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Article

Pollen Morphology of Rosa sericea Complex and Their Taxonomic Contribution

by
Fazal Ullah
1,2,
Yun-Dong Gao
1,
Wajid Zaman
3,* and
Xin-Fen Gao
1,*
1
CAS Key Laboratory of Mountain Ecological Restoration Bioresource Utilization & Ecological Restoration, Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, P.O. Box 416, Chengdu 610041, China
2
University of Chinese Academy of Sciences, Beijing 100049, China
3
Department of Life Sciences, Yeungnam University, Gyeongsan 38541, Gyeongbuk, Korea
*
Authors to whom correspondence should be addressed.
Diversity 2022, 14(9), 705; https://doi.org/10.3390/d14090705
Submission received: 13 July 2022 / Revised: 13 August 2022 / Accepted: 23 August 2022 / Published: 26 August 2022
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Abstract

:
In this research, the pollen morphology of the Rosa sericea complex has been studied by Scanning Electron Microscope (SEM). The present study aimed to provide baseline information for the taxonomic identification of the R. sericea complex taxa. The pollen sculpture, outline, and aperture show variability in the studied taxa. The R. sericea complex includes taxonomically challenging species with undistinguishable boundaries. Identifying taxon boundaries in closely related species is fundamental to investigating evolution and biodiversity. Taxa circumscription of R. sericea complex is insufficient, unresolved, and is a prerequisite for comprehensive systematic revisions. To resolve these issues, we have attempted to identify some important diagnostic characters for the species of R. sericea complex. This research studied different qualitative and quantitative characteristics of R. sericea complex pollen. The qualitative characteristics included polar and equatorial view, sculpture, pollen outline, apertures, exine, size category, and polarity of pollen. In contrast, the quantitative features include polar and equatorial diameter, P/E, colpi length and width, and distance between colpi. Pollen of this complex is mono and tricolporate. The morphological characters studied here provide very few taxonomic details with which to separate the species of the complex into distinct taxa. Some of the studied characters offer important information for species delimitation including sculpture, pollen outline, and apertures.

