ACTA AGROBOTANICA Vol. 64 (2): 25–32 2011 THE BIOLOGY OF FLOWERING OF WINTER ACONITE (Eranthis hyemalis (L.) SALISB.) 1Krystyna Rysiak, 2Beata Żuraw 1Botanical Garden of Maria-Curie Sklodowska University in Lublin, Sławinkowska 3, 20-810 Lublin, Poland e-mail: [email protected] 2Department of Botany, Laboratory of Horticultural Plant Biology, University of Life Sciences in Lublin, Akademicka 15, 20-950 Lublin, Poland, e-mail: [email protected] Received: 07.01.2011 Abstract (Walters et al. 1989; Szweykowscy, 2003) or Eranthis hyemalis belongs to the Ranunculaceae family even ten species (Tutin et al. 1964). whose representatives enrich early spring pollen flow and nec- Winter aconite (Eranthis hyemalis) occurs tar for pollinating insects. Flowering biology and morphological in the wild in Europe from the south-eastern part of characteristics flowers of winter aconite were studied. The fora- France to Bulgaria (Szweykowscy, 2002). It co- ge value was estimated as the rate of nectar production. mes from the fertile forests of France, Italy, Slovenia, Observations were carried out between 2008 and 2011 Serbia, Bosnia, and Croatia (Polunin, 1969; E r - in the Botanical Garden of the Maria Curie-Skłodowska Univer- hardt et al. 2002). It has been cultivated since 1570 sity located in the Lublin area. (Marcinkowski, 2002) and has become wide- In the conditions of Lublin, flowering of winter aconi- spread all over Europe (Tutin et al. 1964; Wal- te plants started at the beginning of February and lasted until ters et al. 1989). In Poland winter aconite occurs the end of March. The seasonal bloom dynamics was strongly sporadically in the western part of the country as a fe- affected by maximum temperatures, which intensified flower ral plant (Szweykowscy, 2003). It is also men- blooming, and snowfalls which hampered this process. During the day, flowers opened between 8.00 am and 3.00 pm, but the tioned among ephemerophytes (Mirek et al. 2002). highest intensity was between 10.00 am and 12.00 am. The pro- This plant grows mainly among light thicket and sha- cess of pollen release, with the average number of 29 stamens dy groves (Amann, 1997). It is an ornament of old shedding pollen in the flowers, lasted from 2 to 3 days. During parks (Szweykowscy, 2003). Winter aconite pro- the day the largest number of anthers opened at noon hours, pagates profusely if the soil is sufficiently moist during between 11.00 am and 1.00 pm, though a certain rise in this the spring (Amann, 1997). It perfectly reproduces number was also observed in the morning hours between 8.00 vegetatively by tubers and is not difficult in cultivation and 9.00 am. Eranthis hyemalis flowers develop funnel-shaped (Marcinkowski, 2002). nectaries, on average 3-6 per flower. The determined amount Winter aconite is a small perennial plant with of nectar per flower was 1.23 mg, while the concentration of a tuberous rhizome (Amann, 1997; Szweykow- sugars in it averaged 72.11%. The weight of nectar sugar per scy, 2003) or small spherical tubers (Walters et flower was 0.88 mg. al. 1989; Marcinkowski, 2002). A characteristic feature of its plants is a whorl consisting of 5 deeply Key words: winter aconite, Eranthis hyemalis, dynamics of dissected leaves (Strasburger et al. 1967). But flowering, nectar, pollen release. Szweykowscy (2003) report that there are three stem leaves, sessile, palmately lobed, arranged in an involucral whorl. The basal leaves, long-petiolate, pal- INTRODUCTION mately lobed, with 5-7 linear sections, appear after flo- The genus Eranthis Salisb. of the Ranun- wering cessation (Szweykowscy, 2003). The flo- culaceae family occurs in the wild in Europe and wers of winter aconite are yellow- or golden-coloured Asia (Walters et al. 1989; Szweykowscy, and cup-shaped. They consist of 6 petals, 10-15 mm 2003). The above-mentioned genus comprises seven in length. The diameter of flowers reaches 20-30 mm 26 Krystyna Rysiak, Beata Żuraw (Tutin et al. 1964; Polunin, 1967; Amann, shedding pollen were marked every 2 hours during 2 1997; Marcinkowski, 2002). The flowers close days of the full flowering period. Then, the number of at 7 pm (Szweykowscy, 2003). There are necta- stamens that shed pollen was determined every 2 hours ries in them (Szweykowscy, 2003). until all the stamens in the flower were empty of pol- The flowering period is at the turn of February len. In total, 50 flowers were observed. and March in western and central Europe (Core, The daily rate of pollen shed in the winter aco- 1955; Amann, 1997; Erhardt, 2002; Szwey- nite flowers was observed in 2010. To this end, the kowscy, 2003). Marcinkowski (2002) reports number of stamens that had started shedding pollen that in the