Pollen morphology of trees, shrubs and woody herbs of the coastal plain and the monsoon slopes of...

Dhofar is a wide region situated in southern Oman,bordering with Yemen and Saudi Arabia. The area ischaracterised by the presence of a plain which lies alongthe coast of the Arabian Sea, at the foot of the steepslopes of the escarpment which rise towards the desertplateau of the Arabian peninsula. The coastal plain is in-terrupted by numerous small estuaries of wadies, whichare often separated from the open sea by sand barriersand contain fresh water.

The coast and the slopes are influenced by Monsoonregime which causes moistness and rains during sum-mer: the clouds are not able to rise over the escarpmentand release precipitations on its slopes.

The coastal plain is covered by a semi-desert grass-land with scattered small trees and xerophytic shrubswhich generally increase towards inland. Wetland vege-tation occurs along wadis and estuaries. In eastern Dho-far, woodlands cover the slopes of the escarpment; scat-tered plants occur on the dry slopes approaching theYemen border, at west.

A Flora of Dhofar was published by Miller and Mor-ris (1988) and many plant groups have been and still areobject of investigation. Numerous papers were devotedto the study of Boswellia sacra Flueck., the frankincensetree, a plant economically important for the trade of its

Pollen morphology of trees, shrubs and woody herbs of the coastal plain and the monsoon slopes of Dhofar (Sultanate of Oman)

M. MARIOTTI LIPPI, T. GONNELLI, M. RAFFAELLI.

Dipartimento di Biologia Vegetale dell’ UniversitàVia G. La Pira 4, I-50121 Firenze

Accettato il 19 Settembre 2007

Morfologia pollinica di alberi, arbusti e erbe perenni della pianura costiera e dei versanti monsonici del Dhofar (Sultanato diOman) – Il presente lavoro è dedicato alla morfologia pollinica delle più comuni piante arboree, arbustive ed erbaceeperenni che crescono in Dhofar, nell’Oman meridionale. Vengono anche riportate informazioni sull’habitus delle pian-te e sul loro ambiente di crescita.

Key word: Dhofar, pollen morphology, Oman, shrubs, trees.

resin, from ancient time. B. sacra grows on the arid slopesof western Dhofar, in the mountains near Hasik, and inpre-desert areas at the edge of the Arabian plateau(Thulin & Warfa, 1987; Raffaelli et al., 2003a,b, 2006).An annotated catalogue of the vascular plants of Oman(Ghazanfar, 1992) and a Flora of Oman, including theFlora of Dhofar, is in progress (Ghazanfar, 2003).

The pollen morphology of the plants which grow inthis area is poorly known. The pollen Flora of Qatar (El-Ghazaly, 1991) is the only exhaustive study in the Ara-bian Peninsula. However, it includes mainly the speciesoccurring in the plateau and covers only a small part ofthe plants growing in Dhofar. The only other useful ref-erence palynoflora seems to be that of African savanes(Bonnefille & Riollet, 1980). This statement underlinesthe affinities between Arabian peninsula and EastAfrica, from a floristic point of view. However, thepollen morphology of many species is still unstudied.Also paleopalinological investigations carried out insouthern Oman are scarce (Lezine et al., 2002; Mariot-ti Lippi, 2002; Hoorn & Cremaschi, 2004).

The aim of this paper is to improve the knowledgeof the pollen morphology of the most common trees,shrubs and woody herbs widespread in the coastal plainand the escarpment of Dhofar (Fig. 1).

Webbia 62(2): 245-260. 2007

Centro Studi Erbario Tropicale, Università di Firenze - Pubbl. n. 110.

M. Mariotti Lippi, T. Gonnelli, M. Raffaelli246

Salalah

Thumrayt

Mirbat

Sadh

Habdin

Hasik

Mare Arabico

Jabal Samhan

Wad

i Hal

it

Wad

i Sal

afab

Wad

i And

ur

Jibjat

Barbazum

Dahabun

1812

Haluf

Al Mughsayl

Ajdarawt

Mudayy

Ashanhib

30 Km

Oman

Dhofar

Ghadow

W.Darbat

Khor RoriTaqah

TawiAttayr

W. Ayn Hilf

Fig. 1 – Dhofar: the grey circles show the localities of plants collection, as reported in Table 1

Materials and Methods

Pollen grains were directly collected from plantsgrowing in Dhofar (Table 1). Reference vouchers ofthe examined species are deposited in the TropicalHerbarium Studies Centre of Florence (FT).

The pollen morphology was studied under lightmicroscope (LM) and under scanning electron mi-croscope (SEM). For LM analysis, pollen grains weredehydrated, acetolyzed (Erdtman, 1969) and placedin a 50% water/glycerol solution. For SEM analysis,acetolyzed pollen grains were washed in acetone,dried, and then gold-coated.

All the measurements were taken from at least 30grains per sample, using a LM. For each pollen-type,the subsequent measurements are given: a) length ofthe polar axis (P) and equatorial axis (E) and their ra-tio (P/E), or the diameter (D) when the grains werespherical; in some cases two equatorial axes are identi-

fied: one larger (Emax) and one smaller (Emin); b)mean diameter of pores and/or mean length of colpiand pseudocolpi; c) mean exine thickness in the mid-dle of the mesocolpium. Other useful parameters arereported, varying from species to species.

