| Allelopathy is a phenomenon that allelochemicals released by plants (includingmicroorganisms) into the environment have a direct or indirect harmful effect on otherplants. Allelopathy is commonly found in nature. Allelopathy among plant species areresponsible for natural selection in plant communities and protect the donor plant againstmicroor-ganisms, viruses, insects and other pathogens or predators. Allellopathy is also anew and potential research field.The allelopathic effects of the aqueous extracts from leaves and stems of Kochiasieversiana on Lactuca sativa, Triticum aestivum, Kochia sieversiana, Suaeda glauca, andArtemisia anethifolia were studied．Effects of the aqueous extracts from leaves and stemsof K. sieversiana on the germination of lettuce (L. sativa) seeds, and the mitotic index oflettuce (L. sativa) tip cells were analysed. Thus, K. sieversiana may have allelochemicalsthat could influence other plants. The root vigor, the photosynthetic pigment content,peroxidase (POD) activity, puperoxide dismutase (SOD) activity, patalase (CAT) activityand malondiadehyde (MDA) content of wheat (T. aestivum) were measured. Allelopathicmechanism of K. sieversiana was studied initially. Additionally, effects of the aqueousextracts of leaves and stems of K. sieversiana on the germination of K. sieversiana, S.glauca and A. anethifolia were measured. At the same time, K. sieversiana and rhizospheresoil were collected in different seasons. Phenol contents changed in K. sieversiana andrhizosphere soil, and phenylalanine ammonia-lyase (PAL) activity of K. sieversianachanged in different growth stages were measured.The results indicated that the germination rate, the germination index, the vigor indexand the mitotic index of lettuce were decreased with increasing in contents of the K.sieversiana extract. The higher concentration of the aqueous extracts induced chromosomalaberration, such as chromosome trail, and chromosome-bridge. And the number of lettuceroot tip cells was increased during prophase. The results indicated that the shoot of K.sieversiana contained some allelochemicals. In the presence of allelochemicals, the processof cell division was stopped in the prophase. Root elongation was inhibited.The aqueous extracts from leaves and stems of K. sieversiana changed physiologicaland biochemical of wheat seedling. With increasing in contents of aqueous extracts, theroot vigor of wheat was increased and then decreased. The increase of root vigor may be anadaptive performance of wheat seedlings for allelochemicals at low concentration.However, the root vigor was inhibited at higher concentration. Similarly, with increasing incontents of the aqueous extracts, photosynthetic pigment contents of wheat leaves werereduced, and photosynthesis was inhibited. Allelochemicals can affect the function andactivity of antioxidant enzymes. With increasing in contents of the aqueous extracts, SODactivity and POD activity were increased, and CAT activity was decreased in wheatseedlings. MDA content was increased. Allelochemicals may destroy the structure and function of cell membrane.The germination rate, the germination index, the vigor index of receptor plants (K.sieversiana, S. glauca, and A. anethifolia) were decreased with increasing in contents of K.sieversiana extracts. The results indicated that the aqueous extracts of K. sieversiana hadan autotoxicity effect on K. sieversiana, and had an allelopathic effect on S. glauca and A.anethifolia. Phenol was one of the main allelochemicals. With growth and development ofK. sieversiana, phenol contents in plants were increased, and some phenols in rhizospheresoil were detected. PAL activity also was increased gradually with seedlings growth,because PAL was an important enzyme of plant secondary metabolites and related to thesynthesis of phenols.The results metioned above indicated that the aqueous extracts of K. sieversianacontained some allelochemicals-phenols, and had an allelopathic effect on the receptorplants. |
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