The effects of activated carbon and plants diversity ... - 华南农业大学

华 南 农 业 大 学 农 学 院 第 三 届 综 述 大 赛 获 奖 作 品 论 文 集一 等 奖 作 品there is increasing interest in the effects of activated carbon and plants diversity research onplants autotoxicity, and it is also critical to provide a greater generality to the overall effect ofmaintaing or enhancing biodiversity.2. Plants autotoxicityAutotoxicity is a common phenomenon in both natural and manipulated ecosystems. Ithas been related to many problems in agriculture and forestry systems, e.g., soil sickness,continuous cropping obstacles, orchard replanting problems, and forest regeneration etc. Innatural ecosystems autotoxicity may have important ecological implications, minimizingintraspecific competition, extending seed dispersal, regulating plant population over spaceand time, and maintaining seed dormancy over a long period of time in stressful environments(Liu et al. 2007; Singh et al. 1999). Autotoxicity can be a driving force in succession of someplant community (Jackson and Willemsen 1976; Quinn 1974).Continuous cropping and monoculture could lead to allelochemical accumulation in thesoils. Mazzoleni (2007) proposed that autotoxicity is a common phenomenon, and it isstronger than phytotoxic effects on other species, thus largely affecting ecosystem stability,productivity and diversity. One of the four main mechanisms which proposed to explainplant-soil negative feedback was the release of phytotoxic compounds during organic matterdecomposition (Armstrong and Armstrong 2001; Singh et al. 1999; Webb et al. 1967).Several agricultural crops such as rice (Chou and Lin 1976), wheat (Einhellig 2004), alfalfa(Chen et al. 2002), barley (Hordeum vulgare L.) (Ben-Hammouda et al. 2002), ryegrass(Lolium perenne L.) (Fageria and Baligar 2003), corn (Lin et al. 2005a; Lin et al. 2005b),mungbean (Vigna radiata) (Kim and Kil 2001), Asparagus officinalis (Kato-Noguchi 2004;Loffredo and Senesi 2006), tomato (Lycopersicon esculentum) (Zhou et al. 1997), cucumber(Cucumis sativus) (Yu and Matsui 1994) have been reported to exhibit strong autotoxicity.During the past three decades many studies have showed that alfalfa (Medicago saliva L.)is not only heterotoxic to other plant species, but also autotoxic to its own (Nielsen et al. 1960;Guenzi and McCalla 1964; McElgunn and Heinrichs 1970; Klein and Miller 1980; Miller 1983;Kehr and Ogden 1983; Hall and Henderlong 1989; Dornbos Jr et al. 1990; Hegde and Miller1992a; Chung 1994; Jennings 1996; 1991; Chon et al. 2000; Chon et al. 2002; Seguin et al.2002). Water-soluble substances in alfalfa fresh leaves, stems, crowns, dry hay, old roots, andsoil residues are autotoxic to alfalfa seed germination and early seedling growth (Jensen et al.1981). However, the autotoxic substances are significantly different among plant parts. Chonand Kim (2002) showed that the growth inhibition by the extracts from leaves was the highest,which were 15.4, 17.5 and 28.7 times more toxic to alfalfa root growth than were those fromroots, stems and seeds, respectively. The type and concentration of allelochemicals in alfalfa2