Small Pollen Research Articles

Mismatch between pollen and pistil size causes asymmetric mechanical reproductive isolation across Phlox species.

Characterizing the mechanisms of reproductive isolation (RI) between lineages is key to determining how new species are formed and maintained. In flowering plants, interactions between the reproductive organs of the flower -the pollen and the pistil- serve as the last barrier to reproduction before fertilization. As such, these pollen-pistil interactions are both complex and important for determining a suitable mate. Here, we test whether differences in style length (a part of the pistil) generate a postmating prezygotic mechanical barrier between five species of perennial Phlox wildflowers with geographically overlapping distributions. We perform controlled pairwise reciprocal crosses between three species with long styles and two species with short styles to assess crossing success (seed set). We find that heterospecific seed set is broadly reduced compared to conspecific cross success and reveal a striking asymmetry in heterospecific crosses between species with different style lengths. To determine the mechanism underlying this asymmetric reproductive isolating barrier we assess pollen tube growth in vivo and in vitro. We demonstrate that pollen tubes of short-styled species do not grow long enough to reach the ovaries of long-styled species. We find that short-styled species also have smaller pollen and that both within and between species pollen diameter is highly correlated with pollen tube length. Our results support the hypothesis that the small pollen of short-styled species lacks resources to grow pollen tubes long enough to access the ovaries of the long-styled species, resulting in an asymmetrical, mechanical barrier to reproduction. Such reproductive isolating mechanisms, combined with additional pollen-pistil incompatibilities, may be particularly important for closely related species in geographic proximity that share pollinators.

Acetolysis modifications to process small pollen samples swabbed from live bees

Abstract Understanding the resources bees use is essential because we depend greatly on their ecosystem services, and this information could help guide conservation efforts. One way to identify the flowers that bees visit is to collect pollen directly from the bee and then identify the pollen with plant taxa. However, the current method for processing such pollen samples, acetolysis, is designed for samples such as those collected across individuals (e.g., pollen trap), bee nests, or, at the very least, from pollen pellets collected from live bees or from the exhaustive removal of pollen from lethally collected individuals. Smaller samples, including those down to just a few pollen grains sampled from live bees, could facilitate additional opportunities for bee-pollen research, if they can be processed effectively. We present a revised acetolysis methodology designed specifically for processing small pollen samples, so that they can then be used for more accurate identification. Using pollen samples from cotton swabs directly applied to live bees in the field, we demonstrate the effectiveness of our methodology for processing small pollen samples, including samples too small to be visually detected. This methodology can permit nonlethal collections in the field from a greater number of bee species.

PALYNOLOGICAL DIVERSITY OF POLLEN MORPHOLOGY IN ENDEMIC NORTHERN IRAQI HYPERICUM SPECIES (HYPERICACEAE)

The presented research investigated the pollen morphology of endemic Iraqi Hypericum species. The study revealed phenotypic features of pollen grains in the polar and equatorial views and their quantitative and qualitative characteristics. The results showed that the pollen grains of the genus Hypericum were radially symmetrical and isopolar, and their apertures were simple and tricolporate, except the species H. davisii, distinguished as tetracolprate. Dividing the studied species based on pollen grain sizes comprised two groups. Small pollen grains with an average length of the equatorial view ranged between 10–16 μm in H. lysimachioides and H. vermiculare. Medium-sized pollen grains with an average extent between 17–26 μm emerged in the species, i.e., H. retusum, H. triquetrifolium, H. perforatum, H. lydium, H. tetrapterum, H. asperulium, H. scabrum, and H. davisii. Pollen grains, also divided according to the P/E ratio, had two main groups. The pollen grains were subprolate and spherical, with the exine sculpturing examined by a scanning electron microscope (SEM), and isolated into four groups: 1) microreticulate reticulum, including H. asperulium, H. lydium, and H. vermiculare, 2) perforate, i.e., H. retusum, H. scabrum, H. tetrapterum, and H. triquetrifolium, 3) psilate with H. perforatum and H. davisii, 4) and reticulate exine sculpturing in H. lysimachioides, all isolated from the rest of the species. SEM images showed the thickness of exine ranged from 0.5 to 2 μm. The topical study also added H. davisii as a new species with no previous records in Iraq. This pollen study added valuable data for taxonomy and suggested that it should proceed with its first-time registration in Iraq. The pertinent research could provide a taxonomical key for Hypericum species in Iraq.

