Abstract
Fifty‐one regional honey samples, collected mainly from Uttarakhand and Uttar Pradesh districts, were studied to determine the pollen composition. Pollen spectra of the local honeys varied according to the vegetation type utilized by the bees within this floristically diverse region. Eight pollen types from Uttarakhand and seven from Uttar Pradesh were the predominant pollen types in honey and included both local naturalized flora as well as cultivated crops. The investigation revealed that in addition to already known bee forage (e.g. Brassica, Coriandrum, and Litchi) some other species including Eucalyptus, Callistemon that are planted for social forestry programs, are also heavily utilized as pollen and nectar sources by honey bees in urban and semi urban areas. Naturalized flora including Myrica, Rumex, Erigeron are also utilized and therefore are important for apiculture in these regions.
Against a backdrop of decreasing biodiversity and attempts to ensure a livelihood for a large number of people in developing and poor countries, apiculture can be encouraged as an ideal eco‐friendly and economically viable enterprise. Apiculture industry can be managed with very little expenditure as it utilizes natural resources. It is an industry that provides employment to rural and tribal people offering an eco‐friendly profitable small scale full or part‐time occupation. Honey is also an excellent food supplement, ideal for large under‐nourished tribal and rural people in developing countries. Honey bees not only enhance the production of agriculture and horticulture crops, they play an important role in maintaining ecosystem and conservation of biodiversity. Analysis of pollen contents of honey samples provides reliable information of floral resources of honeys along with relative preferences of the bees among the diverse assemblages of plant species flowering synchronously (Deodikar, Citation1961, Citation1964; Garg, Citation2006).
Pollen analytical studies of Indian honeys had been conducted by various workers (Vishnu Mittre, Citation1958; Ramanujan et al., Citation1962; Ramanujan & Kalpana, Citation1992; Nair, Citation1964; Sharma & Nair, Citation1965; Chanda & Ganguly, Citation1981; Chaturvedi, Citation1989) but considering the diversity and floristic composition of this large country, the knowledge of potential bee forage plants is inadequate. Pollen spectra of honey samples reflect the prevailing local vegetation and differ with respect to locality and season in which the honeys are collected. The diversity of vegetation types and flora within this vast country means that palynological studies of Indian honeys need to be done on a regional basis in order to characterize the relationship between the local flora, vegetation type and plants utilized by honey bees. The present study aims to determine the key bee‐forage plants of different eco‐floristic and agro‐climatic areas of upper Gangetic region and to identify the major, medium and minor pollen, and nectar yielding plants through analysis of pollen contents of regional honeys of the area.
The scope of the present melissopalynological investigation is confined to Uttarakhand and Uttar Pradesh – two states of north India located between 78°–85°E and 25°–32°N. The state of Uttarakhand encompasses the converging ranges of greater Himalayas, intersected by valleys and plateaus under localized cultivation. Uttar Pradesh is the most populated state of India as well as the highest producer of food grains. Geographically the states constitute the upper Gangetic plain as the river Ganges emerges from the mountains and flows across the plains. The climate of Uttarakhand is temperate to sub‐tropical due to presence of many snow clapped mountain peaks while Uttar Pradesh possesses a tropical monsoon type of climate. As both of the states are mainly occupied by rural areas, cultivated fields and forests, bee keeping may be taken as an eco‐friendly, profitable, small scale, full or part‐time occupation. The objective of the present study was to identify potential bee forage plants of the area. This information can be applied to understand the types of plants and vegetation association that require conservation in order to boost honey production and employment. The honey samples analysed include both apiary and squeezed honeys as the later samples have been collected from those areas where commercial apicultural activities are yet to start.
Material and methods
A total of 51 honey samples collected from Uttarakhand (21 samples) and Uttar Pradesh (30 samples) were palynologically analysed (Figure ). The samples were collected during autumn 2003 and spring 2004. The 21 samples of Uttarakhand include ten regional honeys belonging to four districts (Dehradun, Haridwar, Tehri and Rudrapryag) of Garhwal Division and 11 samples originating from three districts (Almora, Nainital and Champawat) of Kumaon Division (Figure ). The 30 samples from Uttar Pradesh belonged to 24 districts ranging from western to eastern parts of the state (Figure ). Out of the 21 Uttarakhand honey samples 14 are apiary honey and seven are squeezed honey while among 30 samples from Uttar Pradesh, 23 samples are squeezed honey and seven are apiary products.
