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The formation of vacuoles in wheat (Triticum aestivum cv. Highbury) starchy endosperm cells was studied using electron microscopy. Some vacuoles were always present, even in the coenocytic cytoplasm. The first formed endosperm cells were highly vacuolated, but became filled with cytoplasm as they grew older. Various-sized pieces of cytoplasm were found in vacuoles of developing endosperm cells, probably as a result of autophagic sequestration. The membranes of the autographic vacuoles appeared to originate from the rough endoplasmic reticulum and from extensions of already-formed vacuoles. Autographic activity was confirmed by localizing the hydrolytic enzyme acid phosphatase within the vacuoles. The rough endoplasmic reticulum (RER) also stained positive for this enzyme.

Wheat endosperm development has been studied in numerous laboratories. The genera 1 i zed scheme of protein body formation assembled from these data indicates that storage proteins are initially formed in the rough endoplasmic reticulum (RER). The storage proteins in RER may be processed via the Golgi apparatus into vesicles that enlarge by several mechanisms into membrane-bounded protein bodies. The prote in bodies are transported through the cytoplasm to the vacuole where they fuse with the tonoplast and deposit the protein granules into the vacuoles. The protein granules fuse with one another, lose water, and eventually become transformed into the matrix. The starchy endosperm is reduced to small particles of starch and protein during milling. These flour particles are dynamically rehydrated during dough formation. The protein forms the major structural network surrounding starch granules in doughs. The framework of bread crumb, however, is of dual composition; the protein network and a newly formed network of gelatinized starch.

De : BECHTEL Delphine Collections : Histoire, Mémoires en jeu ISBN : 978-2-84174-767-2 Année : 2016 Nombre de pages : 288 Prix : 26 € Email, RSS FollowSous la direction de Delphine Bechtel et Luba JurgensonEn Europe centrale et en ex-URSS, l’espace muséographique dévolu à la mémoire collective des violences de masse a connu, depuis la chute du Mur, un remaniement radical. De nouveaux enjeux politiques, sociaux, culturels, scientifiques, l’accès à des documents jusque-là hors de portée, la circulation des idées et des savoirs à travers des frontières désormais ouvertes ont permis à la fois de créer des façons inédites de documenter le passé trau- matique et d’initier une réflexion à l’échelle européenne, voire mondiale sur cette mise en mémoire du passé. Cette réflexion collective se fonde sur l’analyse des nouvelles représentations culturelles du passé au croisement d’innovations muséales, de cultures mémorielles et du champ de la commémoration des grandes violences du XXe siècle. Elle se veut résolument interdis- ciplinaire et regroupe des contributions d’historiens, sociologues, littéraires et muséographes.