Study on the Ecological Adaptation and Mechanism of the Japanese Foxtail (Alopecurus Japonicus Steud.) Resistent to Haloxyfop-R-Methyl
|School||Nanjing Agricultural College|
|Keywords||Japanese Foxtail (Alopecurus japonicus Steud.) Ecology Stress tolerance Fitness Competition|
The objective of this study was to forecast the occurrence and changes in population structure of the resistant population of Alopecurus Japonicus Steud. In this paper, the resistant population of A.japonicus to haloxyfop-R-methyl was used to study the difference of some biological characteristics between the resistant population and susceptible population, including the seedling growth and optimum growth density. It was emphasized that the effect of stress on germination and growth characteristics of both populations were compared. Also, the affect of aqueous extract of roots and stems of A.japonicus on seed germination and seedling gorwth of associated plant,wheat,oilseed rape,Poa annua and Apecurus aequalis and the competition among these two populations, wheat and oilseed rape were explored.The result of some biological characteristics of both populations showed that the dormancy of both of the two populations could be effectively broken by putting seeds into cold water (4℃) for six days. The resistant population grew slower than the sensitive one just in the former 15 days after planting, while it would be faster than the susceptible population after then. The second leaf of seedless in resistant population would emerge at the 20th day after planting (DAP), which was later than the susceptible population for two days. And at the 25th DAP, the percentage of seedless in both population that had the second leaf was exceeded 95%. The resistant population was growed better than the sensitive population at the same plant densitity. The optimum plant density for growth of A. japonicas was ranged from 150 to 200 plants per0.11 m2.The study of the affect on germination and growth characteristics under stress showed that the germination rates of both populations could reach 90% under 80 mM NaCl, in which the germination rates of both populations were decreased with the increasing NaCl concentration. At the same NaCl concentration the germination rate of resistant population was lower than the susceptible population. There were significant differences between the seedling growth of resistant and susceptible populations at NaCl concentration of 40,80 and 160 mM, in which the seedling growth of resistant population were most prevailing at 80 mM..The affects of osmotic potential were similar with those of NaCl stress. The seed germination rate of both population could reach 80% at the osmotic potential ranged from 0 to-0.3 MPa, and the germination rate of resistant populationwas lower than the susceptible population at the range of -0.4 to -0.7 MPa.At the osmotic potential of -0.6 MPa, significant differences of germination and growth between these two populations were observed. At the pH range from 4.0 to 12.0, the germination rates of both populations could reach more than 80%. Alough at pH 2.5 to pH 3.0 and pH 12.5 the seedling growth of both populations could be inhibited, the seed germination and growth of resistant population were better than the susceptible population. The seed germination of both populations were extremely low at 5℃and 30℃, while the germination and seedling growth of resistant population were better than the susceptible population.The study on its mechanism of A. japonicus under stress showed that tolerance levels to stress of the resistant population greater than the susceptible population no matter at 80 mM NaCl, the osmotic potential of-0.6 MPa, pH 2.5 or 30℃high-temperature stress. Compared to the control, the activities of SOD, CAT and POD of both populations were increased rapidly, in which the increasing of resistant population were lower than the susceptible population. The increasing of MDA content indicated the occurrence of lipid peroxidationin both population. Also the content of proline in both population were increased, in which the increasement of resistant population was larger than that of susceptible population. With the prolonging of treatment time of stress, the chlorophyll content in both populations were decreased gradually with the increasing of stress treating time, but the decreasing rate of resistant population was lower than the sensitive population, which suggested that the photosynthesis of resistant population was slightly stronger than that of susceptible population. Even if the soluable protein contents of both populations’were increased gradually with the increasing of stress treating time, there was no significant differences between both populations.The competition results of A. japonicus showed that the aqueous extract from the roots and stems of A. japonicus were inhibitory to the germination and seedling growth of wheat and oilseed rape, while that from stems could inhibite the root,fresh weigth and dry weigth of wheat and oilseed rape seedlings, and the root of Poa annua and A aequalis., in which the inhibition of aqueous extract from roots was greater than that from stems. With the increasing of planting density of A. japonicas, the affect on the seedling of wheat and oilseed rape was greater. A simple equation was fitted based on the competition between A. japonicas and wheat and oilseed rape, in which the equations for A. japonicus with wheat and oilseed rape were y=-0.1553x+98.332 (R2=0.9793) and y=-0.7465x+97.042 (R2=0.9631), respectively.