1. Introduction

The Rosaceae family consists of 100 genera and about 3000 taxa, including many essential and economic plant species [1]. Apomixis is very common in the family Rosaceae [2]. A commonly adopted classification of the family Rosaceae comprises four subfamilies (Amygdaloideae, Maloideae, Rosoideae, and Spiraeoideae), classified on fruit type [3]. Based on the molecular evidence, three subfamilies, Dryadoideae, Rosoideae, and Spiraeoideae, are proposed [4]. Palyno-morphological features are important in many plant groups’ taxonomic delimitation and identifications [5,6,7,8]. Various pollen traits are particularly taken through strong selective forces involved in plants’ different systematic processes, including reproductive processes, pollination, dispersal, and germination [9,10,11,12]. Palynologists used the pollen for plant identification and permitted ecologists and botanists to recreate past assemblages of plant taxa and recognize periods of environmental change [13].
The use of light and scanning electron microscopy (SEM) showed that the pollen of the genera from all the tribes of the family Rosaceae show variation in pollen morphology and sculpturing [14,15]. Genera in the subfamilies Speraeoideae, Maloideae, and Prunoideae produce tricolporate striate pollens with large perforations in valleys between ridges [16]. Some studies revealed that the palynological characteristics provide significant insight into the subfamilies’ classification within the family and provide evidence of evolutionary relationships [16]. The fossil record shows that Rosaceae is cogent with ancient dicotyledons [17]. Ninety-million-year-old (MYA) Turonian fossils are attributed to Rosaceae [18]. The physiology and anthecology of Rosaceae suggest that it is primitive [19]. Rosaceae is an offshoot of the ancient woody magnolias, leading on an evolutionary line to Umbellales (Araliales), Fabales (Leguminales), Juglanfales, and Fabales, which have more specialized inflorescences. The research supports the APG [20] delimitation of the rosids, of which the rosales and its characteristic family Rosaceae are considered to be the core eudicot group.
The Rosa L. genus is distributed in the Northern Hemisphere. Rosa has about 100–120 species and, some authors consider, about 250 taxa [21,22,23,24]. In modern rose taxonomy (excluding hybrid classification), the Rosa genus has been divided into four subgenera, i.e., Eurosa, Hesperrhodos (R. minutifolia and R. stellate), Hulthemia (Rosa persica), and Platyrhodos, these subgenera are separated based on the structure of the fruit. Except for Eurosa, all subgenera are monotypic or have two species [25,26]. Eurosa is further subdivided into ten sections: Banksianae, Bracteatae, Caninae, Caolinae, Gallicanae, Indicae, Laevigatae, Pimpinellifoliae, Rosa (syn. Sect. Cinnamomeae), and Synstylae [27,28]. R. sericea complex belongs to the subgenera Pimpinellifoliae, consisting of seven taxa, and the taxonomy of this complex is very complicated and challenging [29,30].
Pollen morphology is considered a significant taxonomic tool in classifying and delimiting plant species [31,32]. The taxa of Rosaceae pollen have a similar morphological structure in appearance. The most important features are their membership of trizonocolporate class and exine sculpturing. Some other important characters are costae colpi, operculum, pore structure, grain shape, and pollen size. The most diagnostic feature of pollen grains in the species of the genus Rosa include apertures characteristics, exine sculpture, and operculum structure [33,34,35]. Some authors did work on the pollen grain morphology of Rosa using SEM focusing on the exine sculpture [36] and the structure of the operculum [37]. Many authors work on the palynology of Rosaceae pollen including the morphology of traditional Chinese roses, European Rosaceae pollen, the palynology of the family Rosaceae of western Canada, the palynology of Rosaceae in Canada, the pollen morphology of family Rosaceae, the palynology of wild roses from Pakistan, the palynology of the genus Rosa and allied genera, the palyno-morphological characters of the genus Rosa, and the palynology of the Rosoideae (Rosaceae) of China [16,36,38,39,40,41,42,43,44], respectively.
Rosaceae have a great morphological range, to the point of being “indefinable” [45]; Rosaceae is vigorous as, along with the support of chemical and morphological assessment [46], the rbcl sequences analyses are in support of monophyly of the family [47]. Genus Rosa belongs to a group of plants that are taxonomically critical and systematically complex. The most important causes of the complexity in the systematics of this genus, due to the polymorphism, polyploidy and hybridization [48,49].
Some work has been done on the palynology of Rosaceae regarding subfamilies, tribes, genera, and pollen morphology of Rosaceae [16,50,51]; subfamily Maloideae [52]; subfamily Prunoideae [53]; palynology of subfamily Rosoideae [50]; pollen morphology of the tribe Sorbarieae [54]; and pollen morphology of the genus Rosa has been studied by many authors [35,43,55,56,57,58]. The first three subgenera are monotypic, including one or two species, while the subgenus Eurosa has all the remaining species in the genus Rosa. This subgenus is divided into ten sections: Bracteatae, Bankisanae, Carolinae, Caninae, Indicae, Gallicanae, Laevigatae, Rosa Pimpinellifoliae, and Synstylae (Wrońska-Pilarek et al., 2011). The shrubby Rosaceae, generally the tribe Roseae, genus Rosa section Pimpinellifoliae subsection R. sericea complex, have been poorly understood from a taxonomic and phylogenetic perspective. R. sericea complex consists of seven species in which morphology is highly complicated. Even the molecular work on the complex doesn’t differentiate the species boundaries in several cases [29,30]. Species of the complex are morphologically similar to each other, and the systematic status has been controversial. The present paper examined the pollen morphology of R. omeiensis, R. sericea, R. mairei, and R. sikangensis. The present study is designed to study the palyno-morphological characteristics of the R. sericea complex and provide the potential importance of the palynological characters for taxonomic evidence. Thus, the present study has been designed and documented with the following objectives: to (1) contribute to the palyno-morphological knowledge of several populations of R. sericea complex, (2) to study the detailed morphological features of pollen by SEM, (3) to examine whether the palynological information has potential as evidence in the taxonomy of this complex species.

2. Materials and Methods

2.1. Pollen Sample Collection

Plants specimens of the R. sericea complex were collected from different areas of southwest China (Figure 1). The voucher information for the sample specimens is given in (Table 1). For each individual, more than ten polar and equatorial pollen views were studied. We studied eight populations and 22 samples of R. sericea complex taxa.

2.2. Taxonomic Investigation through Light and Scanning Electron Microscopy

Mature flowers of the studied species were collected, the anthers were detached and kept on a glass slide and the acetolysis method was used. The anther was then treated with acetic acid and crushed on a glass slide to separate the pollen. One drop of glycerin jelly was put on the slide covered with a coverslip. On the margins of slides, transparent nail polish was used to make them permanent. The slides were then examined using a light microscope (Biological Microscope Model: MX5300H). The photos were shot with a microscope model: Leica Dialux Light Microscope model 1000 and at various magnifications.
Pollen grains of the studied species were directly taped on stubs and sputter coated with palladium gold. The pollen was mounted on Agar Scientific adhesive carbon tabs 12 mm in size and placed on aluminum stubs. Stubs were then sputter coated with 250 nm platinum particles, using Emitech K575X sputter coater and run for 2 min. Pollen grains were observed on SEM (Phenom poX, Phenome-world, The Netherlands, Eindhoven) at 10 kV installed in Chengdu Institute of Biology (CIB), Chinese Academy of Sciences. SEM micrographs of the polar and equatorial diameter view and pollen surface ornamentation were captured at a resolution of 1048 × 1088 pixels and saved in TIF format. In this research, we studied different population samples of pollen for each taxon. For polar and equatorial views, ten pollen grains for each were observed. For pollen terminology, we followed [59,60]. Both qualitative and quantitative characteristics of the pollen were studied in detail. On the equatorial and polar view, 15 pollen grains for each sample were observed and measured. For the measurement, ImageJ software was used.

