Allelopathic Effect And Its Mechanism Of Root Active Substance Of Invasive Plant Solidago Canadensis L.

Solidago canadensis L. is a malignant invasive weed, the present study shows that the new weapon hypothesis is one of the widely accepted invasion mechanism, but the key allelochemicals is still unknown. We studied the allelopathy of the aqueous extracts from different parts of S. canadensis L.; allelopathy, autotoxicity and bacteriostasis of monomer compound separated from ethanol extracts of root; and explain the possible mechanism of allelopathy from the level of cytobiology and molecular biology. The main results were as follows:1. The extract from aerial parts of S. canadensis L. inhibited the germination and seedling growth of Zoysia japonica at some extent, and showed dosage effect. The 50 g L-1 aerial parts extract significantly increased the MDA concentration and POD activity of Z. japonica seedlings. Root extract had no effect on POD activity of Z. japonica seedlings at 50 g L-1, but significantly inhibited all parameters except CAT activity at 150 g L-1. Litter extract did not affect the germination and seedling growth of Z. japonica.2.We separated two monomer compounds of phenols(methyl caffeate and ethyl caffeate) from the roots of S. canadensis L., and through the seed germination, autotoxicity and bacteriostasis experiment to study the allelopathic activity. ⅰ) Seed germination experiment showed methyl caffeate and ethyl caffeate had certain inhibitory effect on lettuce seed germination and seedling growth at 100 μg/mL. ⅱ) Autotoxicity experiment found caffeate and ethyl caffeate inhibited both native Pterocypsela laciniata and S. canadensis L. seedling growth, and had stronger inhibitory effect to native P. laciniata seedlings. ⅲ) Caffeate and ethyl caffeate inhibited both Fusarium oxysporium and Rhizoctonia solani growth.3. We used Arabidopsis thaliana to further explore the allelopathy mechanism from the level of cytobiology and molecular biology. The results are as follows: ⅰ) methyl caffeate and ethyl caffeate inhibit A. thaliana seed germination and seedling growth, especially influence the A. thaliana root growth. By observing the A. thaliana root development, we found the higher concentrations result in more seriously damage in root tip cell morphology and weaker cell activity. ⅱ) A. thaliana cell division cycle gene(cdc2a) and cell proliferation marker gene(pcna1) expression quantity decreased, taproot growth regulation gene(AtRRE1) expression quantity significantly increased when treated with methyl caffeate and ethyl caffeate. We can infer that the methyl caffeate and ethyl caffeate in S. canadensis L. root through influence the expression of related genes to regulate the growth and development of A. thaliana seedlings.