The Research About Allelopathic Effects Of Solidago Canadensis L. Under The Drought Stress

Three different extent droughts were treated to Solidago canadensis L.: control(CK) (the water content was 68.23%), drought group 1 (the water content was 37.55%), drought group 2 (the water content was 27.41%) .The aqueous extracts (0.08g /mL, dry weight)from rhizomes, stems and leaves of different groups were prepared, then the content of allelochemical phenols of different groups were measured. The results showed that the content of allelochemical phenols no matter from rhizomes, stems or from leaves had the same rule : drought group 1>drought group 2>control (CK) .The rhizomes were more sensitive to the drought stress than the others . (In the condition of the rhizomes, the OD of the control (CK) was 0.843, equal to 58.22% of drought group2, 41.84% of drought group1). All of above indicated that under drought stress the content of allelochemical phenols increased to some extent in each organs of Solidago canadensis L. while strongest drought made the increase down.Aqueous extracts of 0.08g/mL, 0.04g/mL, 0.02g/mL from rhizomes, stems and leaves of different groups were prepared and used as treatment solutions to assess their effects on seed germination and seedling growth in three target species, radish(Raphanus sativus L.), Chinese cabbage (Brassica pekinensis (Lour.) Rupr.)and Wheat(Triticum aestivum L.) .Corresponding physiological indexes were measured and the results were as follows :(1) Different organs of different groups showed different allelopathy effects to these three target species .In the case of rhizomes, the allelopathy effects to these three target species from strong to weak were as follows : control (CK)>drouht group 1>drought group 2; In the case of stems, the allelopathy effects from strong to weak were : drought group 1>drouht group 2>control (CK) ; In the case of leaves, the allelopathy effects from strong to weak were : drouht group 1> control (CK)>drought group 2.(2) In the same group, under the same concentration, the allelopathy effects of different organs to these three target species were different. Generally speaking, the allelopathy effects of leaves were stronger than rhizomes or stems .Under the higher concentration, aqueous extracts from leaves not only inhibited the seed germination tendency of these three target species strongly, but also decreased the germination percentage, the seedling height, the content of chlorophyll a and the total content of chlorophyll.(3) In the same group, the allelopathy effects of the same organs related to the concentration of the aqueous extracts .Generally speaking, the concentration of the aqueous extracts higher, the allelopathy effects stronger.(4) No matter in which group, no matter under what concentration, the aqueous extracts from any organs deformed the early seedlings to some extent .The deformed seedlings of radish and Chinese cabbage exhibited that the roots grow upward while the stems grow downward . The deformed seedlings of wheat exhibited that the roots can not grow horizontally : only the tips of the roots connected with the filter paper, the base of roots grew upward and deviated from the filter paper.(5) The allelopathy effects of the aqueous extracts from rhizomes of the control (CK) were stronger than those of drought group 1 or drought group2, especially in the effects of seedling height and deformed seedlings .