2.3. Statistical Analysis

Statistical analysis was done using SPSS 16.0 software, IBM (University of Stanford) to obtain maximum, minimum, and mean standard error. The average values were determined for polar diameter, equatorial diameter, colpi length, and width.

P/E Ratio

The P/E ratio of each pollen was calculated using the following formula
P / E = P E × 100
where P is polar diameter and E is the equatorial diameter of the same pollen.

3. Results

3.1. General Pollen Morphology of R. sericea Complex

The palyno-morphological characters showed that the pollen of the studied species showed very little variability (Table 2 and Table 3 and Figure 2, Figure 3, Figure 4 and Figure 5). The pollen aperture was straight and wide in the middle, narrow toward both ends. The edges of the apertures were thickened, with a bridge-shaped hole cover (pontiperculate). The surface ornamentation was rough, the ridges were evenly thick and wavy, and the inter-ridges have tiny perforations about 0.05 µm in diameter. Pollen size was found to be medium (17.97 µm; 32.39 µm) on polar view. The pollen morphological characters showed variation in some characters of sculpture, pollen outline, and apertures.

3.2. Qualitative Morphological Characteristics of Pollen of R. sericea Complex

The pollen grains of the studied specimens were found to be mono/tricolporate (Table 4 and Table 5). Mainly, the pollen of the studied species was observed to be well developed. Along with this, some grains have been noted incompletely and were smaller than in the studied taxon. Most of the pollen grains were consistent with [61]’s pollen size classification. The qualitative morphological description of the study species is given below.

3.3. General Description

3.3.1. Rosa omeiensis

Polar view: 1,3-lobed spherical, with obtuse poles, Equatorial view: 1,3-lobed spheroidal to prolate, Exine sculpture: striae slightly bent, 0.15 µm in diam; 0.18 µm above channels; channels 0.29 µm wide; 7.71 perforations/µm2, round, 0.02–0.05 µm in diam., Pollen outline: polar view almost circular, rarely triangular obtuse, equatorial view often elliptic, rarely circular, Apertures: Tri-ectocolpi, long, deep and sharply tapering, regularly arranged, longitudinal pattern. Having variable width, greater at equatorial with sculpturing of ectocolpus membrane. Operculum on aperture membrane, usually situated symmetrically.

3.3.2. Rosa sericea

Polar view: 1,3-lobed spherical, with round poles, Equatorial view: 1,3-lobed spheroidal to prolate, Exine sculpture: striae slightly bent, different in length, 0.12 µm in diam; 0.20 µm above channels; channels 0.15 µm wide; 7.13 perforations/µm2, round, 0.02–0.08 µm in diam., Pollen outline: polar view a bit longitudinal, almost circular, rarely obtuse or triangular, equatorial view spheroidal to prolate, sometimes elliptic, Apertures: Tri ectocolpi, long deep and sharp tapering, often elliptical, long in outline, deeply set into the exine, ending sharply. The operculum is elongated, narrow, and psilate in the central part of ectocolpus.

3.3.3. Rosa sikangensis

Polar view: 3-lobed spherical, with obtuse poles, Equatorial view: 1,3-lobed subspheroidal to prolate, Exine sculpture: striae straight, 0.10–0.15 μm in diam., strongly divaricated; 0.09 µm above channels; channels 0.22 μm wide; 1.13 perforations/μm2, ovate, different in size, polar axis ca. 0.1 μm long, Pollen outline: polar view circular, obtuse triangular apices, sometimes elliptical, equatorial view circular, rarely elliptical, Apertures: Tri ectocolpi, deep and sharp tapering, ectocolpus are regulated. Operculum on aperture membrane, operculum sculpture psilate.

