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Uncommon, viruslike symptoms (yellowing, line patterns, leaf deformation, and necrosis), were observed in spinach fields in the Marathon area, Greece in 2004. Seedlings from the same seed lot, grown in the greenhouse, also developed the same viruslike symptoms, indicating that the causal agent(s) of the disorder is seed-transmissible. Spinach seedlings of the same variety but a different lot and herbaceous indicators (Chenopodium quinoa, C. amaranticolor, Sonchus oleraceus, and Nicotiana benthamiana) were mechanically inoculated with infected material. Spinach developed yellowing or necrotic spots whereas indicators showed variety of symptoms including mosaic, vein banding, and necrotic lesions. Virus purifications, double-stranded RNA extractions, cloning, and sequencing (2,3) followed by a combination of molecular (reverse transcription [RT]-PCR and immunocapture RT-PCR) and serological (ELISA) techniques with antisera provided by Dr. Avgelis were performed as described (4), verifying the presence of two viruses in the diseased seedlings: Sowbane mosaic virus (SoMV), a sobemovirus, was present in spinach and indicators with mottling and leaf deformation, whereas Olive mild mosaic virus (OMMV), a necrovirus, was present in plants with necrotic spots. All RT-PCR products amplified with primers SoMV-F (5′-CAAATGGTCTTGGTCAGCAGTC)/SoMV-R (5′-GCATACGCTCGACGATCTG) and OMMV-F (5′-CAAACCCAGCCTGTGTTCGATG)/OMMV-R (5′-CATCAGTTTGGTAATCCATTGA) were sequenced and found to confirm the other results. The SoMV-spinach isolate polyprotein gene sequence (GenBank Accession No. DQ450973) has 95% sequence identity with the type isolate from C. quinoa (GenBank Accession No. GQ845002), whereas the OMMV-spinach isolate (GenBank Accession No. JQ288895) has 92% sequence identity with the OMMV type isolate from olive (GenBank Accession No. AY616760). SoMV has been found to naturally infect spinach in the Netherlands (1) and, to our knowledge, this is the first report on spinach in Greece. The presence of OMMV in spinach is, to our knowledge, the first report worldwide. Its natural host range is limited to olive, tulip, and now spinach. OMMV might be transmitted by Olpidium spp. and may, according to data of its close relatives, persist in the soil for several decades. Pollen- and seedborne viruses (PSVs) like sobemoviruses and necroviruses are of particular importance for a crop like spinach where crop increase takes place in small, seed production-designated areas. If a PSV spreads in such an area it has the potential to become a major problem for the industry, especially when it remains undetected. Infected seed can be shipped worldwide with PSVs, causing diseases and becoming endemic in areas where they were absent. For this reason and the fact that field losses can exceed 50%, rigorous monitoring for the presence of SoMV and OMMV in seed fields is essential to minimize the possibility of the viruses moving to new areas. References: (1) L. Bos and N. Huijberts. Eur. J. Plant Pathol. 102:707, 1996. (2) S. M. Girgis et al., Eur. J. Plant Pathol. 125:203, 2009, (3) I. E. Tzanetakis et al. J. Virol. Methods 124:73, 2005. (4) I. E. Tzanetakis et al. Virus Res. 121:199, 2006.

Calcium oxalate crystals are widespread among animals and plants. In land plants, crystals often reach high amounts, up to 80% of dry biomass. They are formed within specific cells, and their accumulation constitutes a normal activity rather than a pathological symptom, as occurs in animals. Despite their ubiquity, our knowledge on the formation and the possible role(s) of these crystals remains limited. We show that the mesophyll crystals of pigweed (Amaranthus hybridus) exhibit diurnal volume changes with a gradual decrease during daytime and a total recovery during the night. Moreover, stable carbon isotope composition indicated that crystals are of nonatmospheric origin. Stomatal closure (under drought conditions or exogenous application of abscisic acid) was accompanied by crystal decomposition and by increased activity of oxalate oxidase that converts oxalate into CO2 Similar results were also observed under drought stress in Dianthus chinensis, Pelargonium peltatum, and Portulacaria afra Moreover, in A. hybridus, despite closed stomata, the leaf metabolic profiles combined with chlorophyll fluorescence measurements indicated active photosynthetic metabolism. In combination, calcium oxalate crystals in leaves can act as a biochemical reservoir that collects nonatmospheric carbon, mainly during the night. During the day, crystal degradation provides subsidiary carbon for photosynthetic assimilation, especially under drought conditions. This new photosynthetic path, with the suggested name "alarm photosynthesis," seems to provide a number of adaptive advantages, such as water economy, limitation of carbon losses to the atmosphere, and a lower risk of photoinhibition, roles that justify its vast presence in plants.

