ECOLOGIA BALKANICA 2019, Vol. 11, Issue 1 June 2019 pp. 108-126

Pollination Ecology of minima (L.) DC. () in the Southern Eastern Ghats, Andhra Pradesh, India

A.J. Solomon Raju1*, K. Venkata Ramana2

Andhra University, Visakhapatnam 530 003, INDIA 1 - Department of Environmental Sciences 2 - Department of Botany *Corresponding author: [email protected]

Abstract. is prostrate climbing herb. In India it flowers during September-March with peak flowering during January. The flowers are hermaphroditic, nectariferous, self-compatible and have explosive pollination mechanism adapted for pollination by bees. They do not fruit through autonomous selfing but fruit through manipulated selfing, geitonogamy and xenogamy mediated by pollen vectoring bees. The flowers not visited by bees fall off while those visited and pollinated by them set fruit. Seed dispersal occurs by explosive pod dehiscence. Perennial root stock resurrects back to life during rainy season. Seeds also germinate at the same time but their continued growth is subject to the availability of soil moisture content. Therefore, R. minima expands its population size and succeeds as a weed in water-saturated habitats only. The is used as medicine, animal forage and human food and hence it has the potential for exploitation commercially.

Key words: economic value, explosive pod dehiscence, explosive pollination mechanism, hermaphroditism, melittophily, Rhynchosia minima.

Introduction suaveolens and R. viscosa. These are Rhynchosia is a genus of the legume either climbers or shrubs (MADHAVA CHETTY family fabaceae, tribe and et al., 2008). Of these, R. minima is a subtribe cajaninae (LACKEY, 1981; pantropical species but it is thought to be JAYASURIYA, 2014). It consists of more than native to the Old World and introduced and 232 species and occurs in both the eastern naturalized in the New World. It is listed as and western hemisphere in warm temperate least concern in bhutan (LOPEZ POVEDA, and tropical regions (GREAR, 1978; JACA et al., 2012). Its population is believed to be stable 2018; SCHRIRE 2005; TURNER 2011). In the and no real threats are known at present. Eastern Ghats, twelve species of this genus The population size of this species is not have been reported to be occurring almost in known, but recent surveys between 1980 and one region, Seshachalam hills of southern 2008 from throughout the range of the Eastern Ghats of Andhra Pradesh. They species in india suggest it occurs in groups include R. albiflora, R. beddomei, R. cana, R. of from 30 to 500 individuals (LOPEZ capitata, R. courtollensis, R. densiflora, R. POVEDA, 2012). In australia, two varieties heynei, R. minima, R. rothii, R. rufescens, R. have been reported in R. minima based on

© Ecologia Balkanica Union of Scientists in Bulgaria – Plovdiv http://eb.bio.uni-plovdiv.bg University of Plovdiv Publishing House Pollination Ecology of Rhynchosia minima (L.) DC. (Fabaceae) in the Southern Eastern Ghats... pod hair character, var. minima as having readily eaten by cattle than sheep; however, pods with short fine hairs only and var. the cattle stay away during its flowering australis as having short fine hairs and long phase due to slight emission of scent from tubercular-based hairs on the pods flowers. SHUKLA et al. (1970) noted that this (ANDREWS, 1952; STANLEY & ROSS, 1983). plant is palatable to sheep in india. Despite Later, HARDING et al. (1989) reported that R. its wide use for humans and animals, this minima is highly variable and there are four species has not been studied for its varieties in australia, var. amaliae, australis, reproductive ecology in any part of the minima and tomentosa. These authors also world to understand the factors that stated that this species with many ecotypes contribute to the success of this plant as a that vary in their adaptation and growth weed in widely different ecological characteristics has the potential to exploit it conditions that prevail in the tropical as a forage plant. Of these infraspecific taxa, latitudes. R. minima var. minima is studied for its Franco (1995, Pers. comm., Campinas, pollination ecology. University of Campinas) provided floral Different authors noted that R. minima is details of Rhynchosia in Brazil. He reported widely used as a medicinal plant. CHUTE & that Rhynchosia is autogamous which is TIWARI (2002) noted that in the indian state limited by spatial segregation between of maharashtra, the tribals of bhandara and stigma and anthers. Levels of out-crossing gadchiroli district use its seed extract as an are maintained by retention of a pollination eye drop to cure conjunctivitis and mechanism. Hypanthidium sp. and Centris sp. inflammation. MUSTAK et al. (2006) are the primary pollinators and the pollen is mentioned that the whole plant is used for deposited on the ventral part of their bath of the mother after delivery in pakistan. abdomen when the flower is probed. GUNDIDZA et al. (2009) stated that the plant is CRAUFURD & PRINS (1979) reported that traditionally used in skin conditioning and Rhynchosia sublobata is self-compatible and to alleviate boils in zimbabwe. LOPEZ pollinated by Xylocopa bees. ETCHEVERRY et POVEDA (2012) described that the plant is al. (2011) reported that Rhynchosia edulis and used for medicines such as abortifacients, R. senna var. texana display valvular ecbolics, general healing, medicines to treat pollination mechanism; the former is sickness such as haemorrhoids, heart, facultative xenogamous while the latter is diarrhoea and dysentery. It is also used as obligately xenogamous. There is no other food (sweets) and its seeds are used as information on flowering phenology, miscellaneous poison or repellents. GILLETT breeding systems, pollen presentation et al. (1971) mentioned that the plant is used mechanisms, pollination mechanisms, as animal forage; its palatability has been pollinators and fruiting ecology of any believed to vary widely with different species of Rhynchosia. It is in this context, the ecotypes that occur in different habitats. present study was contemplated to provide HASSELL (1945) stated that in queensland, the the details of pollination ecology of R. plant is eaten readily by animals when minima to understand the sexual young due to high palatability however, reproduction with which the plant is able to mature plant is not eaten due to fibrous and propagate and occupy different ecological coarse nature. BEESTON (1978) listed R. niches in tropical regions. minima as highly palatable for animals in the blackall district of central west queensland Material and Methods while BOYLAND (1973) mentioned this plant Study site as moderately palatable for animals in the The study region is an integral part of far south-west of queensland. BOGDAN Southern Eastern Ghats of Andhra Pradesh (1977) stated that in kenya, the plant is in Peninsular India. The area is located at