3.3.4. Rosa mairei

Polar view: 3-lobed spherical, with round poles, Equatorial view: 1,3-lobed spheroidals to prolate, Exine sculpture: striae straight, 0.15 μm in diam., strongly divaricated; 0.18 µm above channels; channels 0.11–0.25 µm wide; 6.64 perforations/µm2, nearly round, different in size, 0.04–0.11 µm in diam, Pollen outline: polar view almost circular, obtuse apices, narrowly elliptical, equatorial view almost circular, spheroidal to prolate, Apertures: Tri ectocolpi, profoundly and sharp tapering, ectocolpus regular. The operculum is positioned in the middle of the ectocolpi and covers it partly or entirely.

3.4. Quantitative Features of Pollen of R. sericea Complex

3.4.1. Pollen Size

Pollen of the studied species has spheroidal, subspheroidal, spherical obtuse to spherical rounded poles with polar diameter of the maximum mean value of 32.39 µm in R. omeiensis. In contrast, the minimum mean value is 25.06 µm in R. sikangensis. Whereas the maximum equatorial diameter mean value was 28.58 µm in R. omeiensis, and the minimum mean value 17.97 µm was in R. sikangensis. The other two species have a maximum different mean value of polar and equatorial diameter, i.e., R. sericea has a polar diameter of 29.83 µm and equatorial diameter of 26.67 µm, R. mairei has a polar diameter of 27.10 µm, and the equatorial diameter 22.72 µm (Table 3). Pollen grains of all four species were tricolporate, which has quantitative character diversity. R. sericea colpi mean length was 24 µm with 2.6 µm width, while R. sikangensis colpi have a minimum mean length of 20.4 µm with 1.9 µm width; R. omeiensis colpi mean values were 22.5 µm and 2.5 µm. R. mairei colpi mean length was 23.5 µm and width was 2.3 µm. Distance between colpi was measured; the maximum length found in R. omeiensis was 20 µm, while the minimum was noted in R. sikangensis as 15 µm; whereas R. sericea was 17 µm and R. mairei was 18 µm.

3.4.2. P/E Ratio

P/E ratio was calculated using the polar and equatorial diameter ratio, which ranges from 0.98 µm in R. sikangensis to 1.46 µm in R. mairei. The other two species, R. sericea and R. omeiensis have a 1.11 µm and 1.13 µm P/E ratio, respectively.

3.5. Variation within the Populations of the Species of R. sericea Complex

We studied eight populations and 22 specimens of four species of R. sericea complex (e.g., R. omeiensis, R. sericea, R. sikangensis, and R. mairei). There were three populations of R. omeiensis and R. sericea, eight specimens of each species, and one population of R. mairei and R. sikangensis with three specimens each (Table 5). The specimens of R. omeiensis showed variation in colpus number on polar and equatorial views. Most of the pollen has tricolpate pollen, although some have both mono/tricolpate pollen. Polar diameter showed that two types had pollen size smaller than 29 µm, and some specimens had pollen bigger than 29 µm. The size of the other species’ pollen was also of two types: small and medium. The equatorial diameter also had two kinds of pollen: less than 24 µm were considered small, whereas more than 24 µm were categorized as medium size. The polar view also showed two types, i.e., spherical and semi-spherical. The equatorial view showed spheroidal and prolate kinds of pollen. The pole of the pollen of R. omeiensis was obtuse (Figure 2(1A–1C), Figure 3(7A–8C), Figure 4(9A–9C) and Figure 6(18A–19C).
Rosa sericea have tricolpate pollen. In some specimens, monocolpate pollen has been observed. The pollen of this species has both medium and small-sized pollen. Variations have been observed in the P/E ratio and size category. The polar view has two types, spherical and semi-spherical, whereas the equatorial view has one type, spheroidal. The pole of the pollen was round (Figure 2(2A–2C), Figure 4(12A–12C) and Figure 5(13A–16C).
We studied one population and three specimens of R. mairei. The species showed tricolpate pollen on the polar view, whereas tricolpate and monocolpate pollen were observed on the equatorial view. The size of all studied samples was small, less than 29 µm on the polar view, whereas the equatorial view had a size less than 24 µm. In the polar view, the pollen had a spherical shape, while in the equatorial view, it has the spheroidal shape with a round pole (Figure 2(3A–3C) and Figure 3(5A–6C)).
In this research paper, we studied one population and three specimens of R. sikangensis, which has tricolpate pollen on the polar view and mono/tricolpate pollen on the equatorial view. The pollen size in the polar view was less than 29 µm and more than 24 µm in the equatorial view. The P/E ratio was more than 0.98, and the pollen was considered medium size. The pollen shape on the polar view was spherical, and spheroidal on the equatorial view with an obtuse pole (Figure 2(4A–4C) and Figure 4(10A–11C)). The light micrographs of the studied species are given in (Figure 6).

