Apocynaceae is one of the important angiosperm families founded in 1789 as ‘Apocineae’ by Jussieu (El Gazzar et al., 2018). It comprises 375 genera and 5100 species present mainly in subtropical and tropical regions of the world (Endress et al., 2007). Naz et al. (2019) have reported that Pakistan has 19 genera, comprised of 13 cultivated genera (20 species) and 6 endemic genera (6 species). Brown in 1810 separated Asclepiadaceae from Apocynaceae based on pollinium and classified them into three subfamilies (Secamonoideae, Asclepidoideae and Periplocoideae). Schlechter (1905) segregated Periplocaceae based on tetrads pollens from Asclepiadaceae but Endress and Bruyns (2000) classified the family Apocynaceae into five subfamilies, namely those of Rauvolfioideae, Apocynoideae, Periplocoideae, Secamonoideae and Asclepiadoideae. From a global perspective, Asclepiadoideae are comprised of 250 genera and more than 2,500 species; however, in Pakistan, 23 genera and 41 species are presently reported (El-Fiki et al., 2019).
Apocynaceous plants are perennial shrubs, trees or herbs that occasionally grow as annuals, with five joined petals on flowers, astringent milky latex, tufted seeds, and fruits that are typically in pairs (Shah and Ahmad, 2014). The leaves are exstipulate, lanceolate, alternate, simple, opposite decussate, ovate, obovate, oblong, linear, whorled, elliptic or oblong; sessile; or petiolate with an entire or undulate border and an acute apex while occasionally reduced or turned into spines (El-Fiki et al., 2019). Mesophytes and semi-succulent taxa have cylindrical stems, whereas succulent taxa have angled stems. Flowers have traits such as being actinomorphic, hypogynous, hermaphrodite, sympetalous and possessing pentamerous (sometimes tetramerous) whorls with a range of sizes. Further characteristics are a corolla with five joined petals, imbricate lobes and a calyx with five united imbricate sepals; the corona arises from the base of the petals or staminal filaments, and an androecium with five free stamens. The fruit of a parietal placenta consists of two carpels, two free ovaries, two styles that fuse just beneath the capitate stigma, two seeds that generally contain a distal tuft of silky hairs, and two dehiscent follicles containing multiple seeds (Morais et al., 2021).
In Pakistan, it is mostly present in subtropical regions of Mianwali, Khushab (Sakesar), Chakwal, Talagang, Jehlum, Sindh, Rawalpindi, Islamabad etc. in the form of twining shrubs, lianas, perennial herbs, scramblers, vines and also leafless succulent stems present in the order Gentianales. In Apocynaceae, some plants have medicinal values such as diuretic, antidiabetic, anti-inflammatory, stomachic and laxative, as well as utility in the treatment of respiratory disorders (Bahadur et al., 2018). To treat scorpion sting, snake bite and skin disorders,
Pollen and seed germination tests can be used to identify salt-tolerant crops and pollen grain shapes can be utilised to identify interspecific and intraspecific relationships. These investigations were conducted to ascertain the links, both intraspecific and interspecific, between fruit tree species, which may be significant for processes related to fruit development, fertilisation and pollination (Khaleghi et al., 2019). Breeders and academics have already documented numerous cultivars and genotypes with undesirable pollen. Some cultivars/ genotypes, for example, have sterile pollen or pollen with a low germination percentage. Pollen form and ultrastructure have been linked to growing habitat and pollination biology (Ćalić et al., 2013).
Modern taxonomists are particularly interested in palynological characterisation to distinguish closely related taxa and identification and assessment of interactions among species at several taxonomic levels rely heavily on pollen morphology (Majeed et al., 2023). Palynological studies can help us comprehend plant evolution and phylogeny. Scanning electron microscopy (SEM) is a contemporary technique for studying the micromorphological structure in depth (Majeed et al., 2022). We employ a scanning electron microscope with high-resolution power to examine the surface of pollen grains (Khan et al., 2022; Nabila et al., 2022). SEM is presently known to be one of the most innovative techniques for taxonomic research. Many palynologists are currently using pollen features to precisely and accurately distinguish closely related taxa (Bahadur et al., 2018; Abid et al., 2023).
