天山云杉(Picea schrekiana Fisch et Mey.)凋落物的自毒效应

天山云杉(Picea schrekiana Fisch et Mey.)是亚洲中部山地的特有物种,在中国仅见于新疆,其主要分布在天山南北坡和昆仑山西部北坡,对天山的水源涵养、水土保持和林业生产具有不可或缺的重要作用。然而天山云杉林的天然更新不良和障碍成为困惑新疆林业工作者的一大难题。从植物间的化感与自毒作用研究着手,分析了天山云杉凋落物水提液的乙醚、乙酸乙酯、正丁醇萃取物对自身种子萌发和幼苗生长的影响。以种子发芽率、发芽势和发芽指数作为种子萌发参数,以胚根、胚芽长度和实生苗干湿重的变化作为幼苗生长参数。研究结果表明:种子萌发试验中乙醚萃取物具有最强的抑制效应(IC50=5.00mg/mL),而正丁醇萃取物的抑制效应最弱(IC50>10.00 mg/mL);幼苗生长试验中,1.25 mg/mL的乙醚萃取物对幼苗生长具有显著的抑制作用(P<0.05),1.25 mg/mL的正丁醇萃取物能够促进其幼苗生长,大于2.5 mg/mL的正丁醇萃取物对幼苗生长都具有显著的抑制效应(P<0.05)。采用GC-MS-MS技术分析三种有机萃取物的化学组成,共鉴定并定量分析出了包括酚酸、长链脂肪酸、单宁酸和吲哚类物质在内的17种化合物。乙醚萃取物中存在的2-keto-4a-methyl-8-methoxy-2,3,4,4 a,5,6,11,12-ocahydrochrysene为一新的化感物质,证明了天山云杉凋落物中存在的化感与自毒物质是导致其种群天然更新障碍的最主要原因,同时揭示了自毒作用发生的化学物质基础。

Autotoxic Effect of Aqueous Extracts from Picea schrekiana Fisch et Mey. Litters

Picea schrekiana Fisch et Mey.is widely distributed in the Tianshan Mountain areas in the northwest of China where substantial amounts of litters accumulate on the ground.A unique pattern of regeneration underneath trees is often found.The article studied the potential autotoxic effect of aqueous extracts from P.schrekiana litters.Litters were extracted from water and partitioned against diethyl ether,ethyl acetate and n-butanol,subsequently.The three organic extracts were tested for inhibitory activity of seed germination and seedling growth.The seeds germination rate,germination vigor,and germination index were measured as seed germination parameters and radical and change of plumule elongation and weight(wet and dry) of seedling were measured as seedling growth parameters.The results showed that diethyl ether extract exhibited the strongest inhibitory effect and reduced seed germination at low concentration(IC50=5.00 mg/mL);n-butanol had the least effect(IC50>10.00 mg/mL);Diethyl ether extracts at concentration of 1.25 mg/mL had significant inhibitory effect on seedling growth;while n-butanol extract of 1.25 mg/mL could stimulate the growth of seedling;extracts at concentrations were higher by 2.5 mg/mL,all showed obviously inhibitory effect.An investigation of the chemical basis for the three organic extracts was also conducted by using GC-MS.There were five compounds in the diethyl ether extract,six in ethyl acetate extract and eight in n-butanol extract being identified and quantified;they were phenoli cacid,long-chain fatty acid,tannin and indoles.2-keto-4a-methyl-8-methoxy-2,3,4,4a,5,6,11,12-ocahydrochrysene,which was found but was not reported as allelochemicals previously,was detected to exist in the diethyl ether extract.