Figure 1. Sites of the honey samples studied.
For microscope studies, the acetolysis method adopted by Erdtman (Citation1960) was followed. Briefly, 5 ml of honey from each sample was dissolved in 20 ml of warm distilled water (around 40°C) and centrifuged twice (2500 rpm) for 10 min. Five ml of glacial acetic acid was added to the sediment. The solution was again centrifuged (2 500 rpm) for 10 min. The pollen sediment was then acetolysed with 10 ml of acetolysis solution (one part of conc. sulphuric acid was added drop‐by‐drop to nine parts of acetic anhydride) and warmed in a water bath (at 100°C) for 3 min till the liquid turned brown colour. After cooling it was again centrifuged at 2 500 rpm for 10 minutes. The supernatant liquid decanted off. The sediment then treated with glacial acetic acid, later centrifuged at the same rpm followed by two or three rinsing with distilled water. After each rinsing, centrifugation was carried out at 2 500 rpm for 10 minutes. The 50% aqueous glycerin prepared in distilled water was added and centrifuged for 10 minutes at 3 000 rpm. The supernatant liquid was decanted off. The rotor length r is 15 cm enabling the calculation of RCF or g following the recommendations of Pendleton (Citation2006). The pollen sediment was taken on a pellet of glycerine jelly and transferred to the centre of the slides of 75×25 mm size having 0.8 mm thickness. After being warmed slightly, the melted jelly with pollen sediment was covered by ‘0’ number (22 mm) cover glass. The cover glass was later sealed with paraffin wax (Nair, Citation1960).
The pollen types were identified with the help of reference slides made from ground flora and permanent pollen slides kept in pollen herbarium of Palynology Laboratory of NBRI, Lucknow. Relevant literatures were also consulted for pollen identification and in some cases the pollen types were identified only to family level. Quantitative pollen analysis was based according to the method recommended by the International Commission for Bee Botany (Citation1970). Counts were taken at random covering the maximum mounted area to avoid repetition. Once identified and counted, the pollen grains were placed into one of following pollen frequency classes – predominant pollen types (>45%), secondary pollen types (16–44%), important minor pollen types (3–15%), minor pollen types (<3%) and pollen present (<1%). Honey samples containing more than 45% of a single type of pollen were considered as ‘Unifloral’ honey.
Results
In all 126 plant taxa were microscopically identified by their pollen from the 51 honey samples (Table ). The honeys from Uttarakhand contained more varied pollen types (98) than those belonged to Uttar Pradesh (83). Among the samples studied, the maximum number of pollen types diagnosed from a single sample is 26 (Sample No. 42, from Ukhimath, Rudraprayag District), and the minimum number of pollen types found in a sample is 4 (Sample No. 37, from Ram Nagar, Nainital District), in Uttarakhand both.
Table I. Pollen contents of honey samples of Uttarakhand and Uttar Pradesh with respect to frequency classes
Uttarakhand honeys
Among the 21 Uttarakhand honey samples analysed, 12 samples were found to be unifloral and nine were multifloral (Table ). According to frequency classes, eight pollen types e.g. Brassicae, L., Eucalyptus L'Her., Helianthus L., Litchi Sonn., Prunus L., Rumex, L., Erigeron L., and Myrica L. were identified as predominant (>45%) types. The first six taxa were also categorized as secondary pollen types (16–44%) in some unifloral and many multifloral honeys along with taxa like Coriandrum L., Alnus Mill., Salix L., Ageratum L., and Callistemon R. Br. Pollen grains of Brassica is most dominantly represented in honeys from Uttarakhand as this type was found to be predominant in three samples (No. 45, 78 and 79), secondary types in six samples (No. 43, 44, 52, 38, 77, and 80), important minor type (3–14%) in two (No. 1, 48) and minor type in one sample (No. 73). Eucalyptus pollens were identified as predominant type in two samples (No. 44, 46), as secondary pollen type in five samples (No. 38, 52, 43, 1, 77, and 42) and as important minor pollen in four samples (No. 8, 78, 79, and 80). Pollen of fruit tree litchi (Litchi chinensis) were diagnosed as predominant in two samples (No. 38, 39) and as secondary pollen in one sample (No. 80). Incidentally all the above three litchi containing samples originated from Kumaon division of Uttarakhand. Pollen of Helianthus, cultivated as an oil crop had been recorded as predominant type from one sample (No. 8), as secondary pollen from three samples (No. 41, 47, and 48) and as important minor type in two samples (No. 52, 80). Four temperate plants: Prunus, Rumex, Erigeron and Myrica were identified as predominant pollen contributor to particular sample (No. 47, 72, 73, and 74 respectively). Pollen of the fruit tree Prunus was also diagnosed as secondary type in four samples (No. 41, 46, 48, and 42) and as important minor pollen type in one sample (No. 45) while those of Myrica were found as important minor type in three samples (No. 44, 73, and 74). Likewise, Rumex pollen was recorded as secondary type in one sample (No. 42) and as important minor type in six samples (No. 46, 47, 38, 52, 41, and 80).
