Section 12 — Plasmatic Inheritance 



after meiosis, which was before the shortening 

 effect was evident. Amino acid content of the 

 leaves and tassels at various stages were analyzed 

 by means of paper chromatography. Certain 

 amino acids varied quantitatively and qualita- 

 tively, depending upon the stage of develop- 

 ment of the plants. 



The very fact of the control on and the mode 

 of the transmission through grafts indicated that 

 the cytoplasmic hereditary elements have at- 

 tributes of both plasmids and viruses. This, and 

 the induction in one case of an apparent chromo- 

 somal integration of the trait, after its induction 

 in the progeny of the fertile graft symbionts, 

 resemble an episome-like behaviour. 



12.13. A New Interpretation of Cytoplasmic Inheri- 

 tance in Streptocarpus (Gesneriaceae). Hans 



Marquardt (Freiburg, Germany). 



In Escherichia coli and yeasts regulator sys- 

 tems (i.e. the interaction of structural genes, 

 operator-regions and regulator genes, producing 

 a repressor-protein) have been found. Oehlkers 

 analysed in numerous papers the cytoplasmic 

 inheritance in the formation of the androeceum 

 and gynaeceum in the flowers of Streptocarpus 

 hybrids (Sympetalae, Gesneriaceae). His results 

 can be interpreted on the assumption, that in 

 the genome there are androeceum-determining 

 and gynaeceum-determining genes with their 

 corresponding operator regions. Instead of a 

 regulator gene, regulator units may be present 

 in the cytoplasm. The repressor-protein produced 

 by the regulator-units of the plasmone of various 

 Streptocarpus species either reacts with the 

 operator-region of one of the two structural 

 genes, thereby blocking the normal development 

 of the androeceum and the gynaeceum; or else 

 inactivating substances in the cell metabolism 

 are formed, which affect (inactivate) the repres- 

 sor-protein. On the basis of these assumptions 

 it is possible to interpret the observed variable 

 anomalies in the development of the androe- 

 ceum, especially in the Str. wendlandii hybrids. 

 The hypothesis is supported by a temperature 

 experiment conducted by Oehlkers (1956) and 

 by the observed switching of sex-expression in 

 the androeceum of suitable hybrids during 

 flowering time. Further experimental tests of the 

 hypothesis are envisaged. 



12.14. Alternative Cytoplasmic and Nuclear Heredi- 

 tary Elements in Petunia. Rafael Frankel 

 (Bet Dagan, Israel). 



Asexual transmission of cytoplasmic male 

 sterility in Petunia hybrida through heteroplastic 

 grafts induced two types of male sterility in 

 the progeny of fertile graft components: One of 

 these was maternally inherited, as was the origi- 

 nal trait in the male sterile graft symbiont, whe- 

 reas the other one exhibited mendelian segrega- 

 tion. The progeny of the donor plants for the 

 graft components served as controls. 



12.15. Plasmon Analysis of Species of Solanum. 



Paul Grun, and Mary Aubertin (Univer- 

 sity Park, Pennsylvania, U.S.A.). 



Plasmon factor /« s is sensitive to dominant 

 genes of the In series, the expression of the gene- 

 plasmon interaction being a failure of pollen 

 dehiscence. To date five different In genes have 

 been located any one of which can lead to inde- 

 hiscence when it is combined with plasmon factor 

 /« s . Separate accessions of Solanum chacoense, 

 which have the /« s plasmon factor, are different 

 in the number of alternative In genes to which 

 they are sensitive. The geographical distribution 

 of the individual //; genes appears to be rather 

 wide, for plants sharing the same In genes have 

 been located in populations from Ecuador, 

 Colombia, and Peru. No single distinctive ab- 

 normality in cytological development has yet 

 been identified as the cause of indehiscence, 

 for indehiscent plants even within single proge- 

 nies vary in their anther contents. Some have 

 anthers containing normal pollen, some shrun- 

 ken pollen, some a mixture of normal and shrun- 

 ken pollen, and some degenerate bubble- 

 surfaced sporocytes. It seems, therefore, that 

 the gene-plasmon interaction may operate 

 through failure of normal anther development 

 rather than failure of pollen development. Ab- 

 normality of anther development can, as a 

 result of specific epistatic interactions, lead to 

 other pollen or sporocyte irregularities. 



This research was supported by a grant from 

 the National Science Foundation. 



12.16. Extranuclear Inheritance of Induced Plastid 

 Mutations in Arabidopsis thaliana. G. Rob- 

 belen (Gottingen, Germany). 



Plastid development towards an active, nor- 

 mal green chloroplast is controlled by intra- 

 as well as extranuclear factors. The mutations of 

 both block these processes at many different 

 points. 



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