Effects of Phenolics on seedling growth and ~(15)N nitrate absorption of Cunninghamia lanceolata

摘要

Chinese fir (Cunninghamia lanceolata) has replant problem under field conditions and has been attributed to phenolic allelochemicals, which cause its autotoxicity To determine the mechanism of inhibitory effects of phenolics on Chinese fir, we studiedtheir effects on growth and ~(15)N nitrate absorption by each organ of its seedlings, cultured in pots using ~(15)N-labelled isotope trace technique. The 1x10~(-3) mol L~(-1) vanillic acid and phenolics mixture (0 5x10~(-3) mol L~(-1) vanillic acid and0 5x10~(-3) mol L~(-1) p-hydroxybenzoic acid) significantly inhibited the seedling growth of Chinese fir Phenolics solution of 1x10~(-2) mol L~(-1) concentration decreased total N content of roots, stems and leaves ~(15)N derived from the fertilizer (NDFF) in roots, stems and leaves treated with 1 x 10~(-2) mol L~(-1) vanillic acid was 36,1, 427 and 385% less, respectively, and corresponding values for phenolics mixture at the same concentration were 14 1, 172, and 170% lower, respectively, compared tocontrol In contrast, vanillic acid and p-hydroxybenzoic acid at 1 x 10~(-5) mol L~(-1) stimulated the seedling growth, enhanced total ~(15)N content and increased ~(15)N nitrate absorption. These treatments also increased the ~(15)N nitrate distributionin roots and reduced its distribution in stems and leaves. We suggest that accumulated phenolics in soil could inhibit seedling growth through reducing nutrient absorption by Chinese fir and consequently leading to low productivity of replanted Chinese fir.