The study aims to investigate intraspecific variations in pollen morphology within the Apocynaceae plant family. It seeks to provide a comprehensive understanding of the pollen traits that differ among closely related species, offering insights into their genetic diversity and potential applications in horticultural innovation. By creating a roadmap for this exploration, the study intends to contribute to the development of new horticultural techniques and strategies for the Apocynaceae family.
During the summer, several field trips were organised across the country. Several elements of vegetation were in full bloom. As shown in Table 1, diverse Apocynaceous samples were obtained from Islamabad, and various areas in Punjab such as Namal, Daud Khail, Sawans, Sakesar, Talagang, Chakwal, Rawalpindi and Sindh. The sites of plant collection are represented in the form of a map (Figure 1). Field area coordinates were collected with the help of the global positioning system (GPS) devices Garmin eTrex (Garmin eTrex 10 GPS, Garmin Oregon 750) and eTrex Venture (Garmin eTrex Venture HC GPS Receiver). Photographs of each plant were taken with the use of a Panasonic ZS 20 digital camera DMC-ZS20K as shown in Figures 2–4. Plant species taken from different regions were identified with the assistance of taxonomists and specimens were compared with already deposited specimens forming part of the collection of the Islamabad (ISL) Herbarium, Pakistan. The confirmation of samples was compared from given literature from the flora of Pakistan (
Checklist of Apocynaceous plants sampling and herbarium accession.
Sr. No. | Apocynaceous taxa | Flowering period | Voucher No. | Localities | Coordinates | Collector’s name | Accession No. | Altitude (feet) | District/province |
---|---|---|---|---|---|---|---|---|---|
1. | June to September | AC-01 | Green town | 32.576547° N, 71.575377° E | Rizwan & Salman | ISL-133416 | 688 | Mianwali/Punjab | |
2. | November to January | AS-16 | Cantt. | 31.513099° N, 74.373667° E | Rizwan | ISL-133415 | 712 | Lahore/Punjab | |
3. | June to October | AC-32 | Rawalpindi | 33.567410° N, 73.085568° E | Rizwan | ISL-133428 | 1,680 | Rawalpindi/Punjab | |
4. | October to December | CP-06 | Mirpur | 25.514458° N, 69.023728° E | Rizwan & Prem | ISL-133431 | 60 | Mirpur/Sindh | |
5. | October to November | CM-15 | Chakwal | 32.939325° N, 72.864004° E | Rizwan | ISL-133422 | 1,965 | Chakwal/Punjab | |
6. | July to August | CS-10 | Rumli | 33.752956° N, 73.136338° E | Rizwan & Prem | ISL-133426 | 2,346 | Islamabad | |
7. | June to October | CT-11 | ICT | 33.745615° N, 73.137888° E | Rizwan & Prem | ISL-133418 | 2,031 | Islamabad | |
8. | July to August | CR-03 | QAU | 33.745623° N, 73132074° E | Rizwan | ISL-133419 | 2,031 | Islamabad | |
9. | June to August | CD-13 | Sakesar | 32.541652° N, 71.934362° E | Rizwan | ISL-133430 | 4,960 | Khushab/Punjab | |
10. | July to September | LP-09 | Namal | 32.668914° N, 71.614760° E | Rizwan & Salman | ISL-133425 | 1,129 | Mianwali/Punjab | |
11. | July to September | NO-12 | Talagang | 32.913338° N, 72.426670° E | Rizwan | ISL-133424 | 1,666 | Talagang/Punjab | |
12. | July to January | OE-23 | Mirpur | 25.504108° N, 69.037589° E | Rizwan & Jamil | ISL-133427 | 63 | Mirpur/Sindh | |
13. | October to November | PD-14 | Jehlum | 32.951902° N, 73.689400° E | Rizwan | ISL-133429 | 768 | Jehlum/Punjab | |
14. | June to September | PA-05 | Sakesar | 32.558860° N, 71.913981° E | Rizwan | ISL-133414 | 5,092 | Khushab/Punjab | |
15. | July to October | PR-08 | Mirpur | 25.359219° N, 69.143117° E | Rizwan & Jamil | ISL-133421 | 59 | Mirpur/Sindh | |
16. | August to September | TD-04 | GHS | 32.577587° N, 71.537370° E | Rizwan | 133423 | 650 | Mianwali/Punjab | |
17. | June to August | VS-07 | Daud Khail | 32.888711° N, 71.614760° E | Rizwan | 133420 | 692 | Mianwali/Punjab | |
18. | July to August | WV-02 | QAU | 33.746286° N, 73.138156° E | Rizwan | 133417 | 2,031 | Islamabad |
Map showing the sampling localities of Apocynaceous species.