Terminology is according to Punt et al. (1994).

Results

ACANTHACEAE

Bentia fruticulosa Rolfe - (Plate I, 1-5)Shape: prolate. P/E ratio about 1.6.Outline in polar view: obtuse quadrangular.Outline in equatorial view: elliptic.Dimensions (µm):

MEAN VALUE MIN MAX MODE

P 65.5 56 72 65 E 41 38 49.5.0 38

Pollen morphology of trees, shrubs and woody herbs of the coastal plain … 247

Species site date collectors

Acacia nilotica (L.) Willd. Al Mughsayl 24.04.01 M.Raffaelli, M.Tardelli, S.Mosti

Acacia senegal (L.) Willd. Wadi Darbat 20.03.04 M.Raffaelli, M.Tardelli, S.Mosti

Acacia tortilis (Forssk.) Hayne between Mirbat and Sadh 25.04.01 M.Raffaelli, M.Tardelli, S.Mosti

Adenium obesum (Forssk.) Roem.

et Schult. pass to Thumrayt 14.03.03 M.Mariotti Lippi, T.Gonnelli, G.Lippi

Anogeissus dhofarica A.J. Scott Tawi Attayr 28.04.01 M.Raffaelli, M.Tardelli, S.Mosti

Bentia fruticulosa Rolfe Wadi Darbat 15.03.03 M.Mariotti Lippi, T.Gonnelli, G.Lippi

Blepharispermum hirtum Oliv. hills near Salalah 30.06.01 M.Raffaelli, M.Tardelli, S.Mosti

Boscia arabica Pestalozzi Khor Rori 12.03.03 M.Mariotti Lippi, T.Gonnelli, G.Lippi

Boswellia sacra Flueck. Al Mughsayl 13.03.03 M.Mariotti Lippi, T.Gonnelli, G.Lippi

Cadaba farinosa Forssk. Khor Rori 11.03.03 M.Mariotti Lippi, T.Gonnelli, G.Lippi

Capparis cartilaginea Decne. Al Mughsayl 13.03.03 M.Mariotti Lippi, T.Gonnelli, G.Lippi

Cleome brachycarpa Vahl ex DC. Khor Rori 12.03.03 M.Mariotti Lippi, T.Gonnelli, G.Lippi

Cleome noeana Boiss. ssp. noeana Wadi Ayn Hilf. 6.09.02 M.Raffaelli, M.Tardelli, S.Mosti

Cassia holosericea Fresen. Taqah 11.03.03 M.Mariotti Lippi, T.Gonnelli, G.Lippi

Commiphora foliacea Sprague Sadh 22.03. 04 M.Raffaelli, M.Tardelli, S.Mosti

Fagonia luntii Baker Al Mughsayl 10.09.02 M.Raffaelli, M.Tardelli, S.Mosti

Grewia damine Gaertn. (syn.

G. bicolor Juss.) Al Mughsayl 19.03.04 M.Raffaelli, M.Tardelli, S. Mosti

Jasminum grandiflorum L. ssp.

floribundum (Fresen.) P.S. Green Tawi Attayr 22.09.01 M.Raffaelli, M.Tardelli, S.Mosti

Jatrofa dhofarica A. Radcliffe-Smith Wadi Darbat 15.03.03 M.Mariotti Lippi, T.Gonnelli, G.Lippi

Justicia diffusa Willd. Wadi Darbat 15.03.03 M.Mariotti Lippi, T.Gonnelli, G.Lippi

Maytenus dhofarensis Sebsebe Wadi Darbat 17.02.04 M.Mariotti Lippi, T.Gonnelli, G.Lippi

Ochradenus baccatus Delile Al Mughsayl 24.02.05 M.Mariotti Lippi, T.Gonnelli, G.Lippi

Olea europaea L. Ghadow 26.09.01 M.Raffaelli, M.Tardelli, S.Mosti

Plumbago zeylanica L. Tawi Attayr 22.09.01 M.Raffaelli, M.Tardelli, S.Mosti

Prosopis cineraria (L.) Druce Khor Rori 12.03.03 M.Mariotti Lippi, T.Gonnelli, G.Lippi

Ruellia patula Jacq. Khor Rori 13.03.03 M.Mariotti Lippi, T.Gonnelli, G.Lippi

Ruttya fruticosa Lindau Tawi Attayr 22.09.01 M.Raffaelli, M.Tardelli, S.Mosti

Salvadora persica L. N of Ashanhaib 23.10.00 M.Raffaelli, M.Tardelli, S.Mosti

Senra incana(Cav.) DC. Khor Rori 12.03.03 M.Mariotti Lippi, T.Gonnelli, G.Lippi

Ziziphus leucodermis (Baker)

O. Schwartz Al Mughsayl 27.04.01 M.Raffaelli, M.Tardelli, S.Mosti

Ziziphus spina-christi (L.) Willd. Al Mughsayl 19.03.04 M.Raffaelli, M.Tardelli, S.Mosti

Table 1 – The investigated species: name, site, date of collection and collectors (see also fig. 1).


Pollen class: heterocolpate with 3 colpori and 6colpi anastomosing in pair at the endings. Some grains(13%) are tetracolporate with 8 colpi.

