fruit juice, they are social species that live in large families. Beetles, or Coleoptera, are widely distributed in the world, they live in diverse terrestrial and aquatic habitats. By the mode of nutrition, they are zoophagous, saprofagous and phytophagous. Every third found species is a beetle [2]. Fig. 3. The dynamics of flowering of Polygonum sachalinense during 24 hours Formation and maturation of fruits are staggered. Fruit is a trigonal (three-sided) achene of green colour, which then gradually turns brown. The order of shoots is also important for seed production. On a plant, there are offshoots of st1 , 2nd, 3rd order, and seed formation occurs depending on their position, Fig.4. Systematic distribution of insect species so, on the shoots of the 1st order, there will be more flowers that will produce more seeds, and on the shoots of the 2nd and 3rd order, fewer seeds will be produced. A plant with seven branches, in the The following species were observed on flowers most often: Sarcophaga carnaria, Lucilia caesar, conditions of the Republic of Moldova, bears fruits weighing about 90 g. Apis mellifera and ladybirds. Coccinellidae are common species who live on plants, relatively small Pollinators. The Sakhalin knotweed is pollinated by wind and by insects.

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