| Picea schrenkiana is the endemic species in mountains of Asia and Middle Asia. In China, It only distributes in Xinjiang. Distributing region mainly lies in northern slope of Tianshan Mountains, and a small quantity of Picea schrenkiana distribute in southern slope of Tianshan Mountains and northern slope of western part of Kunlun Mountain. It plays the indispensable vital role in maintaining water source of Tianshan Mountains and conserving water and soil. But with the increasing of forest product in economical construction and the accretion of disturbance intensity due to all kinds of economical action, we can see that the problem of nature regeneration has became more serious during forest nature regeneration. Based on this problem, many studies on light, water and nutrient which saplings need have been researched. But we can see from the results and effects of study that it still needs a long time to solve this problem. Therefore, on the basis of the hypothesis of "the autotoxicity of Picea schrenkiana results to natural regeneration failure", using bioassay method, this research studied effects of the different concentration aqueous extracts from the needles of Picea schrenkiana on its seed germination and seedling growth. And this research was experimented on the premise of simulating the circumstance of the Picea schrenkiana seed germination and seedling growth in the artificial climatic cabinet. Furthermore, the changes of plant endogenous hormone were measured using HPLC (high performance liquid chromatography) during the period of its seed germination and seedling growth. The results as following:In aspect of the bioassay of Picea schrenkiana autotoxicity , the results showed that the aqueous extracts from the needles of Picea schrenkiana has autotoxicity on seed germination and seedling growth of Picea schrenkiana under two different temperature conditions (①photoperiod 20℃, 16h, dark cycle 15℃, 8h;②The photoperiod 15℃, 16h, the dark cycle 10℃, 8h). In bioassay, seed germination was significantly delayed using lower concentration aqueous extracts, and seed germination was significantly restrained using higher concentration aqueous extracts. And the higher the concentration was, the more significant the inhibition was. In the temperature conditions of 15～20℃,the seed germination was markedly inhibited when the concentration of aqueous was 0.1gDWml-1, and the inhibition rate of seed germination is up to 31.3%. Under the same experimental condition, the seedling growth was markedly inhibited, and the inhibition rate of root length and shoot length were 44.0% and 27.8% respectively when the concentration of aqueous was 0.05gDWml-1.In the temperature conditions of 10～15℃,the seed germination was markedly inhibited when the concentration of aqueous was 0.025gDWml-1, and the inhibition rate of seed germination is up to 55.7%. Under the same experimental condition, the seedling growth was markedly inhibited, and the inhibition rate of shoot length was 16.9% when the concentration of aqueous was 0.3gDWml-1.Besides, dry weight was accelerated as using the needles aqueous extracts. It was markedly accelerated when the concentration of aqueous extract was 0.3gDWml-1, and was up to 23.6%.In aspect of the physiological mechanism of Picea schrenkiana autotoxicity, the results using HPLC analysis showed the GA3 elevated remarkably and accumulated largely after treatment by the needles and litters of Picea schrenkiana aqueous extracts during the period of its seed germination and seedling growth. And the synthesis of hormone IAA was promoted, the content of IAA was enhanced, and the hormone balance was destroyed. Meanwhile, the IAA increased with the concentration rising remarkably. It led to accumulating of the IAA content and the increasing of ACC synthesis enzyme mRNA, the transform of the AdoMet to ACC was also promoted. This transform induced ethylene biosynthesis and inhibited seed germination and the seedling growth. Besides, the ABA was accumulated largely with the concentration rising remarkably and the function of the hormone GA3 and IAA were counteracted. Furthermore, it ethylene biosynthesis was induced and seed germination was inhibited. It can be seen from the above results that destroying the balance of endogenous hormone was one of important starting mechanisms of Picea schrenkiana autotoxicity. In addition, the temperature and concentration had interactive effect to seed germination and the seedling growth of Picea schrenkiana and the endogenous hormone. |
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