Apertures: anastomosing colpi delimit a small polartriangle, or square. Colpori about 46 µm long; ora la-longate, about 9.5 µm x 7 µm, with a spinulate borderand two lateral raised areas of sexine (lips) .

Exine: tectate perforate suprareticulate homo-brochate, about 3 µm thick. Trema area perforated.

Plant habit: branched shrub up to 1.5 m tall.Habitat: woodlands on the south slopes of the

coastal mountains.

Justicia diffusa Willd. - (Plate I, 6-8) Shape: bilateral. The ratio P/Emax is about 1.4;

Emax/Emin is about 1.5.Outline in polar view: elliptic. Outline in equatorial view: elliptic.Dimension µm):


P 30 27 33.5 29Emax 20 18 22.5 20Emin 14 11 15.5 13.5

Pollen class: dicolporate.Apertures: colpori very narrow, about 24 µm long;

ora quite circular to lalongate, about 3.7 µm x 2.3 µm.A little granulate stopple projecting from each pore ispresent.

Exine: Peripheral area (mesocolpium) tectate perfo-rate suprareticulate homobrochate, about 2.3 µmthick in the polar area and 0.7 µm at the equatoriallevel. Trema area quite rectangular in shape, some-times showing a slight median constriction, intectate,granulate, usually occupied by two rows (one for side)of 6 insulae, about 2.15 µm in diameter and similar toperipheral area in exine sculpturing; the insulae nearthe poles are often connected to the peripheral exine.

Plant habit: perennial herb.Habitat: dry and open places from the coastal plain

to the top of the southern slopes of the mountains.

Ruellia patula Jacq. - (Plate I, 9-11)Shape: spheroidal.Outline in polar view: circular.Outline in equatorial view: circular.Dimensions (µm):


D 74 63 83 72

Pollen class: tri-pentaporate. Apertures: pore subcircular, about 8 µm in diameter.Exine: semitectate reticulate simplicolumellate, ho-

mobrochate, about 4.5 µm thick; lumina about 9 µmwide with wavy outline and numerous short pila in themeshes.

Plant habit: perennial herb.Habitat: wadi beds and dry areas.

Ruttya fruticosa Lindau - (Plate I, 12-14)Shape: spheroidal to subprolate-spheroidal. P/E ra-

tio about 1.1.Outline in polar view: circular.Outline in equatorial view: circular or elliptic.Dimensions (µm):


P 57 49.5 65.5 56.5E 53 41.5 60 55

Pollen class: heterocolpate with 3 colpori and 6colpi.

Apertures: colpori 40-45 µm long, longer thancolpi; colpus membrane scabrate. Ora circular, about10 µm in diameter, or slightly lalongate.

Exine: semitectata, microreticulata, about 2.5 µmthick.

Plant habit: shrub or small tree up to 3 m tall.Habitat: woodlands on the southern slopes of the

coastal mountains

NOTE: pollen grains of Acanthaceae, particularlyBentia, Justicia and Ruellia, appreciably decrease in sizeduring the preparation for SEM analysis.

APOCYNACEAE

Adenium obesum (Forssk.) Roem. et Schult. - (Plate I,15-17)

Shape: oblate spheroidal. P/E ratio about 0.9.Outline in polar view: spheroidal.Outline in equatorial view: subspheroidal.Dimensions (µm):


P 38 32 45 36 E 43 37 49 45


Pollen class: tetraporate or triporate.Apertures: 4, sometimes 3, well defined pores about

5 µm in diameter, irregularly spaced, surrounded by athin smooth annulus.

Exine: tectate, about 2.5 µm in thickness. Tectumimperforate, slightly scabrate, standing on columellaewhich are ramified at the distal end.

Plant habit: succulent shrub or tree 0.2-4 m tall.Habitat: dry places, from the coastal plain to the

southern slopes of the mountains, to the northern pre-desertic area.

BURSERACEAE

Boswellia sacra Flueck. - (Plate I, 18-21)Shape: subprolate. P/E ratio about 1.2.Outline in polar view: circular to triangular.Outline in equatorial view: elliptic.Dimensions (µm):


P 56 47 63 56 E 48 43 56 49.5

Pollen class: tricolporate.Apertures: colpori about 40 µm long, tapering at

both the ends, with costae thickened at the equator;colpus membrane scabrate. Ora circular, about 5.5 µmin diameter.

Exine: tectate perforate, 2-2.3 µm in thickness; per-forations less than 1 µm wide, irregularly distributed.

Plant habit: tree up to 6-7 m tall, commonlybranched from the base, rarely with a single trunk.

Habitat: north pre-desertic area behind the coastalmountains, but also on the hills and the mountainousslopes facing the Indian Ocean.

Commiphora foliacea Sprague - (Plate I, 22-24)Shape: spheroidal.Outline in polar view: circular.Outline in equatorial view: circular.Dimensions (µm):


D 28 25 29 29

Pollen class: tricolporate.Apertures: short colpori protruding, 8-10 µm long.

Ora circular, about 4 µm in diameter.Exine: semitectate reticulate, simplicolumellate,

homobrochate, microechinate, about 2 µm thick.Reticulum continuous all over the surface; lumina non

homogeneous. Very sharp microspines aligned on themura.

