Polygonum is the largest genus of Polygonaceae and 5 species are reported in Tunisia. In order to characterized flower, seed, and fruit development in Polygonum, flower and fruit of Polygonium equisetiforme (var. graecum and peyerinhoffi), P. aviculare and P. maritimum, collected from Tunisia, were examined. Flowers are composed of five oblong tepals. P. equisetiforme and P. aviculare have whitish-pink distylous flowers with dimorphism of style, filament and anther height, pollen diameter and stigma size. In contrast, P. maritimum shows white homostylous flowers. The floral vasculature showed that the tepals are inserted in one whorl and their traces arise independently in 3+2 manner. The eight stamens are arranged in a 5+3 manner and the staminal bundles arise independently in the two whorls. The epidermis and endothecium cells width were higher in P. maritimum and the lowest endothecium width was observed in P. aviculare. Polygonum aviculare and P. equisetiforme showed circular pollen with shallow colpi and trilobite pollen shape with deep colpi, while P. maritimum rarely showed shallow colpi. The ovule is anatropous with basal placentation in P. equisetiforme and P. aviculare and apical placentation in P. maritimum. The young seed coat was formed by an endotesta with thick-walled cells, a mesotesta and exotesta with thin-walled cells and a tegmen composed of radially elongated cells. The fruits of the studied species are trigonous with ovate-lanceolate shape. In P. aviculare, the exocarp is thicker compared to the two other species, in P. equisetiforme, the mature exocarp consists of smaller rectangular cells with narrow cavities, and in P. maritimum showed a thinner exocarpIn conclusion, P. equisetiforme and P. aviculare are a typically distylous species from the morphological point of view and we discussed the significance of heterostyly in Polygonaceae. From this first morpho-anatomical study of Polygonum species in North Africa, we can conclude mainly that there is no significant difference between P. equisetiforme var. graecum and var. peyerinhoffi supporting a taxonomic grouping of these two varieties.

Polygonum aviculare and Polygonum maritimum, commonly known as knotgrass and sea knotgrass, have been widely used for several purposes. Leaves, stems, and roots of these species were evaluated for mineral composition, phytochemical contents, and antioxidant properties. The minerals were characterized by flame atomic absorption spectrometry (FAAS). The polyphenolics were investigated colorimetrically and by high-performance liquid chromatography-electrospray ionization – mass spectrometry (HPLC-ESI-MS). The antioxidant potential was evaluated by total antioxidant capacity (TAC), DPPH-radical scavenging activity, and reducing power (RPA). The mineral contents differed remarkably between and within species. For P. maritimum, the leaves showed the highest sodium, potassium, calcium, and magnesium contents while the roots accumulated the highest iron. The stems of P. aviculare contained higher Na, K, Ca and Fe compared to roots and leaves. P. maritimum extracts contained higher phytochemical contents compared to P. aviculare. The stems and leaves of P. maritimum were the richest in polyphenols and flavonoids while the roots possessed the highest condensed tannins. For P. aviculare, the stems contained the highest phenolics. HPLC-ESI-MS determined 20 phenolics including quinic acid, gallic acid, protocatechuic acid, (+)-catechin, quercetin-3-O-galactoside, and cirsiliol. P. maritimum extracts contained more antioxidants than P. aviculare. The results suggest that the selected species may be important sources of bioactive molecules.