Pollen morphology of Matthiola and the related genus Dvorakia (Brassicaceae) in Iran

Our study focused on the pollen morphology of 13 species of Matthiola and the closely related genus Dvorakia. We used light and scanning electron microscopes to examine the importance of pollen characteristics in classifying these genera. Pollen grains were acetolysed, measured, photographed, and described based on qualitative and quantitative characteristics. Here, we present statistical analyses and multivariate statistics for quantitative data. Pollen in both genera are tricolpate and varies in shape from subprolate to prolate. We distinguish two pollen types based on lumen width. Matthiola pollen has both reticulate and macroreticulate ornamentation, while Dvorakia alyssifolia pollen is reticulate. The thickness of the exine and the width of the mesocolpium are important traits in addition to exine ornamentation. Iranian Dvorakia and Matthiola species’ pollen size can be divided into four types, one of which is Type I (Dvorakia alyssifolia type). Among the examined species, M. tomentosa has the smallest pollen grains, while D. alyssifolia has the largest grains. Pollen morphology confirms the transfer of D. alyssifolia from Matthiola to Dvorakia. Additionally, we propose a species key for the genera.

BIOMETRIC INDICES OF POLLEN FROM NATURAL POPULATIONS OF <i>PINUS BRUTIA</i> VAR. <i>PITYUSA</i> (PINACEAE) OF THE CRIMEAN MOUNTAINS

The study of biometric characteristics of Pinus brutia var. pityusa pollen was carried out in natural populations of P. brutia var. pityusa in the Crimean Mountains. The pollen was collected during the period of its free flight on sample plots along four hypsometric profiles. In the western part of the southern macroslope of the Main Ridge of the Crimean Mountains on Cape Aya in the Ayazma tract, 3 sample plots were laid at altitudes of 50–290 m above sea level, in Batiliman – 2 plots, at altitudes of 50 and 120 m above sea level; in the eastern part of the macroslope, 3 plots were laid on Karaul-Oba Mt. at altitudes of 40–120 m above sea level, and in the Novyy Svet tract – 2 plots at 50 and 100 m above sea level. Biometric analysis of pollen grains was carried out on temporary acetocarmine slides using generally accepted methods. The results of the study showed that an average size of the pollen grain of P. brutia var. pityusa in natural populations of the Crimean Mountains varies within the following ranges: total grain length from 81.5 to 88.5 μm, the length and height of the pollen grain body 52.2–59.4 μm and 47.8–53.4 μm, respectively, and the length and height of the air sac 40.0–43.0 μm and 25.5–30.4 μm, respectively. The smallest pollen is formed in coastal stands. In the plantations of P. brutia var. pityusa in the western part of the Crimean Mountains, a decrease in the length and height of the air sacs was noted. It was revealed that the indices characterizing the ratio of individual structural elements of the pollen grain, namely γ – the ratio of the body length to the height of the air sac of the pollen grain, δ – the ratio of the body height to the height of the air sac, and Θ – the ratio of the body length to the length of the air sac, allow to analyze aerodynamic properties of P. brutia var. pityusa pollen. The decrease in γ, δ, and Θ pollen indices in the plantations of Ayazma and Batiliman reflects a decrease in the efficiency of its aerial distribution, which has a negative effect on the level of heterogeneity of natural populations in these territories.

Systematic study in Cressa cretica L. (Convolvulaceae) species from Lake Qarun, El-Fayoum province, Egypt

Cressa cretica L. is a monotypic species belongs to the plant family Convolvulaceae, tribe Cresseae. It is an erect, small, dwarf shrub, commonly grown in coastal areas and considered as an important medicinal plant with many therapeutic effects. Individuals of this species became restricted in specific areas in Egypt in became under threat of extinction. This study dealt with careful examination of the external and leaf internal structure beside pollen grain morphology. The study aims to understand the species morphological characteristics and protect it from localization and destruction processes. The results showed that the leaf macro- and micro-morphological characters are of the halophytic ones, with long unicellular hairs as well as T-shaped hairs and sunken stomata. The leaf internal structure has mesophyll differentiated into one layer palisade and spongy layers full of ca-oxalate crystals and salt glands distributed in the mesophyll. Pollen grains productivity was few and they are small, spheroidal to subprolate with tricolporate aperture and tectate perforate with supra-tectum granules. The results obtained show that Cressa cretica has external and internal halophytic structure in addition to few small pollen grains. Germination experiments needed to test the pollen productivity of this plant under non-saline habitats for its conservation.

