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Pak. J. Bot., 42(3): 1395-1399, 2010. POLLINATION MECHANISM AND ROLE OF INSECTS IN ABUTILON INDICUM (L.) SWEET RUBINA ABID, JAN ALAM AND M. QAISER* Department of Botany, University of Karachi, Karachi Pakistan-75270 Federal Urdu University of Arts, Science and Technology, Karachi, Pakistan. * Abstract Flowers of Abutilon indicum (L.) Sweet are slightly protandrous, opening and closing times of flower are temperature and light dependent. Bagging experiments and pollen-ovule ratio reveal that it is a facultative autogamous taxon. Butterflies (Lepidoptera) and Bees (Hymenoptera) are the regular flower visitors. Butterflies are just visitors as they do not take any part in pollination while, Apis sp., and Bembix sp. are found to be the pollinators of Abutilon indicum. Introduction Abutilon indicum (L.) Sweet belongs to the family Malvaceae. In Paksitan it is commonly distributed in Sindh, Punjab and rare in NWFP (Abedin, 1979). A considerable work on pollination biology for the members of Malvaceae has been performed by various workers (Kadyrova et al., 1980; Mcdade & Davidar, 1984; Dawar etal., 1994; Vaidya, 2000; Hajime, 2004; Franceschinelli, 2005). However, little attention was paid to the breeding studies of the genus Abutilon L. (Andersen, 1988; Abid, 2006). Moreover no exclusive reports are available on Abutilon indicum. The study was conducted to determine the pollination mechanism and role of insects in pollination of Abutilon indicum. Materials and Methods Present studies were conducted within the vicinity of Karachi i.e., Karachi University campus, Abul Hasan Isphahani Road, Gulshan-e-Iqbal and Malir. Floral phenology: 5-10 young floral buds/population were tagged to determine the phenological changes. Insects (Visitors): Flower visiting insects were observed for their foraging behavior. Insects were collected by hand net and chloroformed and observed microscopically for the pollen load. The insects carrying pollen were evaluated as pollinators. Breeding studies Pollen–ovule ratio: The flower buds were collected prior to anthesis and pollen ovule ratio was determined by dividing the total number of pollen grains/flower by the total number of ovules/flower and following counts were made: (i) Total number of anthers/flower (ii) Total number of pollen grains/anther (iii)Total number of pollen grains/flower (iv) Number of ovaries/flower (iv) Number of ovules/ovary (v) Number of ovules/flower. 1396 RUBINA ABID ET AL., Bagging experiments: Following Pollination treatments were given in flowering bud stage (N=25). Control (Open pollination): Budd were tagged and left to study the normal seed set. Direct autogamy: Buds were bagged without manipulation to determine the selfpollination. Indirect Autogamy: Buds were hand pollinated and bagged to test the self-pollination. Apomixis: Buds were emasculated and bagged to test the apomixis. Geitonogamy: Pollinated by hand with the pollen grains of the other flowers of the same plant and bagged to test the geitonogamy. Xenogamy: Cross pollinated by hand with the pollen grains of different plants of the same species and bagged to test the xenogomy. The data was statistically analyzed among different pollination treatments by oneway ANOVA and Bonferoni’s Multiple Comparison Test of (Anon., 1999). Observations and Results Floral phenology: A youngest bud took about 18-20 days to become a flower. The time of flower anthesis seems to be effected by temperature and light. At 25-300C temperature anthesis took place between 1-2:00 p.m. Whereas, on cloudy days flower opens at 4:0 p.m. Flower remained open for about 6-7 hours and withering of floral parts took place after 2-5 days of flower closing. Protandry seemed to be present as dehiscence of anthers took place in mature bud stage just prior to flower anthesis. Upper anthers on the staminal column dehisced earlier than the lower ones. Insects behaviour: Different types of insects visited the flower and were attracted due to the presence of nectar, pollen grains, fragrance or colour of the flower. Butterflies (Lepidoptera) namely Pieris sp., Eurema sp., Anthocharis sp., Coletis sp., Lycaena sp., and Danaus sp., regularly visited the flowers. They were merely visitors as not a single pollen grain was found on their body parts. The activity of all butterflies started just after the opening of flower and they behaved in same manner. They usually alight on petals, insert their proboscis in nectaries (at the base of sepals) and suck the nectar without coming into contact with sexual parts (Fig. 1G, H ). Apis sp., (Honey Bee) was the most common and effective pollinator. It started the activity just prior to the anthesis of flower and visited a flower for about 40-50 seconds. It is also very interesting that a group of 3-4 bees compete to visit a single flower out of which sharp ones get success and land on the staminal column and grasp it with the legs. From there, insert their proboscis in the slit between the two petals where nectar accumulated in the form of drops and sometimes they press the anthers to collect the pollen grains. Bees usually try to explore all the five nectaries of a flower by revolving or twisting on the staminal column in this way pollen grains adhere to the abdomen, thorax and legs after that they move to another flower (Fig. 1A-F). POLLINATION MECHANISM IN ABUTILON INDICUM 1397 Fig. 1. Insects foraging behaviours. A-F