Ecophysiological Characteristics And Allelopathy Of An Invasive Plant, Mirabilis Jalapa L.

Mirabilis jalapa L. belongs to the Mirabilis genus, which is classified in the familily Nyctaginaceae. It has become a major invasive plant in China. For evaluating its invasion, we estimated the genetic variation of M. jalapa with different color flowers by using inter-simple sequence repeats(ISSR)markers, investigated Ecophysiological characteristics under various environmental stresses by using artificial control soil water and temperature, and studied allelopathy of M. jalapa by bioassay methods and micronucleus test technique of Vicia faba cells. The results were as follows.Of the 100 primers, 5 produced highly reproducible ISSR bands. These primers were carried out on 3 colonys of M. jalapa with purple, white and yellow flowers from Chengdu City, Sichuan Province. High genetic variation was revealed. 67discernable DNA fragments were with 62(92. 54 %)being polymorphic. Observed number of alleles (Na), effective number of alleles (Ne), Nei's gene diversity (H) and Shannon's information index (I) was 1.9254, 1.2354, 0.1562 and 0.2633, respectively. The values of genetic identity range from 0. 6330 to 0. 9080. Nei's genetic distance in the 3 colonys was from 0. 038 to 0. 0994, which was the closest(0. 0388)between colony with white flower, and colony with yellow flower and the farthest(0. 0994) between colony with yellow flower and colony with purple flower. UPGMA cluster analysis based on Nei's genetic distance showed similar result. The genetic variation mainly occurred in colony of M. jalapa with same color flower, and Nm of different color populations was 1. 279.Under drought and temperature stresses, change of malondialdehyde (MDA) content, antioxidant enzyme system and osmotic adjustment substances (soluble sugar and soluble protein) of M. jalap indicated that M. jalapa had various resistance mechanisms to stress. Comprehensive judgment indicated that sensitivity of this species to stress was in turn low temperature, high temperature, and drought. These results might help to devise innovative approaches to control the spread of this invasive plant.In the present study, we tested the allelopathic effects of aqueous extracts of M. jalapa on seed germination and seedling growth of Triticam Aestivum L. , Lactuca sactiva L. and Brassica Campestris L. The results showed that all aqueous extracts have allelopathy on receptor plants. The aqueous root, stem and leaf extract of M. jalapa inhibited seed germination and seedling growth in a certain extent. The aqueous extracts of M. jalapa produced genetic toxicity and inhibited mitosis of V. faba root tip cells. With the increase of concentration and action time, mitotic indexes decreased and frequencies of micronucleus increased. There were some abnormal phenomenon of root tip cells such as micronucleus, chromosome bridge, chromosome break, chromosome lag, chromosome conglutination, chromosome loop and three pole divide. After drought stress, the allelopathic effect of aqueous extracs of M. jalapa on V. faba root tip cells was stronger than that before stress.