Relationship between pollination syndromes, pollen morphology and plant ecology in Quaternary deposits of the Cerrado

This study presents morphological descriptions and ecological information for 58 terrestrial pollen taxa and seven water-related pollen taxa from the Brazilian Cerrado, obtained from two sediment cores, Lake Feia (LFB1) and Getulio Swamp (VGE-17), encompassing the last 5000 and 15,000 cal yr BP, respectively. The relationships between the ecological and morphological traits (pollination syndrome, vegetation stratum and grain size) within each of the two depositional environments were investigated. In the LFB1 core, the pollen assemblages were dominated by arboreal pollen from closed physiognomies and lower storey trees (<10 m in height), while a combination of closed and open physiognomies was observed in the pollen assemblages from the VGE-17 core. The vast majority of the pollen taxa exhibited the entomophilous pollination syndrome, and a higher influx of entomophilous pollen was observed in both cores. Anemophilous and anemophilous/entomophilous syndromes were less well represented. Small and medium pollen grain classes were the most abundant, while the large pollen grain class was rare. The influx of small pollen grains was slightly more abundant in the lake record, while in the swamp record medium pollen grains were more abundant. Our results show that swamps and lakes differ in their representation of local versus regional pollen and in their sensitivity and responses to water-level changes. Landscape physiognomy also influences pollen dispersion: a closed physiognomy increases the local pollen signal, while a more open physiognomy results in better representation of local and regional signals.

Taxonomic Comparison, Antioxidant and Antibacterial Activities of Three Ebenus pinnata Ait. ecotypes (Fabaceae) from Algeria

Ebenus pinnata is not known as a traditional medicinal plant, but modern research has revealed its richness in components of medicinal value. Yet, the species remains understudied. Here, we assess the climate effect on its morphology, pollen grains size, chromosome numbers, pollen fertility, and antioxidant and antibacterial activities. Plant material was collected from the humid, sub-humid, and semi-arid areas of Northeastern Algeria. Data treatment by principal component analysis and/or cluster analysis and ANOVA post hoc tests revealed three significantly discriminated ecotypes correlated with the climate stage. Significant differences were detected for whole plant morphology, pollen size, and antioxidant activity. No differences were revealed for chromosome numbers, pollen fertility, and antibacterial activity. The studied material showed a chromosome number of 2n = 14, high pollen fertility (94.04 ± 2.64–95.01 ± 2.02%), small pollen grains (polar axis: 17.95 ± 1.10–19.47 ± 1.27 µm; equatorial axis: 12.80 ± 1.18–13.03 ± 0.99 µm), high antioxidant activity (TPC: 50.79 ± 0.51–56.89 ± 0.46 mg/g; DPPH: 71.18 ± 2.24–95.67 ± 2.02 mg/g; RP: 11.09 ± 1.24–25.88 ± 0.26 mg/g), and efficient antibacterial activity (Inhibition area diameter: 9.25 ± 1.06–12.00 ± 1.41 mm). The climate seems to exert a significant impact on multiple aspects of the plant’s biology. It would be interesting to assess the genetic basis of this phenomenon in E. pinnata and other species.

Conflicting constraints on male mating success shape reward size in pollen-rewarding plants.

Pollen-rewarding plants face two conflicting constraints: They must prevent consumptive emasculation while remaining attractive to pollen-collecting visitors. Small pollen packages (the quantity of pollen available in a single visit) may discourage visitors from grooming (reducing consumptive loss) but may also decrease a plant's attractiveness to pollen-collecting visitors. What package size best balances these two constraints? We modeled the joint effects of pollinators' grooming behaviors and package size preferences on the optimal package size (i.e., the size that maximizes pollen donation). We then used this model to examine Darwin's conjecture that selection should favor increased pollen production in pollen-rewarding plants. When package size preferences are weak, minimizing package size reduces grooming losses and should be favored (as in previous theoretical studies). Stronger preferences select for larger packages despite the associated increase to grooming loss because loss associated with nonremoval of smaller packages is even greater. Total pollen donation increases with production (as Darwin suggested). However, if floral visitation declines or packages size preference increases with overall pollen availability, the fraction of pollen donated may decline as per-plant pollen production increases. Hence, increasing production may result in diminishing returns. Pollen-rewarding plants can balance conflicting constraints on pollen donation by producing intermediate-sized pollen packages. Strictly pollen-rewarding plants may have responded to past selection to produce more pollen in total, but diminishing returns may limit the strength of that selection.