The dorsiventral, amphistomatic, hairy leaf of Pelargonium odoratissimum was lacking the variety of the anatomical features considered advantages for the Mediterranean plant life compared to the leaf of most Mediterranean xerophytes. Conversely, it had a well-equipped and intensely functioning secretory apparatus. Light, scanning, and transmission electron microscopy were employed to investigate the leaf structure while histochemical reactions traced the nature of the secreted metabolites. The numerous trichomes of the leaf were very active in producing phenolics, terpenes, and flavonoids mixed in a fragrant essential oil accumulated in an ovoid chamber at the top of each secreting hair. In-vitro cell cultures may be used for the production of novel compounds from low-cost precursors.

Light, scanning and transmission electron microscopy as well as histochemical reactions were employed to study the leaf structure and secretory activity of Ecballium elaterium, a hairy pharmaceutical perennial common in the Mediterranean region. The amphistomatic leaf has a peculiar structure due to special cells supporting the conductive bundles, a remarkable shortage of mechanical tissue, and the existence of pectin strands between mesophyll cells. The secreting activity is limited mostly to secretary hairs. These attributes of the Ecballium leaf fine structures do not resemble the common structure of leaves from Mediterranean plants and point to a peculiar strategy of this species coping with stress conditions of its habitat.

Breads containing fibers or hydrocolloids were frozen stored as dough (DBs) or semi-baked samples (SBs). Their microstructure (e.g. pore characteristics) was evaluated by image analysis and scanning electron microscopy. The sensory characteristics of “fresh” (one-day stored at ambient conditions) and of semi-baked breads (fully baked the day of observations) were determined by a descriptive analysis. Both composition and storage influenced the mean pore area. However, differences among samples were more evident by determining pore roundness and pore size distribution. Frozen storage favored the appearance of large pores in all samples, especially in the control samples (samples without any enrichment). Control DBs presented a 40% increase in the number of large pores in comparison to the respective number of pores of fresh samples. A decrease in pore roundness was correlated to a structural damage during storage. Pore roundness was correlated to organoleptic attributes such as aroma, adhesiveness and pore size.

The tube systems known to exist in tracheophytes are xylem, phloem and laticifers which are composed of living or non-living cells and secretory ducts/canals and aerenchyma that is of schizogenous or lysigenous origin. Here, we describe a novel type of tube network of unknown function that ramifies through the olive tree bark and is composed of groups of apparently empty, anastomosing tubules interrupted by perforated plates; side openings of the tubules connect them to the intercellular spaces of the cortex.

Carbonic anhydrase (CA) (EC 4.2.1.1) is a widespread enzyme catalyzing the reversible hydration of CO 2 to bicarbonate, a reaction that participates in many biochemical and physiological processes. Mesorhizobium loti , the microsymbiont of the model legume Lotus japonicus , possesses on the symbiosis island a gene (msi040) encoding an α-type CA homologue, annotated as CAA1. In the present work, the CAA1 open reading frame from M. loti strain R7A was cloned, expressed, and biochemically characterized, and it was proven to be an active α-CA. The biochemical and physiological roles of the CAA1 gene in free-living and symbiotic rhizobia were examined by using an M. loti R7A disruption mutant strain. Our analysis revealed that CAA1 is expressed in both nitrogen-fixing bacteroids and free-living bacteria during growth in batch cultures, where gene expression was induced by increased medium pH. L. japonicus plants inoculated with the CAA1 mutant strain showed no differences in top-plant traits and nutritional status but consistently formed a higher number of nodules exhibiting higher fresh weight, N content, nitrogenase activity, and δ 13 C abundance. Based on these results, we propose that although CAA1 is not essential for nodule development and symbiotic nitrogen fixation, it may participate in an auxiliary mechanism that buffers the bacteroid periplasm, creating an environment favorable for NH 3 protonation, thus facilitating its diffusion and transport to the plant. In addition, changes in the nodule δ 13 C abundance suggest the recycling of at least part of the HCO 3 − produced by CAA1.

SummaryThe present work examines the effects of substrate additions and incubation conditions on in vitro germination of tomato pollen on semi-solid, agar-based substrates with the ultimate aim of defining a standard semi-solid substrate for tomato pollen germination studies. Partial replacement of sucrose by polyethylene glycol (PEG-6000) for osmotic regulation of the substrate significantly increased pollen germination of both the low temperature-susceptible F1 cultivar ‘Dombito’, and the more temperature-resistant cv.‘Supermarmande’, to a level that varied according to the season of pollen harvest. In contrast, partial substitution of sucrose by mannitol was inhibitory to an extent that depended on the final concentration of mannitol in the medium. The optimum pH for germination was 6.5 and the optimum incubation temperature was 15°C. Among the vitamins (riboflavin, thiamine, pyridoxine, niacin, pantothenic acid, p-aminobenzoic acid), amino acids (glutamic acid, aspartic acid), casein hydrolysate, plan...