Field pictorial view: (A)
Field pictorial view: (A)
Field pictorial view: (A)
Pollen grains’ micromorphological characteristics were investigated using a Meiji light microscope (MX 5200H, Japan). The slide is prepared by applying Blackmore’s (1983) and Erdtman’s (1986) acetolysis procedure with marginal modifications, which is a widely used technique among palynologists worldwide. Anthers were gathered from dried blossomed flowers, typically when they were in the anthesis stage. Polleniferous material such as anthers was removed from flowers and placed in a glass slide using clean forceps. Two to three drops of acetic acid were deposited over the anthers, and this was followed by smashing them with a glass rod. Pollen grains were discharged from the anthers in 2–3 min. While pollen grains were stuck to the slide, the remaining debris was removed. In the case of pollinia, the methodology is slightly different; here we use a tweezer to pick up pollinia and place it over a glass slide without any crushing, because pollinia are fragile and they can easily break up. The pollen was then stained using one to two drops of glycerine jelly, and a cover slip was placed over the glass slide to preserve it over time. Slides that had been prepared were examined both quantitatively and qualitatively.
SEM (Model JEOL-5910, Japan) photomicrographs were used to investigate sculptured components of pollen grain. The pollen was released after one drop of acetic acid (45%) was dropped over the separated anthers from blossomed flowers and they were placed on a glass slide. A rounded stub was adhered to the glass using double-sided adhesive tape so that it could take up pollen grains from the slide. After that, the stub was coated in gold palladium. Specimens were coated in gold using a sputtering apparatus. To capture micrographs of exine sculpture, these stubs were installed in an SEM machine (Mir et al., 2019; Naz et al., 2019). The description of the pollen grains was taken from the glossary of Punt et al. (2007).
The ratio between the polar diameter and equatorial diameter is determined by the following formula:
The percentage of fertility and sterility were calculated by using the following formulae (Umber et al., 2022), as mentioned in Table 2.
Pollen ferity and sterility count among Apocynaceous species.
Sr. No. | Apocynaceous taxa | Fertile pollen/pollinia | Sterile pollen/pollinia | Fertility% | Sterility% |
---|---|---|---|---|---|
1. | 26 | 12 | 68.42 | 31.57 | |
2. | 18 | 06 | 75.00 | 25.00 | |
3. | 05 | 01 | 83.33 | 16.66 | |
4. | 08 | 04 | 66.66 | 33.33 | |
5. | 23 | 09 | 71.87 | 28.12 | |
6. | 14 | 04 | 77.77 | 22.22 | |
7. | 21 | 08 | 72.41 | 27.58 | |
8. | 14 | 06 | 70.00 | 30.00 | |
9. | 12 | 02 | 85.71 | 14.28 | |
10. | 08 | 02 | 80.00 | 20.00 | |
11. | 09 | 02 | 81.81 | 18.18 | |
12. | 10 | 03 | 76.92 | 23.07 | |
13. | 05 | 02 | 71.42 | 28.57 | |
14. | 11 | 04 | 73.33 | 26.66 | |
15. | 11 | 03 | 78.57 | 21.42 | |
16. | 16 | 05 | 76.19 | 23.80 | |
17. | 06 | 02 | 75.00 | 25.00 | |
18. | 07 | 03 | 70.00 | 30.00 |
To construct a taxonomic key for accurately identifying species within the Apocynaceous taxa, the distinct floral palynological features discussed were further scrutinised and differentiated.
