| Chinese fir is one of the most important tree species in the south of China, with fast growth, high yield, and fine material quality. Phosphorus is one of the essential elements for the growth of trees, and the deficiency of Phosphorus had became the important factors which limited the production of plantation at Present, the plant resisted the low-phosphorus stress mainly by means of the roots secreted acidic material to activate hard dissolved Phosphorus. Recently, there were many studies on response mechanism that the plants adapt to the low-phosphorus stress, but it was not clear enough that how the plant to start the complex regulation mechanism to adapt to the low phosphorus stress.Calcium is considered to the second messenger which connected the extracellular signal to physiological and biochemical reaction in cells, which made the plant alleviate the stress hurt and increase the capability of hardiness. Currently, the Phosphorus and Calcium always be taken as an independent factor in study. Therefore, it has important significance for studying the effect of Calcium while Chinese fir adapt to the low phosphorus adversity.In view of these, according to the principle and method of plant physiology, plant nutrition genetics and root biology,and basing on the researches my tutor had done early days, the paper used half compatriots family of Chinese fir collected from state-owned forest in ZhangPing of Fujian, designed different phosphorus calcium level potted plant experiments in water culture and soil culture, and the differences of morphological and physiological process that response to different phosphorus and calcium levels were compared. At the same time, evaluated phosphorus and calcium utilization efficiency in Chinese fir, discussed, the interaction mechanism that Chinese fir adapted to low phosphorus environment, researched the relationship between exogenous calcium level and Chinese fir roots secreted acidic material under low phosphorus, and then to show the effect of exogenous calcium on Chinese fir adapted low-phosphorus stress. The study discussed the adaptation that Chinese fir faced to phosphorus and calcium stress from mechanism, which had the important significance on mining the hard dissolved phosphorus and improving soil phosphorus utilization efficiency in Southern forest.The main results were as follows:1. Different phosphorus and calcium levels had significant effect on the growth of Chinese fir. seedling height、ground diameter and biomass also appear downtrend as the fall in the levels of phosphorus, and the seedling height、ground diameter and biomass in mild calcium stress and moderate calcium stress were better than other calcium levels in soil experiment, but in water experiment, the best were in normal calcium supply and mild calcium stress. The biomass allocation in roots, stems and leaves was different in Chinese fir, but the biomass overground was significantly higher than the underground, and the biomass underground in mild calcium stress was higher than other calcium level. So we draw a conclusion that low-phosphorus made a inhibitory action for the growth of Chinese fir, certain calcium levels were beneficial to the growth of Chinese fir, but calcium level too high or too low were bad.2. The changes of Chinese fir roots system in different phosphorus levels showed as follows: excepted the average root diameter, the differences in total root length, root surface area and root volume were significant in soil experiment, which were increased as for the fall in the levels of phosphorus, especially in heavy phosphorus stress, the total root length, root surface area and root volume got maximum, and had a significant differences with other phosphorus levels. The changes of the Chinese fir root system in different calcium levels showed:they also changed evidently excepted root diameter, and were best in normal calcium supply, and the moderate calcium stress, moderate calcium stress took the second. In the water experiment, the changes were not evidently, but the result is consistent with the soil experiment.3. Photosynthetic characteristics of Chinese fir was different under different phosphorus levels. Under the soil experiment, chlorophyll a, chlorophyll b and total chlorophyll content of Chinese fir were lowest in heavy phosphorus stress, the high phosphorus supply took second. The differences in chlorophyll a, chlorophyll b and total chlorophyll were significant in different calcium levels, which were decreased while the fall in the levels of calcium, and heavy calcium stress was evident with other levels. The chlorophyll fluorescence parameters Fv/Fm changed under the different phosphorus levels, and with the extension of the phosphorus stress time, Fv/Fm was increasing. But under different phosphorus levels, the photosynthetic pigments were no obvious regulation between different calcium levels, only undulate in small area, with the fall in the levels of calcium, Fv/Fm increased at first, then reduced, and the minimum was in the heavy calcium stress, while under heavy phosphorus stress.4. In the soil culture experiment, the change law of MDA, soluble protein and acid phosphatase activity in Chinese fir showed as follow:with the fall in phosphorus level, MDA content increased at first, then decreased, and the highest MDA content was in mild phosphorus stress, compared the5different calcium levels, the highest MDA content was in heavy calcium stress, and had the difference