On Variation Of DNA C-yalues Among Herbaceous Plants And Its Biological Significances

DNA C-value is an important biological concept, it has biological and ecologysignificance. With the accumulation of plant DNA C-value date, the study based onDNA C-value information is also expanding and deepening. So, the expansion ofdatabase of plant DNA C-values is usefull for a comprehensive understanding of plantDNA C-value distribution, and its possible significance on biological, ecological andevolutionary. Though quite a number of herbaceous plants DNA C-value has beenknown, their variation among different groups, and among different geographicalregions is not clear yet. In the present work, we determined the DNA C-value of111species herbaceous plants collected from the Yangtze River Delta region, and44samples of Echinochloa from the main rice cultivaation regions in China. Then weanalyzed the worldwide distribution pattern of the known DNA C-value of3290herbaceous species from145families, to provide basic information for moresystematic and comprehensive understanding of the biological and ecologicalsignificance of the DNA C-value. The main results are as follows:1. We have determined the nuclear DNA contents of111plant speciesbelonging to38families in East China and44samples of Echinochloa inChina, The average DNA C-value of111species of herbaceous plants is1.4464pg, with the highest value in Ranunculus muricatus Linn.(10.7415pg), and the lowest value in Cryptotaenia japonica Hassk.(0.5585pg).Most of the determined DNA C-values are between0.5to1.5pg. The meandata is1.4464pg, significantly lower than the worldwide average value(7.786pg), but similar to the value of the herbaceous from the area withE120-135°, N22.5-30°.2. Significant variations existed between the DNA C-values among theindividuals of Viola tricolor with different colors, and between the individualsof Taraxacum dissectum with different leaf shapes. While the values are notstatistically different between the individuals of Erigeron philadelphicus withdifferent flower colors, the case is the same as in Oxalis corymbosa.3. The DNA C-values of ornamental plants (36species) and others (303species)on China‘s Yangtze River Delta region are1.4335（±0.0895）pg and1.4577（±0.2160）pg, respectively, there is no significant different between thesetwo group.4. We determined the DNA C-values of44samples of Echinochloa from the main rice-cultivated regions in12provinces of China. The DNA C-valuevariation of the genus Echinochloa not only existed among the species, butalso among the intraspecific taxa. The average DNA C-value of the44samples is1.128pg, the lowest is1.0564pg, the highest is1.2048pg. Amongthe six samples of E. crusgalli, the value of the individual collected from Heilongjiang is the smallest (1.0708pg), that from Jiangxi is the highest(1.1876pg); there are only three samples of E. cruspavonis, and the lowestDNA C-value (1.0636pg) was found in the individual from Jilin, tand hehighest (1.556pg) from Jiangsu; the lowest DNA C-value (1.0668pg) of E.crusgalli var. breviseta was alos found in the individual from Jilin, and thehighest (1.186pg) from Fujian; The cases are similar for E. caudate, E.crusgalli var. mitis and E. crusgalli var. zelayensis. From the above results,the samples comes from Jilin province tend to have lower DNA C-value, andthose from Jiang Su, Fu Jian provinces higher.5. having analyzed the known DNA C-value and genome size of3290herbaceous species from145families in the world, we found the averageDNA C-value and genome size is7.784pg and6.77pg, respectively, with ahighest DNA C-value of127.4pg, the highest genome size of63.7pg, theirminimum values being0.1pg. The two sets of data vary much among differentfamilies. Among the51families with more than10species whose DNAC-values had been determined, Melanthiaceae have the highest average DNAC-value (48.072pg), Marantaceae the lowest (0.44pg), their difference beingmore than109times. Among35families with more than10species whosegenome size had been determined, Alstroemeriaceae have the highest averagedata (26.58pg), Marantaceae the lowest (0.37pg), the difference being72times. Significant differences of DNA C-values also existed betweenmonocotyledon and dicotyledon, between annuals to biennials and perennials,between non-weeds and weeds, between polyploidy plants and diploid plants.6. A total of2856herbaceous species, whose DNA C-value, genome size andgeographic ranges are clear, were analyzed to focus the differences betweenmonocotyledon and dicotyledon; annual, biennial and annual to biennial, andperennials; weed plants, non-weed plants. We found a similar variationpattern of DNA C-value and genome size with latitude: the DNA C-value andgenome size in the high latitude are bigger than those in the low latitude.7. We also analyzed the variation pattern of DNA C-values and genome size ofCompositae and Poaceae with latitude, and found the pattern consistent withthat of the whole herbaceous plants. However, the variation degree of DNAC-value and genome size with latitude was different among different families.For example, the variation of DNA C-value and genome size in the familyPoaceae is evident, but not obvious in the family Compositae.8. In this paper, we found the basic geographical variation pattern of DNAC-value and genome size with latitude. Our results did not support theprevious conclusions. We infer that the herbaceous plants DNA C-value in the local geographic area may better be explained by environmental factors,but on the global scale, may be related to the geological history and the casesof biological evolutionary...