For statistical analysis of pollen grains, we use the SPSS 16.0 software, USA. Data were utilised to statistically calculate the equatorial diameter, polar diameter, exine thickness, P/E ratio, colpi width, colpi length and their mean, maximum, minimum and standard error values. For each parameter, the mean (minimum–maximum) standard error (SE) was statistically analysed.
We conducted the study and applied the unweighted pair group method with arithmetic mean (UPGMA) with the help of paleontological statistics (PAST) statistical tool version 3.0 software to create a dendrogram based on Euclidean distances to determine the closer relationship between the species. Using principal component analysis (PCA), the most important features that accounted for the largest share of the variability were identified (Osman et al., 2014).
The pollen grains of different plants species belong to different genera, such as
Light microphotographs of Apocynaceous pollen showing polar and equatorial view taken at 40 × magnification, scale bar 10 μm (A,B)
Light microphotographs of Apocynaceous pollen showing polar and equatorial view taken at 40× magnification, scale bar 10 μm (A)
Scanning electron photomicrographs of Apocynaceae pollen (A–C)
Scanning electron photomicrographs of Apocynaceae pollen (A–C)
Scanning electron photomicrographs of Apocynaceae pollen (A–C)
Scanning electron photomicrographs of Apocynaceae pollen (A–C) Tabernaemontana divaricata; (D–F) Vinca major; (G–I) Vincetoxicum spirale; (J–L) Dregea volubilis.
Dendrogram clustering showing the relationship among different Apocynaceous taxa.
Qualitative pollen micromorphological characters of Apocynaceous taxa.
Sr. No. | Apocynaceous taxa | Size | Pollen type | Pollen shape | Polar view (Amb) | Dispersal unit | Aperture orientation | Exine sculpturing |
---|---|---|---|---|---|---|---|---|
1. | Medium | Tricolporate | Sub-spheroidal | Triangular (convex) | Monad | Colporate | Reticulate | |
2. | Small | Tricolporate | Sub-spheroidal | Lobate & isoplar | Monad | Scabrate | Psilate to perforate | |
3. | Medium | Tricolporate | Oblate spheroidal | Circular & isoplar | Monad | Colporate | Perforate to regulate | |
4. | Medium | Tricolporate | Oblate spheroidal | Lobate & isopolar | Monad | Colporate | Perforate, psilate to regulate | |
5. | Very large | Tricolporate | Prolate spheroidal | Lobate | Monad | Colporus | Microreticulate to perforate | |
6. | Large | Tricolporate | Oblate spheroidal | Irregular | Monad | Colporate | Perforate to scabrate | |
7. | Small to medium | Tetrad | Rhombodial | Rhombodial | Tetrad | Reticulate | ||
8. | Medium | Tetraporate | Oblate spheroidal | Circular | Monad | Porate | Psilate | |
9. | Small to large | Tetrad | Oblong | Rhomboidal | Tetrad | Porate | Psilate | |
10. | Medium | Tricolporate | Prolate spheroidal | Lobate & isoploar | Monad | Colporate | Psilate to scabrate | |
11. | Medium | Tricolpate | Oblate spheroidal | Circular & isopolar | Monad | Colpoate | Perforate |
Qualitative traits of morpho-structure of pollinia.
Sr. No. | Apocynaceous taxa | Pollinium orientation | Pollinium shape | Sterile margins | Orientation of sterile margins | Translator attachment to pollinium | Corpuscular arm | Translator attachment to corpusculum | Colour of pollinia | Exine sculpturing |
---|---|---|---|---|---|---|---|---|---|---|
1. | Pendent | Narrowly oblong | Absent | Absent | Basal | Absent | Sub-apical | Brown | Psilate & Perforate | |
2. | Pendent | Obovate | Absent | Absent | Basal | Absent | Sub-apical | Canary yellow | Psilate | |
3. | Transverse | Orbicular | Present | Apical | Basal | Absent | Apical | Brown | Psilate | |
4. | Pendent | Narrowly oblong | Absent | Absent | Basal | Absent | Apical | Yellow | Perforate | |
5. | Pendent | Obovate | Pseudo-sterile | Parallel | Basal | Absent | Apical | Pinkish Brown | Psilate, perforate | |
6. | Pendent | Narrowly oblong | Absent | Absent | Basal | Present | Apical | Golden | Psilate, perforate | |
7. | Erect | Reniform | Absent | Absent | Basal | Absent | Apical | Sulphur yellow | Perforate |
Quantitative measurement of pollinia.
