INHERITANCE OF NUCLEAR-DNA CONTENT IN LEAF EPIDERMAL-CELLS OF ZEA-MAYS L

The nuclear DNA content (ploidy level) of maize leaf-epidermal cells w as investigated by Feulgen cytophotometry in two lines, Illinois High Protein (IHP) and Illinois Low Protein (ILP), their reciprocal hybrids , and their F(2)s, Epidermal cells have a 2C, 4C or 8C nuclear DNA con tent. The mean DNA content per nucleus in IHP was significantly higher than in ILP; the mean DNA content per nucleus in hybrids was intermed iate between the parental lines, and the same DNA content was measured in reciprocal crosses. In F(2)s the same mean DNA content as in F(1)s was observed but with larger variability than in the F-1, possibly in dicating genetic segregation. It is inferred that the ploidy level in the leaf epidermis is inherited, and incomplete dominance occurs in hy brids. The same behaviour in the different genotypes was observed for epidermal cell-surface area, except that an increase of mean surface a rea occurred in the F-1. probably due to heterotic effects, The differ ence in the accumulation of 4C and 8C nuclei in leaf epidermis paralle ls that reported between two genotypes for the endosperm tissue: to th e greater chromosome endoreduplication found in the endosperm there we re correspondingly higher frequencies of 4C and 8C nuclei in the leaf epidermis, indicating a higher general tendency to chromosome endoredu plication in IHP than in ILP. It is suggested that the accumulation of 4C nuclei (G(2)-block) in the leaf epidermis may be regarded as the i nitial step of chromosome endoreduplication. the two phenomena being r elated to the control of the sequence DNA synthesis-mitosis, possibly involving the same genes in both endosperm and leaf, However, the inhe ritance of DNA content per nucleus in epidermal tissue seems to be dif ferent from that observed in endosperm tissue of the same genotypes, s uggesting that differences may occur in the regulation of the activity of these genes.