109 A.J. Solomon Raju, K. Venkata Ramana

13°40’N latitude and 79°19’E longitude. The placed in a Petri dish. Later, each time a exact study area is the forest cover of single anther was taken out and placed on a Tirumala Hills, a constituent of Seshachalam clean microscope slide (75 x 25 mm) and Hill Range in Chittoor District, Andhra dabbed with a needle in a drop of Pradesh. The entire region represents the lactophenol-aniline-blue. The anther tissue deciduous forest ecosystem. The site is was then observed under the microscope for characterized by a combination of rocky, pollen, if any, and if pollen grains were not undulating and steep terrain with some litter there, the tissue was removed from the slide. content formed from grass and other The pollen mass was drawn into a band, and herbaceous plants. The temperature ranges the total number of pollen grains was from 40ºC to 42ºC during March to May and counted under a compound microscope (40x at other times varies from 26ºC to 34ºC. The objective, 10x hand lens). This procedure rainfall varies from 975 to 1115 mm. In this was followed for counting the number of area, Rhynchosia minima grows as a small pollen grains in each anther collected. The population in open areas of soil rich in mean pollen output per anther was moisture and litter and as isolated multiplied by the number of anthers in the individuals in open rocky areas with less flower for obtaining the mean number of soil, moisture and litter. pollen grains per flower. The characteristics of pollen grains were also recorded. Flowering and floral biology Flowering season was defined based on Pollen-ovule ratio regular field trips made. Twenty The pollen-ovule ratio was determined inflorescences were tagged and followed to by dividing the average number of pollen record the length of flowering and the grains per flower by the number of ovules number of flowers produced. Anthesis was per flower. The value thus obtained was initially recorded by observing twenty five taken as pollen-ovule ratio (CRUDEN, 1977). marked mature buds in the field. Later, the observations were repeated five times on Nectar characters different days in order to provide accurate The presence of nectar was determined anthesis schedule. Similarly, the mature by observing the mature buds and open buds were followed for recording the time of flowers. The average volume of nectar per anther dehiscence. The presentation pattern flower was determined and expressed in µl of pollen was also investigated by recording based; for this ten flowers were used. The how anthers dehisced and confirmed by flowers used for this purpose were bagged observing the anthers under a 10x hand lens. at mature bud stage, opened after cessation The details of flower morphology such as of nectar secretion and squeezed nectar into flower sex, shape, size, colour, odour, sepals, micropipette for measuring the volume of petals, stamens and ovary were described nectar. Nectar sugar concentration was based on twenty five flowers randomly determined using a Hand Sugar collected from five plants. Observations Refractometer (Erma, Japan). Ten samples regarding the position and spatial were used for examining the range of sugar relationships of stamens and stigma in concentration in the nectar. For the analysis mature bud, at anthesis and after during the of sugar types, paper chromatography flower-life with reference to self and/or method described by HARBORNE (1973) was cross-pollination were made very carefully. followed. Nectar was placed on Whatman No. 1 filter paper along with standard Pollen output samples of glucose, fructose and sucrose. Thirty mature but un-dehisced anthers The paper was run ascendingly for 24 hours from five different plants were collected and with a solvent system of n-butanol-acetone-

110 Pollination Ecology of Rhynchosia minima (L.) DC. (Fabaceae) in the Southern Eastern Ghats... water (4:5:1), sprayed with aniline oxalate All these categories of flower spray reagent and dried at 120oC in an pollinations were followed for fruit set. If electric oven for 20 minutes for the fruit set is present, the percentage of fruit set development of spots from the nectar and was calculated for each mode. the standard sugars. Then, the sugar types present and also the most dominant sugar Flower-visitors type were recorded based on the area and The flower foragers included only bees. colour intensity of the spot. The sugar The hourly foraging visits of each bee content/flower is expressed as the product species were recorded on 3 or 4 occasions of nectar volume and sugar concentration depending on the possibility and the data per unit volume, mg/µl. This is done by first was tabulated to use the same for further noting the conversion value for the recorded analysis. Fully flowering plants were sugar concentration on the refractometer selected to record the foraging visits of bees. scale and then by multiplying it with the The data obtained was used to calculate the volume of nectar/flower. Table 5.6 given in percentage of foraging visits made by each DAFNI et al. (2005) was followed for bee species per day in order to understand recording the conversion value to mg of the relative importance of each bee species. sugars present in one µl of nectar. Their foraging behaviour was observed on a number of occasions for the mode of Stigma receptivity approach, landing, probing behaviour, the In visual method, the stigma physical type of forage collected, contact with state (wet or dry) was considered to record essential organs to result in pollination, the commencement of receptivity. H2O2 test inter-plant foraging activity in terms of as given in DAFNI et al. (2005) was followed cross-pollination (Solomon Raju & Radha for the confirmation of stigma receptivity Krishna, 2017). period. Breeding Systems Determination of pollen carryover efficiency Mature flower buds of some of bees inflorescences on different individuals were Ten specimens of each bee species were tagged and enclosed in paper bags. They captured from flowers and brought them to were tested in the following way and the the laboratory. The pollen loads if present in number of flower buds used for each mode the corbiculae of these bees, they were of pollination was given in Table 1. removed prior to pollen analysis. Each 1. The flowers were fine-mesh bagged specimen was washed first in ethyl alcohol without hand pollination for autonomous and the contents stained with aniline-blue on autogamy. a glass slide and observed under microscope 2. The stigmas of flowers were to count the number of pollen grains present. pollinated with the pollen of the same flower From this, the average number of pollen manually by using a brush; they were grains carried by each bee species was bagged and followed to observe fruit set in calculated to know the pollen carryover manipulated autogamy. efficiency of different bee species (SOLOMON 3. The emasculated flowers were hand- RAJU & RADHA KRISHNA, 2017). pollinated with the pollen of a different flower on the same plant; they were bagged Natural fruit set, seed dispersal and and followed for fruit set in geitonogamy. seedling ecology 4. The emasculated flowers were A sample of flowers on twenty five pollinated with the pollen of a different plants were tagged on different plants prior individual plant; they were bagged and to anthesis and followed for fruit set rate in followed for fruit set in xenogamy. open-pollinations. Fruit maturation period,

