Studies on the DNA Base Composition of Varying Higher Plants

Abstract

he DNAs were extracted and purified from varying higher plants, and the plants we examined are as follows. I. Cryptogams Ginkgoaceae Abietaceae I. Phanerogams Salicaceae 2 species Betulaceae 1 species j>apaveraceae 2 species Brassicaceae 5 species Rosaceae 3 species Fabaceae 15 species Apiaceae 4 species Solanaceae 9 species Labiatae 1 species Cucurbitaceae 7 species Asteraceae 11 species The DNA bases were analyzed chemically and the following results were obtained. I. Cryptogams The DNA base compositions of leaves of gingko (Ginkgoaceae) and larch (Abt"etaceae) are 31 and 37 G-C % respectively, showing the same values of the corresponding pollens. I . Phanerogams Salicaceae; The DNA of Salix and Populus has the same 36 G-C%. Papaoeraceae; The DNA of Papaoer and Chelidonium contains the same 34 G-C%, Betulaceae: A. tinctoria······ 35 G-C%. Rosaceae: The DNA of three species has the same 37 G-C%. Brassicaceae: The DNA G-C contents of these species are ::6-38%. Fabaceae: Most of these species possess 3236 G-C% of DNA except higher one of 40-43% in two species of clover (TrifoUum) Apiaceae: The DNA of these species has lower G-C% of 30-32, as compared to that of other higher plants. Solanaceae: The DNA of seven species of this group has the same 33 G-C%, while that of 2 other species (Tabacum and Lycium) has much higher G-C % of 41. Labiatae: L. amplexicaule-r- .. 32 G-C % Cucurbitaceae: The DNA of these species has a narrow range of G-C content such as 33-35%. Asteraceae: The DNA of 11 species of this group has 33-36 G-C%. The DNA of all higher plants examined, contains 5-methyl-cytosine as minor base. Thus, the DNA of varying higher plants has no great divergence of G-C content (30-43%) and the DNA base composition of a majority of higher plants we examined, keeps a narrow range of G-C spectrum (32-38%). But the DNA base composition is similar in species under the same class or group and in closely related species even in higher plants. And it is noteworthy to mentioning that some species of same group are markedly different from its other members in DNA G-C content, in certain classes, such as Solanaceae and Fabaceae. The classical taxonomic criteria was discussed in special reference to such a divergence of DNA base composition in the species under the same class or group. It should be noted that a similarity of DNA base compositions among different species does not mean its sequence homology.