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Ribosomes in incompatible pollen tubes in the Solanaceae (1998)

Walles, Björn ; Han, Shu Ping

Copenhagen : Munksgaard International Publishers

Physiologia plantarum 103 (1998), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Some members of the Solanaceae have a self-incompatibility mechanism preventing self-fertilization. Stylar ribonucleases (S-RNases) are responsible for growth inhibition of self-pollen tubes. A prevalent model postulates that the S-RNases act as intracellular cytotoxins that degrade ribosomal RNA, and possibly also messenger RNA, in the incompatible pollen tubes. Since ribosomes and polysomes are easily noticed with the electron microscope, it should be possible to confirm disintegration of these structures. However, our inspection by electron microscopy revealed the presence of ribosomes and polysomes in pollen tubes formed after self-pollination of the self-sterile species Brugmansia (Datura) suaveolens and Nicotiana alata. There was no decrease over time in the number of bound ribosomes per unit of rough endoplasmic reticulum (RER) membrane. The results indicate that the inhibition of tube growth is not due to a general degradation of ribosomal and messenger RNA. Therefore, the substrate for S-RNases presumably is very specific.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1034/j.1399-3054.1998.1030403.x

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Linear Forms in Finite Sets of Integers (1998)

Han, Shu-Ping ; Kirfel, Christoph ; Nathanson, Melvyn B.

Springer

The Ramanujan journal 2 (1998), S. 271-281

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ISSN: 1572-9303

Keywords: sums of sets of integers ; sumsets ; growth in semigraphs ; additive number theory

Source: Springer Online Journal Archives 1860-2000

Topics: Mathematics

Notes: Abstract Let A_1, ..., A_r be finite, nonempty sets of integers, and let h_1,..., h_r be positive integers. The linear formh_1A_1 + ··· + h_rA_r is the set of all integers of the form b_1 + ··· + b_r, where b_i is an integer that can be represented as the sum ofh_i elements of the set A_i. In this paper, the structure of the linear form h_1A_1 + ··· + h_rA_r is completely determined for all sufficiently large integersh_i .