Sr. No. | Apocynaceous taxa | Length of pollinium Sac mean (min–max) SE (μm) | Breadth of pollinium Sac mean (min–max) SE (μm) | Length of translator mean (min–max) SE (μm) | Breadth of translator mean (min–max) SE (μm) | Length of corpusculum mean (min–max) SE (μm) | Breadth of corpusculum mean (min–max) SE (μm) |
---|---|---|---|---|---|---|---|
1. | 209.60 (200.25–215.75) ± 1.62 | 82.70 (73.75–88.00) ± 0.44 | 90.05 (83.50–100.50) ± 2.85 | 23.25 (22.25–24.25) ± 0.35 | 89.25 (83.75–93.50) ± 1.64 | 33.25 (23.75–41.00) ± 2.800 | |
2. | 315.81 (306.50–323.25) ± 0.48 | 129.44(128.25–130.50) ± 0.55 | 47.25 (41.25–51.25) ± 0.27 | 12.87(11.50–13.75) ± 0.48 | 90.93 (85.25–95.50) ± 0.61 | 56.68 (51.00–65.75) ± 0.20 | |
3. | 46.30 (35.25–55.75) ± 0.82 | 33.35 (26.50–41.25) ± 0.19 | 7.25 (5.25–9.00) ± 0.66 | 7.75 (5.75–12.75) ± 0.26 | 16.80 (10.25–22.75) ± 0.02 | 13.40 (12.75–14.75) ± 0.35 | |
4. | 179.55 (81.25–98.32) ± 0.69 | 37.62 (40.23–35.02) ± 0.25 | 24.7 (23.15 +26.25) ± 0.82 | 8.75(8.3–9.2) ± 0.62 | 74.63 (78.36–70.92) ± 0.82 | 34.40 (32.26–36.55) ± 1.12 | |
5. | 168.45 (159.00–178.00) ± 1.37 | 61.30 (55.25–71.50) ± 0.90 | Absent | Absent | 51.65 (46.00–54.00) ± 0.49 | 41.40 (32.00–60.75) ± 0.23 | |
6. | 74.55 (73.25–77.00) ± 0.73 | 47.65 (42.75–57.75) ± 0.70 | 21.55 (18.25–25.25) ± 1.36 | 21.45 (17.75–25.50) ± 0.33 | 75.85 (71.25–82.75) ± 0.14 | 37.40 (31.25–42.75) ± 0.82 | |
7. | 98.15 (58.25–117.25) ± 1.90 | 38.35 (32.00–43.25) ± 0.01 | 14.85 (12.25–18.00) ± 1.01 | 7.95 (7.25–8.75) ± 0.25 | 258.60 (244–270.50) x± 0.35 | 33.95 (17.75–56.25) ± 7.85 |
Quantitative findings of Apocynaceous pollen.