Identification of prominent airborne pollen in a city situated in foot-hills of Himalayas, Chandigarh, India.

Pollen allergy is considered one of the important critical thrust areas, as 20-30% of the world population suffers from allergic rhinitis. The increase in global surface temperature directly affects pollen physiological (e.g., pollen production) and morphological parameters and indirectly affects the distribution pattern, the allergenic potential of pollen, and plant species. Therefore, periodic sampling and pollen studies of a region have become necessary to assess the status of change in species and its morphological characteristics of different taxa. The current study is conducted to identify the airborne pollen based on studying their unique and distinctive morphological characters to serve as a reference pollen guide for future research. The airborne pollens were trapped using the Burkard volumetric sampler at three different locations in Chandigarh from 2018 to 2020 and analyzed under Leica DM5500B-Automated Upright Microscope System. The study investigated various pollen features such as shape, size, aperture type, and exine/surface pattern for taxonomic classification of plant groups. The majority of LM-analyzed pollen grains were prolate-spheroidal or oblate, whereas the aperture types were 3-zonocolporate, 3-colpate, and 3-zonocolporate. Exine patterns were predominantly psilate, reticulate, and straite and were easily discernible. Nonetheless, the vast majority of airborne pollen belonging to both arboreal and non-arboreal was quite small and fall into small pollen size classes, i.e., 10-24μm. The exine pattern was readily apparent and were predominantly psilate, reticulate, and straight. The current study improved the knowledge on airborne pollen biodiversity, which will help to understand the regional distribution, long-range transport, and construct the current status of morphological features of species/taxa.

Ancillary polymorphic floral traits between two morphs adaptive to hawkmoth pollination in distylous plant Tirpitzia sinensis (Linaceae)

BackgroundFloral morphs are characterized differentiations in reciprocal positions of sexual organs and ancillary floral traits in heterostylous plants. However, it remains unclear how differential floral morphs ensure reproductive success between morphs using the same pollinator.ResultsMeasurements of floral traits in white-flowered Tirpitzia sinensis with long corolla tubes indicated that it is typically distylous, long-styled (L-) morph producing more but smaller pollen grains per flower than short-styled (S-) morph. Both morphs secreted more nectar volume at night than in the day and the sugar composition was rich in sucrose, potentially adaptive to pollination by hawkmoths (Macroglossum spp.) which were active at dusk. A bumblebee species functioned as the nectar robber in both morphs and a honeybee as the pollen feeder in the S-morph. The L-morph secreted more nectar volume but relatively lower sucrose/hexose ratio than the S-morph. Floral visitation rate by hawkmoths was higher but its pollination efficiency was lower in the S-morph than the L-morph. Hand pollination treatments indicated self-incompatibility in T. sinensis and seed set of open-pollinated flowers did not differ between morphs.ConclusionsOur findings suggest that the two morphs differ with respect to traits relevant to pollination. The L-morph, with its exserted stigma, has more pollen grains per anther and a greater volume of nectar, which may prolong the foraging time and increase the pollination efficiency of hawkmoths. The S-morph has a higher sucrose/hexose ratio in its nectar which can be more attractive to hawkmoths and increase the visit rates. Ancillary polymorphic floral traits between two morphs are adaptive to hawkmoth and ensure reproductive success in distylous plant T. sinensis.

Pollen Morphological Peculiarities of Selected Mimosoideae Taxa of Hainan Island and Their Taxonomic Relevance

Mimosoideae is one of the taxonomically complex subfamilies of Fabaceae. Several studies have reported the pollen morphology of Mimosoideae taxa and their taxonomic relevance, but no such study was found specifically for Hainan Island in southern China. Therefore, the present study was designed to investigate the selected Mimosoideae taxa and explore the new palynological traits to support and strengthen the systematics of Mimosoideae using multiple microscopic techniques. The polar axis, equatorial diameter of the pollen grains, colpus length and width were measured. The smallest pollen grain size was found in Mimosa pudica (7.8 × 7.75 µm), while the largest pollen size was found in Albizia lebback (87.54 × 77.97 µm). Similarly, significant variation was found in the exine and colpus surface patterns. The subfamily Mimosoideae is considered eurypalynous because of the variation in pollen traits. In addition, variation was also found in the quantitative traits. Comparatively, the pollen features were found to be helpful at the genus and species levels, as well as in the correct identification and discrimination of the taxa. Hence, this study gives a detailed account of the pollen morphologies of certain selected taxa of Mimosoideae collected from different geographical regions on Hainan Island. The pollen morphological traits were proven to have significant taxonomic potential and can be used as additional tools for the correct identification and discrimination of Mimosoideae taxa. These results will provide the basis for further systematic studies.

