Microsoft Word - 07. Pollen of Verbascum-Revised_3.12.14_EE.doc


Bangladesh J. Plant Taxon. 21(2): 159-165, 2014 (December) 
© 2014 Bangladesh Association of Plant Taxonomists 

  POLLEN MORPHOLOGY OF VERBASCUM L. (SCROPHULARIACEAE) IN 
NORTHERN AND CENTRAL IRAQ 

 

MUAZAZ AL-HADEETHY, ATHIYA AL-MASHHADANI, TALIB AL-KHESRAJI1, SAHAPAT 
BARUSRUX2, HAZIM AL-JEWARI, PIYADA THEERAKULPISUT3 AND PIMWADEE 

PORNPONGRUNGRUENG3,4 
 

Department of Biology, College of Education-Ibn Al-Haitham, University of Baghdad,  
Baghdad, Iraq 

 

Keywords:  Pollen morphology; SEM; Taxonomy; Verbascum; Iraq. 
 

Abstract 
 The present study highlights the taxonomic values of the pollen features of 20 
species of Verbascum L. in Iraq. The pollen grains were acetolysed and observed under 
Light and Electron microscopes. Our results showed that the pollen grains of these 
species are usually radially symmetrical, isopolar, tricolporate and display reticulate 
sculpturing. The variations were found in shape, size, and exine thickness. Most of the 
species are subprolate, prolate spheroidal, and prolate, whereas oblate spheroidal pollens 
were found only in V. thapsus. The pollen size among the species studied ranges from 
16.2-32.5 µm. The majority of species are medium sized except V. agrimoniifolium and 
V. oreophilum that are small sized, and four species i.e. V. palmyrense, V. sinuatum, V. 
songaricum, and V. thapsus having both small and medium sized pollen grains. 
Moreover, the result showed that the exine thickness ranges from 0.87-4.75 µm, but this 
value can overlap between some species. Therefore, only the shape of pollen grains 
could be used to classify these species into groups. 

 

Introduction   
 The genus Verbascum L. (Scrophulariaceae) is mostly herbaceous with few shrubs and 
climbers, comprises about 350 species, and it is distributed all over the world (Zohary, 1974). 
Verbascum is widely spread in the Arabian Peninsula, especially in Saudi Arabia, Oman and 
Yemen (Huber-Morath, 1978; Ghadanfar, 1992; Wood, 1997). In Iraq, Verbascum is represented 
by 26 species (AL-Rawi, 1964; AL-Bermani, 1981). 
 The taxonomy of Verbascum species in Iraq is still uncertain, especially that as related to the 
geographical distribution of the species, the morphological variation and the condition of 
herbarium samples (AL-Bermani, 1981). Therefore, study of different characteristics would help 
in resolving the relationships and delimitation of these species. Pollen morphology is proved to be 
a useful character for improving the accuracy in the identification and classification of several 
plant groups (Erdtman, 1952; Rajbhandary et al., 2012; Özler et al., 2013; Sawar and Takahashi, 
2013). Despite pollen morphology of Verbascum species was studied by several authors (Erdtman, 
1952; Filippini et al., 1990; Perveen, 1993; Lobin and Pormbski, 1994; Bukhari and Alfarhan, 
2006; Kheiri et al., 2006; Pehlivan et al., 2008), the pollens of Verbascum found in Iraq has never 
been investigated. Therefore, this study was designed to investigate constant and diagnostic pollen 
morphological characteristics to be used as a tool for improving the accuracy in the identification 
and classification of Verbascum, and further authentication of the taxa. 
 
1Department of Biology, College of Education, University of Tikrit, Tikrit, Iraq  
2Centre for Research and Development of Medical Diagnostic Laboratories (CMDL), Faculty of Associated 

Medical Sciences, Khon Kaen University, Khon Kaen, Thailand 
3Applied Taxonomic Research Center, Department of Biology, Faculty of Science, Khon Kaen University, 