111 A.J. Solomon Raju, K. Venkata Ramana fruit dehiscence and seed dispersal aspects and 2.6 ± 0.4 mm wide), called wing petals were observed to the extent possible. Field surround the two bottom petals, called keel observations were also made on fruit and petals (4.4 ± 0.4mm long and 2.3 ± 0.4 mm seed dispersal modes, seed germination and wide). The keel petals form a proximal seedling establishment to the extent possible cylindrical part and a distal part consisting (SOLOMON RAJU & RADHA KRISHNA, 2017). of a pressed angular pouch, with an acute porate tip in which the stamens and stigma Results are housed. The keel and the wing petals are attached by means of two notched folds. The Phenology wing petals serve as alighting platform for Rhynchosia minima is a perennial insects visiting the flowers. The stamens are prostrate, climbing herb with slender stem ten, 5.6 ± 0.4 mm long, diadelphous; nine that grows in open areas. The plant re-grows filaments are fused by the basal part into a from below ground perennial root stock and sheath open along the upper side while the from the seed during June-August during tenth filament is free and lies on the others. which growth and leaf flushing occurs. The The distal parts of the filaments are free and plants growing in water saturated soils are contain 1 mm long uniform dithecous robust when compared to those growing in anthers (Fig. 3j). The ovary is sessile, green, water stress soils (Fig. 3a,b). The leaves are villous, 2.3 ± 0.4 mm long and lies in the trifoliate with reticulate venation. The sheath of the filaments along the cylindrical leaflets are petiolate, ovate-rhombic, and part of the keel (Fig. 3l,m). It is puberulous, especially beneath. The monocarpellary and monolocular with two flowering occurs during September-March ovules arranged on marginal placentation with peak flowering in January. The plants (Fig. 3o). It has a long glabrous style with a wither and disappear in April. The flowers capitate wet shiny stigma (Fig. 3n), both are borne in pedunculate axillary and 50-70 together account for a length of 3.6 ± 0.4 mm. mm long lax racemes; individual racemes The stigma is situated at the height of the are 4-6 flowered which open over a period of anthers (Fig. 3j). The distal portion of free 2-4 days (Fig. 3c). filaments and style and stigma are incurved and clamped into the keel petals. Flower morphology The flowers are pedicellate, small (5.9 ± Floral biology 0.6 mm long and 6.1 ± 0.5 mm wide), yellow, Mature buds (Fig. 3f) open during 1230- odorless, papilionaceous, zygomorphic and 1530 h with peak anthesis during 1330-1430 bisexual. The calyx is green with yellow h (Table 1). Unfolding of the standard petal tinge and consists of 5 free, linear-lanceolate, and wing petals indicates flowering opening. pubescent, 3-4 mm long sepals. The corolla is The keel petals do not unfold and remain in bright yellow, pubescent, consists of upper their original position as in mature bud stage standard petal, two wing petals and two keel (Fig. 3g,h). All the ten anthers in a flower petals. The standard petal is large (4.9 ± dehisce at the same time by longitudinal slits 0.3mm long and 5.7 ± 0.4mm wide), yellow in mature bud stage. The number of pollen streaked with purple veins outside and grains per anther is 588.6 ± 65.98 and per inside but prominent at the bottom of the flower is 5,886. The pollen-ovule ratio is inside mid-region which serves as nectar 2,943:1. The pollen grains are monads, guide; the petal base is clawed and consists spheroidal, 17.43 ± 2.49 µm in size, powdery of two inflexed fingernail auricles. The and tricolporate, angulaperturate with standard petal envelops the rest of the petals reticulate exine (Fig. 3k). A nectariferous disc in bud but reflexes when the flower opens. is present at the base of the ovary. The The two adjacent petals (4.7 ± 0.4 mm long initiation of nectar secretion occurs during

112 Pollination Ecology of Rhynchosia minima (L.) DC. (Fabaceae) in the Southern Eastern Ghats... mature bud stage and its cessation occurs an insect visited the other flowers previously hour after anthesis. Individual flowers and carried pollen on its ventral side and produce 1.2 ± 0.03 µl of nectar with 0.38 mg also then the pollen ejected from the anthers of sugar. The nectar sugar concentration is powders the ventral side of the insect 28% (Range 26-30%) consisting of sucrose, instantly. If it is the first visit for the insect glucose and fructose with the first as to the flower, then it effects self-pollination dominant. Nectar is deeply concealed and it upon explosive release of reproductive is open through two windows between the column from the keel boat. With the joined and the free filaments at the flower departure of the insect from the flower, the base. These windows allow access to the reproductive column does not return back nectar. The stigma attains receptivity during to its former position but the keel moves anthesis and remains receptive for about forward partly covering the stamens and three hours. After three hours of anthesis, stigma. The downward movement of keel the standard, wing and keel petals gradually petals occurs in each subsequent foraging move close to each other enclosing the visit by appropriate insects. Tripping of reproductive organs (Fig. 3d,e). The closed keel boat can also occur due to heavy rain flowers remain so even during most part of or high temperature that weaken turgidity the fruit development. of the restraining keel tissues. But, the tripping due to these two factors is ruled Pollination mechanism out since the plant flowers during winter The reproductive column is held under season when heavy rains are rare and the pressure within the keel part in open temperatures are usually low (21-26°C). If flowers and it is exposed when the the flower is untouched or tripping to keel pollinator presses against the wing and the did not occur, the reproductive column is keel petals (Fig. 3i). When insects land on never exposed and remain enclosed in the the wing petals, the latter causes the keel keel boat. Such flowers fall off subsequently petals to release the reproductive column upon withering without fruit set. explosively. Consequently, the reproductive column snaps forward against the standard Breeding systems petal causing most of the pollen to be In mature buds, anthers dehisce but instantly released and the pollen thus autonomous autogamy does not occur. released comes into contact with the ventral Fruit set is absent in un-manipulated side of the insect body. Since the incurved autogamy, 16% in hand-pollinated stigma is situated above the height of the autogamy, 50% in geitonogamy, 88% in anthers, it strikes the insect body first due xenogamy and 46% in open-pollination to which cross-pollination occurs if the (Table 2).

Table 1. Anthesis as a function of time in Rhynchosia minima.

Percentage of Time (h) No. of flowers anthesed Anthesis 1130 0 0 1230 11 15 1330 25 34 1430 29 40 1530 8 11 1630 0 0 No. of mature buds tagged: 73

113 A.J. Solomon Raju, K. Venkata Ramana

Table 2. Results of breeding systems in Rhynchosia minima.

No. of flowers No. of fruits Pollination mode Fruit set (%) pollinated formed Autogamy (un-manipulated and 50 0 0 bagged) Autogamy (hand-pollinated and 50 8 16 bagged) Geitonogamy 50 25 50 Xenogamy 50 44 88 Open-pollination 351 160 46

