Coordinated changes in photosynthetic machinery performance and water relations of the xerophytic shrub Ziziphus lotus (L.) Lam. (Rhamnaceae) following soil drying

Aim of this study was to investigate the effect of water shortage in wild jujube plants, Ziziphus lotus (L.) Lam, and how it is related to its ecological success. All leaf anatomical traits were significantly affected following soil drying. Stressed plants displayed more negative stem water potential (psi(w)) and osmotic potential values of ca. -3.5 and -4.5 MPa, respectively, after 30 d. The relative water content declined although it still maintained high values (>= 75%). The net photosynthetic rate, stomatal conductance, and transpiration rate were significantly inhibited as psi(w) decreased. However, the intrinsic water-use efficiency increased as water deficit was intensified; the difference became significant only after 30 d. As a consequence, the effective quantum yield of PSII photochemistry and the photochemical quenching coefficient significantly decreased although the maximal quantum yield of PSII photochemistry ratio remained statisticaly unchanged. Plants could maintain their water status sufficiently by increasing proline 1.7-fold and sucrose 1.8-fold in their leaves, respectively. The largest accumulation of both solutes may avoid photodamages at cellular level and play a critical role in maintaining osmotic adjustment

Optimized Chemical Extraction Methods of Antimicrobial Peptides from Roots and Leaves of Extremophilic Plants: Anthyllis sericea and Astragalus armatus Collected from the Tunisian Desert

International audienceExtraction methods depend mainly on the chemical nature of the extracted molecule. For these reasons, the selection of the extraction medium is a vital part of obtaining these molecules. The extraction of antimicrobial peptides (AMPs) from extremophile plants is important because of its potential pharmaceutical applications. This work focused on the evaluation of several solvents for the extraction of AMPs from the following two extremophile plants: Astragalus armatus and Anthyllis sericea from southern Tunisia. In order to identify the most efficient solvents and extraction solutions, we used sulfuric acid, dichloromethane, phosphate buffer, acetic acid and sodium acetate, and we tested them on leaves and roots of both the studied plants. The extracts obtained using sulfuric acid, dichloromethane and phosphate buffer extraction did not show any antimicrobial activity, whereas the acetic acid and sodium acetate extracts led to growth inhibition of some of the tested bacterial strains. The extracts of leaves and roots of An. sericea and As. armatus obtained by acetic acid and sodium acetate were proven to be active against Gram-positive bacteria and Gram-negative bacteria. Therefore, the most appropriate solvents to use for antimicrobial peptide extraction from both plants are acetic acid and sodium acetate

Reassessment of Practical Subspecies Identifications of the USDA Daucus carota L. Germplasm Collection: Morphological Data

The genus Daucus includes about 20 recognized species. The most widespread and economically important species, Daucus carota L., occurs on almost every continent. The cultivated carrot, subsp. sativus (Hoffm.) Schübl. and G. Martens, has been selected from wild populations that are extremely diverse, especially in the western Mediterranean. The predominant outcrossing and the lack of sexual isolating mechanisms among recognized infraspecific taxa complicate the taxonomy and identification of the wild populations, resulting in widely different interpretations of the number of infraspecific taxa. We measured 36 morphological characters from multiple individuals within each of 155 accessions of D. carota and from the morphologically similar species D. capillifolius (both species 2n = 18) alongside other species for comparison (D. aureus Desf., 2n = 22; D. broteri Ten., 2n = 20;D. involucratus Sm., 2n = 20; and D. littoralis Sm., 2n = 20) in an experimental field plot. Within D. carota, multivariate analyses were able to identify only two subspecies, but even these showed great overlap of individual characters. Because of the ease of crossability of wild D. carota to the domestic landraces and cultivars and because of the taxonomic challenges, the purpose of our study is to explore morphological support for subspecies within D. carota, including the phenetically similar D. capillifolius, which is part of the same clade as D. carota, with the long-term goal of resolving taxonomic disagreements and developing a practical system to classify variation within this economically important species.This article is from Crop Science 54 (2014): 706–718, doi:10.2135/cropsci2013.04.0231.</p