Khon Kaen, Thailand 
4Corresponding author: Email: ppimwa@kku.ac.th 



160 AL-HADEETHY et al. 

Materials and Methods 
 Pollen sample of 20 species of Verbascum L. grown in the north and central areas of Iraq, 
were collected between April 2012 and May 2013 (Table 1). The voucher specimens have been 
deposited in the herbarium of College of Education, Ibn Al-Haitham, University of Baghdad, Iraq. 
The pollen was prepared using the acetolysis method as described by Erdtman (1960). The 
measurements and observations were carried out using both Light microscope (LM) and Scanning 
Electron microscope (SEM). For LM analysis, the acetolysed pollens were placed in a small vial, 
and 5-7 drops of silicone oil were added, and then the samples were mounted on a glass slide 
sealed with paraffin and observed under light microscope. The measurements of polar axis (P), 
equatorial diameter (E) and exine thickness of pollen were done using 10 reading samples for each 
specimen. For SEM investigation, the acetolysed pollen was suspended in 100% ethanol. Then the 
suspension was dried on an aluminum stub, coated with gold and observed using LEO 1450VP 
Electron Microscopy. The terminology and pollen size classes follow Walker and Doyle (1975) 
and Punt et al. (1994). 
 
Table 1. List of Verbascum L.  species in Northern and Central of Iraq employed in the present study. 
 

Collection numbers Date of 
collections 

Locations Species 

M. AL-Hadeethy 166A14 Jun 2012 Sulaymaniyah Province 1. Verbascum agrimoniifolium   
   (C. Koch) Hub. - Mor. 

M. AL-Hadeethy 235 6 May 2012 Sulaymaniyah Province 2. V. alceoides Boiss. & Hausskn. ex 
Boiss. 

M. AL-Hadeethy 245 11 May 2013 Nineveh Province 3. V. alepense Benth. 
M. AL-Hadeethy 129 27 Jun 2012  Nineveh Province 4. V. andrusii Post 
M. AL-Hadeethy 172 4 Apr 2012 Diyala Province 5. V. assurense (Bornm. & Hand. - 

Mazz.) Hub. - Mor. 
M. AL-Hadeethy 250 14 Jun 2012 Sulaymaniyah Province 6. V. calvum Boiss. & Kotschy ex 

Boiss.  
M. AL-Hadeethy 168 21 Apr 2012 Sulaymaniyah Province 7. V. carduchorum Bornm. 
M. AL-Hadeethy 225 4 May 2012 Sulaymaniyah Province 8. V. cheiranthifolium Boiss.  
M. AL-Hadeethy 152 5 Apr 2013 Anbar Province 9. V. damascenum Boiss.  
M. AL-Hadeethy 230 6 May 2012 Sulaymaniyah Province 10. V. geminiflorum Hochst. 
M. AL-Hadeethy 144 20 Apr 2012 Sulaymaniyah Province 11. V. laetum Boiss. & Hausskn. ex 

Boiss. 
M. AL-Hadeethy 200A4 May 2012 Sulaymaniyah Province 12. V. macrocarpum Boiss. 
M. AL-Hadeethy 223 5 May 2012 Sulaymaniyah Province 13. V. oreophilum C. Koch 
M. AL-Hadeethy  220 27 Jun 2012 Nineveh Province 14. V. palmyrense Post 
M. AL-Hadeethy 123 20 Apr 2012 Sulaymaniyah Province 15. V. pseudodigitalis Nábělek 
M. AL-Hadeethy 112 27 Jun 2012 Nineveh Province 16. V. sinaiticum Benth. 
M. AL-Hadeethy 166B7 Aug 2012 Kirkuk Province 17. V. sinuatum L. 
M. AL-Hadeethy 200B4 May 2012 Sulaymaniyah Province 18. V. songaricum Schrenk 
M. AL-Hadeethy 182 21 Apr 2012 Sulaymaniyah Province 19. V. speciosum Schrad. 
M. AL-Hadeethy 145 20 Apr 2012 Sulaymaniyah Province 20. V. thapsus L.  

 



POLLEN MORPHOLOGY OF VERBASCUM L. 161 

 

Results and Discussion 
 The results of the pollen morphology of Verbascum are summarized in Table 2. It was found 
that the pollen morphology of the species studied is uniform. The general characteristic is monad, 
radially symmetrical, isopolar, tricolporate and reticulate in exine sculpturing (Figs 1 & 2).  
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 1. SEM micrographs of the pollen grains of Verbascum. A, B. V. agrimoniifolium; C, D. V. alceoides; E, 

F. V. alepense; G, H. V. andrusii; I, J. V. assurense; K, L. V. calvum; M, N. V. carduchorum; O, P. V. 
cheiranthifolium; Q, R. V. damascenum; S, T. V. geminiflorum; A, G, I, K, M and Q. polar view; B, D, 
F, H, J, L, N, P, R and T. exine sculpturing; C, E, O, S. equatorial view (Scale bar = 2 µm). 