significant with other levels. With the changes of phosphorus and calcium levels, Chinese fir’s soluble protein content did not have obvious law, compared5different phosphorus level, the highest soluble protein content was in high phosphorus supply, and lowest was in heavy phosphorus stress; however, in the5calcium levels, soluble protein content was high except the high calcium supply and heavy calcium stress. For acid phosphatase activity in Chinese fir, it increased with the decreased of phosphorus levels, and the differences between heavy phosphorus stress and other levels were significant, in5different calcium levels, the highest acid phosphatase activity was in mild calcium stress, and had the obvious difference with other levels. In the water experiment, MDA and soluble protein content also increased with the decreased of phosphorus levels, but it did not have the same change law in different calcium levels; and the difference of acid phosphatase activity was not obvious in different phosphorus and calcium levels.5. The change law of rhizosphere pH and the content of acid materials secreted by roots of Chinese fir showed as follow:in the soil culture experiment, the content of acid materials was different in5phosphorus levels, with the fall in phosphorus level, it decreased at first, then increased, especially in moderate phosphorus stress and heavy phosphorus stress, the content of acid materials was higher than normal phosphorus supply; in the5calcium levels, the difference was also obvious, the highest was in normal calcium supply, and the lowest was in high calcium supply. In the different phosphorus levels, the difference of rhizosphere pH was not significant, but in some degree phosphorus stress, it was significant in5calcium levels, and the highest was in mild calcium supply, the lowest was in high calcium supply. Under water culture trials, the pH appeared the same law in different phosphorus and calcium levels, When incubation time was prolonged, it showed decreased at first then increased in a small range, and in the different phosphorus levels the pH was lower than normal phosphorus supply, it showed that Chinese fir can adapt to the phosphorus deficiency by autoregulation from roots which secreted the acid materials in the phosphorus stress condition.6. In the soil culture experiment, the effect of different phosphorus levels on the phosphorus content, phosphorus accumulation and phosphorus use efficiency was different. Under the normal phosphorus supply and mild phosphorus stress, the phosphorus content in different organ showed: root> leaf> stem; in other3phosphorus levels, it showed:leaf> root> stem, and it had the significant difference in5calcium levels. The change law of phosphorus accumulation was different in different phosphorus levels, in the high calcium supply and mild calcium stress, the phosphorus accumulation showed:leaf> root> stem, and other levels showed:leaf> stem> leaf, and it had the significant difference in5calcium levels. With the fall in phosphorus level, phosphorus use efficiency of roots system reduced first, and increased then, especially in heavy phosphorus stress, which was2.17times as normal phosphorus supply; but the phosphorus use efficiency of stem was opposite, the phosphorus use efficiency of leaf did not have the obvious change law.7. In the soil culture experiment, the change law that the effect of different phosphorus levels on Chinese fir’s the calcium content, calcium accumulation and calcium use efficiency showed as follow:in the different phosphorus levels, the calcium content of root, stem and leaf showed:root>stem>leaf, and with the fall in phosphorus levels, the calcium content of root increase at first then decrease, but it did not have the obvious change law in calcium content of stem and leaf. The calcium accumulation of different organ showed:leaf>stem>root in all phosphorus levels excepted moderate phosphorus stress. In different organ, calcium use efficiency showed:leaf>stem>root, but with the change of phosphorus levels, tcalcium use efficiency of root remain unchanged.8、The results showed that the effect of different calcium levels on root growth and Physiological Metabolism of Chinese fir was different no matter in soil or water culture experiment with low-phosphorus stress. The seedling height, ground diameter, biomass and root length which added calcium were obvious higher than which without calcium, and when the calcium concentration was120mg/L, root-shoot ratio was highest, when calcium concentration was lower than220mg/L, it did not promote Chinese fir’s growth,; in the low-phosphorus stress, the root acid secretion, Chlorophyll and soluble protein content increased significantly, acid phosphatase activity also was higher than the condition with calcium, and MDA content decreased. In addition, phosphorus use efficiency in different organ was closely related to the calcium level, when the fall in phosphorus level, phosphorus use efficiency increased, when in low calcium stress or no calcium, calcium content was low, but calcium use efficiency was higher, and it was a positive correlation between calcium content in cell and calcium use efficiency. It was clear that when the calcium concentration was between40mg/L～120mg/L, the growth of Chinese fir was better and improved the calcium use efficiency, when calcium concentration was higher than200mg/L, it showed no benefits almost Inhibition. |
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