4. Discussion

The present research clarifies the significance of SEM for the correct identification and species delimitation of R. sericea complex taxa based on pollen morphology. The palyno-morphological characters of the pollen grains of R. omeiensis, R. sericea, R. sikangensis, and R. mairei have been examined in detail for the first time. All the studied species have similar morphological characters, and some features showed differentiation even within the same populations (Table 5). The authors of [42] studied many characters in the taxa of Rosaceae like shape, size of the polar and equatorial view, exine thickness, and length of ectocolpi, which were noted as useful features for delimiting the species in the genus Rosa. The authors also mentioned that light microscopy observations show poor results in distinguishing the species. Our observation in the present study provides some characteristics for the delimitation of species, but some of the characteristics were similar and overlapped (Figure 7 and Figure 8). Some of the most important characteristics studied here include qualitative characteristics of polar and equatorial view, sculpture, pollen outline, and apertures, along with the significant features polar and equatorial diameter, P/E ratio, colpi length and width, and distance between colpi; in eight populations and four species of complex these characteristics have been examined in detailed.
Differentiating palyno-morphological types strengthens the possibility of improving the taxonomic resolution of the species of Rosa. Some previous work has been done using different markers and molecular evidence, which does not resolve the problem of R. sericea complex species [29,30]. These studies reveal that the species of this complex could not be delimited through DNA evidence. Maybe the species of this complex is under speciation. Some studies have been done on the pollen morphology of Rosaceae species from north-western Europe [33], which separate the species based on palyno-morphology. They also claim in their study that the type of exine sculpture, costae colpi presence or absence, and structure of operculum are important characters for distinguishing species in Rosa. Many palynologists confirm the diagnostic importance of exine sculpture as a distinguishing characteristic of Rosaceae at both genus and species level [35,40,43,62,63,64,65,66,67] and these authors also mentioned some other important characteristics for species delimitation in different genera of the family Rosaceae. The most significant characteristics of exine sculpture include the number and size of perforations and the interval, number, and diameter of striae [16,41,68]. Two different types of perforation in Rosaceae (striate sculpturing macroperforate and non-striate sculpturing macroperforate, with six subtypes each) possibly point to different evolutionary lines [16]. The genus Rosa was incorporated into large perforations usually extending onto tectal striae. Additionally, Rosa also emphasized striae that were long and parallel to the ectocolpus.
The available literature on the palynology of Rosaceae indicated that pollen size was correlated with the number of chromosomes [69]. The correlation between ploidy and pollen dimensions could not be established in the present study due to our samples’ lack of a large enough ploidy data set. In the R. sericea complex, pollen characters, especially pollen ornamentation, provide useful information for differentiating species boundaries and delimitation. The pollen grains of the examined species are mostly medium medium size, 21.86–36.37 µm, similar to the previous studies [35,40,41]. According to [36], the exine micro-sculpture of R. penduline and some other species of the genus could be differentiated through different perforations. Our pollen morphological characteristics of the R. sericea follow [51]. They studied the pollen morphology of different species of Rosaceae, including the species R. sericea. Ghosh and Saha [51] found that striae ornamentation and pollen size is also almost the same as this species.
The multivariate and PCA analysis results showed that the first five variance components accounted for 88.8% of variance. In contrast, the eigenvalue was between 0.18–0.83 (Table 6). The PCA analysis showed that the palynological characters were very similar in the studied species. The first two plots of principal components have been observed (PC1 vs. PC2; Figure 7). Taxon variation along PC1 designates dissimilarity with the polar view, equatorial view, size category, polar diameter, and colpus number. PC2 provides information in dissimilarity in P/E ratio, pole of pollen, equatorial diameter, colpus on polar and equatorial view of pollen. This PCA analysis showed that the species within the population showed dissimilarity in some characters. The studied characters within the population provide significantly fewer taxonomically distinguishing features for the studied species.
We found that R. sericea’s population shows little taxonomic information to distinguish the complex species. Some characters show little taxonomic importance, such as the distance between colpi, operculum regions, pollen outline, diameter, and ornamentation. According to our current findings, the characters studied here do not provide enough information to classify the complex taxon into different species. Mainly the populations of the varying taxa have similar characteristics. The quantitative features significantly differ between the studied species, but it also shows variation within each population.

5. Conclusions

The species of R. sericea complex are 1,3-lobed spherical, with an obtuse polar view, spheroidal to prolate, and subspheroidal to prolate at the equatorial view. The pollen was found to be different in terms of sculpture characters, pollen outline, and apertures. In the present research, we examined four species, eight populations, and 22 samples of R. sericea complex. In this study, we confirm the diversity of pollen characters within species of the same population and different populations of the observed specimens. The palyno-morphological features of the R. sericea complex are of little taxonomic significance for the delimitation and identification of species. Quantitative characters showed little taxonomic importance for species, whereas the qualitative characters were of little taxonomic importance to separate the species into distinct taxa. This research provides baseline information for the taxonomy of the taxa of the R. sericea complex.

