Applying Some Plant Attributes And DNA C-Values To Evaluate Angiospermous Invasiveness

China is one of the most serious countries suffering plant invasions. With the growing economy, society, and all sorts of internal and international communications, the challenge becomes even more troublesome, and the potential for new plant invasions in China is high. Measures toward predicting and preventing plant invasions are urgently needed. To filter idiographic and effective indices in evaluating angiospermous invasiveness, and explore the potential and methodology of those applications, the present research investigated the relationships between some attributes of invaders and environmental factors, the attributes and plant invasiveness, and the DNA C-values and plant invasiveness. The main results are:1. The native and exotic angiospermous weeds share common attributes, which testified the coincidence between the invasiveness and weediness. Attributes of plants varies greatly among different groups, which suggests that the relative research should keep full attentions to the phylogenetic patterns. The results in the paper fully convinced the utility and necessity of using congeneric non-weedy species as benchmarks, for predicting plant invasiveness.2. Field investigation on 73 sites in the suburb of Jinhua city, Zhejiang province showed that in different types of habitats, invaders would adopt different attributes, which suggests different adaptive strategies. For example, the Canonical correspondence analysis(CCA) based on the environmental variables and botanical attributes showed that the exotic weeds, which are stemless or perennials, or have rhizomes, vegetative reproduction and bilateral symmetry flowers, were often recorded in the habitat with higher water content; in woodland, the weeds are often biennials, toxic, or have rhizome, scramble stem, thorn and thick leaves; the weeds in the soil frequently ploughed are often annuals; and in the residential areas or the environments with heavy traffic, the exotic species are often toxic, or have utricle, larger seeds.3. The statistical analysis on 1750 herbaceous angiosperms in Zhejiang, Shanghai, and Jiangsu showed that in the surveyed area, weedy herbaceous angiosperms are likely to be shade intolerant, toxic, annual or biennial rosette plants adapted to wet, xeric or sunny habitats. They are likely to have wind pollinated bisexual flowers and produce many small mucilaginous or armed seeds. They are unlikely to be mesophytes, have thorns, or reproduce vegetatively.4. Comparisons on seed germinations under temperatures from 10℃to 35℃among 12 weedy and congenous non-weedy species in relation to five genera (Vicia, Avena, Daucus, Lactuca, Solidago) showed interesting results. It is feasible to compare seed germinations among congeneric species with diverse seed weights. The final cumulative germination rate is of low value to evaluating plant invasiveness. Among seeds without obvious dormancy, weeds commonly hold lower germination rate index under favorable conditions comparing to congeneric non-weeds. And seed germinations of weeds are more sensitive to temperature stresses.5. The two nuclear values vary greatly among different groups, for example, significantly higher in herbs than in trees, in monocots than in dicots, in perennials than in non-perennials. The two nuclear values both have significant effects on plant invasiveness, especially in herbs, dicots, monocots, perennials, non-perennials, diploids, polyploids, Compositae, and Poaceae, while not significant in trees and Fabaceae. Similar to weeds, the two values in crops are low, which suggests that crops may commonly hold higher invasive potential. To evaluate the invasiveness of a given species, the information about ploidy level is necessary, and for polyploids, basic genome sizes are more reliable. For the results suggest that the selection favors polyploids in weeds at least partly because of the downsizing of basic genome size along with polyploidization.6. Five Vicia species, Vicia sativa, V. tetrasperma, V. hirsuta, V. tenuifolia, V.faba, which hold different DNA C-values and invasiveness, were taken as material to conduct comparison in cytological and life history indices. The results showed that plants with lower meristematic karyon mass are prone to have smaller masses of total chromosomes, karyons, cells, and seeds; quicker mitosis and seedling growth rates; higher seed production; and shorter generation time. These results support applying the meristematic karyon mass in lieu of, at least supplement to DNA C-value to evaluate plant invasiveness.Together all the above results suggest that an effective plant invasiveness assessing system should include many indices. And the standardized coding methods of different indices may possibly be different according to their relationships with invasiveness and different habitats. In the last part of the present paper, I summarized seven problems and perspectives about my research.