Bottle brush lanceolatus DC () nectar: amount, type of nectar sugars and honeybee foraging Jk Gupta, J Kumar

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Jk Gupta, J Kumar. Bottle brush Callistemon lanceolatus DC (Myrtaceae) nectar: amount, type of nectar sugars and honeybee foraging. Apidologie, Springer Verlag, 1993, 24 (6), pp.564-568. ￿hal- 00891131￿

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Bottle brush Callistemon lanceolatus DC (Myrtaceae) nectar: amount, type of nectar sugars and honeybee foraging

JK Gupta J Kumar

1 Department of Entomology, Dr YS Parmar University of Horticulture and Forestry Nauni, Solan -173 230; 2 RRS, HPKV, Bajaura, Kullu, (HP) India

(Received 28 September 1992 ; accepted 5 May 1993)

Summary — The maximum amount of nectar sugars in the of bottle brush, Callistemon lan- ceolatus, protected from nectarivores was 6.044 mg/ 72 h after flower opening, whereas the 24-h sugar value was only 0.44 mg. Apis mellifera harvested ≈ 90% of the sugar produced by the flo- wers. The concentration of solutes in the nectar ranged between 25 and 40%. Only fructose and glu- cose were found to be present in the nectar. A mellifera visited 9.5 flowers/min to collect nectar. Apis mellifera / Callistemon lanceolatus / nectar secretion / foraging behaviour

INTRODUCTION the nectar sugars produced per flower, and to determine the period of nectar se- cretion and the proportion of various for- Bottle brush, Callistemon lanceolatus DC aging nectarivores. (Myrtaceae), is native to . In India it is cultivated as an ornamental . The bottle brush inflorescence of bright-scarlet MATERIALS AND METHODS this tree is most ornamental, and there is a resulting rapid expansion of roadside plantations of this plant. Although it has in- The observations were carried out during April- variably been included in the honeybee May at Nauni, Solan, India (1 400 m above sea floral calender (Srawan and Sohi 1985; level), near an apiary with 20 Apis mellifera and 2 A cerana indica colonies. The amount of sug- Garg 1989), information on its nectar char- ar present in C lanceolatus flowers of different acteristics and attractiveness to honey- age was determined by enclosing floral buds in bees and other insects is lacking. The nylon cages on 3 different trees. The sampling present study was undertaken to quantify was made at 24-h intervals. At each sampling time, 10 flowers were individually rinsed for Nectar secretion rate 45 min in 5 ml distilled water in a capped vial. After removing the flower, the sugar in the rin- was A sate analysed (Roberts, 1979). parallel The amount of nectar sugars accumulated set of floral buds was left open and flowers were varied in the flowers from insect sampled at 0 (freshly opened flowers), 24, 48, protected visits The nectar content in 72, 96 and 120 h and the dry sugar content de- (table I). sugar to termined. Microcapillary tubes (5 μl) were used the freshly opened flowers amounted to remove nectar from the caged flowers and 0.173 mg/flower. The C lanceolatus 24-h the sugar concentration was recorded with a sugar value (the amount of sugar accumu- hand refractometer (range 0-50% Bellingham lated within 24 h of flower opening) was and Ltd, Wells The Stanley Tunbridge UK). sug- 0.44 mg. This value is generally used to ar concentration was determined in 150 flowers attractiveness of a nectar source (50 flowers each from 3 different trees). Nectar express to nectarivores C lanceola- sugars were identified by descending paper (Crane, 1975). chromatography using butanol, benzene, pyri- tus nectar was found to have increasing dine and water (5:1:3:3) as solvent and aniline amounts of sugar until 72 h after flower phthalate as developer (Zweig and Whitakar, opening. Therefore, the 24-h value may 1971). underestimate the total nectar potential. The counts of different insect foragers were Hence it is suggested that instead of the made on 2 inflorescence/ 5 each in 3 min, trees, 24-h sugar value, the maximum amount of during each observation period. These counts sugar accumulated in a flower should be were continued for 3 sunny days, and the aver- considered as an index of bee flora attrac- age values represented insect activity during dif- ferent day-time hours. tiveness. In 96-h-old flowers the amount of to 4.8 This indi- The data were analysed via factorial random- sugar dropped mg/flower. ised block design (Panse and Sukhatme, 1978). cates a resorption of ≈ 19% of the secreted nectar. This amount is low compared to that observed in flowers of certain other

RESULTS AND DISCUSSION

At the experimental site C lanceolatus mainly bloomed during April-May, with a number of other minor flushes during the year. Each inflorescence contained on av- erage 58 flowers (ranging between 45-71 flowers, n = 100).