Plant habit: dioecious shrub, non-spiny, manybranched, up to 1.5-2 m tall.

Habitat: hilly and mountainous drier areas.

CAPPARACEAE

Boscia arabica Pestalozzi - (Plate I, 25-27)Shape: subprolate. P/E ratio about 1.2.Outline in polar view: triangular.Outline in equatorial view: elliptic.Dimensions (µm):


P 30.5 29.5 34 29.5E 25.5 22.5 27 25

Pollen class: tricolporate.Apertures: colpori about 21 µm long, parallel or

slightly tapering at the ends, with smooth colpusmembrane. Ora lalongate or circular, in this case about4.5 µm in diameter.

Exine: tectate, perforate, microechinate, about 4µm thick in the mesocolpia. Columellae distinct,tightly close together, simple or digitate, longer in themesocolpia and at the poles. Microspine stout, irregu-larly spaced.

Plant habit: evergreen tree up to 5-6 m tall.Habitat: hills at the base of southern slopes of the

coastal mountains.

Cadaba farinosa Forssk. - (Plate II, 1-5)Pollen shape: subprolate to prolate. Mean P/E ratio

1.3.Outline in polar view: trilobate.Outline in equatorial view: elliptic.Dimension (µm):


P 27.5 22.5 29.5 27E 21.5 18 23.5 22.5

Pollen class: tricolporate.Apertures: colpori about 22 µm long, tapering at

the ends, with smooth colpus membrane. Ora with ill-defined limit, about 4 µm wide, covered by scabrousectexine elements.

Exine: tectate perforate, microechinate, about 2 µmthick. Columellae simple or, rarely, digitate, differentin diameter. Microspines irregularly spaced, often withhooked apex, some 1 µm long.


Plate I – Fig. 1-5 Bentia fruticulosa: 1. SEM, equatorial view; 2. SEM, polar view; 3. SEM, detail of the exine; 4. LM, equatorial view,high focus; 5. LM, equatorial view, optical cross-section. Fig. 6-8 Justicia diffusa: 6. SEM, equatorial view showing trema area; 7. SEM,equatorial view; 8. LM, equatorial view, optical cross-section. Fig. 9-11 Ruellia patula: 9. LM, high focus ; 10. SEM ; 11, SEM detailof the exine. Fig. 12-14 Ruttya fruticosa: 12. SEM; 13. LM, equatorial view; 14. LM, polar view. Fig. 15-17 Adenium obesum: 15. SEM;16. LM, optical cross-section; 17. LM, high focus. Fig. 18-21 Boswellia sacra: 18. SEM, equatorial view; 19. SEM, polar view; 20. LM,polar view; 21. LM, equatorial view. Fig. 22-24 Commiphora foliacea: 22. SEM, polar view; 23. LM, polar view; 24. equatorial view.Fig. 25-27 Boscia arabica: 25. SEM, equatorial view; 26. LM, polar view; 27. LM, equatorial view.


Plant habit: shrub up to 2 m tall.Habitat: drier areas, on rocky slopes, gravel plains

and open woodlands.

Capparis cartilaginea Decne. - (Plate II, 6-10)Pollen shape: subprolate. P/E ratio 1.14.Outline in polar view: trilobate.Outline in equatorial view: elliptic.Dimension (µm):


P 18 16 19 18 E 16 16 17 16

Pollen class: tricolporate.Apertures: colpori geniculata converging at the

poles, about 14 µm long; colpus membrane smooth.Ora circular, protruding from colpi, covered by ectex-ine granules.

Exine: tectate with indistinct, minute perforations,about 1.5 µm in thickness. Sexine surface scatteredwith minute, faint microspines with a large basis.

Plant habit: evergreen spiny shrub, climbing andoften hanging from cliffs.

Habitat: drier areas on cliffs and rocky places.

Cleome brachycarpa Vahl ex DC. (Plate II, 11-14)Pollen shape: spheroidal.Outline in polar view: circular.Outline in equatorial view: circular.Dimension (µm):


D 16 13.5 18 16

Pollen class: tricolporate.Apertures: colpori about 11 µm long, with uneven

margins; colpus membrane granulate. Ora inconspic-uous, often not discernible due to overlying granules.

Exine: tectate perforate microverrucate, 2-2.5 µmin thickness. Sexine slightly thicker than nexine.

Plant habit: perennial herb, 10-30 cm tall.Habitat: drier areas, common in the wadi beds.

Cleome noeana Boiss. ssp. noeana - (Plate II, 15-19)Pollen shape: subprolate. P/E ratio about 1.2.Outline in polar view: circular.Outline in equatoril view: elliptic.Dimension (µm):


P 31 27 36 31.5E 26.5 20.5 29.5 27

Pollen class : tricolporate.Apertures: colpori about 22.5 µm long, tapering at

the ends, the middle portion occupied by scabrousectexine elements which cover the ora.

Exine: tectate perforate suprareticulate, about 2 µmthick. Reticulum heterobrochate, simplicolumellate,with circular-elongate lumina. Longitudinal muri gen-erally more pronounced than the transversal ones. Per-forations 1-3 per lumen.

