Reproductive biology of Boswellia serrata, the source of salai guggul, an important gum-resin

Detailed studies were carried out on the phenology, floral biology, pollination ecology and breeding system of Boswellia serrata Roxb. (Burseraceae) the source of 'salai guggul'. The trees remain leafless during the entire period of flowering and fruiting. The inflorescence is a terminal raceme and produces up to 90 bisexual, actinomorphic flowers. On average a flower produces 10 044 ± 1259 starch-filled pollen grains. About 85% of the fresh pollen grains are viable; the pollen to ovule ratio is 3348 : 1. The stigma is of the wet papillate type. The style is hollow with three flattened stylar canals filled with a secretion product. The stylar canals are bordered by a layer of glandular canal cells. The inner tangential wall of the canal cells shows cellulose thickenings. The ovary is trilocular and bears three ovules, one in each locule. Flowers offer nectar and pollen as rewards to floral visitors. The giant Asian honey bee ( Apis dorsata ) and A. cerana var. indica (Indian honey bee) are the effective pollinators. The species is self-incompatible and the selfed pollen tubes are inhibited soon after their entry into the stigma. Self-pollen tubes develop a characteristic 'isthmus' as a result of enlargement of the tube soon after emergence through the narrow germ pore. Cross-pollinated flowers allowed normal pollen germination and pollen tube growth, and resulted in fruit- and seed-set. Under open pollination fruit-set was only about 10%. Although manual cross-pollinations increased fruit set, it was only up to about 20%. Low fruit set appears to be the result of inadequate cross-pollination and other constraints, presumably limitation of available nutrients.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 73–82.     

Pollen and sensorial characterization of different honeys from El Hierro (Canary Islands)

The pollen content of 31 honey samples from 19 different apiaries of El Hierro (Canary Islands) were subject to qualitative and quantitative melissopalynological analysis. The quantitative analysis demonstrated that 13% of the honey belonged to Maurizio Class I (<2?000?grains), 68% to Class II (2?000–10?000?grains) and 19% to Class III (10?000–50?000?grains). The pollen density ranges from 1?042?grains/g of honey to 24?478?grains/g with an average of 7?471?grains/g. According to the qualitative analysis, six honeys were typified as unifloral and 25 as multifloral. The unifloral honey samples were broken down as follows: two of heather (Erica arborea L.), two of Chamaecytisus proliferus (L. f.) Link‐type (“tagasaste”), one of Fabaceae (Genisteae sp.) and one of Lamiaceae Origanum vulgare L. ssp. virens (Hoffmanns. &; Link) Ietsw.‐type (thyme: Micromeria hyssopifolia Webb &; Berthel.). Honeydew elements were practically absent. Sixty‐nine pollen types were identified belonging to 42 families. The number of pollen types range between 18 and 39 (mean of 27.42). Foeniculum vulgare Mill.‐type pollen is present in all the samples. Galactites tomentosa Moench‐type, Echium plantagineum L., Echium L. sp., Bituminaria bituminosa (L.) C. H. Stirt., Chamaecytisus proliferus ‐type and Origanum vulgare ssp. virens ‐type pollen were found in 96.8% of the samples. The sensorial analysis indicated that honey types are generally of good quality, because 62% were evaluated as very high (16%), high (23%), and good (23%).     

Reproductive ecology of the endemic Lecocarpus pinnatifidus (Asteraceae) in an isolated population in the Galápagos Islands

Lecocarpus pinnatifidus is an endemic member of the Asteraceae occurring on only one island in the Galápagos archipelago. The capitula are large with female ray florets and male disc florets. They are self-compatible but this study suggests fruit set is pollen limited. Visits from Xylocopa darwini and other larger insect pollinators are rare, and small insects seem to be the main pollinators. Small insects carry few pollen grains and most likely mediate self-pollinations. Self-compatibility and seed set after selfing are the most common reproductive strategy in the Galápagos Islands and L. pinnatifidus seemingly fits well into this group.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 171–180.     

On the presence of extracellular calcium oxalate crystals on the inflorescences of Araceae

This study presents a survey of the species of the Araceae where extracellular production of calcium oxalate crystals has been observed and discusses the patterns of production of the crystals in different genera. For all Araceae studied using SEM, the oxalate crystals exuding on the epidermal surface correspond to extended aggregate/druses or crystal sand and the oxalate crystals mixed with pollen correspond to raphides or styloids (prismatic crystals). The type of crystals associated with pollen varies among genera. However, the presence of crystals associated with pollen is a specific rather than a generic characteristic. Our results show that the presence of raphides mixed with pollen seems to be a widespread phenomenon in the aroid family.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 181–190.     