162 AL-HADEETHY et al. 

Table 2. Pollen morphological characteristics of Verbascum in Northern and Central Iraq. 
 

Species Polar axis 
(µm) 

Equatorial axis 
(µm)  

P/E 
Ratio 

Shape Size Exine 
thickness (µm) 

Exine 
sculpturing

1. V. agrimoniifolium 16.5-20.5 
(17.54±1.39) 

15.5-21.0 
(17.39±1.65) 

1.01 Prolate 
spheroidal 

small 0.87-1.05 
(0.93±0.10) 

Reticulate 

2. V. alceoides 27.5-32.5 
(28.05±1.78) 

22.5-25.0 
(24.13±1.13) 

1.16 Subprolate medium 2.75-3.00 
(2.65±0.41) 

Reticulate 

3. V. alepense 25.0-27.5 
(26.38±1.04) 

21.3-22.5 
(21.88±0.63) 

1.21 Subprolate medium 3.00-3.72 
(3.22±0.39) 

Reticulate 

4. V. andrusii 26.25-27.5 
(26.88±0.63) 

18.8-20.0 
(19.25±0.61) 

1.40 Prolate medium 1.25-2.5 0 
(2.15±0.48) 

Reticulate 

5. V. assurense 27.5-32.5 
(30.88±1.68) 

25.0-27.5 
(26.50±1.22) 

1.17 Subprolate medium 3.75-4.25 
(4.18±0.44) 

Reticulate 

6. V. calvum 27.5-30.0 
(29.00±1.09) 

22.5-25.0 
(24.13±1.13) 

1.20 Subprolate medium 1.25-2.5 0 
(2.08±0.51) 

Reticulate 

7. V. carduchorum 25.0-28.8 
(27.13±1.38) 

22.5-25.0 
(24.00±1.22) 

1.13 Prolate 
spheroidal 

medium 3.25-4.00 
(3.13±0.76) 

Reticulate 

8. V. cheiranthifolium 26.3-27.5 
(26.88±0.63) 

20.0-22.5 
(21.38±1.18) 

1.26 Subprolate medium 1.25-2.5 0 
(2.00±0.58) 

Reticulate 

9. V. damascenum 27.5-30.0 
(29.25±1.00) 

20.0-22.5 
(21.6±0.98) 

1.35 Prolate medium 3.75-4.75 
(4.00±0.58) 

Reticulate 

10. V. geminiflorum 26.25-27.5 
(26.50±0.93) 

20.0-22.5 
(21.13±1.04) 

1.25 Subprolate medium 3.00-4.75 
(3.58±1.28) 

Reticulate 

11. V. laetum 30.0-32.5 
(31.23±0.97) 

23.8-25.0 
(24.50±0.61) 

1.27 Subprolate medium 2.50-3.75 
(3.05±0.46) 

Reticulate 

12. V. macrocarpum 27.5-28.8 
(28.13±0.63) 

20.0-22.5 
(21.75±1.00) 

1.29 Subprolate medium 2.50-3.75 
(3.23±0.52) 

Reticulate 

13. V. oreophilum 19.1-22.5 
(20.71±0.61) 

18.8-20.0 
(19.25±0.61) 

1.08 Prolate 
spheroidal 

small 1.75-2.50 
(1.90±0.53) 

Reticulate 

14. V. palmyrense 22.5-25.0 
(24.00±1.09) 

20.0-22.5 
(21.25±1.12) 

1.13 Prolate 
spheroidal 

small- 
medium 

1.25-2.5 0 
(2.05±0.53) 

Reticulate 

15. V. pseudodigitalis 27.5-30.0 
(28.75±0.97) 

20.0-21.3 
(20.88±0.57) 

1.38 Prolate medium 2.25-2.50 
(2.53±0.21) 

Reticulate 

16. V. sinaiticum 27.5-30.0 
(29.13±0.98) 

20.0-21.3 
(20.88±0.57) 

1.40 Prolate medium 1.50-2.5 0 
(2.00±0.49) 

Reticulate 

17. V. sinuatum 19.6-25.2 
(23.86±1.09) 

20.6-23.2 
(23.55±0.61) 

1.01 Prolate 
spheroidal 

small -
medium 

2.00-2.5 0 
(2.30±0.22) 

Reticulate 

18. V. songaricum 23.8-26.3  
(25.38±0.98) 

20.0-21.3 
(20.38±0.57) 