Plant habit: perennating or perennial herb or smallshrub, 15-50 cm tall.

Habitat: stony wadi beds.

CELASTRACEAE

Maytenus dhofarensis Sebsebe - (Plate II, 20-24)Pollen shape: spheroidal to subprolate. Mean P/E

ratio 1.1.Outline in polar view: circular.Outline in equatorial view: subcircular.Dimension (µm):


P 26.5 25 31.5 27 E 25 22.5 27 25

Pollen class: tricolporate.Apertures: colpi well distinct, tapering at the ends,

about 18 µm long, apparently interrupted at the equa-tor; colpus membrane scabrous, covered by micro-granules. Ora lalongate to subcircular, about 3.5 µmwide, protruding.

Exine: semitectate reticulate, simplicolumellate,heterobrochate. Lumina irregular in shape, generallymore than 1 µm large, abruptly decreasing in size to-wards the colpi edges.

Plant habit: spiny shrub or small tree, 2-3 m tall.Habitat: woodlands on the south costal mountains

and dry plateaux.

COMBRETACEAE

Anogeissus dhofarica A.J. Scott - (Plate II, 25-29)Pollen shape: subprolate. P/E ratio about 1.25.Outline in polar view: oval.Outline in equatorial view: esalobate.Dimension (µm):


Plate II – Fig. 1-5 Cadaba farinosa: 1. SEM, equatorial view; 2. SEM, detail of the exine; 3. LM, polar view; 4. LM, equatorial view,optical cross-section; 5. LM, equatorial view, high focus. Fig. 6-10 Capparis cartilaginea: 6. SEM, equatorial view; 7. SEM, polar view;8, LM, polar view; 9. LM, equatorial view, high focus; 10. LM, equatorial view, optical cross-section. Fig. 11-14 Cleome brachycarpa:11. SEM, equatorial view; 12. LM, equatorial view, high focus; 13. LM, equatorial view, optical cross-section; 14. LM, polar view. Fig.15-19 Cleome noeana: 15. SEM, equatorial view; 16. SEM, polar view; 17. LM, equatorial view, high focus; 18. LM, equatorial view,optical cross-section; 19. LM, polar view. Fig. 20-24 Maytenus dhofarensis: 20. SEM, equatorial view; 21. SEM, polar view; 22. LM,equatorial mesocolpial view; 23. LM, equatorial apertural view; 24. LM, polar view. Fig. 25-29 Anogeissus dhofarica: 25. LM, equato-rial view; 26. LM, polar view; 27, 28. SEM, equatorial view; 29. SEM, quite polar view.



P 16.5 16 18 17 E 15 13.5 16 16

Pollen class: heterocolpate with 3 colpores and 3colpi.

Apertures: colpori about 13 µm long, with granu-late colpus membrane. Ora circular or approximatelysquared, sometimes slightly rectangular. Colpi shorterthan colpori, about 11 µm long, with granulate colpusmembrane.

Exine: tectate, about 4 µm thick. Tectum imperfo-ratum, covered by almost regularly scattered acute mi-crospines, sometimes transversally coalescent, andforming transversal short crestae.

Plant habit: deciduous tree up to 12 m tall.Habitat: common tree forming luxuriant woods on

the south slopes of the monsoon coastal mountains.

COMPOSITAE

Blepharispermum hirtum Oliv. - (Plate III, 1-5)Pollen shape: spheroidal to subprolate.Outline in polar view: circular.Outline in equatorial view: circular to subcircular.Dimension including spines (µm):


P 36,5 31.5 38.5 36 E 33 22,5 38.5 34

Pollen class: tricolporate.Apertures: colpori tapering at the ends, about 22

µm long; colpus membrane granulate. Ora distinct,circular, less than 2 µm in diameter.

Exine: tectate perforate echinate, 7-8 µm in thick-ness including spinae, these last about 5 µm long,smooth, broad at the bases and gradually tapering to-wards the apices.

Plant habit: deciduous shrub or small tree, 3-3.5 mtall.

Habitat: woodlands on the foothills and southslopes of the coastal mountains.

EUPHORBIACEAE

Jatrofa dhofarica A. Radcliffe-Smith - (Plate III, 6-9)Pollen shape: spheroidal.Outline in polar view: circular.Outline in equatorial view: circular.Dimension (µm):


D 66 59 76.5 65.5

Pollen class: inaperturate.Exine: retipilate, about 4.5 µm thick. Pila with

short columellae, less than 1 µm high, and veryswollen capita, longitudinally costate, tightly close to-gether. The capita appear subsphaerical in transversalsection, about 2 µm in diameter, and quite triangularin tangential view, due to the contiguity with the ad-jacent ones.

Plant habit: deciduous shrub, 1-3 m tall.Habitat: coastal plain, foothills, south mountain-

ous slopes in dry habitats and woodland clearings.

LEGUMINOSAE

Cassia holosericea Fresen. - (Plate III, 10-15)Pollen shape: spheroidal to subprolate.Outline in polar view: triangular.Outline in equatorial view: oval.Dimension (µm):


P 32 29.5 36 29.5 E 28 25 31.5 27

Pollen class: tricolporate.Apertures: colpori geniculate, equatorially costrict-

ed, about 27 µm long, with smooth margines particu-larly developed at the equator, covering the ora; apoc-olpial field very small; colpus membrane smooth. Oracircular, about 4 µm large.