The cytological origin of the polyads and their significance in the reproductive biology of Mimosa bimucronata

The mechanism of polyad formation in Mimosa bimucronata (DC.) Kuntze is described and its significance in the reproductive biology is discussed. In this species c . 500 complexes of two coupled pollen mother cells (PMCs) per pollen sac are formed after the last mitotic division of the sporogenous tissue. All the pollen grains of each complex remain attached and form a bitetrad. This mechanism leads to the formation of many polyads per pollen sac. On this basis, we propose that in Mimosa the number of pollen grains per polyad (eight or 16) is determined by the number of cells that remain attached after the last mitotic divisions of the sporogenous tissue. Concerning the biological significance of the polyads in M. bimucronata , we find that the number of pollen grains per polyad is correlated with the number of ovules per ovary, and that the internal dimensions of the pit-shaped stigma are sufficient just for one polyad to be localized in it. Based on the number of polyads per flower this species has a high pollen/ovule ratio characteristic of xenogamous plants, in opposition to that expected for plants with composite pollen dispersal units. In contrast, it has low pollination efficiency, low fruit set, a 1/1 relationship between the pollen grains of a polyad and the number of ovules per ovary, and high seed set per fruit. These facts support the hypothesis that the occurrence of polyads in M. bimucronata would be an adaptation helping to ensure high seed set following a single cross pollination event.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 343–349.     

Palynological and geographical characterization of avocado honeys in Spain

The present work refers to the pollen analysis of 12 avocado honey samples from Spain. The samples were directly provided by the beekeepers, all professionals. The quantitative analysis showed that nectar is the main honey source in the samples studied, and that most honeys have a medium presence of botanical elements (BE); one sample belong to Class I of Maurizio, seven to Class II and four belong to Class III. The qualitative analysis of the samples showed the presence of 56 taxa belonging to 36 families. The Spanish avocado honeys are characterised by their medium content in pollen grains (NPG; x¯=117000) and their low honeydew indicator elements content (HDE; x¯=6340). Echium plantagineum gr. and Genista f. (present in 90% of the samples), and Eucalyptus f., Olea europaea L., Mentha aquatica gr. and Reseda luteola gr. (present in 80% of the samples), could be mentioned among the characteristic accompanying species of this honey type. The avocado honeys from the Iberian Peninsula and from the Canary Islands can be differentiated by the presence of Asphalthium bituminosum Medic., Cardiospermum grandiflorum Sw., Phoenix canariensis Hort. ex Chabaud and Tropaeolum majus L. in the latter.     

Pollen analysis of honeys from the Mamora forest region (NW Morocco)

The present work refers to the pollen analysis of 35 Moroccan honey samples from the Mamora forest region. The samples were directly provided by the beekeepers, all professionals. The quantitative analysis showed that nectar is the main honey source in the samples studied, and that most honeys have a medium-low presence of botanical elements (BEN). The qualitative analysis of the samples showed the presence of 54 taxa belonging to 29 families, and 31 of the samples were unifloral: 24 of eucalyptus, 3 of orange, 2 of Loeflingia, 1 of mint and 1 of Ridolfia segetum. The eucalyptus honeys of the studied region are characterized by their high content in pollen grains (NGP; x¯=180000) and their low honeydew indicator elements content (HDE; x¯=4000); Plantago f. (present in 70% of the samples), Quercus f. and Brassicaceae (50%) and Ceratonia siliqua (30%) could be mentioned among the characteristic accompanying species of this honey type.     

Pollination by fungus gnats in four species of the genus Mitella (Saxifragaceae)

The first example of pollination by fungus gnats in the eudicots is reported. The genus Mitella (Saxifragales) is characteristically produces minute, inconspicuous, mostly dull-coloured flowers with linear, sometimes pinnately branched, petals. To understand the function of these characteristic flowers, we studied the pollination biology of four Mitella species with different floral traits and different sexual expression: dioecious M. acerina , gynodioecious M. furusei var. subramosa , and hermaphroditic M. stylosa var. makinoi and M. integripetala. Flower-bagging experiments showed that wind pollination did not occur in the dioecious and gynodioecious species. Two years of observations of flower visitors at six study sites in Japan revealed that the principal pollinators of all four Mitella were specific species of fungus gnats (Mycetophilidae), which landed on the flowers with their long spiny legs settling on the petals. Characteristically, numerous pollen grains were attached to the fungus gnats in specific locations on the body. Although, on average, 1.3–2.6 fungus gnats visited each inflorescence per day, the fruit set of both bisexual and female flowers exceeded 63%. These results suggest that fungus gnats are highly efficient pollinators of Mitella spp., and that Mitella flowers are morphologically adapted to pollination by fungus gnats.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 449–460.     

