Anchusa Officinalis L.)

Vol. 51 No. 2 2007 Journal of Apicultural Science 25

CHARACTERISTICS OF FLORAL NECTARY AND NECTAR OF COMMON BUGLOSS (Anchusa officinalis L.)

El¿bieta Weryszko-Chmielewska, Miros³awa Chwil Department of Botany, Agricultural University, Akademicka 15, 20-950 Lublin, Poland. E-mail: [email protected] Received 06 April 2007; accepted 17 July 2007

Summary This study was pointed to the distribution, micromorphology of nectary and nectar secretion of Anchusa officinalis L. flowers. Observations of floral nectary structure were carried out with a scanning electron microscope (SEM). The mass of nectar produced over a flower's life span and sugars concentration in the nectar were determined. Flowers of Anchusa officinalis were eagerly visited by honeybees. The gland of Anchusa officinalis that secretes nectar is located at the base of the ovary and consists of 4 parts. No stomata were found in the epidermis of the nectary. The secretion of nectar proceeded through outer cell walls of the epidermis. Some cells with collapsed walls resembled the stomata. Flowers secreted nectar with sugars concentration of 61%, and the sugar yield of 10 flowers accounted for 4.69 mg. Keywords: floral nectary, micromorphology, nectar mass, sugar concentration, sugar efficiency, Anchusa officinalis L., Boraginaceae.

INTRODUCTION cently, due to the content of toxic Common bugloss Anchusa officinalis L. alcalloids: lycopsamine and 7-acetyllycop- (Boraginaceae) is a plant commonly occur- samine, it has been withdrawn from thera- ring in various regions of Poland peutics (Sadowska 2004). It is also used (Rutkowski 2006, Zaj¹c and Zaj¹c as an important cosmetic plant (Hlava et al 2001). It overgrows roadsides, hills, rail- 1984) and as an ornamental plant in sunlit way embankments and ruderal sites. gardens in a strip of higher plants. In addi- Flowers have a radial corolla, red-violet tion, it is included as an apicultural plant at the beginning and change into vio- providing nectar and pollen (Rawski 1948, let-blue during blooming. The corolla Maurizio and Grafl 1969, Ko³towski reaches 6-15 mm in diameter with a tube 2006, Pogorzelec 2006). length of 5-7 mm. Large, hairy throat This study was aimed at determining the scales close the inlet into the corolla's tube. nectar secretion of Anchusa officinalis L. The blooming stage of the flowers spans flowers under conditions of the city of from April till September (Rutkowski Lublin as well description the morphologi- 2006). cal traits of the floral nectary of this species. Roots and flowers of common bugloss are used in the dyeing industry. Roots were MATERIAL AND METHODS used to produce a dark purple dye, whereas Analyses of the nectar secretion of flowers obtained a yellow dye (Nowiñski Anchusa officinalis L. flowers were carried 1983, Pogorzelec 2006). out at the Botanical Garden of the Maria Common bugloss is believed to be a me- Sk³odowska-Curie University in Lublin in dicinal herb (Sarwa 2001), however re- the years 2005-2006 using the method of 26

Jab³oñski and Szklanowska (1979). The nectar was collected at 9:00 a.m., three times in four samples in the full blooming stage of plants. One sample was made of the nectar mass originating from the entire life span of 40-45 flowers. Microscopic analyses referred to the structure of the floral nectary. For observations of the surface of nectary epidermis in a scanning electron microscope (SEM), fragments of flowers were fixed and the plant material was prepared according to the method described by Weryszko-Chmielewska (2003).

RESULTS Flowers of Anchusa officinalis (Fig. 1) were eagerly visited by honeybees. A plate-like dark blue part of the corolla petals, with whitish or light-pink throat scales, was an attractant to insects. The adaxial surface of the petals was dull and Fig. 2. Segment of adaxial surface of corolla slightly velvet. It resulted from the pres- petal, with visible densely arranged coniform hair. Bar = 30 µm. ence of conoidal hair which densely cov- ered it (Fig. 2). The structure of hair occur- ring on the surface of corolla petals and its density may be an adaptive trait to pollination by specified groups of insects.

