Biological Detection Of Autotoxicity And Identification Of Potential Autotoxins In Picea Schrenkiana

Picea schrenkiana is the endemic species in mountains of Asia and Middle Asia and the most important regional forest cover in Tianshan Mountains. In China, it only distributes in Xinjiang. Distributing region mainly lies in northern and southern slopes of Tianshan Mountains and northern slope of western part of Kunlun Mountain. Forest interference system of P. schrenkiana determines pure forest is its current forest composition and the forest area is about 528.4 thousand square hectares which accounts to half of the woodland area in Xinjiang. P. schrenkiana constitutes the main material of Tianshan Mountain or even the entire forest ecosystem in Xinjiang. P. schrenkiana is the source of life of oasis ecosystems in Xinjiang and plays an indispensable vital role in maintaining water source. However, with the larger jamming intensity on forest ecosystems resulted from economic development, natural regeneration obstacle of P. schrenkiana is more prominent in the course of forest natural recovery absent of fire interference in the limited time.The obtained results showed that autotoxicity might be the main causing of these problems under the current forest interference system. Therefore, based on these conclusions, this research studied effects of diethyl ether, ethyl acetate and n-butanol fractions of aqueous extracts from litters and needles of P. schrenkiana on its seed germination and seedling growth. This research was also experimented on the premise of simulating the circumstance of the P. schrenkiana seed germination and seedling growth in the artificial climatic cabinet. Furthermore, investigations of the chemical basis of each fraction were undertaken using Column chromatography , GC-MS-MS and NMR analysis, and revealed the chemical basis of P. schrenkiana autotoxicity. The results as following:1. In the experiments of seed germination, diethyl ether fraction exhibited the strongest phytotoxicity and reduced seed germination at low concentration (IC₅₀ = 5.00 mg/mL) and n-butanol fraction had the least effect (IC₅₀> 10.00 mg/mL). In the experiments of seedling growth, diethyl ether fraction at concentration of 1.25 mg/mL had significant inhibitory effect on seedling growth (p<0.05), while n-butanol fraction at 1.25 mg/mL could stimulate the growth of seedling; n-butanol fraction at concentrations higher than 2.50 mg/mL all showed obviously inhibitory effect on the growth of seedling (p <0.05). The results of chemical basis of three fractions of aqueous extracts from P. schrenkiana litters showed that there were five compounds present in the diethyl ether fraction, six in ethyl acetate fraction and eight in n-butanol fraction; Seventeen compounds were finally identified. 2-keto-4a-methyl-8-methoxy-2, 3, 4, 4a, 5, 6, 11, 12-ocahydrochrysene (name it schrenkianaone in this article), which was identified but not reported as an allelochemical or autotoxin previously, was detected to exist in the diethyl ether fraction.2. In the experiments of seed germination, diethyl ether fraction exhibited the strongest phytotoxicity and reduced seed germination at low concentration (IC₅₀ = 5.84 mg/mL) and n-butanol fraction had the least effect (IC₅₀> 10.00 mg/mL). In the experiments of seedling growth, diethyl ether fraction at concentration of 1.25 mg/mL had significant inhibitory effect on seedling growth (p<0.05), while n-butanol fraction at 1.25 mg/mL could stimulate the growth of seedling; n-butanol fraction at concentrations higher than 2.50 mg/mL all showed obviously inhibitory effect on the growth of seedling (p <0.05). The results of chemical basis of three fractions of aqueous extracts from P. schrenkiana needles showed that there were phenolic acids, long-chain fatty acids, tannins, indoles and flavonoids identified in the aqueous extracts of P. schrenkiana needles. Schrenkianaone was also existed in diethyl ether fraction.