Pollen of Pterocarya (Juglandaceae) representatives from natural habitats and St. Petersburg environments

Background. Comparative palynomorphological studies of naturally occurring and introduced Pterocarya Kunth representatives reveal the taxonomic significance of pollen morphological features and pollen characters of cultivated plants. The quality of pollen material and the potential of the plants from the Botanical Garden of BIN RAS for introduction are characterized.Materials and methods.Pollen grains were investigated using light, confocal laser scanning and scanning electron microscopes. Fertility was assessed using the standard acetocarmine method.Results.Comparison of pollen morphology in cultivated and naturally growing plants of this genus was made for the first time. Pollen fertility of two cultivated species (Pterocarya rhoifolia Siebold et Zucc., and P. stenoptera DC.) was very high, generally over 90%. Fertility of P. fraxinifolia (Lam.) Spach grains varied from 28 to 73% in different years, which is a low or medium level of pollen quality. Morphologically, pollen grains of all 12 specimens from five taxa are flattened, medium sized, 21–45 μm in diameter, with 4–8 pores; pores are located mainly at or near the equator. The pores are round or oval, with a limbus. Exine is three-layered, thickened near the pore. The sculpture is microechinate. The low-fertile P. fraxinifolia specimen contains small pollen grains, as well as grains in tetrads and dyads. The data on the introduction of the genus in St. Petersburg are presented.Conclusion.The palynonomophological description is diagnostic for the genus Pterocarya. The Pterocarya pollen is well distinguishable from other wind-pollinated taxa; however, species identification by pollen for spore-pollen analysis is not practicable. Morphologically, the most diverse are the grains of the low fertile specimen P. fraxinifolia. The limited possibility of seed propagation of P. fraxinifolia is probably explained by low pollen fertility. The pollen quality of the introduced P. rhoifolia and P. stenoptera is high.

Mixed pollination system and floral signals of Paepalanthus (Eriocaulaceae): insects and geitonogamy ensure high reproductive success.

Eriocaulaceae exhibit a great variety of floral traits associated with insect (e.g. nectariferous structures) and wind pollination (unisexual flowers, exposed sexual organs and small pollen grains), as well as the 'selfing syndrome' (small flowers, short distance between stigma and anthers, and temporal overlap of male and female phases). Paepalanthus bifidus, P. subtilis and P. tortilis are related species that differ in form, size and colour of floral structures. We aimed to investigate the pollination and reproductive biology of these three species. We analysed the floral biology, floral visitors, pollinator behaviour, and the contribution of insects, wind and spontaneous geitonogamy to fruit set. We also evaluated the floral colour and scent of the species. Colour reflectance of capitula of each species was measured and plotted in models of insect vision. Floral scent samples were extracted and the compounds were compared to vegetative scent samples. In all species, the staminate and pistillate flowers are arranged in alternating cycles with a temporal overlap between these phases. Ants were the most frequent floral visitors and were effective pollinators in P. bifidus and P. tortilis, while flies were occasional pollinators in P. tortilis. Floral visitors were not observed in P. subtilis. In all species, fruits were produced by spontaneous geitonogamy, with no evidence of wind pollination. According to the models of insect vision, the colours of the capitula of P. bifidus and P. subtilis are the most inconspicuous for ants and flies. We found no difference between the emission of volatiles of inflorescences and vegetative structures. This study suggests that ant pollination might be more widespread in Eriocaulaceae than currently assumed. Furthermore, for small monocarpic plants, mixed mating strategies are most favourable, by ensuring reproduction either by outcrossing when pollinators are abundant or by spontaneous geitonogamy when pollinations are scarce/absent.