Bee pollinators and pollination Fruiting behavior The flowers were exclusively foraged by The fruit growth and development three species of bees for both nectar and begins immediately after pollination and pollen. The foraging activity began from fertilization. The fruits mature within three 1100 h onwards and ceased at 1700 h (Table weeks (Fig. 4a,b, e-h). The sepals enclose the 3). The bees started probing the mature buds growing fruit initially and the fruit emerges with partial opening of standard petal and out of the sepals gradually with its gradual showed peak foraging activity during 1200- growth and development. Fruit is green 1300 h (Fig. 1). The bees belonged to only initially and brown to dark brown when ripe one order, Hymenoptera, one family, Apidae and dry. It is a non-fleshy, hairy, oblong, and two sub-families, Apinae, and 13.7 ± 1.0 mm long, 3.9 ± 0.2 mm wide, Nomiinae. One bee species belonged to compressed, rounded and apiculated pod Apinae and two species to Nomiinae (Fig. with the remains of the style at the apex and 3p,q). More individuals of A. florea and a few narrowing towards the base. The pods individuals of Ceratina sp. and Nomia sp. produced mostly two seeds but rarely one were recorded at the flowers. Individually, seed; it is compressed between two seeds. In A. florea made 35%, Ceratina sp. 33% and certain 2-seeded pods, one seed is usually Nomia sp. 32% of total foraging visits (Fig. 2). healthy and the other is aborted (Fig. 4i). The body washings of foraging bees showed variation in the pollen carrying capacity; the Seed ecology average pollen recorded on A. florea was Mature and dry fruits display explosive 174.2, Ceratina sp. 134.3 and Nomia sp. 106.4 dehiscence to disperse seeds. The pod with bi- (Table 3). The flowers were visited several valvate configuration dehisce elastically times by bees but new visits lasted shorter ejecting the seeds (Fig. 4c,d). The seed is than the first one. With respect to their greyish to brown, compressed, reniform, finely behavior, the bees landed on the wing petals pubescent, shortly beaked, 2.9 ± 0.2 mm long, and the keel, with their head near the 1.9 ± 0.2 mm wide and shiny without standard petal. They then exerted a certain strophiole (Fig. 4j). Seeds germinate during pressure with legs on the wing petals until rainy season which starts from June to August. these and the keel bent downwards, and Seedlings grow continually but their growth then proceeded to collect nectar during rate is subject to the availability of moisture which the bee's abdomen appeared pollen status of the soil. In areas where soil is smothered (sternotribic pollen deposition). saturated with moisture and contains litter, To collect pollen, the bees took "U" turn after seeds continue growth and produce mature nectar collection and proceeded to the plants within two months and subsequently stamens to collect pollen. commence flowering and fruiting.

114 Pollination Ecology of Rhynchosia minima (L.) DC. (Fabaceae) in the Southern Eastern Ghats...

Fig. 1. Hourly foraging activity of bees on Rhynchosia minima.

Fig. 2. Percentage of foraging visits of individuals bees on Rhynchosia minima.

115 A.J. Solomon Raju, K. Venkata Ramana

Fig. 3. Rhynchosia minima: a. Luxurious growth in water-saturated soil, b. Individual plant in water-stress soils, c. Flowers, d-e. Closure of standard petal covering the wing and keel petals, f. Mature bud, g. & h. Flower with stamens and stigma housed in keel petals, I. Explosive release of stamens and stigma from keel petals, j. Stamens and stigma, k. Pollen grain, l. Pistil, m. Pubescent ovary, n. Capitate stigma, o. Ovules, p. & q. Nomia bees.

116 Pollination Ecology of Rhynchosia minima (L.) DC. (Fabaceae) in the Southern Eastern Ghats...

Fig. 4. Rhynchosia minima: a. Fruiting branch with maturing and mature pods, b. Maturing pods, c. Mature and dry pods partly split for seed release, d. Explosive twisting of pod for seed release , e-h. Different stages of pod development, I. Pod with one healthy seed and one aborted seed, j. Healthy seeds.

117 A.J. Solomon Raju, K. Venkata Ramana

Table 3. Pollen recorded in the body washings of bee foragers on Rhynchosia minima.

Sample size Number of pollen grains Bee species (N) Range Mean S.D Apis florea 10 79-276 174.2 72.05 Ceratina sp. 10 61-183 134.3 38.21 Nomia sp. 10 43-147 106.4 32.43

Discussion Rhynchosia minima is a prostrate, Rhynchosia minima grows in diverse climbing herb which grows from perennial habitats of tropical regions of the world. LOPEZ root stock during rainy season. It also POVEDA (2012) documented that this species produces new plants from seed stock at the occurs in grassland, grassland with scattered same time. Full leaf flushing is complete by trees, woody bush land, ruderal land, the end of August and floral bud initiation roadside, grazed and human disturbed land, takes place in October. The flowering season plain land and sandy black soil. HARDING et al. is well defined and is confined to north-east (1989) also stated that this species occurs in a monsoon and winter seasons. Individual variety of habitats but most often on self- plants produce a small number of flowers mulching heavy clay soils, from sands and during their life time due to production of a sandy loams. With its ability to grow in few inflorescences and each of which different habitats, it appears to have evolved producing a maximum of only six flowers. certain characters that are adaptive to the The plant during flowering phase does not habitat(s) where it occurs. Such evolved attract many flower foragers although characters might have led to the origin of different categories of insects exist in the different ecotypes or varieties in this species. vicinity; the prostrate habit, display of a few In australia, var. minima and var. australis have flowers at ground level and dull banner petal been reported in this species complex based on (standard petal) appear to be responsible for pod hair character (STANLEY & ROSS, 1983; the non-receipt of visits by many insects. ANDREWS, 1952). Later in the same country, In R. minima, hermaphroditic sexual HARDING et al. (1989) described four varieties - system is functional due to production of amaliae, australis, minima and tomentosa in this fertile pollen grains and functional ovary. species complex based on variations in their The flowers display the near synchronous adaptation and growth characteristics. In the hermaphroditism or homogamy due to the present study, R. minima has been found to occurrence of anther dehiscence in mature grow in water-saturated and water stress soils. bud stage and receptivity of stigma during It grows as a population in water-saturated anthesis. The entire reproductive column soils while as scattered or isolated individuals stays inside the keel petals even after in soils experiencing water stress and rocky anthesis; in this situation, there is a areas with little soil content. R. minima did not likelihood of the occurrence autonomous show any notable variations in their growth or autogamy. But, hand-pollination tests morphological characters but the plants indicated that autonomous autogamy does growing in moist soils are comparatively not occur despite self-compatibility but it is robust to those growing in drought or rocky functional because fruiting occurred when areas. However, further work in this line in this mode of pollination is manipulated by different habitats in India may reveal the brushing the stigma with its own pollen. existence of ecotypes or varieties in this Such a situation suggests that the flowers are species. essentially dependent on flower foragers for