Author Contributions

Conceptualization, F.U. and X.-F.G.; methodology, F.U.; software, F.U. and W.Z.; validation, F.U., X.-F.G. and Y.-D.G.; formal analysis, F.U. and W.Z.; investigation, X.-F.G.; resources, X.-F.G.; data curation, X.-F.G.; writing—original draft preparation, F.U.; writing—review and editing, X.-F.G., Y.-D.G. and W.Z.; visualization, F.U.; supervision, X.-F.G.; project administration, X.-F.G. and Y.-D.G.; funding acquisition, X.-F.G. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported by the Second Tibetan Plateau Scientific Expedition and Research (STEP) program (2019QZKK0502) and the National Natural Sciences Foundation of China (Project No. 31670192), and National Natural Science Foundation of China 32171605. We are thankful to the Chinese Government Scholarship Program (CSC No. 2018GXZ017484).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data for this research has been collected from different areas of China. The original specimens used in this research are available in CDBI herbarium, Chengdu Institute of Biology, University of Chinese Academy of Sciences.

Acknowledgments

This work was supported by the Second Tibetan Plateau Scientific Expedition and Research (STEP) program (2019QZKK0502) and the National Natural Sciences Foundation of China (Project No. 31670192). We are thankful to the Chinese Government Scholarship Program (CSC No. 2018GXZ017484 to Fazal Ullah). The authors are also grateful to the curator and staff of CDBI for their help studying specimens.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Distribution of species of the R. sericea complex.
Figure 1. Distribution of species of the R. sericea complex.
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Figure 2. (A,B). Different shapes of pollen (C). surface 16639-(1A–1C) R. omeiensis, 16692-R. sericea, 16692-(2A–2C) R. omeiensis, 16785-(3A–3C) R. mairei, 16677-1-(4A–4C) R. sikangensis.
Figure 2. (A,B). Different shapes of pollen (C). surface 16639-(1A–1C) R. omeiensis, 16692-R. sericea, 16692-(2A–2C) R. omeiensis, 16785-(3A–3C) R. mairei, 16677-1-(4A–4C) R. sikangensis.
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Figure 3. (A,B). Different shapes of pollen (C). surface 16785-(5A–6C) R. mairei, 16639-(7A–8C) R. omeiensis.
Figure 3. (A,B). Different shapes of pollen (C). surface 16785-(5A–6C) R. mairei, 16639-(7A–8C) R. omeiensis.
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Figure 4. (A,B). Different shapes of pollen (C). surface 16639-(9A–9C) R. omeiensis, 16676-(10A–11C), R. sikangensis, 16692-(12A–12C) R. sericea.
Figure 4. (A,B). Different shapes of pollen (C). surface 16639-(9A–9C) R. omeiensis, 16676-(10A–11C), R. sikangensis, 16692-(12A–12C) R. sericea.
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Figure 5. (A,B). Different shapes of pollen (C). surface 16692-(13A–15C) R. sericea, 17017-(16A–16C) R. sericea.
Figure 5. (A,B). Different shapes of pollen (C). surface 16692-(13A–15C) R. sericea, 17017-(16A–16C) R. sericea.
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Figure 6. Light microscopy micrographs of R. sericea (17A–17C), R. omeiensis (18A–18C), R. sikangensis (19A–19C), and R. mairei (20A–20C).
Figure 6. Light microscopy micrographs of R. sericea (17A–17C), R. omeiensis (18A–18C), R. sikangensis (19A–19C), and R. mairei (20A–20C).
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Figure 7. PCA analysis of pollen morphological characteristics in different populations.
Figure 7. PCA analysis of pollen morphological characteristics in different populations.
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Figure 8. Chart box plot of the diameters of the pollen grains. Populations codes are according to Table 4. Different quantitative characters graph of polar length (A), polar width (B), equatorial length (C), equatorial width (D), and P/E ratio (E).
