Carotenoid biosynthesis in Rhodomicrobium vannielii. Experiments with nicotine and 2-(4-chlorophenylthio)triethylammonium chloride (CPTA)

Nicotine and 2-(4-chlorophenylthio)triethylammonium chloride (CPTA) each inhibit production of the normal carotenoids of Rhodomicrobium vannielii (Rhodospirillaceae), especially rhodopin, beta-carotene and spirillixanthin, and cause the accumulation of lycopene. The inhibition of hydration of the C-1,2 double bond as well as cyclization is in agreement with proposals that these two reactions involve similar mechanisms. After removal of nicotine, cells reincubated in buffer solution or in the presence of diphenylamine convert accumulated lycopene into rhodopin. Under other conditions rhodopis is synthesized, on removal of nicotine, not from accumulated lycopene but from early precursors. The pathway of rhodopin and spirilloxanthin biosynthesis in Rm. vannielii is discussed briefly, and the possible involvement of enzyme aggregates in carotenoid biosynthesis is considered.

Estimation of genetic parameters in barley (Hordeum vulgare L.) : II. Partial diallel analysis

Four different sets of partial diallels were analysed for their relative efficiencies for estimating the genetic parameters in barley: (1) partial diallel with 12 parents, each involved in only 5 crosses; (2) partial diallel with 12 parents, each involved in only 3 crosses; (3) partial diallel with 8 parents, each involved in only 5 crosses; and (4) partial diallel with 8 parents, each involved in only 3 crosses. In partial diallel experiments, the estimates of gca effects were higher than in those of full diallel. Ranking pattern of the parents on the basis of gca effects in partial diallels deviated considerably from the ranking in full diallel. With decreasing "s" per parent, the deviation in ranking was also more. This clearly suggests the unsuitability of partial diallel analysis for screening high general combiners. Selection of best cross combinations is also not possible because only a sample of crosses (s out of n) is analysed under partial diallel so that there is every possibility of the best cross being excluded from the sample. In general, overdominance was exhibited, indicating that there is ample scope for heterosis breeding in barley.

Sulfhydryl analogues of adenosine diphosphate: chemical synthesis and activity as platelet-aggregating agents

2-Thioadenosine 5'-diphosphate (2-SH ADP), 2,2'-dithiobisadenosine 5'-diphosphate (2,2'-(S-ADP)2), 8-thioadenosine 5' diphosphate (8-SH ADP), and 6-mercaptopurine riboside 5'-disphosphate (6-MPRDP) were synthesized as potential affinity labels for ADP receptors on the blood-platelet membrane. The mean relative activities of these compounds in aggregating human platelets suspended in homologous plasma were 155% (2,2'-(S-ADP)2), 74% (2-SH ADP), 0.65% (8-SH ADP), and 0.08% (6-MPRDP). The mean relative activities against washed platelets were 249% (2,2"-(S-ADP)2) and 115% (2-SH ADP), whereas no aggregation occurred with 8-SH ADP or 6-MPRDP. The last two compounds were found to be weak inhibitors of ADP-induced aggregation. Therefore, thio-substitution at postition 2 followed by oxidation to a disulfide appears to be the most promising approach to further studies of affinity labelling of membrane ADP-receptors.

Estimation of genetic parameters in barley (Hordeum vulgare L.) : I. full, half and quarter diallel analysis

Four exotic and four indigenous strains of barley were used for making diallel crosses. The sets of parents and crosses making full, half and quarter diallel were analysed in a randomized block design for plant height, number of effective tillers, ear length, grain yield per plant, 100 grain weight and number of grains per ear.The three alternatives of diallel were similar with respect to the estimates of degree of dominance, general combining ability and specific combining ability, indicating that all these three methods of diallel were equally efficient. However, as the number of entries are minimum in quarter diallel, it would be economical in terms of cost, time and labour to estimate genetic parameters by this method. Average degree of dominance was found in the range of overdominance. The ranking of parents on the basis of their array mean was similar to the ranking based on gca effects. Similarly, the ranking of crosses on the basis of per se performance was similar to the ranking based on sca effects. This suggests that the selection of best general combiner or best cross combinations may be easier and more effective through array mean for per se performance rather than through high gca and sea effects, respectively. From among 56 crosses, IB-226 X X C-164 was the one which showed superiority for maximum number of characters followed by AB-12/59 X PTS-57. High sea effect for plant height, ear length, grain yield, 100 grain weight and number of grains per ear was the result of cross between parents having high X low general combining ability, indicating additive X dominance type of gene interaction. For number of effective tillers, high sca was produced by low x low general combiners, indicating dominance x dominance gene interaction.