Potamogeton gramineus Linnaeus (1753: 127)

Abbasi, Shabnam, Afsharzadeh, Saeed, Dinarvand, Mehri & Wiegleb, Gerhard, 2017, Synopsis of Potamogetonaceae in Iran with supplements to the Flora Iranica and a new identification key, Phytotaxa 311 (1), pp. 1-21 : 11-13

Potamogeton gramineus Linnaeus (1753: 127) , Fig. 12

Perennial, rhizome slender to robust, stem slender, repeatedly branched, terete. Leaves dimorphic; submersed leaves 35–90 mm long, 2–5 mm wide, sessile, acute at apex, cuneate at base, margin minutely denticulate, 3–7 veined.; floating leaves petiolate, 50 mm long, 20 mm wide, 7–12 veined, broadly lanceolate; petiole 7–20 mm long. Stipules not fused, 6 mm long. Spike 25–35 mm long, 15–20 mm long, considerably thicker than the stem, peduncle 20–30 mm long, strongly thickened. Carpels, fruits 2.5 mm long. Stele of oblong type, endodermis of U-type, interlacunar bundles present, subepidermal bundles present.

Worldwide distribution: —Circumpolar, boreal and temperate regions throughout the Northern Hemisphere, W

Asia ( Turkey, Afghanistan).

Distribution in Iran: —South.

Flowering time: —in summer.

Specimen examined: — IRAN. Khuzestan: Shimbar wetland, 2000 m, 20 July 2016, Afsharzadeh 20215 (HUI!).

Potamogeton × khuzestanicus Abbasi, Afsharzadeh & Dinarvand. , nothosp. nov., Fig. 13 ( Potamogeton crispus Linnaeus (1753:126) × P. pusillus Linnaeus (1753: 127))

The hybrid differs from P. crispus by the entire leaf margin, the narrower leaf width, the presence of subepidermal bundles and the shorter stipules. It differs from P. pusillus by the oblong stele and the larger leaf width. It differs from P. × lintonii Fryer (1900: 366) and P. × bennetii Fryer (1895: 1) by the higher number of veins, the totally entire leaf margin, the shorter stipules, the regular presence of 4 carpels, and the formation of fruits.

Type: — IRAN. Khuzestan: Dezful: Hamidabad, river, 500 m, 23 May 2014, Dinarvand 8332 (Herbarium of the Research Center of Agriculture & Natural Resources of Khuzestan!).

Perennial, stems slender, compressed to terete, branched. Leaves monomorphic; submersed leaves entire, lanceolate, 3–5 cm long, 2.5–3.5 mm wide, with 3 prominent veins, obtuse to mucronate at apex, green with a reddish or brownish tinge, cuneate at base, stipules 4 mm long. Spike, 2–4 flowered, 5–8 mm, less than in parent species; peduncle 20–30 mm long. Tepals 1 mm long, roundish to spathulate, brown. Stamen 1 mm long, sessile, adnate to base of tepals. Carpels 4, remaining undeveloped, 1.5 mm long. Stele of oblong type, endodermis of O-type, interlacunar bundles absent, subepidermal bundles present.

Table 2 shows a comparison of diagnostic characters between this hybrid and its supposed parents.

The shape of the inflorescence and peduncle is intermediate between P. crispus Linnaeus (1753:126) and P. pusillus Linnaeus (1753: 127) . The lamina of the submersed leaves is also intermediate between supposed parents with respect to width, color and venation. Two similar hybrids have been described before, P. × bennettii Fryer = P. crispus × P. trichoides and P. × lintonii = P. crispus × P. friesii . Although Hagström (1916) mentioned the between P. pusillus and P. crispus , namely P. × bennettii . Today the parental species of P. × bennettii are P. crispus and P. trichoides . Parentage of P. friesii and P. trichoides can be ruled out due to morphological (see Table 2) and distributional arguments. The supposed parent species ( P. crispus and P. pusillus ) were found in the locations of this hybrid at the same time. According to our molecular results, this hybrid is located in ITS tree between P. crispus and P. pusillus , while trnH-psbA suggests P. crispus as a probable maternal parent with a high posterior probability ( Figs. 14 , 15 ).

Eponymy: —This hybrid is named after the Khuzestan province in Iran.

Distribution in Iran: —South.

Flowering time: —From Spring to Summer.

Figures

FIGURE 12. P. gramineus a. cross section of stem (Scale bar: 100 μm, objective lens 4), b. morphological shape.

FIGURE 13. Potamogeton ×khuzestanicus a. cross section of stem (Scale bar: 100 μm, objective lens 4).

FIGURE 14. Species relationship among P.×khuzestanicus and its parents based on ITS tree (numbers at nodes are Bayesian Posterior Probabilities).

FIGURE 15. Species relationship among P.×Khuzestanicus and its parents based on trnH-psbA tree (numbers at nodes are Bayesian Posterior Probabilities).