Nectar solute concentration

The solute concentration in the nectar var- ied between 25-40% in flowers of different ages (25-30% in 24-h, 25-32% in 48-h and 38-40% in 72-h-old flowers); based on forager honey sac contents, Srawan and Sohi (1985) reported the nectar con- centration of C lanceolatus to be 12%. plant species (varying between 42-96%; while collecting nectar. A mellifera foraging Gupta et al, 1984, 1986; Mishra et al, rate was 9.5 flowers/min. Each flower was 1985; Reddy and Gupta, 1987). C lanceol- observed to be foraged by as many as 10 atus flowers started to wither after 120 h bees during a 1-h period. Honeybee forag- but still contained 5.2 mg sugar/flower at ing rate depends upon foraging behaviour that time. and the floral structure of the plant con- Flowers foraged by nectarivores had cerned. A mellifera foraging rates on some other from 3.8 to 9.1 flowers/ sugar amounts that varied between 0.148 vary to 0.261 mg/flower (non-significant differ- min (Free, 1970). In addition to honey- bees, were found to be occasional ences). Thus honeybees (which were the Diptera main foragers) appeared to harvest > 90% visitors but were only observed during the h. of the secreted nectar. The qualitative counts at 10:00 analysis revealed that C lanceolatus nectar contained fructose and only glucose. Résumé — Étude quantitative et qualita- A mellifera activity remained high tive des sucres du nectar de Calliste- throughout the day, constituting 87% of the mon lanceolatus DC (Myrtaceae) et insect visits (table II). A c indica showed no comportement de butinage des abeilles. activity; this was probably due to the pres- L’étude a été faite à Solan (Himachal Pra- ence of only 2 colonies, as compared to 20 desh, Inde, 1 400 m d’altitude) à proximité A mellifera colonies. However, at a dis- d’un rucher comportant 20 colonies d’Apis tance of ≈ 2 km, A c indica activity was mellifera et 2 colonies d’Apis cerana indica very high on C lanceolatus flowers. At this dans le but de déterminer la quantité de distance, the feral population constituted nectar sécrétée, la durée de la sécrétion the source of A c indica. Honeybees show nectarifère, la quantité de sucres prélevée typical foraging behaviour on C lanceola- par les nectarivores, la concentration en tus flowers. They land on the lower flowers sucres et le type de sucres du nectar de and then gradually climb up the flowers Callistemon lanceolatus, plante ornemen- tale largement répandue. La quantité de Menge der von Besuchern gesammelten sucres présente dans les fleurs a été dé- Nektarzucker, die Nektarkonzentration und terminée en rinçant les fleurs à l’eau dis- die Art der produzierten Zucker zu bestim- tillée et en analysant l’eau de rinçage (mé- men. thode de Roberts, 1979). On a prélevé le Die Menge des in den Blüten vorhande- nectar avec des microcapillaires (5 μl) et nen Zuckers wurde nach der Methode von analysé sa concentration à l’aide d’un ré- Roberts (1979) mit einem "Spectronic 20" fractomètre à main (Bellingham et Stanley, bestimmt, wobei nach Spülung der Blüten Angleterre ; domaine de mesure : 0-50%). in destilliertem Wasser die Spülflüssigkeit L’analyse qualitative des sucres du nectar analysiert wurde. Zur Bestimmung der a été faite par chromatographie sur papier. Zuckerkonzentration wurde Nektar in Mi- L’activité des insectes butineurs a été en- krokapillaren (5 μl) entnommen und die registrée sur 2 inflorescences pendant 5 Konzentration in einem Handrefraktometer min à 10, 12, 14 et 16 h. La quantité de (Bellingham and Stanley, England; Meßbe- sucres sécrétée en 24 h par C lanceotatus reich 0-50%) bestimmt. Die Nektarzucker a été de 0,44 mg (tableau I), mais la quan- wurden papierchromatographisch be- tité maximum a été trouvée dans les fleurs stimmt. Das Verhalten von Nektarsamm- âgées de 72 h (6,044 mg/fleur). Ensuite la lern wurde jeweils für 5 min an zwei Blü- quantité redescendait dans les fleurs tenständen um 10.00, 12.00, 14.00 und âgées de 96 h, indiquant la résorption 16.00 h registriert. d’environ 19% du nectar sécrété. Les Der 24-h Zuckerwert von C lanceolatus fleurs butinées par les nectarivores conte- betrug 0.44 mg (Tabelle 1), aber die naient de 0,148 à 0,261 de sucre/fleur. mg größte Zuckermenge wurde in 72 h alten a montré le nec- L’analyse qualitative que Blüten gefunden (6.044 mg/Blüte); danach tar avait une forte teneur en hexoses puis- fiel die Menge in 96 h alten Blüten ab, was ne du fructose et du qu’il comportait que auf eine von etwa 19% des ab- A mellifera 87% des Resorption glucose. représentait Nektars hinweist. Von Samm- insectes visitaient la gesonderten qui plante (tableau II). lern besuchte Blüten enthielten 0.148- Le taux de de l’abeille domesti- butinage 0.261 mg Zucker/Blüte. Die était de fleurs/min. qualitative que 9,5 Nektaranalyse ergab einen hohen Gehalt an Hexosen, bestehend ausschließlich aus mellifera / Callistemon lanceola- Apis Fruktose und Glukose. Bei den blütenbe- tus / nectar / glucide / butinage suchenden Insekten (Tabelle 2) stellte A mellifera 87%. Die Sammelfrequenz von A mellifera betrug 9.5 Blüten/min. Zusammenfassung — Nektar des "Bottle Callistemon lanceolatus brush", Callistemon lanceolatus / Nektar- DC Art der Nektar- (Myrtaceae): Menge, zucker / Sammelverhalten zucker und Sammelverhalten der Bienen. 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