Apis sp. collecting pollen and nectar; G, Anthocharis sp. sucking the nectar; H, Lycaena sp. sucking the nectar. RUBINA ABID ET AL., 1398 No. of flowers studied 90 Average no. of anthers / flower 72.88 ± 2.83 Table 1. Pollen ovule Ratio of Abutilon indicum Average no. Average no. Average no. Average no. of pollen/ of pollen / of ovaries / of ovules / anther flower flower ovary 210.12 15313.54 1.0 48.8 ± 9.88 ± 27.62 ± 1.66 Pollen-ovule ratio 313.65 ± 18.88 Table 2. Effect of various pollination treatments on fruit set in Abutilon indicum. Bonferoni’s Multiple Comparison Test One-way ANOVA (BMCT) Sv Df Ss Ms F-value Treatments Rank Mean Treatments 4 8526.2 2131.55 Control 1 64a Error 15 7360.75 490.7166 4.343* Direct autogamy 2 62.5a Total 19 15886.95 Indirect autogamy 3 50ab Geitonogamy 4 18.25b Xenogamy 5 17.5b Bembix sp., visited the flower for nectar and pollen. It alights on staminal column and collect the pollen grains and after collecting the pollen also insert its proboscis between the slits of petals to suck the nectar, pollen grains were found to be attached on its legs and ventral sides of thorax and abdomen and before moving to another flower insect tries to detach the heavy pollen load by moving its legs and wings then move towards the other flowers of the same or other plant. Pollen-ovule ratio (P/O): The pollen ovule ratio was 313.65 ± 18.88 (Table 1). According to Cruden (1977), the species with this P/O value seems to be facultative autogamous. Bagging experiments: Fruits were properly formed in all the treatments except that of the apomixis. Fruit set in all the treatments was statistically significant (Table 2). However, control and direct autogamy significantly showed the highest fruit set as compared to the geitonogamy and xenogamy where fruit set was significantly lowest.While, in indirect autogamy fruit set did not differ significantly from all of the above treatments (Table 2). Discussion The flowering period of Abutilon indicum ranges from August to December. The time of flower anthesis seems to be temperature and light dependent. The flowers are protandrous and anther dehiscence takes place just prior to flower opening but this protandrous condition is not so pronounced. Though the upper anthers mature first and till the maturation of all anthers stigmas also become mature and this protandrous condition is observed in most of the members of the family Malvaceae (Faegri & Pijl, 1980; Dawar et al., 1994). Mainly Bees (Hymenoptera) and Butterflies (Lepidoptera) are found to visit the flowers of Abutilon indicum. Apis sp. (Honey bee) seems to be responsible for pollination either by bringing the stigmas near to the anthers or by transferring pollen grains from their body parts which are adhered while visiting the flowers. A variety of butterflies (Lepidoptera) regularly visit the flowers of Abutilon indicum and may be regarded as opportunist as they suck the nectar without coming into contact with reproductive organs.Similar results were obtained by Gottsberger (1967) on some Brazilian genera of Malvaceae and Dawar et al., (1994) on Sida ovata complex. POLLINATION MECHANISM IN ABUTILON INDICUM 1399 Breeding experiments revealed that A.indicum is self compatable and facultative autogamous taxon and no significant difference was found in fruit set of open pollination and autogomy. While, fruit setting was significantly reduced in geitonogamy and xenogamy. Besides this pollen ovule ratio also supports the facultative autogamous nature of the species. Thus in A. indcum both selfing and insect mediated crossing occur. Acknowledgement We are thankful to Dr. Rukhsana Perveen (Taxonomist, Zoological Museum) Department of Zoology, University of Karachi for identifying the insects and Mr. Abrar Ali for photographic enhancement. References Abedin, S. 1979. Flora of Pakistan. Malvaceae. No. 130. In: (Eds.): E. Nasir and S. I. Ali .Dept. Bot. Univ. Karachi, Karachi. Abid, R. 2006. Reproductive Biology of Abutilon fruticosum Guill.& Perr. Int. J. Biol. Biotech., 3(3): 543-545. Andersen, R. W. 1988. Outcrossing in velvet leaf (Abutilon theophrasti). Weed Science, 36(5): 599602. Anonymous. 1999. SPSS Ver.9 for Windows. SPSS,Inc. Chicago. Cruden, R.W. 1977. Pollen-ovule ratios: A conservative indicator of breeding system in flowering plants. Evolution, 31: 32-46. Dawar, R., T. Ali and M. Qaiser. 1994. Hybridization in Sida ovata complex II. Evidence from breeding studies. Pak. J. Bot., 26(1): 83-97. Faegri, K. and L. VanDer Pijl. 1980. The principles of Pollination Ecology. Pergamon press. Oxford. Franceschinelli, E.V. 2005. The pollination biology of two species of Helicteres (Malvaceae) with different mechanisms of pollen deposition. Flora-Morph. Distr., Funct Ecology Pl., 200(1): 65-73. Gottsberger, G. 1967. Observations on the floral biology of Brazilian Malvaceae. Osterr. Bot., 2, 114(4/5): 349-378 Hajime, T. 2004. Pollination Ecological study of Hibiscus syriacus L. (Malvaceae). Jap. J. Palyn. 50(2): 109-112 Kadyrova, R.U., M.M. Akhmedova and R. Choudri. 1980. Growth of cotton pollen tubes on an artificial nutrient medium. Uzb. Biol. Zh., 3: 38-40. Mcdade, L.A. and P. Davidar. 1984. Determinants of fruit and seeds set in Pavonia dasypetala (Malvaceae). Oecologia (Berl.), 64(1): 61-67. Vaidya, K.R. 2000. Natural cross-pollination in roselle, Hibiscus sabdariffa L. (Malvaceae). Gen. Molec. Bio., 23(3): 667-669. (Received for publication 7 February 2010)