1.25 Subprolate small -
medium 

1.25-3.00 
(2.13±0.75) 

Reticulate 

19. V. speciosum 25.0-27.5 
(26.50±1.09) 

20.0-22.5 
(21.25±1.25) 

1.25 Subprolate medium 3.50-4.00 
(3.70±0.29) 

Reticulate 

20. V. thapsus 22.5-25.0 
(23.75±0.77) 

24.0-27.0 
(25.00±0.50) 

0.95 Oblate-
spheroidal 

small -
medium 

1.24-2.16 
(1.91±0.35) 

Reticulate 

 

 In Verbascum, pollen grains vary in shape, size and exine thickness. The shape can be prolate 
spheroidal, subprolate, prolate and oblate-spheroidal. The pollens are small to medium-sized. Most 
of the species have medium-sized pollens (25.0-32.5 µm) except in V. agrimoniifolium and V. 
oreophilum, where small-sized pollens (16.5-24.0 µm) are observed. Verbascum palmyrense, V. 
sinuatum, V. songaricum, and V. thapsus have both small and medium sized pollen grains. The 
polar axis (P) ranged from 16.5-32.5 µm. The largest polar axis was recorded in V. alceoides, V. 
assurense and V. laetum with 32.5 µm long and the smallest was found in V. agrimoniifolium with 



POLLEN MORPHOLOGY OF VERBASCUM L. 163 

 

16.5 µm long. The equatorial diameter (E) ranged from 15.5-27.5 µm and the largest one was 
present in V. assurense with 27.5 µm, while the smallest was found in V. agrimoniifolium. In 
addition, the exine thickness of the pollen of species studied ranged from 0.87 to 4.75 µm.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 2.  SEM micrographs of the pollen grains of Verbascum. A, B. V. laetum; C, D. V. macrocarpum; E, F. 

V. oreophilum; G, H. V. palmyrense; I, J. V. pseudodigitalis; K, L. V. sinaiticum; M, N. V. sinuatum; O, 
P. V. songaricum; Q, R. V. speciosum; S, T. V. Thapsus; A, E, K, M, O, Q and S. polar view; B, D, F, H, 
J, L, N, P, R and T. exine sculpturing; C, G and I. equatorial view (Scale bar = 2 µm).   

 

 The overlapping of exine thickness is found among the taxa studied, thus this character is of 
little taxonomic value. Results obtained from the present study agree with previous studies on 
some species of Verbascum (Erdtman, 1952; Filippini et al., 1990; Lobin and Pormbski, 1994; 



164 AL-HADEETHY et al. 

Bokhri and Alfarhan, 2006; Asmat et al., 2011). Several authors reported two types of exine 
sculpturing for Verbascum i.e. microreticulate and macroreticulate (Kheiri et al., 2006; Pehlivan et 
al., 2008; Karavelіoğullari et al., 2010). Pehlivan et al. (2008) concluded that the pollen 
morphological characteristics observed under the light microscope seems to have little value for 
taxonomic study but the sculpturing investigated under SEM provides a better result for dividing 
the Verbascum taxa into two groups with reticulate and coarsely reticulate. However, all taxa 
included in our study showed a uniform reticulate exine sculpturing pattern.  
 Our results showed that only the shape of pollen grains can be used for grouping the 
Verbascum into four groups viz. the Subprolate group including: V. alceoides, V. alepense, V. 
assurense, V. calvum, V. cheiranthifolium, V. geminiflorum, V. laetum, V. macrocarpum, V. 
songaricum, V. speciosum, the Prolate spheroidal group including: V. agrimoniifolium, V. 
carduchorum, V. oreophilum, V. palmyrense, and V. sinuatum; the Prolate group includes: V. 
andrusii, V. damascenum, V. pseudodigitalis, V. sinaiticum and the Oblate spheroidal with only 
one species V. thapsus. Even though the pollen characters alone cannot be used for species 
identification, they provide some information for the classification of these plants. Moreover, 
using this character in combination with other characters may help in clarifying some problematic 
taxa.  
 
Acknowledgement 
 We gratefully acknowledge the staff of the Department of Biology, Faculty of Science, Khon 
Kaen University (KKU), Thailand, for their technical support and laboratory assistance. This study 
was supported by grants from the Scholarships & Cultural Affairs Directorate, Ministry of Higher 
Education Scientific Research, Iraq.  
 
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(Manuscript received on 3 July 2014;  revised on 3 December 2014)