Tapetum development in Cucurbita pepo (Cucurbitaceae)

The tapetal cell walls are of uniform thickness before prophase; from leptotene onwards, those of the inner tangential and the proximal half of the radial wall swell. At late tetrad stage the swollen walls disappear, only the outer (distal) tangential and the distal part of the contiguous radial walls persist until degeneration. In prophase, plastids are undifferentiated, resembling those of microspore mother cells, but their development pattern changes from the first meiotic division: they divide actively in the early tetrad stage and differentiate into elaioplasts in the late microspore stage. Elaioplast and spherosome lipids contribute to pollenkitt formation. Degeneration of the tapetal cells results in a single lipid sphere for each cell; these spheres are pollenkitt precursors and cover the pollen grain in the late bicellular stage. Sporophytic proteins are deposited under the operculum during late microspore stage, face to face with gametophytic proteins localized in the pectocellulosic part of the pore. The tapetal cells degenerate during early bicellular pollen stage, in contrast to other species in which the degeneration takes place in the late microspore stage

Development and ultrastructure of Cucurbita pepo nectaries of male flowers

The development of the nectary of the male flower of Cucurbita pepo L. was studied from 5 d before to 2 d after anthesis. The nectary consists of parenchyma that stores starch in the presecretory stages, and epidermis. An hour before nectar secretion begins, the starch is hydrolyzed. The nectar exudes from the stomata and forms a continuous layer on the nectary surface. During anthesis the nectar may all be collected by pollinators or some or all of it may remain in the nectary and be successively resorbed. The nectary parenchyma stores material for synthesizing the sugar component of nectar and stores similar material again after nectar resorption. It is also responsible for nectar production and secretion. The epidermis is actively involved in the reabsorption process. The resorption of nectar is a phenomenon that allows the plant to recover invested energy. Few observations on this phenomenon have hitherto been published

Conclusioni

Questo lavoro sulla predittività dei test di accesso TOLC-E e TOLC-I si inserisce, a pieno titolo, in due progetti di ricerca promossi da alcuni autori di questo rapporto. Il primo, del 2016, è il “Protocollo di Ricerca per lo studio della mobilità universitaria (MS) e delle carriere universitarie” tra gli atenei di Palermo, Napoli Federico II, Firenze, Torino, Cagliari, Sassari e Siena e il Miur. Il secondo è un Progetto di Rilevanza Nazionale 2017HBTK5P dal titolo “From high school to job placement: micro-data life course analysis of university student mobility and its impact on the Italian North-South divide”, linea Sud, finanziato nel 2019 con la partecipazione degli atenei sottoscrittori del protocollo col Miur con sede nel Sud. La questione di fondo (a cui sicuramente non riusciamo a dare una risposta in questa sede) è capire se lo studente è stato orientato e in che modo, a quali informazioni ha avuto accesso per “riconoscere” i propri interessi e, conseguentemente, se ha scelto il corso di laurea e l’ateneo che si addicono alle sue aspettative. Il lavoro qui proposto, analizzando a livello nazionale la predittività dei test di accesso in due grossi gruppi disciplinari, vuole aggiungere un tassello di conoscenze nel passaggio cruciale tra la scuola secondaria e l’università

Short Tandem Repeats (STR) per verificare la tracciabilità delle carni bovine

In order to improve the confidence of consumers and guarantee quality and safety of beef meat along the whole production chain, several techniques have been developped in the last years for traceability. Biomolecular methods, based on genetic fingerprinting, seem to be the most reliable tools; among these, analisys of DNA polymorphism, based on microsatellite molecular markers (Short Tandem Repeats –STR) seems to be the most applicable technique. Data concerning the field application of STR are reported in the discrimination between animals,STR analysis has been performed on 11 mocrosatellites of 415 samples of blood and beef meat , collected before slaughter and at retail respectively. All the samples originated from tao distribution companyes which had already improbe a documental traceability system. Resuld demostrated that STR analyses is a reliable tool for the comparison of blood and meat , and no differences were observed between samples originating from the same animal. However, in five cases, STR analyses evidenced the mismatching of documental traceability, in addiction, STR analyses has been also successfully applied to boiled, roasted and stuffed meat. Therefore, STR analyses can be used to guarantee traceability along the whole beef chain, from live animal to meat, distribution and consumption included