Pollen of some plants were frequently found in considerable proportion in several honey samples of Uttarakhand although none of these plants was accounted as predominant type according to frequency classification. Mention may be made towards cultivated spice crop Coriandrum, pollen of which were identified as secondary type in two samples from Ranikhet (No. 77, 79) and as important minor pollen in three samples (No. 46, 78, and 80). Pollen of temperate trees e.g. Alnus (No. 48) and Salix (No. 42) were diagnosed as secondary pollen type in one sample each and as important minor pollen in three honey samples (Alnus – No. 72, 73, and 75; Salix – No. 1, 41, and 75) each. Pollen grains of Ageratum, a herbaceous weed of the family Asteraceae had been encountered frequently in numerous honey samples and it was categorized as secondary pollen type in two samples (No. 1, 37) and important minor pollen type in seven samples (No. 8, 44, 38, 79, 43, 48, and 77). Callistemon pollen was identified as secondary pollen type in two regional honeys of Uttarakhand (No. 74, 80)
In addition to the taxa mentioned above, pollen grains of plants like Celtis L., Salvia L., Quercus L., and those of members of Fabaceae, Fagaceae, Moraceae, Poaceae and Euphorbiaceae were recorded in the category of important minor types in honeys from Uttarakhand. Reflection of local cultivated and naturalized flora, many of which are temperate in distribution were noted in Uttarakhand honeys which include Aster L., Bidens L., Saussurea DC., Rosa L., Rubus L., Spiraea L., Acer L., Aconitum L., Berberis L., Potentilla L., Strobilanthus Blume, etc. but their contribution in total pollen contents is less than considerable amount. It was curiously noted that pollen grains of a number of anemophilous taxa e.g. Alnus, Rumex and members of Poaceae also contribute to the pollen contents of honeys, sometimes in appreciable proportion.
Uttar Pradesh honeys
Pollen analysis of 30 regional honey samples from Uttar Pradesh confirmed 15 samples as unifloral honey and the other 15 samples as multifloral (Table ). Seven plant taxa were identified as predominant pollen types in regional honey samples of various districts distributed in this large state, most of which belong to cultivated crops and regionally naturalized plants. The analysis indicates Brassica being the most important bee forage crop of Uttar Pradesh as its pollen emerged as predominant type in four honey samples (No. 6, 28, 13, and 24) as secondary pollen type (16–44%) in eight samples (No. 23, 36, 53, 24, 31, 27, 55, and 85) and as important minor pollen types (3–15%) in six samples (No. 21, 58, 32, 2, 5 and 40). The next important bee crop appears to be Coriandrum as its pollen were found as predominant contributor in three samples (No. 33, 21, and 26) as secondary type in six samples (No. 34, 81, 31, 50, 36, and 24) and as important minor pollen type in three samples (No. 32, 27, and 40). The weed Ageratum conyzoides (Asteraceae) was found to be one of the prominent bee favoured plant as its pollen were recorded as predominant in three samples (No. 3, 30, and 32), as secondary pollen type in two samples (No. 5, 27) and important minor pollen type in six samples (No. 58, 11, 13, 36, 31, and 54). Pollen grains of Eucalyptus were observed in maximum number of honey samples (24 of 30) of Uttar Pradesh. Eucalyptus pollen was diagnosed as predominant type in two samples (No. 58, 81) as secondary pollen type in nine samples (No. 2, 50, 53, 5, 36, 24, 40, 83, and 85) as important minor pollen in other ten samples (No. 28, 3, 13, 26, 34, 30, 32, 64, 23, and 55) and as minor pollen (1–3%) in three samples (No. 7, 18, and 27). Three other plant taxa e.g. Callistemon, Syzigium cumini and Zea mays were also identified as predominant types in honeys of Uttar Pradesh, but unlike the preceding types which were extensively represented, occurrence of these types were restricted to few regional honeys. Callistemon, a beautiful road side ornamental tree and Syzigium cumini the fruit tree producing ‘Jamun’ both belonging to the Myrtaceae were categorized as predominant type in one sample each of two samples collected from adjacent districts of eastern Uttar Pradesh (No. 39 and 64, respectively). Syzigium was also recorded as secondary type in one sample (No. 31) also from eastern Uttar Pradesh. Pollen of the cereal crop maize (Zea mays) was recognized as predominant type in one sample (No. 7) from western part of the state and as secondary type in another sample originating from eastern part (No. 54) of Uttar Pradesh.
