Section 13— Plant Genetics and Breeding 



to have ventral resin ducts in some needles, in 

 addition to those reported in a recent report by 

 other workers: P. flexilis (0 to 2), P. strobus 

 (0-1), P. ayacahuite (2 to 4), P. strobus X flexilis 

 (0-1), P. monticola ■ P. ayacahuite (0-1). A 

 ventral medial resin duct was found in a needle 

 of a P. monticola griffithii hybrid from Pla- 

 cerville, California. 



Comparison of results with previous work 

 indicates that more research is necessary on all 

 species and hybrids of pines before definitive 

 descriptions are prepared. Evidently more 

 sampling is needed to avoid overlooking varia- 

 tion. Additional analyses are also needed be- 

 cause of variation caused by environment, 

 intraspecific genetic variation, or a combination 

 of both factors. 



13.34. Some Biochemical Aspects of the Phenomenon 

 of Heterosis in Maize. T. Craciun, A. Ciofu, 

 M. Ivanescu, M. Ferrando, M. Birsan, 

 I. BJrnaure and M. Ionescu (Bucharest, 

 Rumania). 



The present paper was written on the basis of 

 research work carried out by the Chair of Gene- 

 tics and Plant Breeding of the "N. Balcescu" 

 Agricultural College of Bucharest. 



In the framework of the more complex prob- 

 lem of the development dynamics of some char- 

 acters and special features in simple and double 

 hybrids in Fi in connection with the nature of 

 the crossed organisms and of hybridization, 

 detailed research work was carried out on the 

 chemical composition in different phases both 

 in the parents and in the maize hybrids. 



After the chemical analyses, the following was 

 found, inter alia: 



In the first phases of growth the general ten- 

 dency was observed that the inbred lines have a 

 higher percentage of starch-protein than the 

 simple hybrids. The relationship starch-protein 

 is in favour of protein, namely higher in the 

 inbred lines and lower in the simpler hybrids. 

 The amount starch + protein is higher in the 

 inbred lines and lower in the simpler hybrids, 

 while the amount of cellulose and hemicellulose 

 is higher in the simple hybrids than in the inbred 

 lines. 



At the end of July, in the milk-dough stage, 

 and taking in view precocity, the starch contents 

 of the simple hybrids have a tendency to equal 

 or to exceed the inbred lines. The protein con- 

 tents decrease and the relationship starch-pro- 

 tein is getting favourable to starch, generally in 

 hybrids. 



13.35. The Phenomenon of Heterosis and Vitamin 

 Concentration in Maize Plant. W. N. Stole- 

 tov, Ye. N. Odintsova and M. Shinkovitz 

 (Moscow, U.S.S.R.). 



In our investigations of the biological founda- 

 tions of heterosis the simple interlinear maize 

 hybrid and its two parent forms were used. 



We observed the growth and the development 

 (in hothouses and under field conditions) as 

 well as the distribution of the vitamins of the B 

 group in root, stem, leaves and reproductive 

 organs (panicle and corncobs). 



Also the leaves development and the dynamics 

 of vitamin accumulation in them were studied 

 (up to the stage of the appearance of panicle). 



Using Odintsova's microbiological micrometh- 

 ods the following six vitamins of the B group 

 were determined: meso-inositol, biotin, pan- 

 tothenic acid, thiamin, pyridoxin, nicotinic 

 acid. 



As was found, the vitamins of the B group are 

 concentrated mainly in the leaves and in the re- 

 productive organs — in panicle and corncobs. 

 Their total amount in these organs is very high. 



The above six vitamins are present in a very 

 small amount in the roots and in the stems. 

 Often they are absent entirely in these organs. 



Therefore the vitamin content in the leaf and 

 in the panicle can be used as the indicator of the 

 concentration of the vitamins of the B group in 

 the plant. 



The phenomenon of heterosis correlates 

 to the sharply increased concentration of the 

 vitamins of the B group in reproductive organs — 

 panicle and corncobs. In the leaves the more 

 high concentration of the vitamins of the B 

 group was observed for only two vitamins— 

 biotin and meso-inositol. 



The great ability to the accumulation of the 

 vitamins of the B group by the heterosis plant 

 in the process of its development, i.e. the ability 

 to the higher concentration of biocatalitical 

 substances is one of the important factors which 

 provides the most high accomodation by this 

 plant to the synthesis of plastic substances, to 

 the most powerful development of the vegetative 

 organs. 



13.36. Observations on Heterosis in Zea mays L. 



Helena Bankowska (Warsaw, Poland). 



Twenty-one inbred lines of maize of American 

 origin have been intercrossed. Their Fi exhibited 

 heterosis. Selection and inbreeding of some of 

 the most vigorous plants in F2 and in succeeding 

 generations resulted in isolating stable inbred 



221 



