Study On Ecology Of Weed Community In Wheat Fields And Biology Characteristics Of Beckmannia Syzigachne

Weed communities in the wheat fields of Jiangsu and Anhui Province were investigated. Dominant rate, niche width and association relationships between main weed populations were caculated, and principal component analysis (PCA) of main weed populations was conducted. After that, the biology characteristics of Beckmannia Syzigachne, the dominant population of the weed communities in both Nanjing and Chuzhou, such as influential factors of seed germination, growth and photosynthesis characteristics, water contents, general nitrogen contents, and karyotypes of different ecotypes were studied, Results are as follow:1. In the wheat fields investigated in Nanjing and Chuzhou, 20 weed populations were found, which belonged to 19 genera and 8 families. Beckmannia Syzigachne was the dominant population in both two cities.2. Among all the association relationships, Beckmannia Syzigachne had positive associations with Lapsanastrum apogonoides, Galium aparine, and Alopecurus japonicum,while had negative associations with Avena fatua, Malachium aquaticum, Euphorbia helioscopia, Vicia sativa, Geranium carolinianum, Alopecurus aequalis and Hemistepta lyrata.3. In the wheat fileds investigated in Nanjing, weed population differentiation occurred mainly in five directions of Beckmannia syzigachne, Vicia sativa , Poa annua, Euphorbia helioscopia and Lolium perenne. While in that of Chuzhou, weed population differentiation mainly occurred in five directions of Beckmannia syzigachne, Vicia sativa, Geranium carolinianum, Alopecurus aequalis and Avena fatua.4. The niche width of Beckmannia syzigachne was rather wide. It had the largest niche overlap with Euphorbia helioscopia in Nanjing and with Galium aparine in Chuzhou. What's more, niche overlap also occurred between Beckmannia syzigachne and Vicia sativa, Geranium carolinianum, and Alopecurus aequalis.5. The optimum seed germination conditions of different ecotype Beckmannia syzigachne were quite the same, which were 20℃, darkness, and at the surface of soil. The highest germination rate of all the 8 ecotype was No.Ⅲ,Ⅳ,Ⅴ, while the lowest of that was No.Ⅱ.6. In general, the growing characteristics of all the 8 ecotype Beckmannia syzigachne were same. However, it also had a little differences among different ecotypes.7. The lowest net photosynthesis speed of the 8 ecotype Beckmannia syzigachne was that of No.Ⅱ(10.00μmolCO2 /s), while the highest was that of No.Ⅲ(15.10μmolCO2 /s). The lowest chlorophyll content (SPAD value) was that of No.Ⅲ(16.9), while the highest was that of No.Ⅵ(29.5). In general, except for No.Ⅲ, there was a direct ration between net photosynthesis speed and chlorophyll content. In addition, among all the ecotypes, No.Ⅵhad the relatively high net photosynthesis speed and chlorophyll content.8. The lowest water contents of all the 8 ecotype Beckmannia syzigachne was that of No.Ⅰ(78.8%), while the highest was that of No.Ⅴ(85.5%). There were not obvious differences of the general nitrogen contents among different ecotypes. The expected mathematical expectation of nitrogen content was 0.772%, while that of crude protein content was 4.825%.9. Polyploidy was found in Beckmannia syzigachne of all the 8 ecotypes, among which No.Ⅷhad the highest polyploidy probability (18%). The chromosome number Beckmannia syzigachne was 14 ( 2 n = 14), and the karyotypes of all the ecotypes were 2C.