In addition to these taxa, which are categorised as predominant contributor in one or more honey samples of Uttar Pradesh, pollen of some other plants were noted in considerable proportions in several regional honeys. These include cultivated oil crop Helianthus, which was identified as secondary type in three samples (No. 23, 33, and 85) from three districts of western Uttar Pradesh and as important minor pollen from one district (No. 6). Pollen grains of Citrus were determined as secondary pollen type in four samples (No. 58, 39, 53, and 18) and as important minor type in three samples (No. 36, 24, and 54) and the relevant districts are distributed in all directions of the state. In a few samples, considerable presence of some localized taxa was noted and they include plants like Cassia sp., Drypetes roxburghii, Embellica officinalis, Lagerstroemia, Litchi etc., all of these were classified as secondary type occurring in a single sample each. Pollen of anemophilous taxa like Ailanthus, Holoptelea and Rumex were also recorded in considerable amount in some honey samples indicating bee's visit to these plants. Some taxa which were recorded as important minor pollen type in pollen spectra of few to several samples are Argemone, Azadirachta, Chenopodium, Erythrina, Morus, Pisum, Prosopis and members of Cucurbitaceae, Polygonaceae, Poaceae, Rosaceae etc. Some of locally naturalized trees like Acacia, Bombax, Moringa, Phyllanthus, etc. along with undershrubs like Carthamus, Occimum, Salvia, and Vernonia etc have sporadic presence in pollen spectra of honey samples which indicate honey bees do visit these plants but not very frequently.
Discussion
The pollen spectra of regional honeys of Uttarakhand and Uttar Pradesh depicts that the bee forage plants of this area includes both localized flora and cultivated plants. The observation also reveals that in relation to native and wild plants considerable dominance of cultivated plants and crops is apparent. The reason behind it may be the fact that honeys were mainly collected from villages where agricultural fields prevailed. India is an agriculture based country and most of its inhabitated rural area is under cultivation. This fact is reflected in pollen content of the honeys where the hives were in proximity of cultivated fields. However, a number of plants including Erigeron, Myrica and Rumex were also found as predominant pollen when the sites of origin of the honeys were near forest land. While the data indicated prevalence of some entomophilous crops like Brassica and Coriandrum which are known bee forage plants of India, it also depicts that some other common plants e.g. Eucalyptus which are not accounted for apicultural purpose in India can be considered as important bee floral resource (Figure ).
Figure 2. Comparative representation of main pollen types in regional honeys of Uttarakhand and Uttar Pradesh(India).
The present melissopalynological study identifies Brassica as the most predominant bee crop of Upper Gangetic area (Uttarakhand and Uttar Pradesh) as it had been diagnosed as predominant pollen in seven regional honeys (Uttarakhand ‐ 3 and Uttar Pradesh ‐ 4), secondary type in 14 samples (Uttarakhand ‐ 6, Uttar Pradesh ‐ 8) and important minor pollen in seven samples from Uttar Pradesh (Figure ). Brassica is cultivated as oil crop throughout India as mustard oil made from its seed is the main cooking ingredient in north Indian households. The period of cultivation and flowering of this oil crop ranges from autumn to onset of summer depending upon variations of species, varieties and agriculture practices of different eco‐floristic regions of this vast stretch of land. This long duration might be the reason behind the position of Brassica on top of the list. Among the 51 honey samples analyzed for pollen component, the most frequently represented taxa was Eucalyptus because this type was found as prevalent to minor pollen contributor in a total of 35 samples (11 from Uttarakhand and 24 from Uttar Pradesh) which confirms the plant as a significant bee forage (Figure ). Though Eucalyptus is an introduced plant, due to integrated plantation under social forestry programme, Eucalyptus trees had become a component of naturalized vegetation throughout India and the data emerging from pollen spectra clearly indicate that the plant is preferred by bees and therefore can be advantageously used as natural resource of bee forage in apicultural programmes. In fact Eucalyptus is considered as a very important melliferous plant in many countries and Eucalyptus honey is highly regarded as an apicultural product (Méndez et al., Citation2003).
