Effect of Seasonal Environmental Changes on Leaf Anatomical Responses of Limoniastrum guyonianum in Sabkha Biotope

Climate change conditions can strongly influence the kinetics of morphogenetic processes. Our study showed that the total thickness of leaf lamina, adaxial palisade parenchyma, abaxial palisade parenchyma and spongy parenchyma increased significantly during the dry period, especially in August (31.4%, 52.1%, 37.6%, 27.69%, respectively). Moreover, the adaxial and abaxial epidermis becomes thicker during the most dry months (July and August). Likewise, the adaxial cuticle thickness increased during the dry period. The stomata density in the adaxial and abaxial leaf sides is 1.36- and 1.4-fold higher than those recorded during the wet periods. However, the salt glands’ density showed a much greater increase in the abaxial face (+2.4-fold). The bundle sheath size was unchanged under the seasonal environmental fluctuation in the sabkha. The xylem vessels diameter showed a maximum reduction in August (–63.8%). Likewise, the xylem vessels density increased significantly during the dry period. The closer relationship between the anatomical proprieties with soil salinity allows us to conclude that salt stress is one of the most limiting factors for Limoniastrum guyonianum in its natural biotope

Flower, seed, and fruit development in three Tunisian species of Polygonum: Implications for their taxonomy and evolution of distyly in Polygonaceae.

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

Phylogenetic placement, floral anatomy, and morphological characterization of the North African pastoral halophyte Atriplex mollis Desf. (Amaranthaceae)

Atriplex mollis Desf. (Amaranthaceae), a North African endemic halophytic species, is further described in this study. Phylogenetic analysis based on a combined dataset of ITS and ETS rDNA and atpB-rbcL and trnK cpDNA showed that A. mollis is closely related to the Malta- and Gozo-endemic Cremnophyton lanfrancoi Brullo & Pavone. Given this close phylogenetic relationship, A. mollis is also considered among the oldest species of Atriplex, together with C. lanfrancoi. Molecular data also suggest that A. mollis in North Africa, C. lanfrancoi on Malta Island, and Atriplex cana Ledeb. in Eurasian semideserts constitute a separate clade within the tribe Atripliceae. As an 18-month-old shrub, A. mollis can reach a mean height of 44.06 ± 8.09 cm with a leaf area around 1.24 ± 0.15 cm2, and can produce seeds in order of 113.08 ± 28.52 g plant−1. The anatomy of A. mollis shows the presence of male and female developed flowers. Hermaphroditic flowers that may lead to the appearance of male flowers with underdeveloped female organs were rarely found. Three main shapes of ovule (campylotropous, amphitropous, and orthotropous) were found in A. mollis.This study was supported by the ERANETMED2-72-303 PACTORES project financed by the Ministry of Higher Education and Scientific Research of Tunisia and the University of Malta (Argotti Botanic Gardens).Peer reviewe

Characterization of <i>Silybum marianum</i> and <i>Silybum eburneum</i> seed oils: Phytochemical profiles and antioxidant properties supporting important nutritional interests

Corresponding authors: [email protected] (MM); [email protected] (RA); [email protected] (GL)International audienceMilk thistle seed oil is still not a well-known edible oil. Silybum marianum (milk thistle), is present in several countries and is the only known representative of the genus Silybum . However, Silybum eburneum , which is an endemic plant in Spain, Kenya, Morocco, Algeria, and Tunisia, is considered a marginalized species. The present work is the first report that gives information on the lipid and phenolic profiles of Tunisian S . eburneum seed oil compared to those of Tunisian S . marianum seed oil. In addition, the antioxidant properties of these oils were determined with DPPH, FRAP, and KRL assays, and their ability to prevent oxidative stress was determined on human monocytic THP-1 cells. These oils are characterized by high amounts of unsaturated fatty acids; linoleic acid and oleic acid are the most abundant. Campesterol, sitosterol, stigmasterol, and β-amyrin were the major phytosterols identified. α-tocopherol was the predominant tocopherol found. These oils also contain significant amounts of phenolic compounds. The diversity and richness of Silybum marianum and Silybum eburneum seed oils in unsaturated fatty acids, phenolic compounds, and tocopherols are associated with high antioxidant activities revealed by the DPPH, FRAP, and KRL assays. In addition, on THP-1 cells, these oils powerfully reduced the oxidative stress induced by 7-ketocholesterol and 7β-hydroxycholesterol, two strongly pro-oxidant oxysterols often present at increased levels in patients with age-related diseases. Silybum marianum and Silybum eburneum seed oils are therefore important sources of bioactive molecules with nutritional interest that prevent age-related diseases, the frequency of which is increasing in all countries due to the length of life expectancy