Figure 8. Chart box plot of the diameters of the pollen grains. Populations codes are according to Table 4. Different quantitative characters graph of polar length (A), polar width (B), equatorial length (C), equatorial width (D), and P/E ratio (E).
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Table
Table 1. Collection of information on different populations of Rosa sericea complex specimens.
Table 1. Collection of information on different populations of Rosa sericea complex specimens.
TaxonPopulation CodeAltitudeLocation Latitude Longitude
R. sericeaGXF-16734 3188Xizang, Gyaca29.1392.69
R.omeiensisGXF-16639 3800Xizang, Yadong27.5789.02
R. sericeaGXF-16646 2806Xizang, Yadong27.4188.94
R.omeiensisGXF-16751 3588Xizang, Mainling29.4994.91
R. sericeaGXF-16771 3704Xizang, Mainling29.4994.92
R.omeiensisGXF-17018 3127Sichuan, Baoxing30.83102.72
R.omeiensisGXF-170223593Sichuan, Xianojin30.88102.65
R. sericeaGXF-166922912Xizang, Cuona27.9191.80
R. sericeaGXF-170172325Sichuan, Baoxing30.77102.72
R. sericeaGXF-170283591Sichuan, Xiaojin30.88102.65
R.sikangensisGXF-16776 Xizang, Bangda30.3196.55
R.maireiGXF-16785 2185Yunnan, Huize26.48103.58
R. sericeaGXF-16692 2935Xizang, Cuona27.9191.80
R.omeiensisGXF-16639 3800Xizang, Yadong27.5789.02
R.omeiensisGXF-17018 3127Sichuan, Baoxing30.83102.72
R.omeiensisGXF-17022 3593Sichuan, Xianojin30.88102.65
R. sericeaGXF-16692 2912Xizang, Cuona27.9191.80
R. sericeaGXF-17017 2325Sichuan, Baoxing30.77102.72
R. sericeaGXF-17028 3591Sichuan, Xiaojin30.88102.65
R.sikangensisGXF-16776 Xizang, Bangda30.3196.55
R.maireiGXF-16785 2185Yunnan, Huize26.48103.58
Table
Table 2. Qualitative characteristics of pollen of R. sericea complex species.
Table 2. Qualitative characteristics of pollen of R. sericea complex species.
Taxon Polar ViewEquatorial ViewSculpture Pollen Outline Apertures
R. omeiensis1,3-lobed spherical, with obtuse polesSpheroidal to prolateStriae slightly bent, 0.15 µm in diam; 0.18 µm above channels; channels 0.29 µm wide; 7.71 perforations/µm2, round, 0.02–0.05 µm in diam.The polar view is almost circular, rarely triangular obtuse, equatorial view often elliptic, rarely circular.Tri-ectocolpi, long, deep and sharply tapering, regularly arranged, longitudinal pattern. Having variable width, greater at equatorial region with sculpturing of ectocolpus membrane. Operculum on aperture membrane, usually situated symmetrically.
R. sericea1,3-lobed spherical, with round polesSpheroidal to prolateStriae slightly bent, different in length, 0.12 µm in diam; 0.20 µm above channels; channels 0.15 µm wide; 7.13 perforations/µm2, round, 0.02–0.08 µm in diam.Polar view a bit longitudinal, almost circular, rarely obtuse or triangular, equatorial view spheroidal to prolate, sometimes elliptic. Tri ectocolpi, long deep and sharp tapering, often elliptical, long in outline, deeply set into the exine, ending sharply. Operculum in central part of ectocopus, elongated, narrow and psilate.
R. sikangensis1,3-lobed spherical, with obtuse polesSubspheroid al to prolateStriae straight, 0.10–0.15 μm in diam., strongly divaricated; 0.09 µm above channels; channels 0.22 μm wide; 1.13 perforations/μm2, ovate, different in size, polar axis ca. 0.1 μm long.Polar view circular, triangular obtuse apices, sometimes elliptical, equatorial view circular, rarely elliptical. Tri ectocolpi, deep and sharp tapering, ectocolpus is regulated. Operculum on aperture membrane, operculum sculpture psilate.
R. mairei1,3-lobed spherical, with round polesSpheroidal to prolateStriae straight, 0.15 μm in diam., strongly divaricated; 0.18 µm above channels; channels 0.11–0.25 μm wide; 6.64 perforations/μm2, nearly round, 0.04–0.11 μm.The polar view is almost circular, obtuse apices, narrowly elliptical, and the equatorial view is almost circular and spheroidal to prolate.Tri ectocolpi, deeply and sharp tapering, ectocolpus regular. Operculum is positioned in the middle of the ectocolpi and covers it partly or completely.
