关键词: 毛红椿, 凋落叶, 腐解, 化感作用, 化感物质

Abstract: [Objective] Toona ciliata var. pubescens is a second class national-level protected endangered species.A large number of its leaves fall to the surface of the soil every year, however it is not clear whether the leaf litter cause sallelopathy.This paper aimed to evaluate the allelopathic potential of leaf litter on itself seed germination and identify major compounds in leaching solution of the leaf litter, to explore the endangered mechanism of the species and provide the reference for the promotion of its seedling regeneration.[Method] Three kinds of materials froma plantation of T. ciliata var. pubescens,including the leaves, the leaves mixed with forest soil and forest soil, were decomposed.Allelochemicals were extracted from the decomposed ploducts by mixing them with solution(ethanol:acetone:water=2:2:1, V/V).Seed germination experiment of T. ciliata var. pubescens was used for the biological detection. The weak polar allelochemicals were extracted with acetone and were analyzed by gas chromatography mass spectrometry (GC-MS).[Result] The results showed that low concentration leaching solution of the humus and the decaying leaves of T.ciliata var. pubescens had inhibitory effects on its seed germination. The inhibition effect of extracts from the humus on germination was significantly stronger than that of extracts from the decaying leaves. The higher the concentration the stronger the inhibition.Low concentration (10 g·L^-1) leaching solution of the humus and the decaying leaves had no significant effect on seedlings survival, but high concentration (1 000 g·L^-1) leaching solution of the humus significantly reduced survival rate of seedlings of T.ciliata var.pubescens. Low concentration leaching solution of the decaying leaves had an extremely significant promoting effect on seedling root length.Low concentration leaching solution of the humus had significant promotion effect on stem and root length.However,high concentration leaching solution of leaf decomposition significantly inhibited the growth of seedlings. Low concentration leaching solution of the humus and the decaying leaves significantly increased the seedlings biomass. High concentration leaching solution of the humus and the decaying leaves significantly decreased the seedlings biomass. The GC-MS analysis results showed that there were six substances in the extract of humus, and benzoic acid derivatives were the main components.A total of 36 substances were identified from the water decaying leaves, and the major components were sitosterol, stigmast and fatty acids such aspalmitic acid and their esters.[Conclusion] The decomposed leaves of T. ciliata var. pubescens have inhibitory effect on itself seed germination. Low concentration decomposition promotes the growth of T.ciliata var. pubescens seedlings. The high concentration extract of decomposition has inhibitory effect on the seedling growth. Benzoic acid derivatives in the leaching solution of the humus may be the main allelochemicals.The weak polar components in the leaching solution of the decaying leaves are mainly sterols,fatty acids and their esters.

Key words: Toona ciliata var. pubescens, leaf litter, decomposition, allelopathy, allelopathic substances