Fig. 3. Four-segment ovary (o) with a nectary (n) at the base. Bar = 300 µm. The nectary gland of Anchusa officinalis consisted of 4 parts, accompanying the base of particular segments of the ovary (Fig. 3). Each segment of nectary sur- rounded the basal segment of the ovary from the outside, thus forming a noticeable protrusion growing out beyond the ovary. Fig. 1. Flowers of Anchusa officinalis visited Nectariferous tissue formed some whole by a honeybee. with the ovary and was separated from it Vol. 51 No. 2 2007 Journal of Apicultural Science 27

Fig. 4. Fragment of the surface of nectary (n) epidermis

Fig. 8. Fragments of secretory tissue, in some cells there are visible convex outer cell walls with smooth cuticule, in others - walls collapsed in the central part

Fig. 5. Fragments of secretory tissue, in some cells there are visible convex outer cell walls with smooth cuticule, in others - walls collapsed in the central part

Fig. 9. Fragments of secretory tissue, in some cells there are visible convex outer cell walls with smooth cuticule, in others - Fig. 6. Fragments of secretory walls collapsed in the central part tissue, in some cells there are visible convex outer cell walls with smooth cuticule, in others - walls collapsed in the central part

Fig. 10. Fragments of secretory tissue, in some cells there are visible convex outer cell walls with smooth cuticule, in others - Fig. 7. Fragments of secretory walls collapsed in the central part tissue, in some cells there are visible convex outer cell walls gland reached ca. half of that value. The with smooth cuticule, in others - mean radial thickness of the nectary ac- walls collapsed in the central part counted for 79 µm. The thickness of the only with a minute hollow. The height of nectary constituted 14% of the diameter the ovary together with the nectary reached covering the pistil ovary and nectariferous 566 µm, whereas the height of the nectary tissue. 28

Table 1 Abundance of nectar secretion by Anchusa officinalis flowers.

Mass of nectar per Sugars concentration Mass of sugars per Year of study 10 flowers (mg) in nectar (%) 10 flowers (mg) min. - max. x min. - max. x 2005 7.62 - 8.43 8.41 61.0 - 64.5 61.68 5.19 2006 7.02 - 9.17 7.03 59.0 - 61.5 59.70 4.20 x 7.72 60.69 4.69

Cells of nectary epidermis were of a size 1995). In turn, Andersson (1988) claims similar to that of cells of ovary epidermis that more visits of bumble bees were re- (Fig. 4). When analyzed under a scanning corded on small plants of common bugloss electron microscope they were multi-angle, than on the large flowers of that species. slightly elongated and isodiametric with Ko³towski (2006) also reports that single sizes ranging from 10 to 15 µm. The exter- plants of common bugloss are often occu- nal wall of most of the cells was convex pied by bumble bees and solitary bees. and was characterized by smooth cuticula Floral nectaries of common bugloss are (Figs. 5, 7, 8, 9). Between this type of cells located beneath the base of the ovary and there were cells with collapsed walls, usu- are characterized by large sizes as com- ally in the central part (Figs. 6-10), which pared with that part of the flower, since may point to their adaptation facilitating their height constitutes ca. half the height nectar secretion. No stomata were observed of the ovary. In this species, the shape of in the epidermis of nectary. It indicates that the nectary is similar to that described by nectar secretion proceeded through the Stpiczyñska (2003) in Symphytum outer walls of the epidermis cells. Some officinale (Boraginaceae). No stomata were cells with collapsed walls resembled the found in epidermis of Anchusa nectary, stomata (Figs. 6, 7, 9). whereas they occurred in high numbers in Flowers of Anchusa officinalis secreted the nectarines of other species of that nectar with a high concentration of sugars family: in Symphytum officinale ranging from 59 to 65%, with the mean (Stpiczyñska 2003) and in Myosotis value accounting for 61%. Ten flowers of sylvatica (Weryszko-Chmielewska Anchusa officinalis secreted ca. 8 mg of 2003). This indicates that nectar secretion nectar and their sugar efficiency reached in Anchusa proceeds through the surface of 4.69 mg (Table 1). cell walls of nectary epidermis in which typical hollows were observed which might DISCUSSION facilitate nectar exudation. The study demonstrated that flowers of The calculated mean mass of nectar se- Anchusa officinalis were eagerly visited by creted by a single flower of Anchusa honeybees, which has also been confirmed officinalis reached 0.77 mg. The concentra- by other authors (Maurizio and Grafl tion of sugars in nectar accounted for ca. 1969, Pogorzelec 2006). They are also a 61%. In turn, the mass of sugars obtained source of food for bumble bees which pre- from nectar of a single flower reached fer large plants of that species, providing 0.47 mg. This value is considerably lower abundant secretion of nectar (Dreisig compared to values reported for that spe- Vol. 51 No. 2 2007 Journal of Apicultural Science 29 cies by Demianowicz et al. (1963), i.e. Hlava B., Starý F., Pospíšil F., Krejèová 0.8 - 1.2 mg, as well as by Ko³towski Z. (1984) – Roœliny kosmetyczne. PWRiL, (2006), i.e. 1-2 mg. That author evaluated Warszawa. the apiarian value of Anchusa officinalis as Jab³oñski B., Szklanowska K. (1979) – good. In contrast, Rawski (1948) deter- Propozycje zmiany metody badañ nektarowania roœlin. Pszczeln. Zesz. Nauk. mined nectar secretion by that taxonomic 23: 105-113. unit as medium. Pogorzelec (2006) points Ko³towski Z. (2006) – Wielki atlas roœlin to the great diversification of nectar secre- miododajnych. Przeds. Wydawn. Rzeczy- tion by Anchusa depending on soil condi- pospolita SA. tions and emphasizes that in field cultiva- Maurizio A., Grafl I. (1969) – Das Tracht- tion it secretes remarkably more nectar pflanzenbuch. Ehrenwirth Verlag, München. than in natural conditions. In turn, the mass Nowiñski M. (1983) – Dzieje upraw i of sugars secreted by the flower of com- roœlin leczniczych. PWRiL, Warszawa. mon bugloss, due to their high concentra- Pogorzelec M. (2006) – Roœliny miodo- tion in nectar, was considerably higher in dajne. Wyd. S¹decki Bartnik, Nowy S¹cz. the plants examined as compared to the Rawski M. (1948) – Po¿ytki pszczele. Cz. mass of sugars contained in nectar of III. Wartoœæ po¿ytkowa roœlin dzikich i upra- Symphytum officinale (0.33 mg) described wnych. Wydaw. „Ex Libris”, Warszawa. by Stpiczyñska (2003). Rutkowski L. (2006) – Klucz do oznacza- Despite considerable apiarian values of nia roœlin naczyniowych Polski ni¿owej. Wydawnictwo Naukowe PWN, Warszawa. common bugloss, attention should be given to its toxic properties that may also refer to Sadowska A. (2004) – Rakotwórcze i truj¹- ce substancje roœlinne. SGGW, Warszawa. its nectar. Toxic alcalloids of that species are assumed to be able to penetrate into the Sarwa A. (2001) – Wielki leksykon roœlin leczniczych. Ksi¹¿ka i Wiedza, Warszawa. human body with consumed honey originating from nectar of that plant Stpiczyñska M. (2003) – Sekrecja nektaru w kwiatach ¿ywokostu lekarskiego (Sadowska 2004). (Symphium officinale L.) i jego sk³ad chemiczny. Acta Agrobot. 56 (1-2): 27-31. REFERENCES Weryszko-Chmielewska E. (2003) – Andersson S. (1988) – Size-dependent Morphology and anatomy of floral nectary pollination efficiency in Anchusa officinalis and corolla outgrowths of Myosotis sylvatica (Boraginaceae): causes and consequences. Hoffm. (Boraginaceae). Acta Biol. Crac. Oecologia 76(1): 125-130. Ser. Bot. 45(1): 43-48. Demianowicz Z., Jab³oñski B., Zaj¹c A., Zaj¹c M. (Red.) (2001) – Atlas Ostrowska W., Szybowski S. (1963) – rozmieszczenia roœlin naczyniowych Wydajnoœæ miodowa wa¿niejszych roœlin w Polsce. Wydaw. Pracownia Chorologii miododajnych w warunkach Polski. Komputerowej Instytutu Botaniki UJ i Pszczeln. Zesz. Nauk. 2: 95-111. Fundacji dla UJ, Kraków. Dreisig H. (1995) – Ideal free distributions of nectar foraging bumblebees. Oikos 72(2): 161-172. 30