Exine: tectate perforate, scabrate-rugulate, about2.5 µm thick.

Plant habit: perennial herb or shrub, 0.3-0.7 mtall.

Habitat: Coastal plain and sandy depression in thepre-desert and desert areas.

Acacia nilotica (L.) Willd. - (Plate III, 16-18)Pollen shape: 16-celled bicovex disc.Dimension of the whole polyad (µm):


Main diameter 47.5 45 49.5 49.5Minor diameter 45 40.5 49.5 45Thickness 30 27 31.5 31.5

Pollen class: polyad.Monads: central cell with squared outline, 3 syncol-

porate, with pores circular with a thin annulus; pe-

Plate III – Fig. 1-5 Blepharispermum hirtum: 1. SEM, equatorial view; 2. SEM, polar view; 3. LM, equatorial view, high focus; 4. LM,equatorial view, optical cross-section; 5. LM, polar view. Fig. 6-9 Jatrofa dhofarica: 6. LM; 7. LM, detail of the exine; 8. SEM, detail of theexine; 9. SEM, cross section of the exinic wall. Fig. 10-15 Cassia holosericea: 10. SEM, equatorial view; 11. SEM, polar view; 12, SEM, de-tail of the exine; 13. LM, equatorial mesocolpial view; 14. LM, equatorial apertural view; 15. LM, polar view. Fig. 16-18 Acacia nilotica:16. SEM, polyad, main diameter; 17. LM, polyad, main diameter; 18. LM, polyad, minor diameter. Fig. 19-21 Acacia senegal: 19. SEM,polyad, main diameter; 20. LM, polyad, main diameter; 21. LM, polyad, minor diameter. Fig. 22-24 Acacia tortilis: 22. SEM, polyad, maindiameter; 23. LM, polyad, main diameter; 24. LM, polyad, minor diameter. Fig. 25-29 Prosopis cineraria: 25. SEM, equatorial view; 26.SEM, polar view; 27. LM, equatorial mesocolpial view; 28. LM, equatorial apertural view; 29. LM, polar view.


ripheral cell square to rectangular in outline, 4 syncol-porate, colpi H-shaped.

Exine: tectate perforate, foveolate, about 2.5 µmthick. Few perforations approximately circular, irregu-larly spaced.

Plant habit: tree to 5 m tall. Spines strong andstraight.

Habitat: at the base of the southern slopes of thecoastal chain, especially in wet places.

Acacia senegal (L.) Willd. - (Plate III, 19-21)Pollen shape: 16-celled biconvex disc.Dimension of the whole polyad (µm):


Main diameter 50.5 47.5 54 52 Minor diameter 48 45 52 49.5 Thickness 35.5 34 38.5 36

Pollen class: polyad.Monads: central cell with almost squared outline, 8

porate; peripheral cell more or less rectangular in out-line, 8 porate.

Exine: tectate perforate, smooth, about 2.5 µmthick. Perforations approximately circular, different indiameter, closely spaced in shallow depressions.

Plant habit: tree or rarely shrub, 6 m tall. Spines inthrees at the nodes.

Habitat: dry lower southern slopes of coastal chain.

Acacia tortilis (Forssk.) Hayne - (Plate III, 22-24)Pollen shape: 16-celled bicovex disc.Dimension of the whole polyad (µm):


Main diameter 53 49.5 56.5 52 Minor diameter 50.5 43 55 49.5 Thickness 35 29.5 38.5 36

Pollen class: polyad.Monads: central cell with tetrangular outline, 3 syn-

colporate; peripheral cell square to rectangular in out-line, 4 syncolporate, colpi H-shaped.

Exine: tectate perforate, smooth, about 2 µm thick.Perforations closely spaced in shallow irregularlyshaped depressions.

Plant habit: tree up to 4 m tall. Spines in pairs atthe nodes.

Habitat: drier places on the coastal hills and driernorthern areas behind the mountains.

Prosopis cineraria (L.) Druce - (Plate III, 25-29)Pollen shape: subprolate-spheroidal.Outline in polar view: circular.Outline in equatorial view: elliptic.Dimension (µm):


P 33.5 29 40.5 34 E 31 25 36 31.5

Pollen class: tricolporate. Apertures: colpori tapering at the ends, with almost

smooth colpus membrane, about 27 µm long; apoc-olpial field small; ora distinctly circular, with a thin an-nulus, about 4 µm in diameter.

Exine: tectate perforate, smooth or lightly rugulate,about 2.5 µm thick.

Plant habit: tree up to 12 m tall.Habitat: synanthropic in many places of Dhofar

MALVACEAE

Senra incana (Cav.) DC. - (Plate IV, 1-3)Pollen shape: spheroidal.Outline in polar view: circular.Outline in equatorial view: circular.Dimension (µm):


D 155 139.5 168.5 157.5 D without spines 117.5 105.5 130.5 117

Pollen class: periporate.Apertures: pores approximately circular, about 5.5

µm in diameter, operculate, regularly spaced at about18 µm each from the other. Operculum persistent, witha sculpturing different from the surrounding surface.

