Nikolaos S. Christodoulakis

Structural analysis of sclerophylly in eleven evergreen phanerophytes in Greece

In the past (Grisebach 1872; Schimper 1898; Turrill 1929) as well as recently (Johnson 1973; Mooney et al. 1974), an evolutionary and ecological importance has been attributed to the leaf structure of the mediterranean evergreen sclerophyllous phanerophytes. Nevertheless, anatomical data on these leaves are sporadic and rather superficial (Kummerow 1973).

Structural and cytochemical investigation of the leaf of silverleaf nightshade (Solanum elaeagnifolium), a drought-resistant alien weed of the Greek flora

Light and scanning electron microscopy as well as histochemical reactions were employed to investigate the leaf structure and secretory activity of an adventive perennial pest that is rapidly dispersing in the Mediterranean region. Interesting structural characteristics, not common among the well-adapted native Mediterranean phanerophytes, were observed. Although ‘unconventional’, these structural characteristics produce an ecologically equivalent, xeromorphic leaf on a plant that proves to be competitive and very efficient under the Mediterranean climatic conditions.

Leaf anatomy and histochemistry of Lippia citriodora (Verbenaceae).

Lippia citriodora H.B.K. is an aromatic plant indigenous to South America. It is cultivated and commercialised as an ornamental for its lemon-like scent emitted from its leaves and flowers. The present morphoanatomical and histochemical study revealed that leaves of L. citriodora possess one type of setae (non-glandular) and at least five types of glandular trichomes, with the latter differing anatomically and in the composition of their secondary metabolites. Scanning electron microscopy revealed that the same types of trichomes exist also on the calyces. Histochemical tests indicate that the glandular trichomes contain a combination of terpenoids, flavonoids, carbohydrates, phenolics and alkaloids. However, within the vacuoles of the mesophyll cells, terpenoids, phenolics, flavonoids and tannins are stored. The presence of lamellar cytoplasmic inclusions in the mesophyll cells, possibly precursors of tannins stored in the vacuoles, is reported for the first time.

Histological investigation of the leaf and leaf-originating calli of Lavandula vera L.

Structures or cells with secreting activity were localized in the leaves of Lavandula vera. Light and electron microscopy, both TEM and SEM, were applied for the investigation of the secreting sites. A series of histochemical reactions was applied and a spectrum of metabolites produced was identified. Terpenes, flavonoids, steroids, alkaloids, and various types of phenolics were present. Leaf tissue was cultured and callus was produced. Callus cell masses were also investigated for their structure and secreting activity. Callus cells were found to be synthetically active and to produce—as leaf cells do—compounds of potential interest.

The Annual Rhythm of Cambial Activity in Two Woody Species of the Greek “Maquis”

Summary The annual rhythm of cambial activity is compared in Arbutus unedo and Quercus coccifera , two typical shrubs of the maquis in the Mediterranean-type ecosystem of Greece. The growth activity of the species is more or less focused on the favourable periods. The behaviour of Arbutus unedo revealed stronger correlation with moisture conditions, while that of Quercus coccifera seems to be more restricted in time and less controlled by moisture availability. These results indicate that both species, although growing together have different adaptive strategies to the same climatic conditions.

Leaf Structure of Cistus creticus L. (Rock Rose), a Medicinal Plant Widely Used in Folk Remedies Since Ancient Times

The dorsiventral, amphistomatic, hairy, summer and winter leaves of Cistuscreticus had a secretory apparatus in which the secreted resinous material was not preserved in a cutinous wrap, as common during excretion in xerophytes, but was directly spread all over the protective trichomes and the leaf surface. Summer and winter leaves differed in trichome function and density, mesophyll structure, and compactness and secondary metabolite accumulation, mainly phenolics, secreted in excess in the mesophyll cells of the summer leaves. In vitro cell cultures may be used for the production of novel compounds from low-cost precursors.

A contribution to the root study of the evergreen sclerophylls anatomy of the primary root of Quercus coccifera L.

Summary The structure of the primary root of Quercus coccifera , an evergreen sclerophyllous species common in maquis formations in Greece, has been studied by light and electron microscopy with special reference to the differentiation of endodermis. Histochemical identification of phenolic compounds in root tissues has also been carried out. Polyphenolic compound accumulation and extremely thin radial walls of endodermal cells observed in these roots are proposed to be adaptations contributing to a more effective water uptake and transport by the plant.

Structural and phytochemical investigation of the leaves of Ricinus communis

Ricinus communis L., also known as the castor oil plant, is a highly toxic species indigenous to the south-eastern Mediterranean. Leaf anatomy was investigated by light and electron microscopy (SEM and TEM). Histochemistry and composition of secondary metabolites, were also investigated. The amphistomatic leaves of R. communis are of simple structure with a single layered palisade parenchyma. They contain numerous idioblasts with crystals and present a strong positive reaction to histochemical reagents for terpenes, flavonoids, phenolics and alkaloids. Only a few protective trichomes appear on the adaxial epidermis. The phytochemical analysis of leaf extracts using UHPLC-HRMS and GC-MS confirmed the results of the histochemical tests and, among other metabolites, the flavonoids rutin, isoquercetin, and nicotiflorin, as well as the toxic alkaloid ricinine were detected.

A two-season impact study on Globularia alypum: adaptive leaf structures and secondary metabolite variations

Abstract A detailed histo-anatomical and phytochemical study on Globularia alypum was carried out to investigate season-induced plant responses related to leaf morphology and content of secondary metabolites (SMs). Leaf tissue analysis by light and scanning electron microscopy showed neither morphological nor significant anatomical adaptions/variations to the coldest and the hottest seasons. Both summer and winter leaf tissue resulted amphistomatic with compact mesophyll and capitate glandular trichomes. Epidermal and mesophyll cells showed a significant accumulation of osmiophilic compounds, further characterized as phenolics by the histochemical screening. Beside the morpho-anatomical similarities in tissue arrangement, SMs production, within and among the different natural product classes, resulted seasonally dependent. In total, 24 SMs belonging to iridoids, flavonoids and phenylethanoid glycosides were tentatively assigned by UHPLC-HRMS analysis. Among iridoids, (E)-globularicisin showed to be the prevalent constituent, with content up to 70%. Total iridoid production was increased by 48.1% during summer. Similarly, flavonoid anabolism was more active during the same period, although with less remarkable seasonal variation reaching 25.6%. In contrast to the overall higher production of iridoids and flavonoids, a drastic fall (33.5%) of phenylethanoids was observed during summer.

Post fire cambial activity of two evergreen sclerophyllous species in Greece

Summary Cambial activity of post fire resprouted stems of two evergreen sclerophylls ( Quercus coccifera and Olea europaea ssp. oleaster) is demonstrated. These resprouters, disregarding the severe climatic problems (particularly drought conditions) which inhibit all growth activities of the same species in the neighbouring unburned area, present increased cambial activity. The high cambial activity is indicated by a wide cambial zone in resprouters while cambial cells are difficult to discern in unburned neighbouring individuals. Besides, pith cells of the latter occupy abundant starch grains, but the absence of starch from resprouters pith cells is evident. This shifts the water problem of the mediterranean evergreen sclerophylls towards their overground part and gives an indication that these plants can at least withstand fire.