118 Pollination Ecology of Rhynchosia minima (L.) DC. (Fabaceae) in the Southern Eastern Ghats... fruit set through self- as well as cross- family Papilionoideae have developed the pollination. It appears that the stigma most complex floral mechanisms. Plants although receptive blocks the germination of within the papilionoideae have zygomorphic the self-pollen while it is in keel petals and flowers that are mainly bee-pollinated hence, it essentially requires the rupture of (Westerkamp, 1997; LPWG, 2017) although its surface by a pollinator to allow the self - bird pollination and bat pollination have or cross pollen to germinate. Such a also been recorded (ORTEGA-OLIVENCIA et stigmatic regulatory function appears to al., 2005). In bee-pollinated flowers of have evolved to discourage selfing and Papilionoideae, each part of the corolla is promote out-crossing. SHIVANNA & OWENS specialized for a particular role in pollinator (1989) stated that the rupture of the stigmatic attraction and the success of pollination. The surface by pollinator permits the pollen to flag or standard petal attracts pollinators; the germinate in the flowers of phaseoleae keel protects androecium and gynoecium members with thick stigmatic cuticle. On the and, together with the wings, provides a contrary, CASTRO & AGULLO (1998) reported platform for the insects to land on. The that in vigna, a member of the tribe wings also operate as levers that raise or phaseoleae, autonomous self-pollination lower the keel (STIRTON, 1981). The flowers may occur by spontaneous rupture of the typical of pollination by the bee family stigmatic membrane. Similar stigmatic apidae are zygomorphic, bright yellow or surface that prevents self-fertilization has blue with nectar guides, and frequently with also been reported in vicia faba (tribe vicieae) hidden rewards such as those in the (LORD & HESLOP-HARRISON, 1984) and in lamiaceae, scrophulariaceae, fabaceae and scutellata (tribe ) (KRIETNER orchidaceae (FAEGRI & VAN DER PIJL, 1979). & SORENSEN, 1985); however, in these species In the present study, the Fabaceae member, auto-fertile lines have been reported to have R. minima has papilionaceous corolla with thin stigmatic cuticles allowing spontaneous flag, wing and keel petals; the flag petal disruption and self-fertilization. In R. serves as a visual attractant, wing petals minima, the stigmatic surface appears to have provide landing platform and keel petals thick cuticle and does not have the protect the entire reproductive column. The mechanism of causing spontaneous rupture flowers are typical of pollination by bees to facilitate autonomous self-pollination. In since they are zygomorphic, standard petal effect, the tripping of keel petals appears to with nectar guide, hidden nectar at the be essential to cause rupture on the stigmatic corolla base and hidden pollen in keel petals. surface by the tripping agent due to which Within the sub-family Papilionoideae, there is more likelihood of the occurrence of primary and secondary pollen presentations either geitonogamy or xenogamy. The fruit have been reported. In plants with primary set rates recorded in hand-pollinated pollen presentation, pollen is delivered geitonogamy and xenogamy also directly from the anthers to the vector's substantiate that the plant is facultative body. In plants with secondary pollen xenogamous, a breeding system that is presentation, pollen grains are delivered first flexible and keeps the options open for both on a floral part such as the keel petals in selfing and out-crossing mediated by pollen papilionoideae and then on the body of the vectors. vector implying an accurate delivery of SCHRIRE (1989) stated that the ecological pollen on the vector's body (HOWELL et al., and evolutionary success of leguminosae has 1993). These two pollen presentation been related to biotic pollination patterns are associated with the four types of mechanisms. The six sub-families within this basic pollination mechanisms - valvular, family have achieved a characteristic floral pump, explosive and brush, all of them are architecture, in which plants within the sub- associated with a particular floral

119 A.J. Solomon Raju, K. Venkata Ramana architecture and kinetics. In the valvular rich. BAKER & BAKER (1983) stated that type, pollen presentation is primary, flowers with long corolla tube possess more whereas in the other three mechanisms, it is sucrose in their nectar while those with short secondary (YEO, 1993). In the explosive tubes possess more hexoses in their nectar. mechanism, commonly only one pollination In the present study, R. minima with short event occurs and it has evolved corolla tube presents sucrose-rich nectar independently in several tribes (SMALL, because the nectar is perfectly concealed and 1988), while in the other three mechanisms, hence is not exposed for the breakdown of repeated visitation is possible (WESTERKAMP, sucrose into hexoses. Concealment of nectar 1997). In the present study, R. minima in this species is adaptive to protect against flowers have explosive pollination microorganisms, particularly yeasts, whose mechanism and deliver pollen directly from metabolic activities dramatically change the anthers to the bee's body when keel nectar chemistry and the plant gains a petals are tripped by the foraging bee; this benefit from keeping the nectar as sterile as type pollen delivery is the representative of possible to maintain control over its primary pollen presentation associated with chemical composition in order to maximize explosive pollination mechanism. In the pollination rate by attracting appropriate flowers, the staminal column is held under pollinators (HERRERA et al., 2008). Honey pressure within the keel, and when the bees prefer the flowers with sucrose as chief tension is released by the forager, the same constituent of nectar (KEVAN, 1995). The column snaps forward against the standard flowers pollinated by long-tongued bees petal causing all the pollen to be instantly produce sucrose-rich nectar (BAKER & released. The reproductive column remains BAKER, 1990). In line with this, R. minima exposed and does not return back to its with melittophilous pollination syndrome original state but the keel petals return back also produces sucrose-rich nectar which is partially covering the stamens and stigma. utilized exclusively by long-tongued bees. The efficiency of explosive pollination Apis, ceratina and nomia bees recorded on this mechanism depends on the ambient weather herb have been documented as long-tongued conditions, especially temperature and bees (CRUDEN et al., 1983; ROUBIK, 1992; relative humidity. Since R. minima flowers ROUBIK, 2006). Bee-flowers tend to produce during winter season, it accordingly small volume of nectar with higher sugar commences anthesis from noon onwards by concentration than the nectar of flowers which time the ambient air will be relatively pollinated by other animals (OPLER, 1983; dry and hence is conducive for the efficient CRUDEN et al., 1983). Honey bees prefer functioning of the explosive pollination sugar concentration of 20 to 40% in the mechanism. Further, the bees also commence nectar (WALLER, 1972). On the contrary, their foraging activity from around noon BAKER & BAKER (1983) noted that honey bees time and continue forage collection until the prefer sugar concentration of 30 and 50% in flowers close back. The concealment of the the nectar. The honey bees have the ability to stamens within the keel petals until it is regurgitate liquid onto concentrated or even tripped is an advantage for the plant to crystallized nectar, in this way, reduce its secure pollen from unusual rains and concentration so that it may be imbibed. The ambient moisture conditions during the preferred sugar concentrations of nectar by flowering season of this plant (PETER et al., other categories of bees have not been found 2004). in the literature. But, PYKE & WASER (1981) PERCIVAL (1961) stated that plants with stated that the nectar sugar concentration of deep-tubed flowers tend to produce sucrose- flowers pollinated by bees is generally rich nectar, whereas those with open or higher than that of those pollinated by shallow-tubed flowers tend to be hexose- butterflies and hummingbirds; bee-