The analysis also confirms that Coriandrum sativum (Apiaceae) as an important bee crop in this region as its pollen are found in considerable amount in many regional honeys specially in Uttar Pradesh (Figure ). The herbaceous plant is cultivated throughout the region for vegetable and spice and is rated as a good source of both nectar and pollen for the bees (Chaudhary, Citation2003). In the present study, pollen of another oil seed crop Helianthus annus was recorded as predominant type in one sample from Uttarakhand (Figure ), secondary pollen type in six samples (three each from Uttarakhand and Uttar Pradesh) and as important minor type in three samples from Uttarakhand and one from Uttar Pradesh. Presence of Helianthus pollen in more samples of Uttarakhand may be related to greater cultivation of this crop in that state than in Uttar Pradesh. Chaudhary (Citation2003), reported Helianthus as a major pollen source of bees from Haryana another state of North India. Exploitation of this oil seed crop Helianthus annus as bee forage would be doubly beneficial as remarkable enhancement in crop yield of Helianthus had been effected by bee pollination (Viraktamath & Patil, Citation2002). Litchi chinensis (Sapindaceae) and Syzigium cumini (Myrtaceae) are two common fruit trees which attracts bees during their flowering and may well considered as honey yielding plants where they grow in abundance. Melissopalynological analysis of several samples of Litchi and Jamun honeys collected from various places of India, conducted by Suryanarayana et al. (Citation1981) included one sample from Uttar Pradesh. The present study showed two samples from Uttarakhand having Litchi and one sample from Uttar Pradesh containing Syzigium as predominant pollen of regional honeys.
The present analysis confirms presence of pollens of four temperate plants e.g. Prunus, Myrica, Erigeron and Rumex in considerable percentage in several honey samples from mountainous areas of Uttarakhand. Among these types, Prunus was recorded from honey samples belonging to Garhwal division. Myrica and Erigeron were found in samples of Champawat district of Kumaon division, while pollen of Rumex was recorded from many samples from both the divisions. In earlier studies, Chaturvedi (Citation1983, Citation1989), reported Prunus as dominant pollen of unifloral spring honeys from Kumaon division. The information of present survey indicates that apiaries can also be set in Tehri region of Garhwal near the Prunus orchards. The present study also identifies two road side ornamentals e.g. Callistemon sp. and Lagerstroemia sp. as potential bee forage resources in semi urban areas as pollen of these plants contributed a considerable pollen contents in the honeys where these trees flowers profusely. Recently, Bottle brush trees (Lagerstroemia sp.) have been used in plantation programmes in urban colonies and industrial belts as ‘green belt’ plants owing to its green foliage and profusely blooming beauty. Now, as the apicultural potential of this species is revealed, this plant can be planted for its multipurpose use.
The weed Ageratum conizoides is important bee forage based on its occurrence as prevalent, secondary and important minor pollen in honey samples from various localities analysed in present study and from other geographical places throughout the country (Datta, Citation2003; Garg, Citation1996). The preference towards this particular plant indicates its success in commanding pollination service above the other taxa flowering synchronously in that locality. Thus while considering Ageratum as potentially good bee forage it should be remembered that presence of this weed in vicinities of the crop field may induce negative impact of floral competition to the target crop and as a result the crop may get insufficient pollination. This highlights the importance of balancing the needs of bee keepers against the management of crops.
Conclusions
The scope of the present survey is location specific analysis of honeys from two states of north India situated in upper Gangetic area. The study throws light in the role of honey bees in agro‐ecosystem and forest ecosystem. Mapping of key bee flora of different floristic and geographical area helps to determine the suitability of the area to undertake apicultural activities. The information, apart from promoting apicultural industry, will help agricultural production and shall provide both impetus to food security and conservation of biodiversity.
In fact, in spite of tremendous scope in apicultural activities owing to its enormous floristic diversity, the bee keeping industry in India has achieved only a fraction of its full potential. This is mainly due to lack of information regarding the role of regional floral resources in context of its apicultural value. In this context it should be kept in mind that pollination management is also important for improving output of the target crop but that these needs must be balanced against the resource value of these plants in other industries such as honey production.
Acknowledgements
Director, NBRI is acknowledged for infrastructural facilities.
References
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