Pollen morphology of some species in family Amaranthaceae from Thailand

Abstract. Saensouk S, Saensouk P. 2021. Pollen morphology of some species in family Amaranthaceae from Thailand. Biodiversitas 23: 601-611. The aim of this study was to study the pollen morphology of 14 species, eight genera from the family Amaranthaceae in Thailand by the applied acetolysis method and it was taken under light and scanning electron microcopies. All pollen grains had monad, radial symmetry and apolar. The pollens in this study can be divided into several groups based on shape, size, aperture, mesoporia, the character of aperture, and exine sculpturing. The sizes of the pollen can be divided into three groups, i.e., very small pollen group, small pollen group, and medium pollen group. The shapes of the pollen can be divided into three groups, i.e., spheroidal, pentagon, and dodecahedric. Exine sculpturing can be divided into three groups, i.e., granular, macrogranular, and microspine. The pollen in this study can be divided into five groups based on the character of the aperture, i.e., aperture with convex circular-like shape, aperture with deeply collapsed circular-like shape, aperture with collapsed circular-like shape, aperture with collapsed pentagon-like shape, and 6-angular element or hexagon-like shape. The pollen in this study can be divided into three groups based on the mesoporia, i.e., mesoporia broadly flat, mesoporia moderately and broadly vaulted, and mesoporia narrow and highly vaulted. The number of apertures was found to be between 12-54 apertures per pollen. The aperture diameters of Amaranthaceae pollen in this study ranged from 0.5-5 µm. The exine thickness of the pollen in this study was 1.12±0.04 - 2.14±0.31 µm. The pollen character of this study can be divided into eight types, i.e., Achyranthes-type, Alternanthera-type, Amaranthus-type, Celosia-type, Cyathula-type, Gomphrena-type, Ouret-type, and Psilotrichum-type. The pollen characteristic of Alternanthera pungens Kunth, A. Sessilis (L.) R. BR., Amaranthus blitum subsp. oleraceus (L.) Costea, Cyathula prostrate (L.) Blume., Ouret sanguinolenta (L.) Kuntze, and Psilotrichum ferrugineum (Roxb.) Voigt were reported for the first time.

Pollen typification and palynotaxonomy of subfamily Salsoloideae Ulbr. (Chenopodiaceae Vent.) in the flora of South Transcaucasia

The article presents the results of a comparative palyno-morphological analysis of the representatives of the Salsoloideae subfamily (Chenopodiaceae) in South Transcaucasia. Out of 25 species belonging to 13 genera of Salsoloideae subfamily in South Transcaucasia, pollen morphology of 23 species from 12 genera was investigated, as well as an analysis of the pollen characteristics was conducted. Data on five key features of pollen (on LM level) were statistically analyzed including pollen diameter, pore number, pore diameter, exine thickness, and mesoporium width. The results indicated that within the Salsoloideae subfamily of South Transcaucasian flora the first three features may be considered diagnostic. The application of a scanning electron microscope (SEM) has revealed the fourth diagnostic feature of the pollen within the Salsoloideae subfamily, specifically, the number of spinules on the unit surface of the pollen, which enables, in several cases, to conduct intergeneric or interspecific differentiation. Based on the obtained data, typification of pollen within the Salsoloideae subfamily of South Transcaucasia was carried out for the first time. As a result, two morphological types and four subtypes combined in two palynogroups were distinguished. The subdivision into palynogroups is based on differences in the size of pollen grains. Only species Climacoptera crassa with pollen of average sizes (26–33/29 μm in diameter) is included into the monotypic Palynogroup I, all other investigated species with small pollen grains (10–25 (27)/22 μm in diameter) are joined in Palynogroup II. Allocation of species into two different Types of Palynogroup II is based on the presence of a significant difference in the size of small pollen grains of individual species. In particular, species with relatively large pollen grains (&gt; 20 μm in diameter) are included in Type 1, while species with relatively small ones (≤ 20 μm in diameter) are joined in Type 2. And finally, the distribution of species into the subtypes and variations of Palynogroup II is based on differences in pore number and size. The identified key palyno-morphological features made it possible in some cases to specify the taxonomic boundaries, as well as the relationship between taxa within the subfamily Salsoloideae.

Studies on size, sterility and germination of pollen grains of certain members of the family Malvaceae

The present study attempted to evaluate the pollen size, percentage of sterility using acetocarmine, percentage of germination in sucrose medium among the members of the family Malvaceae like Malvaviscus arboreus Cav., Sida rhombifolia L., Urena lobata L. Hibiscus furcatus Roxb. Hibiscus rosa-sinensis L. and Gossypium arboreum L. Regarding the size pollen grains of Hibiscus rosa-sinensis showed largest pollen. The smallest pollen grains belong to Urena lobata, L. The pollen sterility using acetocarmine indicated that the pollens of Hibiscus furcatus were completely fertile, while Sida rhombifolia showed highest amount of sterility. The germination of pollen grain in sucrose medium indicated that the pollen grain of all the members studied showed poor germination.