120 Pollination Ecology of Rhynchosia minima (L.) DC. (Fabaceae) in the Southern Eastern Ghats... pollinated flowers tend to produce nectar xenogamy. Several workers followed these with sugar concentration more than 35% P/O ratios to classify breeding systems of while butterfly or hummingbird pollinated the plant species studied by them. ARROYO flowers tend to produce nectar with sugar (1981) stated that the p/o varies according to concentration ranged between 20 and 25%. the pollination mechanism within In line with these reports, the present study papilionoideae. These authors suggested shows that the flowers of R. minima produce that the plants with explosive mechanism a small volume of nectar with 28% sugar have a low P/O because a single pollinator concentration. Further, the energy yield from visit is needed for efficient transference of nectar appears to be in tune with the pollen; this low P/O is a consequence of the requirement of energy by bees. Therefore, R. highly specialized, irreversible pollination minima flowers with explosive pollination mechanism, which allows only one effective mechanism, primary pollen presentation, exchange of pollen with pollinators. SMALL and hidden nectar and pollen have evolved (1988) stated that medicago species of the to discourage other foragers from visiting tribe trifolieae with explosive pollination the flowers and to ensure that the bees get mechanism displays the lowest pollen-ovule the floral rewards. Accordingly, the flowers ratios. LOPEZ et al. (1999) recorded explosive of R. minima never received visits from other pollination mechanism with highest pollen- categories of insects. ovule ratios in certain genera of the fabaceae In R. minima, the keel tripping process is such as cytisus, pterospartum, teline, , not self-activated to effect pollination. The stauracanthus and . ETCHEVERRY flowers depend on bees for tripping of the et al. (2011) stated that the fabaceae plants keel petals to enable the working of which they studied with explosive explosive pollination mechanism. The pollination mechanism had intermediate flowers that were not tripped by external pollen-ovule ratios. These authors agents subsequently fall off. This situation mentioned that Rhynchosia edulis and R. explains that the plant is obligately senna var. texana have valvular pollination dependent on bees for pollination. The bees mechanism with primary pollen visiting the flowers seem to be efficient in presentation. Both the species are classified tripping the flowers because the flower size as obligate xenogamous based on P/O ratio and petal strength are commensurate with but R. edulis has been found to be facultative the bee size and the force employed to xenogamous in hand-pollination tests. depress the wing petals to access the nectar. CRAUFURD & PRINS (1979) reported that r. MISHRA & RAJESH KUMAR (1997) reported sublobata is self-compatible and facultative that the pollen has great importance for a xenogamous in hand-pollination tests; it is bee colony as pollen provides proteins, pollinated by xylocopa bees. In the present which are essential for worker honey bees to study, r. minima shows highest p/o ratio secrete glandular food (royal jelly) for when compared to that of facultative rearing brood. Availability of enough pollen xenogamy used by CRUDEN (1977). The directly helps in more brood rearing, which highest P/O ratio in this plant species ultimately leads to gradual colony build up. appears to be a consequence of pollen R. minima serves also as a pollen source for collection activity by bees. Therefore, it is foraging bees. inevitable for R. minima to produce high P/O CRUDEN (1977) used the pollen-ovule to compensate the pollen loss caused by (p/o) ratios as indicators of breeding pollen collectors and ensure the function of systems of plants. He provided P/O ratios its vector-dependent facultative xenogamous for different breeding systems - 168.5 + 22.1 breeding system. for facultative autogamy, 798.6 + 87.7 for TRAN & CAVANAGH (1984) reported that facultative xenogamy and 5859.2 + 936.5 for in leguminosae, seeds of many taxa exhibit

121 A.J. Solomon Raju, K. Venkata Ramana physical (exogenous) dormancy due to the saturated and hence there it becomes a presence of a water impermeable seed coat. successful weed in farmlands but certainly With this dormancy, they remain viable for not in areas where soil is deficient in long period of time. ALI et al. (2012) reported moisture during rainy season. Therefore, R. such physical dormancy in Rhynchosia minima is not a very widespread species capitata due to which this species is because it is habitat-specific and requires successful as a weed. SHAUKAT & BURHAN sufficient moisture and nutrient content in (2000) described seed characteristics and the the soils to establish populations. factors regulating germination of r. minima Nevertheless, r. minima although not in pakistan; it exhibits differential success in successful in establishing populations in different habitats with different micro- water-stress soils is a hardy plant and climates. RANGASWAMY & NANDAKUMAR tolerant of drought as stated by HARDING et (1985) reported that the seed coat of al. (1989). Rhynchosia minima is composed of three R. minima is widely used as a medicinal gradative barriers to water uptake a surface plant. It is used to cure eye conjunctivitis deposit of waxy material interfused with a and inflammation (CHUTE & TIWARI, 2002), lipoidal substance, β-sitosterol; a subjacent 3- body care (MUSTAK et al., 2006), skin μm adcrustation of hemicellulose-cellulose conditioning and boils (GUNDIDZA et al., complex; and a layer of palisade cells in 2009), haemorrhoids, heart, diarrhoea and which the secondary walls are impregnated dysentery (LOPEZ POVEDA, 2012). It is also with arabinan and the lumen contains tannin used as animal forage (HASSELL, 1945; and phenolic compounds. The micropyle SHUKLA et al., 1970; GILLETT et al., 1971; and hilum function as hygroscopic valves BOYLAND, 1973; BEESTON, 1978; BOGDAN, when seed coat breaks open. In this study, a 1977). Further, LOPEZ POVEDA (2012) noted few seedlings have been sighted and this is that the seed of this species is used as food, not in tune with the abundant seed especially in making sweets. In this production through open-pollinations by r. connection, it is pertinent to mention the minima; hence this species appears to have report of HARDING et al. (1989) that this physical dormancy as reported by species is likely a potential grain crop RANGASWAMY & NANDAKUMAR (1985). because it is a large seed producer. Since Many seeds germinate in the vicinity of the significant variations exist in agronomic parental plants in areas of water-saturated attributes such as days to flowering, pod soils during rainy season but their growth indehiscence and seed size of R. minima suppressed when long dry spells continued growing in different habitats, there is a huge during this season. In areas of water stress, a potential to identify and select desirable few seeds germinated here and there but genotypes to improve grain production in they soon perished due to water stress as a this species. Therefore, further studies are consequence of long dry spells. In both suggested to exploit the varieties or ecotypes water-saturated and water stress habitats, of R. minima for medicine, animal forage and the perennial root stock of this species human food. seasonally resurrects and produces new REMANANDAN (1981) stated that growth during rainy season. The explosive Rhynchosia, being generically related to the pod dehiscence results in the settlement of genus cajanus, some of its species can be seeds mostly in the parental sites but rain used to provide substantial contributions water may disperse them to new places towards crop improvement in pigeon pea. during rainy season. Seed dormancy seems Furthermore, some species of Rhynchosia to be regulating the proliferation of R. have been experimented in India to provide minima. It is successful in building up physiological resistance against insect pests populations only in areas where soil is water such as pod-borer and pod-fly in pigeon pea.