Exine: tectate perforate echinate. Perforationsminute, closely spaced. Spinae smooth, conical, withblunt apices, regularly spaced. Tectum covered by ir-regularly spaced microgranules. Columellae longer atthe spine bases, swollen in the middle.

Plant habit: perennial herb or small shrub, 0,5- 1 mtall.

Habitat: sandy places of the coastal plain as well asin the wadi beds of drier areas.

OLEACEAE

Jasminum grandiflorum L. ssp. floribundum (Fresen.)P.S. Green - (Plate IV, 4-7)

Pollen shape: spheroidal.Outline in polar view: circular.

Outline in equatorial view: circular.Dimension (µm):


D 47 45 54 47.5

Pollen class: tricolporate.Apertures: colpori very narrow, about 31.5 µm long.

Ora distinctly circular, about 2 µm in diameter. Exine: semitectate reticulate, simplibaculatae, het-

erobrochate, about 4.5 µm thick. Lumina irregular inshape, main axis measuring 1-4 µm. Muri withsmooth tangential surface.

Plant habit: trailing or scrambling perennial herbor shrub up to 3 m tall.

Habitat: over trees and shubs in the woodlands ofthe southern slopes of the monsoon coastal moun-tains.

Olea europaea L. - (Plate IV, 8-12)Pollen shape: spheroidal.Outline in polar view: circular.Outline in equatorial view: circular.Dimension (µm):


D 20.5 18 23 20

Pollen class: tricolporate.Apertures: colpori very narrow, about 13.5 µm long.

Ora circular. Exine: semitectate reticulate, microechinate, about

2.5 µm thick. Reticulum simplicolumellate, hetero-brochate. Lumina very irregular in shape, main axismeasuring 1-3 µm. Muri with a row of microspine onthe tangential surface.

Plant habit: evergreen tree, 2-10 m tall.Habitat: woodlands of the coastal mountains.

PLUMBAGINACEAE

Plumbago zeylanica L. - (Plate IV, 13-17)Pollen shape: spherical.Outline in polar view: circular to lobate.Outline in equatorial view: circular.Dimension (µm):


D 68.5 60 75.5 67.5

Pollen class: tricolpate; some grains syncolpate.Apertures: colpi tapering at the ends, about 44.5

µm long, sometimes confluent with the adjacent ones(syncolpate grains).

Exine: tectate echinate, about 4.5 µm thick. Theexine presents: a thin foot-layer, a layer of columellae,an indistinct/ill-defined tectum, a layer of spinesslightly longer than the underneath columellae,swollen at the distal end, with acute apex. The spinesare irregularly scattered, single or in clusters of 2-6units. Some spines are digitate.

Plant habit: scrambling perennial herb or shrub, 1-2 m tall.

Habitat: southern slopes of the coastal mountainsin wet places.

RESEDACEAE

Ochradenus baccatus Delile - (Plate IV, 18-22)Pollen shape: subprolate. P/E ratio about 1.1.Outline in polar view: circular to lobate.Outline in equatorial view: elliptic.Dimension (µm):


P 28.5 27 31.5 29.5E 25.5 22.5 27 25

Pollen class: tricolporate.Apertures: colpori narrow, about 19 µm long; col-

pus membrane granular. Ora indistinct.Exine: semitectate reticulate, simplicolumellate,

heterobrochate. Lumina circular or irregular in shape,decreasing in size towards the poles.

Plant habit: dioecious shrub up to 1-1.5 m tall.Habitat: drier areas, in coastal plain, hills and

mountainous slopes.

RHAMNACEAE

Ziziphus leucodermis (Baker) O. Schwartz - (Plate V,1-6)

Pollen shape: suboblate to spheroidal. P/E ratioranging from 0.8 to 1.

Outline in polar view: triangular.Outline in equatorial view: circular-irregularly elliptic.Dimension (µm):


P 24 22.5 27 25E 26 23.5 27.5 25

Pollen class: tricolporate.Apertures: colpori narrow, with thickened costae

particularly near the ora, about 22 µm long; colpus



Plate IV – Fig. 1-3 Senra incana: 1. SEM; 2. LM, optical cross-section; 3. LM, high focus. Fig. 4-7 Jasminum grandiflorum L. ssp. flo-ribundum : 4. SEM, equatorial view; 5. SEM, polar view; 6. LM, equatorial view; 7. LM, polar view. Fig. 8-12 Olea europaea: 8. SEM,equatorial view; 8. SEM, polar view; 10. SEM, detail of the exine; 11. LM, equatorial view; 12. LM, polar view. Fig. 13-17 Plumbagozeylanica: 13. SEM, equatorial view; 14. SEM, polar view; 15. SEM, cross-section of the exinic wall; 16. LM, equatorial view; 17. LM,polar view. Fig. 18-22 Ochradenus baccatus: 18. SEM, equatorial view; 19. SEM, polar view; 20. LM, equatorial view, high focus; 21,LM, equatorial view, optical cross-section; 22. LM, polar view.


membrane granulate. Ora circular, about 1.8 µm indiameter, often not exactly located on the equatorialplane.

Exine: rugulate-striate, less than 2 µm thick. Murashort, variously oriented, interwoven in the meso-colpia; longer and quite parallel near the poles.