Palyno-anatomical characters and their systematic significance in the family Apiaceae from Chitral, eastern Hindu Kush, Pakistan.

The present study was performed to provide a detailed explanation of leaf epidermal anatomy and pollen micromorphological features of selected species of family Apiaceae from Chitral, eastern Hindu Kush region as the basis of forthcoming studies. In the present article pollen morphology of eight species and foliar epidermal of seven species of family Apiaceae have been examined through microscopic techniques. In results two types of pollen prolate (five species) and perprolate (three species) with three colpi have been recorded. The exine ornamentation was found to be regulate, striate, and cerebroid. Largest pollen was found in Heracleum leucocarpum with the polar diameter of 43.25 μm and equatorial diameter of 21.6μm. Smallest pollen was observed in Elaeosticta chitralica with the polar diameter of 18.4μm. The P/E ratio varied from 1.59 to 2.16. Regarding to foliar epidermal anatomy, three types of epidermal cells including rectangular, irregular, and polygonal with variation in anticlinal wall pattern were determined. In the selected species three kinds of stomata comprising anisocytic, anomocytic, and paracytic type were reported in the current research. The size of epidermal cells ranged from 106 × 42.50 μm in Bupleurum falcatum subsp. cernuum and 77.25 × 26.35 μm in Prangos pabularia in adaxial surface. Largest stomatal complex was found in Prangos pabularia both in adaxial 33.55 × 20.05 μm and abaxial 50.25 × 39.40 μm. All the observed quantitative and qualitative features of the species were proved to be useful in the delimitation of species at generic and species level.

Floral displays suffer from sulphur deprivation

Nutrient deficiency is known to constrain plant growth in numerous ways, but how it impacts floral displays and pollination success remains unclear. Here we investigate how insufficient availability of sulphur – a vital plant nutrient that is a limiting factor in natural and agricultural regions throughout the world – influences the production of floral displays in Brassica rapa, Physalis philadelphica and three Petunia species with differently coloured flowers. Sulphur deficiency led to a drastic reduction in the number of open flowers, an aberrant flower morphology and smaller pollen with an altered mineral nutrient content. Intriguingly, sulphur deprivation also led to a clear reduction in pigmentation of yellow flowers, but not in flowers with white, purple and red colours. The pale yellow flower colour was due to decreased amounts of violaxanthin, lutein and other carotenoids, suggesting that the carotenoid synthesis pathway is particularly susceptible to sulphur deficiency. Additional experiments with nitrogen and phosphorus depletion confirmed that observed colour and morphological changes were not a general nutrient limitation response, but could be ascribed to sulphur depletion specifically. Taken together, our results showed that (mild) sulphur deficiency deteriorates a suite of floral traits, and that the effects may cascade to pollinators and so have the potential to undermine (agro-)ecosystem functioning.

Pollen morphology and its taxonomic significance of the genus Crucianella L. (Rubiaceae) in Iran

AbstractThe Pollen morphology of nine species of Crucianella L. and ten subspecies of C. gilanica representing two sections: Roseae and Crucianella, was investigated using light microscopy (LM) and scanning electron microscopy (SEM). All the studied species (except for C. angustifolia) are palynologically described here for the first time. The results revealed considerable pollen character variation among the studied species. The pollen grains are monads, isopolar, radial symmetrical and relatively small. The largest pollen grains were observed in C. angustifolia (P = 24.12 µm, E = 26.04 µm), while the smallest pollen was found in C. gilanica subsp. carduchorum (P = 16.32 µm, E = 12.57 µm). The outline pollen grains varied from subcircular to circular in polar view and elliptical to quadrangular and circular in equatorial view. The shape of pollen changed from spheroidal to oblate‐spheroidal, prolate‐spheroidal, suboblate, subprolate and prolate. The pollen grains are zonocolpate and their number of colpi ranges from 6 to 10. The results showed five different types of sexine ornamentation: perforate, reticulate, microreticulate, microfoveolate and psilate. The sexine of all examined specimens is covered with microspines. The current survey shows that the pollen morphological characters of the studies species are taxonomically informative and may provide good help in identification purposes. We used multivariate analysis to determine the potential contribution of palynological data to the species relationships. The result of cluster analysis and principal component analysis showed pollen morphological affinities between the two studied sections.