The exine ultrastructure of pollen grains in Gnetum (Gnetaceae) from China and its bearing on the relationship with the ANITA Group

Pollen grains of six species of Gnetum , G. parvifolium , G. hainanense , G. luofuense , G. pendulum , G. cleistostachyum and G. montanum , collected from China were examined using light, scanning and transmission electron microscopy. Pollen grains of Gnetum are subspheroidal or irregular-apolar, inaperturate, 11.21–22.44 µm in long axis and 9.34–20.47 µm in short axis. The exine surface is covered with spinules, 0.50(0.30–0.71) µm long spaced on average 1.12(0.81–1.46) µm apart. The exine is about 0.55 µm thick and comprises ectexine and endexine. The ectexine includes a thin tectum and an infratectal granular layer. The tectum protrudes outwards, forming the spinules. The endexine is composed of discontinuous lamellae, with lacunae between lamellae. The pollen grains of Gnetum are compared with those of Ephedra and Welwitschia , and also those of the ANITA Group of angiosperms, including Amborellaceae, Nymphaeales, Illiciales, Trimeniaceae and Austrobaileyaceae. The exine ultrastructures of Gnetum , Ephedra and Welwitschia are quite similar, consisting of tectum, granular layer and lamellated endexine. The exine ultrastructure of Gnetum is also similar to that of Nymphaea colorata (Nymphaeaceae) in the transitional region between the proximal and distal poles, but differs from that of Amborellaceae, Illicium religiosum (Illiciaceae), Schisandra (Schisandraceae), Trimeniaceae and Austrobaileyaceae. This comparison of exine ultrastructure provides new evidence for consideration of the relationship between Gnetum and the ANITA Group.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 415–425.     

On the origin and development of Artemisia (Asteraceae) in the geological past

Fossil records combined with phytogeographical data reveal that Artemisia L. possibly originated from the existing arid or subarid area of temperate Asia in the mid-Tertiary. The earliest recorded Asteraceae pollen grains are mostly ornamented with medium to long spines, whereas Artemisia L. with short spinules is recorded slightly later. It may be deduced that the latter evolved from the former. Pollen morphological data confirm the coexistence of the two pollen patterns in the subtribe Artemisiinae containing Artemisia L. The development and evolution of the genus suggest three major stages in its history. Artemisia L. did not become abundant until the Middle to Late Miocene in spite of its earlier presence in the Late Palaeogene. Its representation remained low even though there are many records of the genus in the Late Miocene around the world. The Pliocene was an important time for the development of angiosperm herbs including Artemisia L., and the Quaternary has been a major period for the diversification and further worldwide expansion of the genus. The origin and subsequent development of Artemisia L. are considered to be closely related with increased environmental variation, including global climate changes and some important tectonic movements.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 145 , 331–336.     

Cytogenetics of species of Chamaecrista (Leguminosae – Caesalpinioideae) native to southern Brazil

Chromosome numbers, karyotypes, meiotic behaviour and pollen analysis are presented for species of Chamaecrista Moench (Leguminosae, Caesalpinioideae, Cassieae ) native to southern Brazil: C. nictitans ssp. patellaria , C. nictitans ssp. disadena , C. repens , C. rotundifolia , C. flexuosa , C. vestita and C. desvauxii . Meiotic behaviour is reported for the first time for all the taxa and was very regular; only bivalents were formed at diakinesis and metaphase I, chromosome disjunction and segregation were regular at anaphases I and II, meiotic indexes were over 99% and pollen fertility was over 92%. Pollen grains were subprolate in C. flexuosa and C. vestita and prolate–spheroidal in the other taxa. Karyotypes were symmetrical in all six species and the data are original, except for C. nictitans ssp. p atellaria. Chromosome number is presented for the first time for C. repens (2 n  = 16) and has been confirmed for the other taxa: 2 n  = 14 for C. desvauxii , 2 n  = 32 for the tetraploid C. nictitans ssp. patellaria and C. nictitans ssp. disadena , and 2 n  = 16 for the other species. These two basic numbers found in the genus, x  = 7 and x  = 8, point to chromosome evolution by dysploidy, which has also been accompanied by polyploidy.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 150 , 429–439.     

