| Chenopodium ambrosioides L. is the annual or perennial plant of Chenopod. It is an invasive plant, having strong aroma and usually growing on the riverside, road, badlands or cropland, and always forms ruderal community with Erigeron annuus L.and Artemisia annua L.It can be seen all the country, but in some places (like drainage area of the Changjiang River), it has become preponderant species, disturbing growth and propagation of the native plants, and bringing harms to native agriculture. Eradicating C.ambrosioides L.thoroughly and controlling its damage and spread has turned into these places'agricultural requests. At present, the research of C.ambrosioides L. is still nothingness, only having researches in its chemic components and officinal value, and starting pilot study on the seed storage and germination. So for managing this invasive plant effectively, it's meaning to investigate the adaptability of growth and physiology in adversity, and the result also can provide new theoretical method and practical experience for mechanism of biological invasion.Chenopodium album L. is a sort of weed which is difficult to dispose of, and is the relatives plant to C.ambrosioides L..It is the annual plant of Chenopod, always growing on the roadside, badlands or field. The experiment is taken to research adaptability of growth and physiology of C. ambrosioides L. in comparison with C.album L.n the way of morphological indicators, biomass allocation, antioxidant enzymes activity, and osmotic adjustment substances (proline and soluble sugar), under simulating the salt and alkali stress, acid rain, heavy metal-Cadmium stress, and different light intensity (overshadowing). The results of researches showed that:Under the simulated salt and alkali stress, the growth of C.ambrosioides L.was inhibited, and this restraining effection was obvious along with extent of intimidation. Under NaCl stress, morphology indicators datas of C.ambrosioides L.decreased, root length increased at first and then decreased, root weight ratio and crown-root ratio were higher than comparison; malondialdehyde content changed gently in low concentrations and gained in high concentrations; SOD activity had changed little, POD and CAT activity had increased firstly and then decreased. Under Na2CO3 stress, trend of morphology indicators and antioxidant enzymes activity of C.ambrosioides L. was similar to that under NaCl stress, but root weight ratio and crown-root ratio were lower than comparison, malondialdehyde content increased all through, and SOD,CAT and POD activity also had different changes. A result between the two stresses showed Na2CO3 stress did more harm to C. ambrosioides L. than NaCl stress. The growth of C.album L.was also inhibited, and its'SOD,CAT and POD activity had different diversifications with C. ambrosioides L. The root weight ratio,crown-root ratio and antioxidant enzymes activity of C.album L. was lower than that of C.ambrosioides L., indicating that C.ambrosioides L. had stronger tolerance to the salt and alkaline stress than C.album L..In addition, the proline of C. ambrosioides L. accumulated under NaCl stress, proline of C.album L.got together in low concentrations of Na2CO3 stress, and soluble sugar of these two species all gained in low concentrations of salt and alkali stress, indicating that the osmotic adjustment function of proline and soluble sugar had definite limitation.Under simulated acid rain, it had small influence on morphology of C. ambrosioides L.,except root length and the number of laminae and ramification had markedly otherness, other morphology indicators changed little. It seriously affected C. ambrosioides L.'s root, promoted its growth from pH 3.5 to 4.59,but root weight ratio and crown-root ratio decreased clearly as simulated acid rain's pH values declined, besides leaves ratio increased slightly. As stress of acid rain increased, malondialdehyde content increased, SOD activity gained a little, CAT activity declined, and POD activity increased at first and then decreased. Acid rain also had little effect on morphology of C.album L..Except acidity of pH 2.0, other acidity promoted its root growth. Root weight ratio and crown-root ratio of C.album L. were higher than comparison at pH 2.0, but the reason was unaware. In addition, activity of CAT and POD had different trends with C. ambrosioides L., but SOD activity was accordant with it. At pH 4.59, antioxidant enzymes activity was higher than comparison, indicating that C.album L. had been adapted to the local acid rain, whereas, under strong acid rain, the antioxidant enzymes activity of C. ambrosioides L. was higher than that of C. album L., showing C. ambrosioides L. was more tolerant than C.album L. under adversity. Proline of C. ambrosioides L. was influenced a little, but that of C. album L. was gained under weak acid rain, and soluble sugar synthesization of these two species was all restrained.Under simulated heavy metal-Cadmium stress, the growth of C. ambrosioides L. and C.album L.were inhibited seriously, and their morphology and biomass allocation had obvious changes. Stem height and the number of laminae and ramification of C. ambrosioides L. had dropped, and its root length, root weight ratio and crown-root ratio had increased at first and then decreased. Except leaf length, other morphology indicators of C.album L. also had markedly otherness, the root length also had the trend like C. ambrosioides L., but root weight ratio and crown-root ratio changed little. Their malondialdehyde content still increased firstly and then decreased, reducement of malondialdehyde content under high concentrations of Cd treatment showing Cd stress had exceeded cells'resist capability farthest. Their SOD and POD activity was unstable, CAT activity was degressive, indicating the functiong of enzyme system was maladjusted or unactivated. Low concentrations of Cd can effectively promoted accumulation of proline, specially for C. ambrosioides L., and also availably added soluble sugar, yet specially for C.album L.. At the 10 mg-L'concentration of Cd, root length, root weight ratio, crown-root ratio and proline of C. ambrosioides L. had come to the most, figuring that C. ambrosioides L.had put up some resistance for Cd stress.Under the simulated different light intensity (overshadowing), the growth of C. ambrosioides L. and C.album L. were inhibited seriously, at the overshadowing of three layers stress, their growth had been completely repressive. Their morphology indicators datas decreased. Root weight ratio and crown-root ratio of C. ambrosioides L. were increased firstly and then decreased, higher than comparison at one layer's overshadowing, but lower than comparison at two layers'overshadowing. By contraries, root weight ratio and crown-root ratio of C.album L. dropped all through. At the overshadowing of two layers stress, their malondialdehyde content declined, showing stress had exceeded cells'resist capability farthest. Low light restrained CAT and POD activity, except SOD activity. Low light intensity promoted proline and soluble sugar's accumulation of C. ambrosioides L., but accumulation of osmotic adjustment substance of C.album L. had some limitation, its proline content had decreased at first and then increased, soluble sugar content had the opposite trend, guessing synthesization of proline had been maladjusted. At the overshadowing of one layer, root weight ratio and crown-root ratio of C. ambrosioides L. had come to the most, showing certain resistance to the decrease of light intensity.According to these results above, C. ambrosioides L. has some phenotypic plasticity,and can change configuration and physiology in answer to variety of environment; has stronger resistance to adversity and higher physiological adjustment level than C.album L., testifying that invasive plant can quickly adapt to new environment due to its predominances of adaptability and endurance. In adversity, indexes of C. ambrosioides L. are nonsynchronous, the resistance can't measure with single index, and some index is more principal than others in some phase. Since C. ambrosioides L. has the ability of resisting salt and Cd in low concentrations, it's meaning that making use of it as grass of saline and restoration of Cd-contaminative soil. |
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