Limited evidence up to now indicates low linear photosynthetic electron flow and CO(2) assimilation rates in non-foliar chloroplasts. In this investigation, we used chlorophyll fluorescence techniques to locate possible limiting steps in photosystem function in exposed, non-stressed green fruits (both pericarps and seeds) of three species, while corresponding leaves served as controls. Compared with leaves, fruit photosynthesis was characterized by less photon trapping and less quantum yields of electron flow, while the non-photochemical quenching was higher and potentially linked to enhanced carotenoid/chlorophyll ratios. Analysis of fast chlorophyll fluorescence rise curves revealed possible limitations both in the donor (oxygen evolving complex) and the acceptor (Q(A)(-)--> intermediate carriers) sides of photosystem II (PSII) indicating innately low PSII photochemical activity. On the other hand, PSI was characterized by faster reduction of its final electron acceptors and their small pool sizes. We argue that the fast reductive saturation of final PSI electron acceptors may divert electrons back to intermediate carriers facilitating a cyclic flow around PSI, while the partial inactivation of linear flow precludes strong reduction of plastoquinone. As such, the photosynthetic attributes of fruit chloroplasts may act to replenish the ATP lost because of hypoxia usually encountered in sink organs with high diffusive resistance to gas exchange.

The structure and development of Myrtus communis L. secretory cavities has been studied in young and expanded leaves, using light and scanning electron microscope. Secretory cavities are continuously formed during leaf development, but in mature leaves the rhythm of their appearance shows steep decrease. Each secretory cavity is developed from a single epidermal cell, which undergoes a periclinal division followed by anticlinal and several oblique cell divisions. The lumen of the secretory cavity is initiated by cell wall separation, i.e., schizogenously. The secretory cells line the cavity, where the secreted material is collected. Secretory cavities are covered by modified epidermal cells, which do not seem to form any special aperture. Essential oils seem to be discharged after mechanical treatment of the leaf.Additional key words: anticlinal and periclinal divisions, essential oils, myrtle, scanning electron microscope.

The structure of primary lenticels of the Mediterranean evergreen Olea europaea and the winter deciduous species Cercis siliquastrum was investigated during the year using scanning electron, conventional brightfield and epi-fluorescence microscopy. It was revealed that lenticels of O. europaea do not undergo significant structural changes over this time period. The filling tissue of O. europaea lenticels consists of fully-suberized cells that form small intercellular spaces. The air-exposed filling cells are replaced during spring and early summer by new early-suberized cells. Further notable structural modifications during the year were not observed. By contrast, lentice1s of C. siliquastrum possess a closing layer of suberized cells delimiting an underlying mass of non-suberized filling cells. During the period of high metabolie activity of the plant, i.e. during spring and early summer, the suberized closing layer is ruptured from the pressure exerted by the newly formed underlying cells. During late summer a new closing layer is formed, delimiting again the non-suberized underlying filling cells during winter. The possible role of lenticels in the gas exchange process is discussed. In both species the shade-adapted parenchyma cells of the cortex beneath lenticels shows bright red auto-fluorescence of chlorophyll, a phenomenon that is not yet fully understood.

In this study, we characterized Hypericum vesiculosum Griseb. (sect. Drosocarpium), Hypericaceae, a Balkan endemic and Greek subendemic species, which was collected from the Peloponnese (Greece). The anatomical study showed that its leaves are dorsiventral and hypostomatic, and the major part of its circular stem is filled with xylem. High-performance liquid chromatography coupled with diode-array detection and mass spectrometry analysis of the methanolic extract of the aerial parts revealed 25 compounds, and the concentration of the 18 major ingredients was determined with a validated method of liquid chromatography coupled with diode-array detection. Flavonoids were the most abundant group of compounds (> 100 mg/g of dry extract) with I3,II8-biapigenin, apigenin hexoside, isoquercitrin, quercetin, and hyperoside as the major dereplicated constituents. Chlorogenic acid was abundant (9.34 ± 0.22 mg/g) and the content of naphthodianthrones was comparable to that in H. perforatum. Only one phloroglucinol could be quantified at a very low concentration and that was not hyperforin. This is the first chemical analysis of its methanolic extract and anatomical characterization of its vegetative tissues.

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