CHARAKTERYSTYKA NEKTARNIKÓW KWIATOWYCH I NEKTARU FARBOWNIKA LEKARSKIEGO (Anchusa officinalis L.)

Weryszko-Chmielewska E., Chwil M.

Streszczenie W pracy zbadano po³o¿enie i mikromorfologiê nektarników oraz obfitoœæ nektarowania kwiatów Anchusa officinalis L. Obserwacje struktury nektarników przeprowadzono w skaningowym mikroskopie elektronowym (SEM). Okreœlono masê nektaru wyproduko- wanego w ci¹gu ca³ego ¿ycia kwiatu oraz zawartoœæ cukrów w nektarze. Kwiaty Anchusa officinalis by³y chêtnie oblatywane przez pszczo³y. Gruczo³ nektarnikowy Anchusa officinalis po³o¿ony by³ u podstawy zal¹¿ni i sk³ada³ siê z 4 czêœci. W epidermie nektarnika nie stwierdzono obecnoœci aparatów szparkowych. Sekrecja nektaru odbywa³a siê za poœred- nictwem zewnêtrznych œcian komórek epidermy. Niektóre komórki z zapadniêtymi œcianami komórkowymi przypomina³y aparaty szparkowe. Kwiaty wydziela³y nektar o koncentracji cukru 61%, a ich wydajnoœæ cukrowa z 10 kwiatów wynosi³a 4,69 mg. S³owa kluczowe: nektarnik kwiatowy, mikromorfologia, masa nektaru, koncentracja cukrów, wydajnoœæ cukrowa, Anchusa officinalis L., Boraginaceae.