Pollen Analysis of Natural Honeys from the Central Region of Shanxi,North China

Based on qualitative and quantitative melissopalynological analyses, 19 Chinese honeys were classified by botanical origin to determine their floral sources. The honey samples were collected during 2010–2011 from the central region of Shanxi Province, North China. A diverse spectrum of 61 pollen types from 37 families was identified. Fourteen samples were classified as unifloral, whereas the remaining samples were multifloral. Bee-favoured families (occurring in more than 50% of the samples) included Caprifoliaceae (found in 10 samples), Laminaceae (10), Brassicaceae (12), Rosaceae (12), Moraceae (13), Rhamnaceae (15), Asteraceae (17), and Fabaceae (19). In the unifloral honeys, the predominant pollen types were Ziziphus jujuba (in 5 samples), Robinia pseudoacacia (3), Vitex negundo var. heterophylla (2), Sophora japonica (1), Ailanthus altissima (1), Asteraceae type (1), and Fabaceae type (1). The absolute pollen count (i.e., the number of pollen grains per 10 g honey sample) suggested that 13 samples belonged to Group I (<20,000 pollen grains), 4 to Group II (20,000–100,000), and 2 to Group III (100,000–500,000). The dominance of unifloral honeys without toxic pollen grains and the low value of the HDE/P ratio (i.e., honey dew elements/pollen grains from nectariferous plants) indicated that the honey samples are of good quality and suitable for human consumption.     

A palynological study of the genus Mentha L. (Lamiaceae)

The pollen morphology and exine structure of 10 Mentha L . species were investigated using light microscopy and scanning electron microscopy. The pollen grains of all 11 species were hexazonocolpate with granular membranes and a circular amb, varying in shape from prolate-spheroidal to suboblate. Different colpus shapes were recognized in M . ×  dumetorum . The exine was bireticulate in section Pulegium , and reticulate in section Menthae . A correlation was found between pollen size and chromosome number. The results indicate that the pollen characters of the genus Mentha are valuable for taxonomic applications and may be useful for classification.  © 2008 Uludag University. Journal compilation © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 141–154.     

Phylogeny of the Afro-Madagascan Aristea (Iridaceae) revisited in the light of new data on pollen morphology

Scanning and electron microscopic studies of the pollen grains of several species of the sub-Saharan African and Madagascan genus Aristea of c . 50 species, supplement data from an earlier study and enable us to include these species in a phylogenetic analysis. TEM examination of a range of pollen grains of representative pollen types in Aristea makes it possible to reinterpret past SEM results so that apertures covered with exine masses and previously called sulculate, are now seen to be either zonasulculate or dizonasulculate. Revised and expanded data are combined in a matrix together with new data for seed morphology in the genus, which like the capsules is remarkably diverse, including angular seeds with reticulate sculpturing, lamellate or triangular-columnar seeds with smooth or reticulate surfaces and with smooth or papillate or areolate margins. This new phylogenetic analysis suggests that Aristea should remain treated as comprising three subgenera. In subgenus Eucapsulares we add a new section Latifolieae for A. latifolia , which seems an isolated relic restricted to the mountains of the Cape Region of South Africa, an area of winter rainfall. Species with similar unspecialized capsule and seed morphology occur only in eastern south and tropical Africa and Madagascar, but they have derived pollen morphology whereas the pollen of A. latifolia is plesiomorphic. This species appears to be the closest living ancestor of the genus. In subgenus Aristea we continue to recognize three sections, sect. Racemosae , sect. Singulares and sect. Aristea. Nesting of subgenus Pseudaristea within section Racemosae of subgenus Aristea is probably an artefact of the analysis and does not receive bootstrap support, and hence we continue to recognize this group of species at subgeneric rank.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 41–68.     

Palynological characteristics of different unifloral honeys from Greece

Three hundred and twenty-nine Greek honey samples of different botanical and geographical origin were collected and examined by organoleptic evaluation, melissopalynological analysis, measurement of electrical conductivity and colour. The results showed that 208 samples were unifloral with 178 of them representing the main types of unifloral honey produced in Greece; that is fir, pine, chestnut, cotton, orange and thyme honey. All honeys had the sensory characteristics typical of their origin and complied with the electrical conductivity standards set by Council Directive 2001/110/EC.

Fir and pine honeydew honey had a low honeydew element/pollen (HDE/P) ratio and belonged to Maurizio's Classes II or III. The pollen types identified in these honeys ranged from 11 to 45%. Chestnut nectar honey contained >90% chestnut pollen, had a total number of plant elements of >245,000/10?g, and low pollen diversity. Cotton honey contained 1.2 to 16.5% cotton pollen, belonged to Maurizio's Class II, and had 22 pollen types, with Castanea sativa L. present in all samples. Orange honey contained 2.9 to 26.5% Citrus spp. pollen, belonged to Maurizio's Class II, and was characterized by the presence of Brassicaceae, Fabaceae, Olea europea L., Quercus coccifera L. and Rosaceae. In thyme honeys Thymus capitatus Hoffm. &; Link. pollen was secondary or predominant ranging from 18.3 to 69.3%. These honeys belonged to Maurizio's Classes I or II and contained greater than 30 pollen types. Other Lamiaceae, Hypericum spp., Brassicaceae, Fabaceae, Rosaceae, and Cistus spp. pollen types appeared in the greatest number of thyme samples.     