Table
Table 3. Quantitative characteristics of pollen of R. sericea complex species.
Table 3. Quantitative characteristics of pollen of R. sericea complex species.
TaxaPolar Diameter (µm)Equatorial Diameter (µm)P/E (µm)Colpi Length Colpi Width Distance between Colpi
R. omeiensis32.39 (21.86–36.37) 28.58 (26.27–32.35)1.1322.5 µm2.5 µm20 µm
R. sericea29.83 (25.39–34.61) 26.67 (23.73–29.22)1.1124 µm2.6 µm17 µm
R. sikangensis25.06 (21.90–28.83) 17.97 (15.20–20.37)0.9820.4 µm1.9 µm15 µm
R. mairei27.10 (22.94–30.20)22.72 (15.29–28.14)1.4623.5 µm2.3 µm18 µm
Table
Table 4. Mean values of quantitative characters of different populations of R. sericea complex species.
Table 4. Mean values of quantitative characters of different populations of R. sericea complex species.
TaxonPopulation CodePolar LengthPolar WidthEquatorial LengthEquatorial WidthP/EShapeAperture Exine
R. omeiensisGXF-1663921.86 µm19.5 µm26.27 µm19.5 µm1.12Colpus3Thick
R. omeiensisGXF-1701833.7 µm23.5 µm32.35 µm27 µm1.2Colpus3Thin
R. omeiensisGXF-1702236.37 µm27.35 µm28.2 µm23.4 µm1.5Colpus3Thin
R. sericeaGXF-1669228.83 µm25.4 µm23.73 µm19.2 µm1.5Colpus3Thick
R. sericeaGXF-1701727.20 µm25.3 µm29.22 µm24.32 µm1.11Colpus3Thin
R. sericeaGXF-1702834.61 µm32.20 µm27.30 µm24.4 µm1.41Colpus3Thick
R. sikangensisGXF-1677624.5 µm22.5 µm28.7 µm25 µm0.98Colpus3Thin
R. maireiGXF-1678525.3 µm23.5 µm23.43 µm17.3 µm1.46Colpus3Thick
Table
Table 5. Morphological variation within different populations of R. sericea complex species.
Table 5. Morphological variation within different populations of R. sericea complex species.
Population Code Colpus on PolarColpus on Equatorial Polar Diameter Equatorial DiameterP/ESize CategoryPolar ViewEquatorial ViewPole of PollenFigure
GXF-16639-22121121111A, 1B, 1C
GXF-16639-11111111117A, 7B, 7C
GXF-16639-3111111½218A, 8B, 8C
GXF-16639-42222121119A, 9B, 9C
GXF-17018-121222212117A, 17B, 17C
GXF-17018-221221211118A, 18B, 18C
GXF-17022-222211211119A, 19B, 19C
GXF-17022-321212212120A, 20B, 20C
GXF-16692-42222122/1122A, 2B, 2C
GXF-16692-111112111212A, 12B, 12C
GXF-16692-211112111213A, 13B, 13C
GXF-16692-321111111214A, 14B, 14C
GXF-16692-521222211215A, 15B, 15C
GXF-17017-122121211216A, 16B, 16C
GXF-17028-12122122/112-
GXF-17028-2222222112-
GXF-16785-22211111123A, 3B, 3C
GXF-16785-12211211125A, 5B, 5C
GXF-16785-32111211126A, 6B, 6C
GXF-16676-121122211 14A, 4B, 4C
GXF-16676-221122211110A, 10B, 10C
GXF-16676-321122211111A, 11B, 11C
Keys 1 = one/three colpi
2 = three colpi 		1 = one/three colpi
2 = three colpi		1 = less than 29 µm
2 = more than 29 µm		1 = less than 24 µm
2 = more than 24 µm		1 = less than 1.14 µm
2 = more than 1.14 µm		1 = small
2 = medium 		1 = spherical
2 = semi-spherical
1 = spheroidal
2 = prolate		1 = obtuse pole
2 = round pole
Table
Table 6. PCA summary with eigenvalue and percentage variance.
Table 6. PCA summary with eigenvalue and percentage variance.
PCEigenvalue% Variance
10.83635.777
20.42518.209
30.40417.304
40.2279.732
50.1888.042
60.1636.984
70.0672.903
80.0241.045
95.3822.302
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Ullah, F.; Gao, Y.-D.; Zaman, W.; Gao, X.-F. Pollen Morphology of Rosa sericea Complex and Their Taxonomic Contribution. Diversity 2022, 14, 705. https://doi.org/10.3390/d14090705

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Ullah F, Gao Y-D, Zaman W, Gao X-F. Pollen Morphology of Rosa sericea Complex and Their Taxonomic Contribution. Diversity. 2022; 14(9):705. https://doi.org/10.3390/d14090705

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Ullah, Fazal, Yun-Dong Gao, Wajid Zaman, and Xin-Fen Gao. 2022. "Pollen Morphology of Rosa sericea Complex and Their Taxonomic Contribution" Diversity 14, no. 9: 705. https://doi.org/10.3390/d14090705

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