| Cinnamomum camphora,is an evergreen tree of Cinnamomum camphora in Lauraceae,with luxuriant branches and magnificent momentum.It is listed as the second level key protected wild plant by the state,and is also an important economic,timber tree species and mountain greening tree species in Southern subtropical region of China.Cinnamomum camphora has a strong ecological function.If we can clarify the adaptability and mechanism of camphor tree to karst high calcium environment,and select excellent provenances with high calcium tolerance,we can effectively conserve water and soil,improve the fragile ecological environment in karst areas,and promote the healthy development of local society and economy.Therefore,in this study,two-year-old seedlings of Cinnamomum camphora from different provenances were selected as the research object,and CaCl2 was set at different levels to simulate the soil high calcium environment in limestone area.The effects of different concentrations of CaCl2 on the growth and biomass,morphology and structure of leaves and roots,and related physiological and biochemical characteristics of Cinnamomum camphora were studied,and the effects of CaCl2 on high calcium content in karst areas of South China were discussed The adaptability of Cinnamomum camphora to high calcium was compared among different provenances.The changes of aboveground and underground dry matter accumulation,chlorophyll content,chlorophyll fluorescence parameters,mad,pod and osmotic adjustment substances of Cinnamomum camphora from Different Provenances under calcium stress were compared.The physiological and ecological adaptation mechanism of Cinnamomum camphora to high calcium environment was revealed in the first stage,aiming at the development of community ecology The rapid restoration of karst vegetation and ecological reconstruction in karst areas provide theoretical support.The main results are as follows:1、The growth of aboveground and underground parts of Cinnamomum camphora was significantly inhibited in high calcium environment.With the increase of calcium stress,the stem and leaf dry weight of Cinnamomum camphora seedlings first increased and then decreased,but the root system did not change significantly.When the concentration of Ca2+reached 20 mmol/L,the dry weight of leaves and stems were the largest,and then began to decrease gradually,and the leaf dry weight decreased faster,which is a typical negative feedback regulation mechanism of plants under stress conditions[93]When plants are under high calcium stress,the biochemical reaction process of plants will be negatively affected,which leads to the significant reduction of water absorption in the roots.Therefore,in order to ensure the normal life function of plants.The results showed that when the concentration of Ca2+exceeded 20 mmol/L,camphor seedlings began to start the regulation mechanism of root shoot ratio to maintain the homeostasis of internal environment.With the increase of Ca2+concentration,the root shoot ratio of Cinnamomum camphora increased gradually.When the concentration of Ca2+reached 50 mmol/L,the leaves began to wilt.When the Ca2+concentration exceeded 100 mmol/L,the leaves of Cinnamomum camphora seedlings began to turn yellow,dehydrated and the root system shrank The maximum tolerance concentration of Ca2+in Cinnamomum camphora seedlings was about 100 mmol/L.2、With the increase of exogenous Ca2+concentration,the content of mad in leaves of Cinnamomum camphora increased gradually,while the activities of protective enzymes such as pod increased first and then decreased rapidly.When the concentration of Ca2+was 20 mmol/L,the content of MDA in Cinnamomum camphora seedlings from different sources was the lowest,and the damage ability to membrane system of Cinnamomum camphora seedlings reached the minimum,and pod enzyme activity was higher,which could adapt to the calcium environment at this time.However,when the concentration of Ca2+exceeded 20 mmol/L,the content of MDA began to increase,and the activity of pod enzyme began to decrease rapidly.When the concentration of Ca2+reached 50 mmol/L,the MDA content of Cinnamomum camphora seedlings increased The amount has reached 15～20 mmol/g,while the activity of pod enzyme is only about 20%of that when it is not under calcium stress,which indicates that the damage of cell membrane exceeds the defense ability of protective enzyme system,leading to the enhancement of membrane lipid peroxidation and further destruction of cell membrane[97,which further leads to the physiological reaction of increasing the content of malondialdehyde,the product of membrane lipid oxidation.The increase of malondialdehyde content and the change of pod antioxidant enzyme activity caused the lipid to be oxidized by reactive oxygen species formed in high calcium environment,which seriously affected the growth of Cinnamomum camphora seedlings.3、The chlorophyll content of Cinnamomum camphora seedlings in the three provenances reached the peak when the concentration of Ca2+was 20 mmol/L,and the net photosynthetic rate PN increased curvilinearly with the increase of par intensity.When par intensity of par reached 1500 μ mol M2S-1,the net photosynthetic rate reached saturation.The results showed that the photosynthetic rate and stomatal conductance decreased with the increase of Ca 2+ and Ca 2 +Among them,the seedlings of Cinnamomum camphora from Hengnan provenance were significantly different from those of Taoyuan and Ningxiang provenances in response to high calcium environment,showing higher stomatal regulation ability and photosynthetic regulation ability.It may be similar to the leaf regulation mechanism of honeysuckle under high calcium environment,and it is related to the ability of stomatal Ca2+ efflux.4.The results showed that Cinnamomum camphora had good tolerance and adaptability to high calcium environment,and could grow well in the soil irrigated with 5-50 mmol/L Ca2+solution,and could survive in the soil irrigated with 50-100 mmol/L Ca2+ solution.The response mechanism of Cinnamomum camphora seedlings from three different provenances in plant growth index,photosynthetic characteristics and physiological and biochemical indexes under high calcium environment was basically consistent.However,in high calcium environment,Hengnan provenance showed stronger adaptability to high calcium environment than Ningxiang provenance and Taoyuan provenance. |
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