Genome size in Hedera helix L. - a clarification

摘要

The correct genome size in Hedera helix L. has long been problematic, because several authors have reported nuclear DNA content plasticity in connection with phase change from juvenile to adult. Although this has been disproved, nevertheless uncertainty existed on the correct genomic DNA amount, due to one significantly higher Row-cytometric estimate in the more recent literature. The present analysis is concerned with this problem of a possibly variable genome size within the species or other reasons for this discrepancy. Plants of typical H. helix (2n = 48), H. helix f. arborescens (2n = 48), H. canariensis Willd. (2n = 48) and H. colchica (2n = 192) were measured with flow cytometry (propidium iodide staining) and video based Feulgen densitometry for genome size. Internal standards used were Glycine max (flow cytometry, 2C taken as 2.226 pg) and Pisum sativum (Feulgen densitometry, 2C taken as 8.84 pg). With flow cytometry, the H. helix varieties and H. canariensis were statistically invariant, 1.263-fold of G. max with a 2C value of 2.81 pg. Hedera colchica was 4.895-fold of G. max with a 2C value of 10.90 pg in agreement with its higher polyploidy level. Feulgen estimates were slightly higher but basically in agreement with these data. Neither value is close to the deviating value for H. helix in the literature mentioned above, that must remain unsupported. [References: 20]