122 Pollination Ecology of Rhynchosia minima (L.) DC. (Fabaceae) in the Southern Eastern Ghats...

In this study, the seeds of R. minima have not ARROYO M.T.K. 1981. Breeding systems and been infested by any pod-borer or pod-fly pollination biology in Leguminosae. - both in water-saturated and water-stress - In: Polhill R.M., P.H. Raven (Eds.) habitats suggesting that it has physiological Advances in Legume Systematics. Part resistance against insect pests. Therefore, 2, Royal Botanical Gardens, Kew, intensive and extensive research is suggested London, Part 2, pp. 723-769. to identify and select desirable genotypes of BAKER H.G., I. BAKER. 1983. Floral nectar R. minima that give physiological resistance sugar constituents in relation to against pod or seed pests in order to use pollinator type. - In: Jones C.E., them for crop improvement in pigeon pea. Little, R.J. (Eds.), Handbook of Experimental Pollination Biology. Conclusion Scientific and Academic Editions, Rhynchosia minima is a winter blooming New York, pp. 117-140. prostrate climbing herb in India. It is BAKER H.G., I. BAKER. 1990. The predictive hermaphroditic, self-compatible and value of nectar chemistry to the equipped with explosive pollination recognition of pollinator types. - Israel mechanism adapted for melittophily. It is Journal of Botany, 39: 157-166. [DOI] essentially vector-dependent for both self- BEESTON G.R. 1978. Vegetation. - In: Western and cross-pollination. Mature pods dehisce Arid Region Land Use study - Part V. explosively to disperse seeds which Technical Bulletin No. 23, Division of germinate during wet season. The seedlings Land Utilization. Department of grow successfully only in soils with Primary Industries, Brisbane. sufficient moisture or else they subsequently BODGAN A.V. 1977. Tropical pasture and fodder perish. Therefore, this plant grows as a plants. London. Longman Group Ltd. 475 p. successful weed in farm lands only where BOYLAND D.E. 1973. Vegetation of the mulga soil is wet and nutrient-rich. Previous lands with special reference to south- reports indicate that it has medicinal, animal western Queensland. - Tropical forage and human food values and hence Grasslands, 7: 35-42. there is a potential for its exploitation CASTRO M.A., M.A. AGULLO. 1998. Anatomy commercially. of the stigma of Vigna adenantha (G.F. Mayer) Marechal. Mascherpa and Acknowledgements Stainer (Leguminosae, Papilionoideae). We thank the Andhra University, - Biocell, 22: 9-18. Visakhapatnam, India, for providing CHUTE G.S., V.J. TIWARI. 2002. Indigenous physical facilities to carry out this research ethnomedicinal plants used by tribal work. We thank Dr. Ch. Prasada Rao, people of Bhandara and Gadchiroli Department of Botany, Andhra University, Districts of Maharashtra State. - Indian for providing field assistance. Journal of Natural Products, 15: 3-8. CRAUFURD R.Q., W.H. PRINS. 1979. Munkolo References (Rhynchosia sublobata), a promising ALI H.H., A. TANVEER, M.A. NADEEM. 2012. pasture legume for Zambia. - Evaluation of some seed dormancy Tropical Grasslands, 13: 45-52. breaking methods on germination of CRUDEN R.W. 1977. Pollen-ovule ratios: a Rhynchosia capitata (Roth DC). - conservative indicator of breeding Pakistan Journal of Weed Science systems in flowering plants. - Research, 18: 423-432. Evolution, 31: 32-46. ANDREWS F.W. 1952. The flowering plants of CRUDEN R.W., H.M. HERMANN, S. the Anglo-Egyptian Sudan. Scotland. J. PETERSON. 1983. Patterns of nectar Bungel & Co. production and plant-pollinator

123 A.J. Solomon Raju, K. Venkata Ramana

coevolution. - In: The Biology of communities degrade floral nectar of Nectaries. Bentley B., T. Elias (Eds.) bumble bee-pollinated plants. - New York, Columbia University Ecology, 89: 2369–2376. [DOI] Press, pp. 80-125. HOWELL G.J., A.T. SLATER, R.B. KNOX. 1993. DAFNI A., P.G. KEVAN, B.C. HUSBAND. 2005. Secondary pollen presentation in Practical Pollination Biology. Canada, angiosperms and its biological Enviroquest Ltd. significance. - Australian Journal of ETCHEVERRY A.V., M.M. ALEMAN, T. FIGUEROA- Botany, 41: 417-438. [DOI] FLEMING, D. LOPEZ-SPHAR, C.A. JACA T.P., J.S. BOATWRIGHT, A.N. MOTEETEE. GOMEZ, C. YANEZ, D.M. FIGUEROA- 2018. Taxonomic studies of the genus CASTRO, P. ORTEGA-BAES. 2011. Pollen: Rhynchosia Lour. (Phaseoleae, ovule ratio and its relationship with Fabaceae) in South Africa: a review other floral traits in Papilionoideae of section Chrysoscias. - South African (Leguminosae): an evaluation with Journal of Botany, 117: 119-133. Argentine species. - Plant Biology JAYASURIYA A.H.M. 2014. Rhynchosia velutina, (Stuttgart), 14: 171-178. [DOI] a critically endangered legume crop FAEGRI K., L. VAN DER PIJL. 1979. The wild relative in Sri Lanka. - Ceylon Principles of Pollination Ecology. Journal of Science (Biological sciences), Oxford, Pergamon Press. 43: 147-150. [DOI] GILLETT J.B., R.M. POLHILL, B. VERDCOURT. KEVAN P.G. 1995. Bee botany, pollination, 1971. Leguminosae (Part 4) Subfamily foraging and floral calendars. - In: Papilionoidea (2). - In: Milne-Redhead Kevan P.G. (Ed.), The Asiatic hive bee: E., R.M. Polhill (Eds.). Flora of Tropical Apiculture, Biology and role in East Africa. London, Crown Agents, Sustainable Development in Tropical pp. 1016-1036. and Subtropical Asia. Ontario, GREAR J.W. 1978. A revision of the New Enviroquest Ltd., pp. 113-116. World species of Rhynchosia KREITNER G.L., E.L. SORENSEN. 1985. Stigma (Leuminosae-). Mem. - development and the stigmatic New York Botanical Gardens, 31: 1-168. cuticle of Medicago scutellata. - GUNDIDZA M., N. GWERU, M.L. MAGWA, N.J. Canadian Journal of Botany, 63: 813- RAMALIVHANA, G. HUMPHREY, A. SAMIE, 818. [DOI] V. MMBENGWA. 2009. Phytochemical LACKEY J.A. 1981. Phaseoleae. - In: Pohill composition and biological activities of R.M., P.H. Raven (Eds.), Advances in essential oil of Rhynchosia minima (L.) Legume Systematics. Royal Botanical (DC) (Fabaceae). - African Journal of Garden, Kew, Richmond, England, Biotechnology, 8: 721-724. Vol. 1, pp. 301-327. HARBORNE J.B. 1973. Phytochemical Methods. LOPEZ POVEDA L. 2012. Rhynchosia minima. London. Chapman and Hall. 279 p. The IUCN Red List of Threatened HARDING W.A.T., B.C. PENGELLY, D.G. Species 2012: e.T19379374A20135353. CAMERON, L. PEDLEY, R.J. WILLIAMS. [DOI] 1989. Classification of a diverse LOPEZ J., T. RODRIGUEZ-RIANO, A. ORTEGA- collection of Rhynchosia and some allied OLIVENCIA, J.A. DEVESA, T. RUIZ. species. Brisbane, CSIRO Division of 1999. Pollination mechanisms and Tropical Crops and Pastures. pollen-ovule ratios in some HASSEL O.L. 1945. Native pasture legumes in (Fabaceae) from Southwestern the central coast. - Queensland Europe. - Plant Systematics & Agriculture Journal, 60: 5-13. Evolution, 216: 23-47. [DOI] HERRERA C.M., I.M. GARCIA, R. PEREZ. 2008. LORD E., Y. HESLOP-HARRISON. 1984. Pollen Invisible floral larcenies: microbial and stigma organization in