Sr. No. | Apocynaceous taxa | P/E ratio | Exine thickness mean (min–max) SE (μm) | Polar diameter mean (min–max) SE (μm) | Equatorial diameter mean (min–max) SE (μm) | Length of colpi mean (min–max) SE (μm) | Width of colpi mean (min–max) SE (μm) | Mesocolpium mean (min–max) SE (μm) |
---|---|---|---|---|---|---|---|---|
1. | 0.99 | 1.95 (1.25–2.75) ± 0.26 | 30.1 (27.25–32.75) ± 0.89 | 30.25 (28.00–33.75) ± 0.95 | 13.65 (12.25–16.25) ± 0.70 | 6.05 (4.75–7.25) ± 0.48 | 21.60 (21.75–23.75) ± 0.74 | |
2. | 0.86 | 3.10 (3.75–2.75) ± 0.18 | 20.75 (15.25–23.25) ± 0.51 | 23.40 (20.25–27.75) ± 0.30 | 5.30 (4.50–6.50) ± 0.34 | 4.80 (2.00–6.25) ± 0.72 | 21.95 (20.50–23.75) ± 0.62 | |
3. | 0.99 | 3.20 (2.75–3.50) ± 0.14 | 36.80 (34.50–39.50) ± 0.89 | 36.95 (35.75–38.25) ± 0.46 | 3.00 (2.25–4.00) ± 0.34 | 5.50 (4.50–7.25) ± 0.48 | 35.85 (32.75–38.50) ± 0.07 | |
4. | 0.92 | 3.35 (2.75–4.50) ± 0.32 | 24.30 (23.25–26.25) ± 0.55 | 26.35 (25.25–27.75) ± 0.46 | 2.8 (2.25–3.25) ± 0.16 | 2.25 (2.00–3.00) ± 0.18 | 20.55 (18.50–23.75) ± 0.93 | |
5. | 1.02 | 2.8(3.20–4.10) ± 0.28 | 113.45 (109.4–114.2) ± 0.8 | 109.20 (107.7–110.2) ± 0.40 | 5.20 (4.70–5.57) ± 0.13 | 15.20(15.30–15.20) ± 0.50 | 18.33 (17.50–19.25) ± 0.55 | |
6. | 0.98 | 4.85 (4.50–5.25) ± 0.37 | 56.45 (55.75–57.75) ± 0.89 | 57.30 (55.25–61.25) ± 0.38 | 13.60 (13.00–14.25) ± 0.48 | 6.50 (6.00–7.00) ± 0.395 | 44.25 (44.25–47.25) ± 0.379 | |
7. | 0.74 | 1.35 (0.25–2.50) ± 0.43 | 20.30 (19.75–20.75) ± 0.16 | 27.10 (25.25–29.50) ± 0.78 | Absent | Absent | Absent | |
8. | 0.98 | 3.20 (2.75–3.75) ± 0.20 | 33.65 (32.00–35.75) ± 0.69 | 34.25 (33.25–37.00) ± 0.70 | 3.10 (1.25–4.25) ± 0.52 | 5.25 (4.00–6.00) ± 0.34 | 36.70 (33.75–38.50) ± 0.89 | |
9. | 3.53 | 4.90 (4.50–5.50) ± 0.20 | 52.00 (49.50–55.25) ± 0.72 | 24.16 (21.25–26.00) ± 1.02 | Absent | Absent | Absent | |
10. | 1.08 | 3.10 (2.75–3.50) ± 0.12 | 36.85 (31.00–40.25) ± 0.63 | 33.95 (29.50–37.00) ± 0.32 | 0.45 (0.25–0.75) ± 0.09 | 10.50 (10.25–10.75) ± 0.11 | 38.55 (38.00–39.50) ± 0.25 | |
11. | 0.96 | 1.65 (0.75–2.25) ± 0.28 | 28.85 (28.25–30.50) ± 0.42 | 29.80 (27.75–32.75) ± 0.86 | 8.45 (2.75–10.75) ± 0.50 | 8.45 (2.75–10.75) ± 0.50 | 14.100 (13.25–15.25) ± 0.35 |
1+ Pollen tetraporate, oblate-spheroidal, psilate ornamentation.................. | |
− Pollen tetrad, tricolporate...................... | 2 |
2 + Tetrad, oblong, psilate sculpturing.................... | |
2 − Tetrad, rhomboidal, reticulate sculpturing................. | |
3 + Tricolporate, oblate spheroidal, perforate-regulate exine............ | |
3 − Tricolporate, lobate, psilate-regulate sculpturing............. | |
4 + Oblate-spheroidal, tricolporate, perforate-scabrate................. | |
4 − Colporate, perforate exine sculpturing.................... | |
5 + Sub-spheroidal, reticulate exine, tricolporate............... | |
5 − Lobate, psilate-perforate exine................. | |
6 + Prolate-spheroidal, tricolporate, psilate to scabrate exine............. | |
6 − Colporus, micro-reticulate exine, lobate.................. |
Cluster analysis based on Euclidean distance was performed based on analytical pollen data of selected Apocynaceous species. Two major associations were formed, named Association C1 and Association C2. Association C1 consists of three species. These species have similarities based on colpi length and width and exine thickness. Association C2 consists of 15 species and these associations have similarities based on mesocolpium distance, polar and equatorial distance, and the P/E ratio, as shown in Figure 11. PCA analysis was used on the pollen quantitative mean data of Apocynaceae species to determine the variance among different variables in the context of eigenvariables. PCA illustration showed that the length of colpi on the PC1 axis of
PCA performed with the pollen quantitative data from Apocynaceous taxa. PCA, principal component analysis; CL, colpi length; CW, colpi width; ED, equatorial diameter; ET, exine thickness; MC, mesocolpium; PC, polar diameter.
