Abstract

The growth of two wetland forage grasses Leptochloa fusca (L.) Kunth. and Echinochloa stagnina (L.) P. Beauv. was investigated under NaCl salinity regarding the morphological traits, plant chemical composition, photosynthesis and the antioxidant enzymes POD and CAT. Plants of both species were irrigated with 0, 50, 100, 200, 300 and 400 mM NaCl in a sand/perlite mixture of 1:1 (v/v). Salinity negatively affected morphological traits and plant biomass of both species, particularly E. stagnina. Soluble sugars and proline within limits, protein contents of the foliage were increased to different extents by increasing salinity, but insoluble sugar decreased. K⁺/Na⁺ ratio of shoot and root of both species was decreased as a consequence of Na⁺ accumulation and restricted K⁺ uptake. NaCl salinity adversely affected photosynthetic rate, transpiration rate, stomatal conductance and water use efficiency of both species particularly E. stagnina. Tolerance of L. fusca and E. stagnina to salinity stress can be based on stomatal closure and reduction in leaf area, in order to minimize water loss via transpiration and increase the activity of some antioxidant enzymes to detoxifying ROS generated during stress.

Abstract and figures

We performed a comprehensive study of trichomes considering the medicinal importance of the essential oils produced in glandular trichomes of Salvia aegyptiaca L. and lack of data about leaf trichome characteristics. Micromorphological and histochemical analyses of the trichomes of S. aegyptiaca were carried out using light and scanning electron microscopy. We report that the leaves contained abundant non-glandular unbranched trichomes and two types of glandular trichomes, peltate and capitate, on both leaf surfaces. The abaxial leaf side was covered with numerous peltate and capitate trichomes, while capitate trichomes were more abundant on the adaxial leaf side, where peltate trichomes were rarely observed. The non-glandular trichomes were unicellular papillae and multicellular, uniseriate, two-to-six-celled, erect or slightly leaning toward the epidermis. Peltate trichomes were composed of a basal cell, a short cylindrical stalk cell and a broad head of eight secretory cells arranged in a single circle. Capitate trichomes consisted of a one-celled glandular head, subtended by a stalk of variable length, and classified into two types: Capitate trichomes type I (or short-stalked glandular trichomes) and capitate trichomes type II (or long-stalked glandular trichomes). Histochemical tests showed that the secreted material in all types of S. aegyptiaca glandular trichomes was of a complex nature. Positive reactions to lipids for both types of glandular trichomes were obtained, with especially abundant secretion observed in peltate and capitate trichomes type II.

Abstract

Aims: In the present work, the Libyan wild-growing Thymus capitatus essential oil (EO) was evaluated for its biological properties.

Methods and results: Carvacrol (68.19%) and thymol (12.29%) were found to be the main compounds of the oil. Antioxidant properties, determined by 2,2-diphenylpicrylhydrazyl (DPPH) assay, revealed that IC50 values were 119, 403 and 105 μg ml(-1) for oil, thymol and carvacrol respectively. Microdilution method showed strong antibacterial and especially antifungal potential. Tetrazolium (MTT) colorimetric assay indicated moderate cytotoxicity towards human cell lines MRC-5, HCT 116 and HT-29 (IC50 = 30-150 μg ml(-1)). In adhesion-inhibition assay oil and main compounds reduced adhesion of Escherichia coli and Listeria monocytogenes on colon cells HT-29 (51 and 39% of inhibition against L. monocytogenes and E. coli respectively).

Conclusions: Essential oil of Th. capitatus showed moderate cytotoxic activity, together with excellent antimicrobial effect, in particular against fungi, and significant potential to reduce pathogen colonization in colon.