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A population genetic model is proposed for the reproduction of self-incompatible inbred lines in which incompatibility is controlled by 1-4 loci. From theoretical considerations it was expected that: a) with the random matings of lines In, (obtained by self-pollination of n generations), some lines would be cross-incompatible (all the plants within these lines would be homozygous for S-genes) and the rest would be cross-compatible (retain heterozygosity for one or more S-genes); b) in the case of random matings of Unes InGm (obtained by self-pollination of n generations and by random pollination for m generations), some lines would be cross-incompatible (heterozygous for one S-gene) and the rest would be cross-compatible (retain heterozygosity for two or more S-genes); c) the relative proportion of sterile plants, obtained by random pollination of cross-compatible lines, would be related to the number of segregating S-loci and to the generation in which the lines are studied.Forty-four inbred lines of sugar beet derived from self-incompatible plants of a population were analysed. Comparisons of the observed values with the theoretically expected ones demonstrated that: a) of 18 In (I1-I4) lines, 6 were cross-incompatible (homozygous for S-genes) and 12 were cross-compatible having one S-locus segregating in 7 lines and two S-loci segregating in 5 lines; b) of 22 InG1 (I2G1 and I3G1) lines, one line was self-fertile, 7 lines were cross-incompatible (heterozygous for one S-loci) and 14 lines were cross-compatible (heterozygous for two S-loci).No line was found to have three or more segregating S-loci. The results of this population genetics analysis of self- and cross-incompatibility in sugar beet comply with diallel analysis data on sugar beet incompatibility and indicates that it is under the gametophytic control of two basic S-loci.

Glutamate dehydrogenase extracted from wheat leaves (Triticum aestivum L. cv. Capitole) taken at two different physiological stages was analysed by electrophoretic and immune‐chemical techniques. Two NAD‐dependent antigens were identified which bear the balk of the glutamate dehydrogenase activity in the two extracts. The first enzyme was found in much larger amounts in young than in senescent leaves and the reverse situation was observed for the second antigen. The possible relationships between this antigenic polymorphism and the heterogeneity detected by isoelectric focusing from the two extracts were investigated. A charge heterogeneity (isoelectric points about 5.7 and 4.8) was found for the first antigen in both extracts. The second antigen appeared homogeneous (isoelectric point about 5.7) at least in senescent leaves. The last result indicates that two quite different antigens appear in the same isoelectric focusing zone.

No abstract

The activity of glutamate dehydrogenase and the amounts of two antigens, bearing the bulk of this activity, were determined in wheat leaves (Triticum acstivum L. cv. Capitole) at different ages. These results were compared to those obtained with leaves deprived of light (darkness‐stressed) during three days, at different stages of leaf life. The glutamate dehydrogenase activity increased in the leaves during normal senescence of the whole plant. De novo synthesis of one of the glutamate dehydrogenase proteins was shown, which correlated with this, increase in activity. The considerable differences between She effects of darkness‐stress, according to the leaf age, may characterize three steps in the leaf life: a first step during which leaves were not affected by stress, a second one for which the stress effect was partially reversible, and a final one during which stress impact was irreversible.