Plant habit: intricately spiny shrub to 2 m tall, withzig-zaging branches.

Habitat: dry places and desert areas.

Ziziphus spina-christi (L.) Willd. - (Plate V, 7-12)Pollen shape: suboblate to spheroidal. P/E ratio

ranging from 0.85 to 1.Outline in polar view: triangular.Outline in equatorial view: circular-irregularly elliptic.Dimension (µm):


P 27 25 29.5 27 E 28.5 25 31.5 29.5

Pollen class: tricolporate.Apertures: colpori narrow, with thickened costae

particularly near the ora, about 23 µm long; colpusmembrane granulated. Ora circular, less than 2 µm indiameter, often not exactly located on the equatorialplane.

Exine: rugulate, about 2.5 µm thick, with veryshort interwoven mura; almost smooth at the polesand along the colpore margines.

Plant habit: tree to 12 m tall or shrub with zigzag-ging branches.

Habitat: coastal plain, hills and mountains, natu-ralised and also cultivated.

SALVADORACEAE

Salvadora persica L. - (Plate V, 13-16)Pollen shape: subprolate to prolate. P/E ratio from

1.2 to 1.4.Outline in polar view: lobate.Outline in equatorial view: circular.Dimension (µm):


P 19.5 17 22.5 20.5 E 15.5 13.5 19 16

Pollen class: tricolporate or tricolpate.Apertures: colpori about 16 µ long, with almost

parallel edges, constricted at the equator; colpus mem-brane smooth. Ora ill-defined.

Exine: tectate perforate, about 1.5 µm thick. Perfo-rations minute, circular, different in size, homoge-neously scattered.

Plant habit: evergreen shrub or small tree up to 2-3 m tall.

Habitat: coastal plain, drier places, wadi banks.

TILIACEAE

Grewia damine Gaertn. (Syn.: G. bicolor Juss.) - (PlateV, 17-19)

Pollen shape: prolate.Outline in polar view: circular to slightly lobate.Outline in equatorial view: elliptic.Dimension (µm):


P 81 65.5 94.5 85.5 E 55.5 38.5 67.5 54

Pollen class: tricolporate.Apertures: colpori slit-shaped, about 65 µm long;

colpi costae along the sides, abruptly thickened to-wards the equator where they are interrupted; colpusmembrane smooth, with few isolate ectexine elements,scabrous at the equator. Ora lalongate, often with in-distinct edges, about 11 µm long.

Exine: tectate perforate, suprareticulata, simplicol-umellate, about 3 µm thick; reticulum continuous allover the surface, with lumina irregular in shape, angu-lar, sometimes longitudinally or obliquely elongated atthe equator, ranging from 2 to 4 µm in wide; perfora-tions distinct.

Plant habit: shrub or small tree, 2-3 m tall. Habitat: monsoon mountains and dry areas

touched by the monsoon moisture.

ZYGOPHYLLACEAE

Fagonia luntii Baker - (Plate V, 20-22)Pollen shape: subprolate. P/E ratio about 1.1.Outline in polar view: trilobate.Outline in equatorial view: elliptic.Dimension (µm):


P 25 22.5 27 25 E 22.5 18 25 22.5

Pollen class: tricolporate.Apertures: colpori geniculate, about 19 µm long,

slightly constricted at the equator; colpus membranesmooth. Ora often not easily discernible, lalongate.


Plate V – Fig. 1-6 Ziziphus leucodermis: 1. SEM, polar view; 2, SEM, particular of the exine at the pole; 3. SEM, detail of the exine; 4.LM, equatorial view, optical cross-section; 5. LM, equatorial view, high focus; 6. LM, polar view. Fig. 7-12 Ziziphus spina-christi: 7.SEM, equatorial view; 8, SEM, polar view; 9. SEM, detail of the exine; 10. LM, equatorial view, optical cross-section; 11. LM, equa-torial view, high focus; 12. LM, polar view. Fig. 13-16 Salvadora persica: 13. SEM, equatorial view; 14. SEM, polar view; 15. LM, equa-torial view; 16. LM, polar view. Fig. 17-19 Grewia damine: 17. SEM, equatorial view; 18. SEM, detail of the exine; 19. LM, equatorialview. Fig. 20-22 Fagonia luntii: 20. SEM, equatorial view; 21. LM, equatorial view; 22. LM, polar view.

Exine: tectate microreticulate, about 2.5 µm thick.Lumina oval to irregular in shape, abruptly decreasingin shape towards the colpi.

Plant habit: unarmed perennial herb or small shrubwith orbicular leaves, up to 0.8-1 m tall.

Habitat: hills and wadi beds.

Acknowledgments

We wish to thank the Adviser for Cultural Affairs, Sul-tanate of Oman, for the logistic assistance during our visitto Dhofar. We also thank Gilberto Montuori e Patrizio Nu-ti for the technical assistance and Dr. Cristina Bellini for therevision of the language.


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Summary: This paper describes the pollen morphology of the most common trees, shrubs and woody herbs growing in thecoastal plain and the escarpment of Dhofar, a wide region in southern Oman. The plant habit and habitat are also reported.

Pollen morphology of trees, shrubs and woody herbs of the coastal plain and the monsoon slopes of...

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