Karyomorphology of Incarvillea (Bignoniaceae) and its implications in distribution and taxonomy

The karyomorphology of 11 species of the genus Incarvillea Juss. is reported. The chromosome numbers of all species studied are 2 n  = 22. The interphase nuclei and prophase chromosomes were found to be of the simple chromocentre type and the interstitial type, respectively. The asymmetry of the karyotype of I. arguta (two populations) in subgenus Amphicome is type 2A. The karyotypes of Incarvillea s inensis var. sinensis , I.  s inensis var. przewalskii, and I. olgae in subgenus Incarvillea are of asymmetry type 3A. The remaining nine species and one variety in subgenus Pteroscleris are also of asymmetry 3A. Data on three species and one variety studied are first reports. This study indicates that karyotype variation at the diploid level appears to be the predominant feature of chromosome evolution in the genus Incarvillea . According to this study of karyomorphology, morphological characteristics and geographical distribution, it seems that the three subgenera should be regarded as three independent genera. The geography of the genus is discussed.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 113–121.     

Karyomorphology of Davidia involucrata and Camptotheca acuminata, with special reference to their systematic positions

Davidia involucrata Baill. and Camptotheca acuminata Decne were investigated and compared karyomorphologically. Their idiogrammatic formulae are, respectively, 2 n  = 42 = 20m (2SAT) + 16sm + 4st + 2t and 2 n  = 42 = 22m (2SAT) + 14sm + 4st + 2t. The plants are very similar: both belong to the 2B asymmetry karyotype (the karyotypes are reported here for the first time) and in both the prophase chromosomes are of the interstitial type. Davidia is believed to be closely related to Camptotheca . We do not consider it appropriate to remove Davidia from Camptotheca into a different family or subfamily. The cytological data support Davidia and Camptotheca forming a subfamily (Davidioideae) of the broadly circumscribed Cornaceae.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 193-198.     

The pollen morphology of Phyllanthus (Euphorbiaceae) section Choretropsis

The pollen grain morphology of the eight South American species of the genus Phyllanthus , subgenus Phyllanthus , section Choretropsis , endemic to Brazil, was investigated using light and scanning electron microscopy. The high homogeneity in pollen shape, as well as aperture number and configuration, allowed the definition of a basic pollen type for this section, viz. prolate spheroidal or subprolate, zonocolporate with 4–5 invaginated colpi, sexine reticulate. Two subtypes have been observed, based on pollen grain apertures and exine sculpture. The first subtype is characterized by straight and narrow colpi provided with costae, lalongate endoapertures and a reticulum of rectilineous muri as in P. choretroides and P. spartioides . The second subtype has wider colpi without costae, circular endoapertures and a reticulum with curvilineous muri as in P. flagelliformis , P. goianensis and P. scoparius , or curvilineous-rectilineous muri as in P. angustissimus , P. gladiatus and P. klotzschianus . It was demonstrated that the pollen shape and the number of colpi varied within and between some of the species. The results suggest that pollen grain morphology, in association with plant architecture and the presence of phylloclades, constitute additional evidence to delimit the species of the section Choretropsis and to further understand their evolutionary origin within the genus Phyllanthus.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 243–250.     

Systematic relevance of pollen and orbicule characters in the tribe Hillieae (Rubiaceae)

Pollen and orbicule morphology of 26 species in the tribe Hillieae is described based on observations by light, scanning and transmission electron microscopy. Pollen and orbicule characters are critically evaluated and discussed in the context of existing hypotheses of systematic relationships within the tribe. Pollen is 3-zonocolporate with a perforate, microreticulate, reticulate or eutectate sexine. In the two species of Blepharidium , however, the pollen has one, four or five apertures. These pollen morphological data were incorporated into an existing macromorphological matrix of the group and cladistically analysed. The resulting phylogenies indicate that it may be appropriate to reduce Cosmibuena to a subgenus of the genus Hillia , while Blepharidium should be removed from Hillieae because of the deviating pollen type that is unique to the Rubiaceae. All species investigated produce orbicules, which are mostly spherical and possess an electron-lucent core that is sometimes characteristically flattened.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 303−321.