Polish conditions blooming may extend was counted in 10 flowers every hour during 3 days of even into April. the full flowering period. The yellow-coloured flowers of plant species of In 2011 the rate of nectar production in the the buttercup family lure many pollinators (Amann, flowers was examined by J a b ł o ń ski’s method 1997; Lipiń ski, 2010) and can be a valuable so- (2003). In order to determine the weight of nectar, urce of pollen (Szklanowska, 1995; Denisow 12 samples with 5 flowers in each were collected. Nec- and Ż uraw, 2003). In the period when there is no tar sugar concentration was measured with an Abbe pollen, bees can not produce royal jelly or even be- refractometer. The nectaries in the flowers were exa- eswax, the mother bee stops laying eggs and larvae die mined under a stereoscopic microscope. in the cells (Howes, 1979; Lipiń ski, 2010). In most of the area of Poland, currently there is a shortage RESULTS AND DISCUSSION of important early spring bee forage (J a b ł o ń ski, 1994). This is why flower gardens that provide to in- Plant morphology. The tuberous rhizome is sects an abundant and easy food source in the form of an underground organ of winter aconite (Fig. 1b,c). It nectar and pollen are of great importance (J a b ł o ń - can easily be divided into fragments that are single tu- ski, 1994; K o ł towski, 2006). bers, which are described by Walter et al. (1989) The aim of the present study was to determine and Marcinkowski (2002). Winter aconite sel- the rate of flowering and pollen release of winter aco- f-propagates through seeds, which readily germinate nite cultivated in gardens, which can be an excellent shortly after they are shed from the follicles (Fig. 2a), supplement to the food resource for bees waking up provided that there is adequate moisture in the soil. in the spring. The nectar production rate was also was Many young seedlings were observed in the observa- determined. tional plot which had suitable growth conditions. In the first and second year after sowing, only long-pe- tiolate palmate leaves grow out of the ground, charac- MATERIALS AND METHODS terized by a deeply lobed leaf blade (Fig. 1a,b). In the The investigations were conducted in 2008- third year, flower stalks also grow out of the rhizomes 2011 in the Botanical Garden of the Maria Curie-Skło- (Fig. 1c). One whorl, composed of three sessile, deeply dowska University located in the Lublin area. Speci- lobed leaves, occurs just below the flower on the stem mens of winter aconite (Eranthis hyemalis (L.) Salisb.) (Fig. 2), in accordance with a description by Szwey- growing in a dense patch on a slope, under the canopy kowscy (2003). The leaves create a kind of ruff situ- of a branchy maple, were selected for the observations. ated under the terminal flower (Figs 3-5). The flowers This site had a south-eastern exposure. Every year the of winter aconite reached a diameter between 2.5 cm flowering time was determined; the start of flowering and 3.0 cm (Fig. 6). According with Szafer`s and was determined to be when 10% of the plants in a de- Wojtusiakowa`s (1969) classification, winter signated area opened the perianth leaves. In 2009 the aconite flowers are included in bowl-shaped flowers seasonal flowering rate was investigated and it was with completely hidden nectaries (Fig. 6c). Many in- analysed against the background of the atmospheric sects from different groups have access to these flowers, conditions during the flowering period of the plants. except insects with a short proboscis. These authors To this end, newly opened buds were counted every say that this kind of nectaries are attractive for insects day at 10 am in the designated area of 1 m2 and marked because of their shape and colour (Fig. 7). Stamens in with a coloured thread. the flowers are arranged spirally on an elongated floral The daily rate of flower opening was analyzed axis (Fig. 6d). Apocarpic gynoecium consisted from in 2009 every hour during a period of three days of 3-5 free pistils with an elongated one-chambered ovary full bloom, by counting newly opened flowers on the and a stigma on a short style (Fig. 6e). After flowering, designated experimental area of 1 m2. elongated follicles appeared at the tip of the flower. The duration of pollen release was examined in The flowering pattern. The development of 2009. For this purpose, 5 new flowers that had started flowers took place in very early spring, and even in The biology of flowering of winter aconite (Eranthis hyemalis (L.) Salisb.) 27 winter. Buds of winter aconite, covered by the ruff The structure of the nectary and the process the lobed leaves, grew out of the litter created from of nectar secretion in flowers.