PCA % variance loadings for the Apocynaceous pollen.
PC | Eigenvalue | % variance |
---|---|---|
1 | 2.35994 | 39.332 |
2 | 1.53998 | 25.666 |
3 | 1.0319 | 17.198 |
4 | 0.82796 | 13.799 |
5 | 0.239496 | 3.9916 |
6 | 0.000728 | 0.012128 |
PCA, principal component analysis.
The study on intraspecific pollen morphology variation in Apocynaceae is of significant importance as it provides a roadmap for horticultural innovation. Understanding these variations can aid in breeding programmes, helping to develop more resilient and productive cultivars. This research can also contribute to conservation efforts, as it aids in the preservation of genetic diversity within the family. Ultimately, the study’s findings have far-reaching implications for both horticulture and biodiversity conservation.
In the present study, the palynological traits of 18 Apocynaceae species were studied quantitatively and subjectively with the use of microscopy. The systematic study of palynomorphological features in flowering plants at higher taxonomic levels has considerably benefitted from the use of both a light and a scanning electron microscope (Al-Hakimi et al., 2015). Based on the traits of pollen that were studied, a taxonomy key was developed for fast and precise identification. Apocynaceae identification at the species level is too difficult because of its increased diversity and variable pollen and pollinia forms. The primary objective of this work was to morphologically evaluate the Apocynaceae family using pollen and pollinia to identify traits that would be helpful for taxonomic classification.
Previous studies that attempted to provide important and useful palynomorphological data on this family were unsuccessful in combining a comprehensive approach to pollens and pollinia in a single investigation. In this study, we present palynological studies on the Apocynaceae, which would help taxonomists correctly identify several highly significant plants. When examining pollen, microscopy is crucial for comprehending the taxonomic significance of plant species within families (Raza et al., 2020).
Colpi, mesocolpium, translator, corpusculum, exine sculpturing, aperture ornamentation, exine thickness, pollen type, size, polar and equatorial views, pollen sac length and width, pollinium ornamentation, pollinium shape and many other features were examined using SEM. These palynological characteristics are essential for correctly classifying different species in plant taxonomy (Ur Rahman et al., 2019).
The pollen grains and pollinia of the family Apocynaceae exhibited a considerable degree of morphological variety. Pollens ranged in size from small to quite large, and tricolpate to tetracolporate. Pollen shapes ranged from sub-spheroidal, to oblate spheroidal to rhomboidal, while exine sculptures ranged from psilate, through scabrate, to rugulate. Polar views were lobate, isopolar to irregular. On the other hand, in pollinia, the orientation was pendent to transverse, the shape was obovate to narrowly oblong, sterile margin was mostly absent and translator attachment to corpusculum was sub-apical to apical. The pollen of
In the present research,
In
The morphopalynological study linked to horticultural exploration harnesses the knowledge that contributed to the development of more resilient and productive horticultural practices within the Apocynaceae family.
Comparative studies of pollen structures among Apocynaceous taxa reveal that the taxonomy of exine wall characteristics has raised scholarly interest in pollen biology. This research focusses on the qualitative and quantitative micromorphological microscopic features of 18 Apocynaceae pollen. The microscopic authentication of closely related pollen characters of species is identified based on pollen taxonomy. The maximum mesocolpium distance was noted in