Summary. Programmed-cell-death events in the tapetum of two angiosperms (Lobivia rauschii Zecher and Tillandsia albida Mez et Purpus) are described by ultrastructural methods. Tapetum degradation appears to be a type of programmed cell death, with the cellular remnants necessary for pollen development, acting as products of holocrine secretion. Diagnostic features of apoptosis during tapetum development are: general shrinkage of the whole cell and the nuclei; condensation of the chromatin at the periphery of the internal nuclear membrane; the enlargement of the endoplasmicreticulum cisternae to circumscribe portions of the cytoplasm; the persistence of mitochondria together with microfilament bundles until the last stages of tapetal degeneration.

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The degeneration of three of four meiotic products is a very common process in the female gender of oogamous eukaryotes. In Tillandsia (and many other angiosperms), the surviving megaspore has a callose-free wall in chalazal position while the other three megaspores are completely embedded in callose. Therefore, nutrients and signals can reach more easily the functional megaspore from the nucellus through the chalazal pole with respect to the other megaspores. The abortion of three of four megaspores was already recognized as the result of a programmed cell death (PCD) process. We investigated the process to understand the modality of this specific type of PCD and its relationship to the asymmetric callose deposition around the tetrad. The decision on which of the four megaspores will be the supernumerary megaspores in angiosperms, and hence destined to undergo programmed cell death, appears to be linked to the callose layer deposition around the tetrad. During supernumerary megaspores degeneration, events leading to the deletion of the cells do not appear to belong to a single type of cell death. The first morphological signs are typical of autophagy, including the formation of autophagosomes. The TUNEL positivity and a change in morphology of mitochondria and chloroplasts indicate the passage to an apoptotic-like PCD phase, while the cellular remnants undergo a final process resembling at least partially (ER swelling) necrotic morphological syndromes, eventually leading to a mainly lipidic cell corpse still separated from the functional megaspore by a callose layer.

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which were previously treated in tribe Galegeae, were transferred to tribe Hedysareae by . Members of Hedysareae are commonly found in dry open habitats with a continental, temperate, or Mediterranean climate, including Eurasia, North America, and the Horn of Africa (Ahangarian et al., 2007). Some taxa of the tribe are economically important as fodder legumes due to their high protein content (Hayot Carbonero et al., 2011).Molecular analyses by Wojciechowski et al. ( 2004) and Lavin et al. (2005) showed that Caragana Fabr. was the most closely related sister group to the rest of the tribe Hedysareae.Hedysareae is included in the Inverted Repeat Lacking Clade (IRLC) group sensu Wojciechowski et al. (2000Wojciechowski et al. ( , 2004 and Wojciechowski (2003Wojciechowski ( , 2005. In more recent studies, it has been suggested that Hedysareae sensu Lock ( 2005) is a sister group to the Astragalean clade, which includes genera such as Astragalus L., Oxytropis DC., and Colutea L., in addition to Chesneya Bertol. and its close relatives . According to Lavin et al. (2005) the most recent common ancestor of the Hedysareae and the Astragalean clade originated between 25.0 and 39.2 million years ago.The genus Onobrychis is divided into 2 subgenera:

Two-component signal transduction systems (TCSs) consist of sensor histidine kinases and response regulators. TCSs mediate adaptation to environmental changes in bacteria, plants, fungi and protists. Histidine kinase 2 (Hik2) is a sensor histidine kinase found in all known cyanobacteria and as chloroplast sensor kinase in eukaryotic algae and plants. Sodium ions have been shown to inhibit the autophosphorylation activity of Hik2 that precedes phosphoryl transfer to response regulators, but the mechanism of inhibition has not been determined. We report on the mechanism of Hik2 activation and inactivation probed by chemical crosslinking and size exclusion chromatography together with direct visualisation of the kinase using negative-stain transmission electron microscopy of single particles. We show that the functional form of Hik2 is a higher-order oligomer such as a hexamer or octamer. Increased NaCl concentration converts the active hexamer into an inactive tetramer. The action of NaCl appears to be confined to the Hik2 kinase domain.

Contributo alla Flora del Dhofar centro-meridionale (Sultanato dell'Oman) -Dal 2000 al 2009 sono state effettuate10 missioni scientifi che dedicate all'esplorazione fl oristica del Dhofar centro meridionale (Oman). Le raccolte hanno interessato i litorali sabbiosi, la pianura costiera e numerosi wadis che sboccano nell'Oceano Indiano (da Rachyut, Al Mughsayl, Salalah, Khor Rori, Mirbat, Hadbin fi no ad Hasik). Particolare attenzione è stata dedicata all'esplorazione dei versanti monsonici delle montagne (soprattutto Jabal Qara) dove si concentra la maggiore ricchezza fl oristica e il maggior numero di taxa endemici. Raccolte sono state effettuate anche su Jabal Samhan, la montagna più alta del Dhofar, e nell'area pre-desertica di Wadi Andur, alle spalle di Jabal Samhan. Sono state inoltre indagate quelle aree dove ancor oggi sono presenti i maggiori nuclei di Boswellia sacra, l'albero dell'incenso, come Al Mughsayl, Adownib, Aluf, Uyun, Wadi Dowkah e Hasik. Sporadiche esplorazioni sono state effettuate nella vasta area pre-desertica che, oltre Thumrayt, si spinge verso nord fi no al confi ne con l'Arabia Saudita, da Muddy, Al Mathafah, Ginan Bin Nawatish fi no a Shisr (l'antica Ubar), Sayh al Kharyat e Dawka. In totale sono state esaminate 233 stazioni di raccolta che nel loro complesso coprono dettagliatamente l'area del Dhofar centro-meridionale. L'elenco fl oristico riporta 606 taxa di cui alcuni sono segnalati per la prima volta o per l'Oman (17 taxa) o per il Dhofar (13 taxa). Numerose sono le specie endemiche rinvenute (14 endemismi del Dhofar, 35 endemismi regionali: Dhofar/Oman e Yemen) presenti soprattutto sui versanti monsonici delle montagne costiere.

Using collection specimens, we measured the density and wing area of trichomes in 37 species of the bromeliad genus Tillandsia, specifically the abaxial proximal, abaxial distal, adaxial proximal and adaxial distal parts of the leaf. The product of the trichome "wing" area by the number of trichomes (means) produced a pure number (T) that was correlated to ecological features. The correlation was positive with respect to arid environments (xeric Tillands) and negative with respect to humid environments (mesic Tillands). Bulbous, and particularly myrmecophytic species and species with tanks, represented particular categories. Other intermediate types were identified based on the T number, totalling five ecological types. In comparison with other systems of ecological typification for Tillands and other Bromeliaceae, the present system offers measurable data whose analysis is reproducible.