Presenting Eco-Anatomical Data for Saponaria jagelii, a Species on the Edge of the Blade.

The seeds, roots, leaves, flowers and fruits of the critically endangered (CR) species Saponaria jagelii Phitos & Greuter (Caryophyllaceae) were studied. The morphology of the seeds was investigated with scanning electron microscopy. The seeds were imbibed, germinated and developed into young plants. These plants, along with strictly selected wild-growing plants, were used for optical microscopic observations. The leaves and flowers were observed with scanning electron microscopy as well. At least two types of active glandular trichomes were detected on both the leaves and the calyxes of the flowers. The structures of the primary and secondary roots were also investigated. The roots turned into secondary structures very quickly and very close to the root tip. Light microscopy and histochemical reagents were employed to detect secondary metabolites of interest in the leaves. All the metabolites detected were already reported to be synthesized in stressed plants. Distribution data are presented. Conservation actions based on the habitat morphology and the human activities within it, such as the limitation of beach access during the seed-dispersing period and the prohibition of vehicle usage, are recommended in order to protect this tolerant yet severely stressed plant species.

Structural and Physiological Traits of Compound Leaves of Ceratonia siliqua Trees Grown in Urban and Suburban Ambient Conditions.

Ceratonia siliqua L. (carob tree) is an endemic plant to the eastern Mediterranean region. In the present study, anatomical and physiological traits of successively grown compound leaves (i.e., the first, third, fifth and seventh leaves) of C. siliqua were investigated in an attempt to evaluate their growth under urban and suburban environmental conditions. Chlorophyll and phenolic content, as well as the specific leaf area of the compound leaves were determined. Structural traits of leaflets (i.e., thickness of palisade and spongy parenchyma, abaxial and adaxial epidermis, as well as abaxial and adaxial periclinal wall) were also investigated in expanding and fully expanded leaflets. Fully expanded leaflets from urban sites exhibited increased thickness of the lamina and the palisade parenchyma, while the thickness of the spongy parenchyma was thicker in suburban specimens. The palisade tissue was less extended than the spongy tissue in expanding leaflets, while the opposite held true for the expanded leaflets. Moreover, the thickness of the adaxial and the abaxial epidermises, as well as the adaxial and abaxial periclinal wall were higher in suburban leaflets. The chlorophyll content increased concomitantly with the specific leaf area (SLA) of both expanding and expanded leaflets, and strong positive correlations were detected, while the phenolic content declined with the increased SLA of expanding and expanded leaflets. It is noteworthy that the SLA of expanding leaflets in the suburban site was comparable to the SLA of expanded leaflets experiencing air pollution in urban sites; the size and the mass of leaf blades of C. siliqua possess adaptive features to air pollution. These results, linked to the functional structure of expanding and expanded successive foliar tissues, provide valuable assessment information coordinated with an adaptive process and yield of carob trees exposed to the considered ambient conditions, which have not hitherto been published.

Heat and Cold-Stressed Individuals of Pistacia lentiscus (Mastic Tree) Do Modify Their Secreting Profile.

Seedlings from the germinated seeds of Pistacia lentiscus were cultured in plant growth chambers for three months. Then, the plants were separated into three groups. Each group was cultured under different conditions. The first group was left to grow under normal Mediterranean conditions, as those recorded in spring. The other group was subjected to a ten-day heat stress while the last one also suffered a cold stress for ten days. The anatomical features of the leaves (leaf thickness, epidermal cell thickness, number of palisade layers, and development) between these three groups differed. The stressed plants accumulated large amounts of phenolics within their mesophyll cells. The biomass of the cold-stressed plants was minor, while it was high for the control plants. The oxidative stress was hardly detectable in the leaves of the control plants, while their heat-stressed counterparts suffered the highest concentration of reactive oxygen species. Differences concerning the absorption spectra of the three groups of leaves were not significant. An interesting incompatibility between the three groups concerned the expression of L-Dopa Decarboxylase, which climbed significantly in the heat-stressed plants. Finally, an interesting variation was observed concerning the concentrations of some biogenic amines/amino acids. This variation can be correlated to the other stress-induced reactions of the plants and, in some cases, was impressive. In conclusion, environmental stress can shift Pistacia lentiscus' metabolism to synthesize different biogenic products, which can be considered as exploitable for the pharmaceutical or food industry.

Structure and organization of the secretion apparatus of the mastic tree (Pistacia lentiscus L.) and LC-HRMS analysis of leaf extracts.

MAIN CONCLUSION: The quantitative profile of the biochemicals secreted by summer and winter leaves, present noticeable differences and appear to be qualitatively different from the biochemical profile of the commercially valuable mastic. The anatomy of the root and the primary and secondary shoot as well as that of the summer and winter leaves of P. lentiscus was thoroughly investigated. The secreting network was tracked throughout the plant axis, from the root to the leaves, and the active secreting cells of the duct epithelium were localized, while the secondary metabolites produced within the cells of the summer and winter leaf tissues were identified histochemically. Numerous phytochemicals were identified in the leaf extracts with UHPLC-qTOF MS analysis. The analyzed extracts from summer and winter leaves displayed similar qualitative profile, although quantitative differences were evident, since, during the summer, the leaves tend to synthesize the more complex amongst the identified compounds. The phytochemical profile of the leaf extracts turns to be completely different compared to that of the valuable mastic harvested from the injured trunks. Many of the compounds common in mastic were not detected in the analyzed leaves samples. The numerous secreting ducts either fail to form a unified network, so composition of the secreted material varies in the different organs of the plant or they compose a continuous network, but the biochemical profile of the secreted material differs along the plant axis. Such a detailed investigation of the secretion network of the mastic tree may assist the improvement of the yield and promote the production of valuable phytochemicals through in vitro cultures.

Response of young Nerium oleander plants to long-term non-ionizing radiation.

MAIN CONCLUSION: Although exposure to low frequency electromagnetic radiation is harmful to plants, LF-EM irradiated Nerium oleander seedlings exhibited enhanced development and growth, probably taking advantage of defined structural leaf deformations. Currently, evidence supports the undesirable, often destructive impact of low frequency electromagnetic (LF-EM) radiation on plants. The response of plants to LF-EM radiation often entails induction in the biosynthesis of secondary metabolites, a subject matter that is well documented. Nerium oleander is a Mediterranean plant species, which evolved remarkable resistance to various environmental stress conditions. In the current investigation, cultivated N. oleander plants, following their long-term exposure to LF-EM radiation, exhibited major structural modifications as the flattening of crypts, the elimination of trichomes and the reduction of the layers of the epidermal cells. These changes co-existed with an oxidative stress response manifested by a significant increase in reactive oxygen species at both the roots and the above ground parts, a decline in the absorbance of light by photosynthetic pigments and the substantially increased biosynthesis of L-Dopa decarboxylase (DDC), an enzyme catalyzing the production of secondary metabolites that alleviate stress. The exposed plants exhibited greater primary plant productivity, despite a manifested photosynthetic pigment limitation and the severe oxidative stress. This unique response of N. oleander to severe abiotic stress conditions may be owed to the advantage offered by a structural change consistent to an easier diffusion of CO2 within the leaves. A major plant response to an emerging "pollutant" was documented.