Amount of DNA complementary to ribosomal RNA in polyploid series of Scilla autumnalis L. and Urginea maritima (L.) Baker

1976 ◽  
Vol 110 (4-5) ◽  
pp. 331-335 ◽  
Author(s):  
Fabio Maggini ◽  
Paola Bassi ◽  
Pasquale Stanziano
Chromosoma ◽  
1974 ◽  
Vol 46 (1) ◽  
pp. 23-28 ◽  
Author(s):  
C. Cullis ◽  
D. Roy Davies

2012 ◽  
Vol 22 (4) ◽  
pp. 299-309 ◽  
Author(s):  
I. Marques ◽  
D. Draper

AbstractThe seasonality of the Mediterranean climate has important implications for plant physiology and some specific conditions must be met before germination can occur. Most plants sprout during the spring season although a few germinate during the autumnal rainy period. To understand the patterns of germination under autumn conditions we selected five Mediterranean autumn-flowering geophytes that usually co-exist in fire-prone habitats:Leucojum autumnale,Narcissus cavanillesii, Narcissus serotinus, Scilla autumnalisandUrginea maritima. Experiments were performed under conditions simulating those prevailing in the habitat during the autumnal Mediterranean season when seeds of these species usually germinate. In all species, germination occurred quickly ( < 7 d), was usually higher at the lowest temperatures tested (15°C, 20°C; >89%) and no signs of delayed germination were detected. Nevertheless, species usually had different patterns of seed germination, a strategy that might avoid interspecific competition when co-occurring in the same habitats. Germination was lower and slower in light than in darkness, suggesting that under natural conditions germination of seeds directly exposed to sunlight can be severely restricted. Several fire-dependent treatments (heat and ash) revealed a lack of fire-stimulated germination, and treatments even had a negative effect. In addition, only a small fraction of seeds remained viable after 1 year of dry lab storage and their germinability was very low, suggesting the absence of a permanent soil seed bank in the life cycle of these geophyes.


Author(s):  
Daniel Beniac ◽  
George Harauz

The structures of E. coli ribosomes have been extensively probed by electron microscopy of negatively stained and frozen hydrated preparations. Coupled with quantitative image analysis and three dimensional reconstruction, such approaches are worthwhile in defining size, shape, and quaternary organisation. The important question of how the nucleic acid and protein components are arranged with respect to each other remains difficult to answer, however. A microscopical technique that has been proposed to answer this query is electron spectroscopic imaging (ESI), in which scattered electrons with energy losses characteristic of inner shell ionisations are used to form specific elemental maps. Here, we report the use of image sorting and averaging techniques to determine the extent to which a phosphorus map of isolated ribosomal subunits can define the ribosomal RNA (rRNA) distribution within them.


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