124 Pollination Ecology of Rhynchosia minima (L.) DC. (Fabaceae) in the Southern Eastern Ghats...

Leguminosae: stigma organization impermeability in the legume and the breeding system of Vicia faba. Rhynchosia minima. - Botanical - Annals of Botany, 54: 827-836. Gazette, 146: 501-509. LPWG, 2017. A new subfamily classification of the REMANANDAN P. 1981. The wild gene pool Leguminosae based on a taxonomically of Cajanus at ICRISAT, Present and comprehensive phylogeny. - Taxon, 66: Future. - In: Proc. Intl. Workshop on 44-77. [DOI] Pigeon-peas, Vol. 2, pp. 15-19, 1980, MADHAVA CHETTY K., K. SIVAJI, TULASI Patancheru, Andhra Pradesh, India. R.A.O. 2008. Flowering plants of ROUBIK D.W. 1992. Ecology and natural Chittoor District, Andhra Pradesh, history of tropical bees. London, India. Tirupati, Students Offset Cambridge University Press, pp. 526. Printers. ROUBIK D.W. 2006. Pollination ecology and the MISHRA R.C., R. KUMAR. 1997. Bee flora and rain forest: Sarawak studies. Berlin, beekeeping maps of India. - In: Springer Science & Business Media. Mishra R.C. (Ed.) Perspectives in SCHRIRE B.D. 1989. A multidisciplinary Indian Apiculture. Bikaner, Agro- approach to pollination biology in the Botanica, pp. 40-65. Leguminosae. - In: Stirton C.H., J.L. MUSTAK A., M.A. KHAN, S. MANZOOR, M. Zarucchi (Eds.). Advances in Legume ZAFAR, S. SULTANA. 2006. Check list Biology. Monographs in Systematic of medicinal flora of Tahsil Isakhel, Botany from the Missouri Botanical district Mianwali, Pakistan. - Garden, Vol. 29, pp. 183-242. Ethnobotanical Leaflets, 10: 41-48. SCHRIRE B.D. 2005. Tribe Phaseoleae. - In: OPLER P.A. 1983. Nectar production in a Lewis G.B., B. Schrire, B. tropical ecosystem. - In: Bentley B., Mackinder, M. Lock (Eds.). Legumes T. Elias (Eds.), The Biology of of the World. Royal Botanic Gardens, Nectaries. Columbia, Columbia Kew, UK, pp. 409-410. University Press, pp. 30-79. SHAUKAT S.S., N. BURHAN. 2000. Fecundity, ORTEGA-OLIVENCIA A., T. RODRIGUEZ- seed characteristics and factors RIANO, F.J. VALTUENA, J. LOPEZ, J.A. regulating germination of Rhynchosia DEVESA. 2005. First confirmation of a minima (L.) D.C. - Pakistan Journal of native bird-pollinated plant in Botany, 32: 211-226. Europe. - Oikos, 110: 578-590. SHIVANNA K.R., S.J. OWENS. 1989. Pollen- PERCIVAL M.S. 1961. Types of nectars in pistil interactions (Papilionoideae). angiosperms. - New Phytologist, 60: - In: Stirton C.H., J.L. Zarucchi 235-281. [DOI] (Eds.). Advances in Legume Biology. PETER C.I., A.P. DOLD, N.P. BARKER, B.S. Monographs in Systematic Botany RIPLEY. 2004. Pollination biology of from the Missouri Botanical Bergeranthus multiceps (Aizoaceae) Garden, Vol. 29, pp. 157-182. with preliminary observations of SHUKLA K.S., S.K. RANJHAN, R.C. KATIYAR. repeated flower opening and 1970. Rhynchosia minima as a feed closure. - South African Journal of for sheep. - Indian Journal of Dairy Science, 100: 624-628. Science, 23: 82-84. PYKE G.H., N.M. WASER. 1981. The production SOLOMON RAJU A.J., J. RADHA KRISHNA. of dilute nectars by hummingbird and 2017. Contribution to the honeyeater flowers. - Biotropica, 13: knowledge of three Indian 260-270. [DOI] Spermacoce (Rubiaceae) and some RANGASWAMY N.S., L. NANDAKUMAR. 1985. preliminary information about their Correlative studies on seed coat pollination ecology. - Anales de structure, chemical composition, and Biologia, 39: 111-126.

125 A.J. Solomon Raju, K. Venkata Ramana

SMALL E. 1988. Pollen-ovule patterns in tribe Trifoliae (leguminosae). - Plant Systematics and Evolution, 160: 195-205. [DOI] STANLEY T.E., E.M. ROSS. 1983. Flora of South- eastern Queensland. Volume 1. Brisbane, Department of Primary Industries. STIRTON C.H. 1981. Petal sculpturing in Papilionoid legumes. - In: Polhill R.M., R.H. Raven (Eds.). Advances in Legume Systematics. Part 2, Royal Botanical Gardens, Kew, London, pp. 771-788. TRAN V.N., A.K. CAVANAGH. 1984. Structural aspects of dormancy. - In: Murray, D.R. (Ed.). Seed physiology, Germination and Reserve Mobilization. Sydney, Academic Press, Sydney, Vol. 2, pp. 1-44. TURNER B.L. 2011. Systematics of the Rhynchosia senna complex (Fabaceae). - Lundellia, 14: 27-31. [DOI] WALLER G.D. 1972. Evaluating responses of honeybees to sugar solutions using an artificial-flower feeder. - Annals of Entomological Society of America, 65: 857-862. WESTERKAMP C. 1997. Keel blossoms: bee flowers with adaptations against bees. - Flora, 192: 125-132. YEO P.F. 1993. Secondary pollen presentation. Form, function and evolution. New Received: 08.02.2018 York, Springer. Accepted: 31.05.2018

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